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1.	Azad, AK, et al. (författare) Preparation, Crystal and Magnetic Structure of the Double Perovskite Ba2FeWO6 2002 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. ; A 74, s. S763-765 Tidskriftsartikel (refereegranskat)abstract Single-phase polycrystalline material of the double perovskite Ba2FeWO6 was prepared and characterized by X-ray and neutron powder diffraction (NPD). The crystal structure was tetragonal with lattice parameters a=b=5.7479(4) Å and c=8.1444(9) Å at room temperature (295 K). NPD data at 10 K shows the evidence of an antiferromagnetic ordering of the Fe atoms. The reverse Monte Carlo powder (RMCPOW) technique was used to find the magnetic structure, which showed that it is based on a unit cell related to that of the nuclear structure by the propagation vector 0 \frac[¯]1[¯][¯]2[¯] \frac[¯]1[¯][¯]2[¯] . An ordering of collinear spins was found with alternate layers in the c-direction or in the a-b plane. The model was checked by Rietveld refinement and the magnetic moment of iron was found to be 3.39(2)7B at 10 K.
2.	Bahaloo, Hassan, et al. (författare) Mapping of density-dependent material properties of dry manufactured snow using μCT 2024 Ingår i: Applied Physics A. - : Springer Nature. - 0947-8396 .- 1432-0630. ; 130 Tidskriftsartikel (refereegranskat)abstract Despite the significance of snow in various cryospheric, polar, and construction contexts, more comprehensive studies are required on its mechanical properties. In recent years, the utilization of μ CT has yielded valuable insights into snow analysis. Our objective is to establish a methodology for mapping density-dependent material properties for dry manufactured snow within the density range of 400–600 kg/m 3 utilizing μ CT imaging and step-wise, quasi-static, mechanical loading. We also aim to investigate the variations in the structural parameters of snow during loading. The three-dimensional (3D) structure of snow is captured using μ CT with 801 projections at the beginning of the experiments and at the end of each loading step. The sample is compressed at a temperature of − 18 o C using a constant rate of deformation (0.2 mm/min) in multiple steps. The relative density of the snow is determined at each load step using binary image segmentation. It varies from 0.44 in the beginning to nearly 0.65 at the end of the loading, which corresponds to a density range of 400–600 kg/m 3 . The estimated modulus and viscosity terms, obtained from the Burger’s model, show an increasing trend with density. The values of the Maxwell and Kelvin–Voigt moduli were found to range from 60 to 320 MPa and from 6 to 40 MPa, respectively. Meanwhile, the viscosity values for the Maxwell and Kelvin–Voigt models varied from 0.4 to 3.5 GPa-s, and 0.3–3.2 GPa-s, respectively, within the considered density range. In addition, Digital Volume Correlation (DVC) was used to calculate the full-field strain distribution in the specimen at each load step. The image analysis results show that, the particle size and specific surface area (SSA) do not change significantly within the studied range of loading and densities, while the sphericity of the particles is increased. The grain diameter ranges from approximately 100 μ m to nearly 400 μ m, with a mode of nearly 200 μ m. The methodology presented in this study opens up a path for an extensive statistical analysis of the material properties by experimenting more snow samples.
3.	Bahaloohoreh, Hassan, 1983-, et al. (författare) Material mapping strategy to identify the density-dependent properties of dry natural snow 2024 Ingår i: Applied Physics A. - : Springer Nature. - 0947-8396 .- 1432-0630. ; 130:2 Tidskriftsartikel (refereegranskat)abstract The mechanical properties of natural snow play a crucial role in understanding glaciers, avalanches, polar regions, and snow-related constructions. Research has concentrated on how the mechanical properties of snow vary, primarily with its density; the integration of cutting-edge techniques like micro-tomography with traditional loading methods can enhance our comprehension of these properties in natural snow. This study employs CT imaging and uniaxial compression tests, along with the Digital Volume Correlation (DVC) to investigate the density-dependent material properties of natural snow. The data from two snow samples, one initially non-compressed (test 1) and the other initially compressed (test 2), were fed into Burger’s viscoelastic model to estimate the material properties. CT imaging with 801 projections captures the three-dimensional structure of the snow initially and after each loading step at -18C, using a constant deformation rate (0.2 mm/min). The relative density of the snow, ranging from 0.175 to 0.39 (equivalent to 160–360 kg/m), is determined at each load step through binary image segmentation. Modulus and viscosity terms, estimated from Burger’s model, exhibit a density-dependent increase. Maxwell and Kelvin–Voigt moduli range from 0.5 to 14 MPa and 0.1 to 0.8 MPa, respectively. Viscosity values for the Maxwell and Kelvin–Voigt models vary from 0.2 to 2.9 GPa-s and 0.2 to 2.3 GPa-s within the considered density range, showing an exponent between 3 and 4 when represented as power functions. Initial grain characteristics for tests 1 and 2, obtained through image segmentation, reveal an average Specific Surface Area (SSA) of around 55 1/mm and 40 1/mm, respectively. The full-field strain distribution in the specimen at each load step is calculated using the DVC, highlighting strong strain localization indicative of non-homogeneous behavior in natural snow. These findings not only contribute to our understanding of natural snow mechanics but also hold implications for applications in fields such as glacier dynamics and avalanche prediction.
4.	Bano, Nargis, et al. (författare) Study of Au/ZnO nanorods Schottky light-emitting diodes grown by low-temperature aqueous chemical method 2010 Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 100:2, s. 467-472 Tidskriftsartikel (refereegranskat)abstract High quality vertically aligned ZnO nanorods (NRs) were grown by low-temperature aqueous chemical technique on 4H-n-SiC substrates. Schottky light-emitting diodes (LEDs) were fabricated. The current-voltage (I-V) characteristics of Schottky diodes reveal good rectifying behavior. Optical properties of the ZnO nanorods (NRs) were probed by cathodoluminescence (CL) measurements at room temperature complemented with electroluminescence (EL). The room-temperature CL spectra of the ZnO NRs exhibit near band edge (NBE) emission as well as strong deep level emission (DLE) centered at 690 nm. At room temperature the CL spectra intensity of the DLE was enhanced with the increase of the electron beam penetration depth due to the increase of defect concentration at the interface and due to the conversion of self-absorbed UV emission. We observed a variation in the DLE along the nanorod depth. This indicates a relatively lower structural quality near the interface between ZnO NRs and n-SiC substrate. The room-temperature CL spectra of SiC show very weak emission, which confirms that most of the DLE is originating from the ZnO NRs, and SiC has a minute contribution to the emission.
5.	Baranowski, M., et al. (författare) Nitrogen-related changes in exciton localization and dynamics in GaInNAs/GaAs quantum wells grown by metalorganic vapor phase epitaxy 2015 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 118:2, s. 479-486 Tidskriftsartikel (refereegranskat)abstract In this work, we show the results of low-temperature photoluminescence (PL), time-resolved photoluminescence, and photoreflectance (PR) investigations, performed on a series of three Ga0.64In0.34As1-x N (x) /GaAs single quantum wells (SQW) grown by metalorganic vapor phase epitaxy with the nitrogen content of 0, 0.5, and 0.8 %. Comparing the PL and PR data, we show that at low excitation intensity and temperature, the radiative recombination occurs via localizing centers (LCs) in all samples. The excitation intensity-dependent PL measurements combined with theoretical modeling of hopping excitons in this system allow us to provide quantitative information on the disorder parameters describing population of LCs. It has been found that the average energy of LCs increases about two times and simultaneously the number of LCs increases about 10 and 20 times after the incorporation of 0.5 and 0.8 % of nitrogen, respectively. The value of average localization energy E > (0) determined for N-containing samples (similar to 6-7 meV) is in the range typical for dilute nitride QWs grown by molecular beam epitaxy (MBE). On the other hand, the "effective" concentration of LCs seems to be higher than for GaInNAs/GaAs QW grown by MBE. The dramatic increase in localizing centers also affects the PL dynamics. Observed PL decay time dispersion is much stronger in GaInNAs SQW than in nitrogen-free SQW. The change in PL dynamic is very well reproduced by model of hopping excitons.
6.	Batvandi, Mohammadreza, et al. (författare) Visible-light-driven photocatalysis with Z-scheme Ag3PO4@N-GQDs@g-C3N4 nano/hetero-junctions 2022 Ingår i: Applied Physics A. - : Springer Nature. - 0947-8396 .- 1432-0630. ; 128:10 Tidskriftsartikel (refereegranskat)abstract The fabrication and improved performance of Z-scheme visible-light-driven Ag3PO4@N-GQDs@g-C3N4 ternary nano/hetero-junctions have been described in this study. Fern-like silver orthophosphate (Ag3PO4) microstructures have been modified using nitrogen-doped graphene quantum dots (N-GQDs) and then have been coated by ultrathin graphitic carbon nitride (g-C3N4) sheets via a combined technique including freeze-drying and refluxing methods. Photocatalytic studies have been conducted through visible-light photo-degradation of standard methylene blue dye in aqueous media. The Ag3PO4@N-GQDs@g-C3N4 ternary nano/hetero-junctions have exhibited the promoted photocatalytic efficiency of 97.91%, which is about 1.07 and 1.34 times higher than that of Ag3PO4@g-C3N4 binary nano/hetero-junctions (91.46%) and pristine-Ag3PO4 microstructures (85.91%), respectively. The excellent recyclability of the Ag3PO4@N-GQDs@g-C3N4 photo-catalyst has been verified in the cycle operations in which the recycling efficiency could have been maintained at 94.92% after five runs of experiments. The quenching effects of scavengers have suggested that the superoxide radicals (O-2(-center dot)) and holes (h(+)) are the predominant active species governing the photocatalytic reaction of the Ag3PO4@N-GQDs@g-C3N4 ternary composite due to a Z-scheme junction. The improved photocatalytic activity of Ag3PO4@N-GQDs@g-C3N4 nano/hetero-junctions could have been ascribed to the higher visible-light harvesting capacity, better charge carrier separation and stronger oxidation and reduction ability relevant to the indirect Z-scheme system where N-GQDs act as an efficient electron transfer media.
7.	Bhatt, Pramod, et al. (författare) Electronic structure of thin film iron-tetracyanoethylene : Fe(TCNE)x 2009 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 95:1, s. 131-138 Tidskriftsartikel (refereegranskat)abstract Thin film iron-tetracyanoethylene Fe(TCNE) x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE) x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T C ) seen for Fe(TCNE) x -type magnets.
8.	Blomqvist, M., et al. (författare) Structural and tribological properties of cluster-assembled CNx films 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 87:4, s. 767-772 Tidskriftsartikel (refereegranskat)abstract We report the structural and tribological characterization of nanostructured CNx thin films produced by the deposition of a supersonic carbon cluster beam assisted by nitrogen ion bombardment. The influence of the deposition parameters on the chemical composition and structure of the films has been systematically studied by X-ray photoelectron spectroscopy, elastic recoil detection analysis, transmission electron microscopy and atomic force microscopy. Depending on the deposition parameters, the films show a structure ranging from amorphous to disordered graphitic with interlinked planes. Nitrogen content depends on the nitrogen ion kinetic energy. The films have a very low density with a high surface roughness. Friction measurements at the nanoscale show a correlation between nitrogen content and mechanical properties of the system.
9.	Bulgakov, Alexander, 1956, et al. (författare) Phosphorus cluster production by laser ablation 2004 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 79, s. 1369-1372 Tidskriftsartikel (refereegranskat)abstract Neutral and charged phosphorus clusters of a wide size range have been produced by pulsed laser ablation (PLA) in vacuum at 532, 337, and 193 nm ablating wavelengths and investigated by time-of-flight mass spectrometry. The neutral Pn clusters are even-numbered with local abundance maxima at n=10 and 14, while the cationic and anionic clusters are preferentially odd-numbered with P7+, P21+, and P17- being the most abundant ions. The dominance of the magic clusters is more pronounced at 337-nm ablation that is explained by efficient direct ejection of their building blocks under these conditions. Nanocrystalline phosphorus films have been produced by PLA in ambient helium gas.
10.	Bulgakova, Nadya, 1956, et al. (författare) A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: the problem of Coulomb explosion 2005 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 81, s. 345-356 Tidskriftsartikel (refereegranskat)abstract We present a continuum model, based on a drift-diffusion approach, aimed at describing the dynamics of electronic excitation, heating, and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, for near-infrared femtosecond irradiation, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, application of the model to UV nanosecond pulsed laser interaction with bulk silicon has pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) and material properties are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.
11.	Bulgakova, Nadya, 1956, et al. (författare) Model description of surface charging during ultrafast pulsed laser ablationof materials 2004 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 79, s. 1153-1155 Tidskriftsartikel (refereegranskat)abstract We present a model describing the dynamical mechanisms responsible for generating fast ion ejection under ultra-short pulsed laser irradiation. The model is based on a simplified drift–diffusion approach describing the evolution of the laser-generated charge carriers, their transport, and the electric field generated as a result of quasi-neutrality breaking in the irradiated target. The importance of different processes in generating the non-thermal material-ejection mechanisms is discussed. A common frame is applied to dielectrics, semiconductors, and metals and different dynamical behaviour is observed. The modelling results are in good agreement with fs pump–probe studies and measurements of the velocity distributions of the emitted ions.
12.	Bulgakova, Nadya, 1956, et al. (författare) Possible role of charge transport in enhanced carbon nanotube growth 2006 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 85, s. 109-116 Tidskriftsartikel (refereegranskat)abstract We consider the role of electric fields during metal-catalysed thermal chemical vapour deposition growth of carbon nanotubes and show that enhanced growth occurs from a negatively biased electrode. An electric field, applied externally to the growing tubes and/or generated as a result of electron emission or self-biasing, may strongly affect the carbon supply through the catalyst nanoparticle, enhancing the growth rate. Different aspects of the growth process are analysed: the nature of the nanoparticle catalysis, carbon dissolution kinetics, electron emission from the nanotube tips, charge transport in the nanotube-catalytic nanoparticle system and carbon drift and diffusion through the catalyst under the action of the electric field. A fundamental tenet for modelling of charge-transport dynamics during the nanotube growth process is proposed.
13.	Callini, Elsa, et al. (författare) Complex and liquid hydrides for energy storage 2016 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 122:4 Tidskriftsartikel (refereegranskat)abstract The research on complex hydrides for hydrogen storage was initiated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized, and the knowledge regarding the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant portion of the research groups active in the field of complex hydrides is collaborators in the International Energy Agreement Task 32. This paper reports about the important issues in the field of complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and is an excellent summary of the recent achievements.
14.	Castellote, M, et al. (författare) In situ accelerated leaching of cement paste by application of electrical fields monitored by synchrotron X-ray diffraction 2004 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 79:3, s. 661-669 Tidskriftsartikel (refereegranskat)abstract An external dc voltage was applied to a cured cement paste to simulate its natural degradation as a function of time. The electrical treatment was monitored in situ by simultaneous acquisition of diffraction patterns every 10 min. The analysis of the diffraction patterns has confirmed that the microstructure of the whole paste changes during the treatment, with precipitation and dissolution of several phases. This work contributes to the understanding of the fundamentals of the microstructure alterations that take place upon application of an electrical field, allowing the establishment of a first approach to the understanding of the mechanism of these changes.
15.	Comini, E., et al. (författare) Functional nanowires of tin oxide 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 89:1, s. 73-76 Tidskriftsartikel (refereegranskat)abstract Quasi-one-dimensional nanostructures of tin oxide were produced in controlled conditions through condensation from the vapor phase. The preparation was assisted by noble metal catalysts and uniform single-crystalline nanowires were produced. The nucleation of nanowires was achieved at 470 °C, owing to the vapor-liquid-solid growth mechanism activated by the catalytic Pt clusters. The peculiar microstructural properties of these semiconducting metal oxide nanostructures will be summarized. The high aspect ratio and the high degree of crystallinity achieved for the nanowires foresee their functional exploitation. © 2007 Springer-Verlag.
16.	Da Silva, Adrien, et al. (författare) Acceleration of metal drops in a laser beam 2021 Ingår i: Applied Physics A. - : Springer. - 0947-8396 .- 1432-0630. ; 127:1 Tidskriftsartikel (refereegranskat)abstract Different processes require the detachment of metal drops from a solid material using a laser beam as the heat source, for instance laser drop generation or cyclam. These techniques imply that the drops enter the laser beam, which might affect their trajectory. Also, many laser processes such as laser welding or additive manufacturing generate spatters that can be accelerated by the laser beam during flight and create defects on the material. This fundamental study aims at investigating the effects of a continuous power laser beam on the acceleration of intentionally detached drops and unintentionally detached spatters. Two materials were studied: 316L steel and AlSi5 aluminium alloy. High-speed imaging was used to measure the position of the drops and calculate their acceleration to compare it to theoretical models. Accelerations up to 11.2 g could be measured. The contributions of the vapor pressure, the recoil pressure, and the radiation pressure were investigated. The recoil pressure was found to be the main driving effect but other phenomena counteract this acceleration and reduce it by an order of magnitude of one to two. In addition, two different vaporization regimes were observed, resulting respectively in a vapor plume and in a vapor halo around the drop.
17.	Dancila, Dragos, et al. (författare) Compact cavity resonators using high impedance surfaces 2011 Ingår i: Applied Physics A. - : Springer Netherlands. - 0947-8396 .- 1432-0630. ; 103, s. 799-804 Tidskriftsartikel (refereegranskat)
18.	Das, Soumyadeep, et al. (författare) Implantable antenna gain enhancement using liquid metal-based reflector 2020 Ingår i: Applied Physics A. - : SPRINGER HEIDELBERG. - 0947-8396 .- 1432-0630. ; 126:9 Tidskriftsartikel (refereegranskat)abstract This article presents gain enhancement methodology for a dual-ring slot antenna using a frequency selective surface (FSS) as reflector. The FSS structure is formed with liquid metal placed inside the microfluidic channels created on the surface of the polydimethylsiloxane. Non-toxic liquid metal galinstain has been used to ensure biocompatibility. The FSS structure is placed below the ring slot antenna to reflect the back radiation, which in turn enhances the antenna directivity. Subsequently, the antenna gain has been increased as well. A fabricated prototype of the antenna-FSS system, operating at 2.45 GHz, has been analysed both inside human tissue mimicking fluid and pork slab to validate the simulation results. The inclusion of the liquid metal-based reflector increases antenna gain by almost 4 dB as well as ensures required biocompatibility and flexibility. Also the specific absorption rate of the antenna is observed to be reduced.
19.	Dash, Saroj Prasad, 1975, et al. (författare) 23. Near-surface compositional oscillations of Co diffused into Si (100) at-60° C: a study by high-resolution Rutherford backscattering 2009 Ingår i: Applied Physics A: Materials Science and Processing. - 1432-0630 .- 0947-8396. ; 97:3, s. 651- Tidskriftsartikel (refereegranskat)
20.	Dittmer, Staffan, 1970, et al. (författare) Low ambient temperature CVD growth of carbon nanotubes 2006 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 84, s. 243-246 Tidskriftsartikel (refereegranskat)abstract We show that good quality single-walled and multi-walled carbon nanotubes can be grown on CMOS-compatible metal electrodes at ambient room temperature using highly localised catalyst heating at nanostructured electrodes. The method is relatively straightforward and allows considerable flexibility in the kinds of devices that can be fabricated as well as allowing CVD nanotube growth to take place in the close vicinity of temperature-sensitive materials and devices.
21.	Echresh, Ahmad, et al. (författare) Effect of NiO intermediate layer on the optical and electrical properties of n-ZnO nanorods/p-GaAs heterojunction 2015 Ingår i: Applied Physics A. - : Springer Verlag (Germany). - 0947-8396 .- 1432-0630. ; 119:3, s. 1013-1018 Tidskriftsartikel (refereegranskat)abstract ZnO nanorods were grown hydrothermally on bare and NiO-coated p-GaAs substrate to fabricate p-n heterojunctions. The NiO intermediate layer was deposited using thermal evaporation technique. The X-ray diffraction patterns revealed that ZnO nanorods grown on the bare p-GaAs do not have any preferential orientation along the c-axis, but those on the NiO-coated p-GaAs have preferential orientation along the c-axis, i.e. along the (002) direction. The scanning electron microscope images show that the NiO intermediate layer improved the uniformity and the alignment of the ZnO nanorods. Photoluminescence spectra demonstrated that increasing the thickness of NiO intermediate layer leads to improve the optical quality of the ZnO nanorods. Current-voltage characteristics showed that the presence of the NiO intermediate layer leads to increase the threshold voltage and decrease the leakage current of the n-ZnO nanorods/p-GaAs heterojunction. The energy band diagram of heterojunctions drown using Anderson model revealed that the NiO intermediate layer acts as an electron-blocking layer in the ZnO side and at the same time increases the hole injection from the GaAs to the ZnO side. Therefore, most of electron-hole pair recombination could occur at the ZnO site.
22.	El Hamri, M., et al. (författare) Phase diagrams of a transverse cubic nanowire with diluted surface shell 2016 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 122:3 Tidskriftsartikel (refereegranskat)abstract The effective-field theory with correlations based on the probability distribution technique has been used to investigate the phase diagrams (critical and compensation temperatures) of a transverse antiferromagnetic spin-1/2 Ising cubic nanowire with diluted surface shell. It is found that the phase diagrams of the system are strongly affected by the surface shell parameters. Indeed, two compensation points appear for certain values of Hamiltonian parameters, and the range of appearance of these latter points depends strongly on the surface shell transverse field.
23.	Enculecu, I., et al. (författare) Current perpendicular to plane single-nanowire GMR sensor 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 86:1, s. 43-47 Tidskriftsartikel (refereegranskat)abstract By electrochemical deposition in a single nanopore membrane we fabricate Cu/Co layered single nanowires, that exhibit up to 10% magnetoresistance at room temperature. Single nanopore membranes are prepared by irradiating polycarbonate membranes with exactly one swift heavy ion, and by subsequent chemical etching of the single ion track. Both dc and pulsed electrodeposition of single wires consisting of Cu-Co alloy and Cu/Co multilayers respectively, are performed from a bath containing the two metal ions. By sputtering a gold electrode on the upper membrane surface, the single nanowire embedded in the flexible polymer foil is reliably contacted. While alloy wires exhibit anisotropic magnetoresistance (AMR), multilayer wires display current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) behavior. This demonstrates that both the fabrication and contacting methods are very suitable for the investigation of transport properties, without the necessity of lithographic processes and without manipulation of the nanowires. In addition, the method opens up many new possibilities for single nanowire-based sensors.
24.	Erts, D, et al. (författare) Instrumentation of STM and AFM combined with transmission electron microscope 2001 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 72:7, s. 71-74 Tidskriftsartikel (refereegranskat)abstract A scanning tunneling microscope (STM) combined with a transmission electron microscope (TEM) is a powerful tool for direct investigation of structures, electronic properties, and interactions at the atomic scale. Here, we report on two different designs of such TEM-STM as well as an extension with an atomic force microscope (TEM-AFM). In the first TEM-STM design, a stepper motor, combined with a one-dimensional inertial slider, was used to perform the coarse approach. The advantage of this design was the strong pulling force that enabled notched metallic wires to be broken inside the TEM, which lead to clean sample surfaces. A second design, with a three-dimensional inertial slider, allowed lateral motion inside the TEM, which simplified the adjustment of tip location on the sample. By replacing the STM tip with a standard AFM-cantilever chip, a new combination was demonstrated: TEM-AFM. Here the force was simply measured by direct TEM imaging of the motion of the AFM tip. Some experimental results are included to illustrate the capabilities of TEM-STM and TEM-AFM.
25.	Fu, Y, et al. (författare) Capacitance analysis for a metal-insulator-semiconductor structure with an ultra-thin oxide layer 2003 Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 76:1, s. 27-31 Tidskriftsartikel (refereegranskat)abstract We have studied theoretically the capacitance characteristics of a metal-insulator-semiconductor structure with an ultra-thin oxide layer by self-consistently solving Schrodinger and Poisson equations. It is demonstrated that a diffused interface between Si and SiO2 results in a better agreement between the theoretical prediction of conduction current and experimental I-V data. The calculated steady-state capacitance, obtained both analytically and numerically, increases following the increase of the gate bias when the gate bias is small; it reaches a saturation value at intermediate gate bias. The capacitance decreases with increasing gate bias when the gate bias is rather large due to the depletion of the gate material. Simple analytical expressions for the gate capacitance are derived, based on quantum-mechanical considerations, for future device design. The steady-state capacitance of a metal-insulator-semiconductor structure with an oxide layer of 1.5-2.0 nm by state-of-the-art technology is 20 mF/m(2), while it is 40 mF/m(2) when the practical limit of SiO2 layer thickness, i.e. 10-12 Angstrom, is reached.
26.	Fu, Y, et al. (författare) Formation and charge control of a quantum dot by etched trenches and multiple gates 2002 Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 74:6, s. 741-745 Tidskriftsartikel (refereegranskat)abstract We have fabricated a GaAs/InGaAs/AlGaAs-based single-electron transistor (SET) formed by etched trenches and multiple gates. Clear Coulomb-blockade oscillations have been observed when the gate biases are scanned. By self-consistently solving three-dimensional Schrodinger and Poisson equations, we have studied the energy-band structure and the carrier distribution of our SET. General agreement between numerical simulation results and measurement data has been obtained, thus indicating the effectiveness of our SET-device design as well as the necessity of a complete three-dimensional quantum-mechanical simulation.
27.	Fu, Y, et al. (författare) Peak response wavelengths of p- and n-type InxGa1-xAs-InP quantum well infrared photodetectors 2005 Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 80:3, s. 523-528 Tidskriftsartikel (refereegranskat)abstract p- and n-type InxGa1-xAs-InP quantum wells are suitable for multi-color infrared photodetector applications in atmospheric windows due to improved barrier quality and carrier-transport properties. We apply the k . p method to study the energy band structures and optical transition properties, which show that the peak response wavelengths of p- and n-type InxGa1-xAs-InP quantum well infrared photodetectors (QWIPs) are determined not only by the energy distance from the ground sublevels in the quantum well to the energy band edges of extended states, but also by the characteristics of the extended states. The optical phonon scattering process converts the broad absorption spectrum of the p-QWIP from 0 to 16 mum into a short-wavelength spectrum centered at 4.5 mum. The transport of electrons in the extended states of the n-QWIP is characterized by running wave boundary conditions, resulting in a theoretically optimal absorption rate by a 8-nm-thick In0.53Ga0.47As quantum well. Moreover, a conduction-band offset of 0.5 for an InxGa1-xAs- InP (x = 0.53) heterostructure gives the best data fitting of theoretical and experimental response peaks, whereas 0.55 is generally recommended in the literature.
28.	Fu, Ying, 1964, et al. (författare) Photoluminescence spectra of doped GaAs films 2004 Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 79:3, s. 619-623 Tidskriftsartikel (refereegranskat)abstract We have studied the dependence of the photoluminescence (PL) spectrum on the doping level and the film thickness of n-GaAs thin films, both experimentally and theoretically. It has been shown theoretically that modification of the PL spectrum of p-type material by p-type doping is very small due to the large valence-band hole effective mass. The PL spectrum of n-type material is affected by two factors: (1) the electron concentration which determines the Fermi level in the material; (2) the thickness of the film due to re-absorption of the PL signal. For the n-type GaAs thin films under current investigation, the doping level as well as the film thickness can be very well calibrated by the PL spectrum when the doping level is less than 2 x 10(18) cm(-3) and the film thickness is in the range of the penetration length of the PL excitation laser.
29.	Fu, Y., et al. (författare) Reduced effective temperature of hot electrons in nano-sized metal-oxide-semiconductor field-effect transistors 2003 Ingår i: Applied Physics A. - Berlin / Heidelberg : Springer Berlin/Heidelberg. - 0947-8396 .- 1432-0630. ; 77:6, s. 799-803 Tidskriftsartikel (refereegranskat)abstract Hot electron effects have been extensively studied in metal-oxide-semiconductor field-effect transistors (MOSFETs). The importance of these effects when the dimensions are drastically reduced has so far not been thoroughly investigated. The scope of this paper is therefore to present a detailed study of the effective temperature of excess electrons in nanoscale MOSFETs by solving coupled Schrödinger and Poisson equations. It is found that the increased doping levels and reduced junction depths lead to substantially higher local Fermi levels in the source and drain regions. As a result, the temperature difference between electrons injected into the drain and local electrons is reduced. The scaling of the gate oxide thickness, as well as the drain voltage furthermore reduces the electron temperature in the drain. The detrimental effects of hot electron injection are therefore expected to be decreased by scaling the MOSFET.
30.	Fu, Ying, et al. (författare) Surface-plasmon-assisted electromagnetic field enhancement in semiconductor quantum dots 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 87:2, s. 167-169 Tidskriftsartikel (refereegranskat)abstract The temporal development of incident electromagnetic plane waves across semiconductor quantum dots (QDs) is analyzed by the finite-difference time-domain method. By coating the QDs using thin metal films, surface plasmon polaritons (SPPs) can be created. As illustration, our modeling approach is applied to fluorescent multiphoton quantum dots made of cadmium sulphide of particular size (3.7 nm) and energy band gap (2.67 eV). When such a QD is coated by a metal film, a dipole-formed SPP is generated at the external surface of the coated QD by the incident electromagnetic wave with a photon energy of 1.34 eV corresponding to a two-photon process. When the thickness of the metal film is 0.37 nm, the peak intensity of the SPP oscillates through both the thin metal film and the core QD, resulting in an electromagnetic field inside the QD enhanced by a factor of 10, and thus an increased two-photon excitation that can be useful for bioimaging applications. Further increasing the metal film thickness blockades the SPP initially generated at the external surface of the coated QD from penetrating through the metal film, reducing the electromagnetic field inside the QD.
31.	Gibmeier, Jens, et al. (författare) Residual stress in clinched joints of metals 2002 Ingår i: Applied Physics A. - : Springer. - 0947-8396 .- 1432-0630. ; 74:SUPPL.II, s. s1440-s1442 Tidskriftsartikel (refereegranskat)abstract Diffraction methods are used for the determination of characteristic residual stress (RS) distributions in undismantled clinched samples for the assessment of the influence of RS on the mechanical behaviour of clinched joints. While X-ray diffraction enables merely the determination of near-surface RS distributions, the higher penetration depth of neutron radiation allows the determination of triaxial RS states inside the material. In addition, the complex geometry of clinched joints restricts the application of X-ray RS analysis. Therefore a combined RS determination by X-ray and neutron diffraction has been used to obtain an expressive assessment of the RS distributions in the immediate vicinity of clinched joints. Two different materials with different mechanical behaviour were used for clinching, as well as two different common clinching techniques.
32.	Granqvist, Claes-Göran, et al. (författare) Electrochromics : Fundamentals and energy-related applications of oxide-based devices 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 89:1, s. 29-35 Tidskriftsartikel (refereegranskat)abstract We first introduce electrochromic (EC) device technology, which uses transparent conducting oxides as one of its critical components, and consider how this technology can be employed to obtain urgently needed energy savings for modern buildings. The discussion then focuses on two of the most suitable EC materials, WO3 and NiO; we cover recent advances in basic physics and chemistry as well as the properties of flexible foil-type devices combining the two oxides. The final part of the paper provides a broader, more general overview of chromogenic materials.
33.	Grishin, Michael A., et al. (författare) Electron structure and electron dynamics at InSb(111)2×2 semiconductor surface 2003 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 76:3, s. 299-302 Tidskriftsartikel (refereegranskat)abstract The conduction band electronic structure and the electron dynamics of the clean InSb(111)2 x 2 surface have been studied by laser based pump-and-probe photoemission. The results are compared to earlier studies of the InSb(110) surface. It is found that both the energy location and the time dependence of the photoexcited structures are very similar for the two surfaces. This indicates that the dominant part of the photoemission signal in the conduction band region is due to excitations of electrons in the bulk region and that the surface electronic states play a minor role. The fast decay of the excited state, tau similar to 12 ps, indicates that diffusion of hot electrons into the bulk is an important mechanism.
34.	Gustafsson, Mats (författare) Bandwidth constraints for passive superluminal propagation through metamaterials 2012 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 109:4, s. 1015-1021 Tidskriftsartikel (refereegranskat)abstract Superluminal transmission of electromagnetic waves is usually observed in a narrow bandwidth range and the velocity outside this range is subluminal. In this paper, it is shown that the transmission coefficient for superluminal propagation through a periodic metamaterial structure satisfies a sum rule. The sum rule and its corresponding physical bound relate frequency regions with a phase velocity above an arbitrary threshold with the thickness of the slab. The theoretical results are illustrated with numerical examples.
35.	Hailu, Girma, 1982-, et al. (författare) Nonlinear optical absorption properties of porphyrins confinedin Nafion membrane 2009 Ingår i: Applied Physics A. - : Springer-Verlag New York. - 0947-8396 .- 1432-0630. ; 96:3, s. 685-689 Tidskriftsartikel (refereegranskat)abstract The nonlinear absorption (NLA) properties of five different types of porphyrins were studied using the Z-scan technique. The porphyrins under investigation were confined into Nafion column matrix membrane in order to protect them from possible degradation. The results of the experiments have indicated that all the porphyrins tested exhibited interesting NLA properties. The nonlinear absorption coefficients (β’s) were determined at different porphyrin concentrations by comparing the Z-scan data with the theoretical functions.
36.	Han, Tiantian, et al. (författare) Room-temperature photoluminescence of doped 4H-SiC film grown on AlN/Si(100) 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 86:1, s. 145-149 Tidskriftsartikel (refereegranskat)abstract Well-defined room-temperature photoluminescence (PL) was observed from 4H-SiC films on AlN/Si(100) complex substrates grown at temperatures below 1150 degrees C by the chemical vapor deposition method. The PL spectrum consists of three major emission peaks in the vicinities of 3.03, 3.17 and 3.37 eV. By the combination of experimental measurements and theoretical analysis, the origins of the PL emission peaks have been identified and associated with N donors, Al acceptors in the 4H-SiC films and the band-to-band transition between the second minimum of the conduction band and the top of valance band of the 4H-SiC. The room-temperature SiC PL can be much utilized for optoelectronic high-power, high-frequency and high-temperature applications in the ultraviolet spectral regime.
37.	Harbst, Michael, et al. (författare) Studies of resolidification of non-thermally molten InSb using time-resolved X-ray diffraction 2005 Ingår i: APPLIED PHYSICS A: MATERIALS SCIENCE & PROCESSING. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 81:5, s. 893-900 Tidskriftsartikel (refereegranskat)abstract We have used time-resolved X-ray diffraction to monitor the resolidification process of molten InSb. Melting was induced by an ultra-short laser pulse and the measurement conducted in a high-repetition-rate multishot experiment. The method gives direct information about the nature of the transient regrowth and permanently damaged layers. It does not rely on models based on surface reflectivity or second harmonic generation (SHG). The measured resolidification process has been modeled with a 1-D thermodynamic heat-conduction model. Important parameters like sample temperature, melting depth and amorphous surface layer thickness come directly out of the data, while mosaicity of the sample and free carrier density can be quantified by comparing with models. Melt depths up to 80 nm have been observed and regrowth velocities in the range 2-8 m/s have been measured.
38.	Herzog, M., et al. (författare) Analysis of ultrafast X-ray diffraction data in a linear-chain model of the lattice dynamics 2012 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 106:3, s. 489-499 Tidskriftsartikel (refereegranskat)abstract We present ultrafast X-ray diffraction (UXRD) experiments which sensitively probe impulsively excited acoustic phonons propagating in a SrRuO3/SrTiO3 superlattice and further into the substrate. These findings are discussed together with previous UXRD results (Herzog et al. in Appl. Phys. Lett. 96, 161906, 2010; Woerner et al. in Appl. Phys. A 96, 83, 2009; v. Korff Schmising in Phys. Rev. B 78, 060404(R), 2008 and in Appl. Phys. B 88, 1, 2007) using a normal-mode analysis of a linear-chain model of masses and springs, thus identifying them as linear-response phenomena. We point out the direct correspondence of calculated observables with X-ray signals. In this framework the complex lattice motion turns out to result from an interference of vibrational eigenmodes of the coupled system of nanolayers and substrate. UXRD in principle selectively measures the lattice motion occurring with a specific wavevector, however, each Bragg reflection only measures the amplitude of a delocalized phonon mode in a spatially localized region, determined by the nanocomposition of the sample or the extinction depth of X-rays. This leads to a decay of experimental signals although the excited modes survive.
39.	Holmström, Petter, et al. (författare) Electro-optic switch based on near-field-coupled quantum dots 2014 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 115:4, s. 1093-1101 Tidskriftsartikel (refereegranskat)abstract The propagation of exciton polaritons in near-field-coupled quantum-dot (QD) chains is modeled by a density-matrix formalism. It is shown that at least for low-temperature operation it is possible using electronically controlled switching by the quantum-confined Stark effect in such QD chains to rival and outperform room-temperature CMOS electronics in footprint and switch energy, though not in speed.
40.	Inganäs, Olle, et al. (författare) Low bandgap alternating polyfluorene copolymers in plastic photodiodes and solar cells 2004 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 79:1, s. 31-35 Tidskriftsartikel (refereegranskat)abstract We report a comparative study of plastic photodiodes using four different copolymers of fluorene, with a variation of alkyl side chain length and chemical structure. Photodiode materials are formed by blending the polymers with a fullerene derivative and spincoating the blend solution. A photovoltage of 1 V is obtained in devices, where the anode is a doped polymer and the cathode is LiF/Al. Monochromatic quantum efficiencies are better than 40% over most of the absorption range, and under solar light AM 1.5 simulation, we reach energy efficiencies beyond 2%. The high fill factors obtained in some of the devices indicate that these are of interest for more elaborate optimisation. Reasons for the benign electrical transport are discussed. © Springer-Verlag 2004.
41.	Jonsson, Martin, et al. (författare) DC plasma enhanced chemical vapour deposition growth of carbon nanotubes and nanofibres: in situ spectroscopy and plasma current dependence 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 88, s. 261-267 Tidskriftsartikel (refereegranskat)abstract Dc plasma-enhanced CVD growth of nanotubes and nanofibres is studied as a function of plasma power (3–40 W). The dependence of the nanotube/nanofibre morphology for growth on thin iron films and lithographically prepared individual nickel dots is investigated. In both cases, large differences in the morphology of the carbon nanostructures are observed as the plasma power is changed. In situ optical emission spectroscopy is used to obtain insight into the important parameters affecting the growth. The best growth results are found for intermediate plasma powers (15 W).
42.	Josic, Lidija, et al. (författare) Energy selective neutron radiography in material research 2010 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 99:3, s. 515-522 Tidskriftsartikel (refereegranskat)abstract Energy selective neutron radiography was performed to describe a complex structure in polycrystalline materials. Experiments were performed with currently the highest energy and spatial resolutions achieved simultaneously, by employing a double crystal monochromator for selecting narrow energy bands from the initially polychromatic neutron beam and the neutron absorbing scintillator screen coupled with the cooled CCD camera as a detection system. It was shown that the detailed structure of the welded steel sample can be visualized and quantified by performing energy selective neutron imaging in the cold energy range, where elastic coherent scattering dominates the total cross section of the sample, showing characteristic Bragg edges. With the maps of crystallographic orientations over the sample area of similar to 2x2 cm(2) and thickness similar to 11.2 mm, obtained directly from radiographs, the complex structure was energy resolved with a spatial resolution of similar to 50 mu m.
43.	Jurgilaitis, Andrius, et al. (författare) X-ray diffraction from the ripple structures created by femtosecond laser pulses 2010 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 100:1, s. 105-112 Tidskriftsartikel (refereegranskat)abstract In this paper, we present the investigation and characterization of the laser-induced surface structure on an asymmetrically cut InSb crystal. We describe diffraction from the ripple surface and present a theoretical model that can be used to simulate X-ray energy scans. The asymmetrically cut InSb sample was irradiated with short-pulse radiation centred at 800 nm, with fluences ranging from 10 to 80 mJ/cm(2). The irradiated sample surface profile was investigated using optical and atomic force microscopy. We have investigated how laser-induced ripples influence the possibility of studying repetitive melting of solids using X-ray diffraction. The main effects arise from variations in local asymmetry angles, which reduce the attenuation length and increase the X-ray diffraction efficiency.
44.	Kalem, S., et al. (författare) Ellipsometry studies of Si/Ge superlattices with embedded Ge dots 2013 Ingår i: Applied Physics A: Materials Science and Processing. - : Springer Science and Business Media LLC. - 1432-0630 .- 0947-8396. ; 112:3, s. 555-559 Tidskriftsartikel (refereegranskat)abstract In this paper, we present an analysis for treating the spectroscopic ellipsometry response of Si/Ge superlattices (SLs) with embedded Ge dots. Spectroscopic ellipsometry (SE) measurement at room temperature was used to investigate optical and electronic properties of Si/Ge SLs which were grown on silicon (Si) wafers having aOE (c) 111 > crystallographic orientation. The results of the SE analysis between 200 nm and 1000 nm indicate that the SL system can effectively be described using an interdiffusion/intermixing model by assuming multicrystalline Si and Si1-x Ge (x) intermixing layers. The electronic transitions deduced from the analysis reveal Si-, Ge- and alloying-related critical energy points.
45.	Kalem, S., et al. (författare) Transformation of germanium to fluogermanates 2010 Ingår i: Applied Physics A: Materials Science and Processing. - : Springer Science and Business Media LLC. - 1432-0630 .- 0947-8396. ; 98:2, s. 423-428 Tidskriftsartikel (refereegranskat)abstract The surface of a single-crystal germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure to a vapor of HF and HNO3 chemical mixture. Structure analysis indicates that the transformation results in a germanate polycrystalline layer consisting of germanium oxide and ammonium fluogermanate with preferential crystal growth orientation in aOE (c) 101 > direction. Local vibrational mode analysis confirms the presence of N-H and Ge-F vibrational modes in addition to Ge-O stretching modes. Energy dispersive studies reveal the presence of hexagonal alpha-phase GeO2 crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder-induced band tailing effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit yellow photoluminescence at room temperature.
46.	Karlsson, Martin, et al. (författare) Size-controlled nanoparticles by thermal cracking of iron pentacarbonyl 2005 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 80:7, s. 1579-1583 Tidskriftsartikel (refereegranskat)abstract A gas-phase method has been developed for producing size-controlled nanoparticles by thermal cracking of iron pentacarbonyl. The method includes the formation of iron particles from vapor emanating from the cracking of the volatile compound and subsequent compacting of the selected particles. Different temperature steps were involved in the process, and their effects on the particle production were investigated. On-line differential mobility measurements and off-line transmission electron microscopy (TEM) were used to study the morphology, composition and structure of the generated particles. The aim of the study was to produce nanoparticles of pure iron. After transportation in air, the composition of the particles was analyzed by TEM and found to be magnetite, Fe3O4. The oxidation may be attributed to the exposure to air and humidity during the transport. The phase of the uncontaminated particles could not be determined. Tests for growth of silicon nanowhiskers using nanoparticles produced with this method were successful.
47.	Kemerink, Martijn, et al. (författare) Optical detection of ballistically injected electrons in III/V heterostructures 2001 Ingår i: Applied Physics A. - : Springer Verlag (Germany). - 0947-8396 .- 1432-0630. ; 72, s. S201-S204 Tidskriftsartikel (refereegranskat)abstract We present a novel spectroscopic technique that is based on the ballistic injection of minority carriers from the tip of a scanning-tunneling microscope into a semiconductor heterostructure. By analyzing the resulting electro-luminescence spectrum as a function of tip-sample bias, both the injection barrier height and the carrier relaxation rate Gamma(s) after injection can be determined. At 4.2 K we found Gamma(s) = 5 x 10(13) s(-1) and at 77 K we found Gamma(s) = 8 x 10(13) s(-1). From current-dependent measurements we find that, at room temperature, a large fraction of the carriers is trapped prior to radiative recombination. At high currents or low temperatures the traps become saturated. We tentatively identify the Be acceptors in the structure as trapping centers.
48.	Kemerink, Martijn, et al. (författare) Optical properties of a tip-induced quantum dot 2001 Ingår i: Applied Physics A. - : Springer Verlag (Germany). - 0947-8396 .- 1432-0630. ; 72, s. S239-S242 Tidskriftsartikel (refereegranskat)abstract We have performed optical spectroscopy measurements on a STM-tip-induced quantum dot in a GaAs layer. The dominant confinement in the (hole) quantum dot is found to be in the direction parallel to the tip axis. Electron confinement is achieved by a sub-surface AlGaAs barrier. Current-dependent measurements indicate that many-body interactions can cause spectral blueshifts up to 75 meV for a tunneling current of 10 nA. Consequently, a full treatment of the many-body problem is required for an accurate description of this type of system.
49.	Kocka, J., et al. (författare) Controlled growth of nanocrystalline silicon on permalloy micro-patterns 2007 Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 88:4, s. 797-800 Tidskriftsartikel (refereegranskat)abstract Lithographically prepared micrometer-sized permalloy ellipses were used to control the growth of nanocrystalline Si in otherwise amorphous Si film prepared by plasma enhanced chemical vapor deposition. Atomic force microscopy and micro-Raman spectroscopy were employed to study the surface structures before and after the deposition of the Si film. The possible applications of the controlled growth of nanocrystalline Si micro-patterns are discussed as well as the mechanisms leading to the growth of these patterns.
50.	Kresse, G, et al. (författare) Complex surface reconstructions solved by ab initio molecular dynamics 2003 Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630 .- 0947-8396. ; 76:5, s. 701-710 Tidskriftsartikel (refereegranskat)abstract Complex surface reconstructions and surface oxides, in particular, often exhibit complicated atomic arrangements, which are difficult to resolve with traditional experimental methods, such as low energy electron diffraction (LEED), surface X-ray diffraction (SXRD) or scanning tunnelling microscopy (STM) alone. Therefore, ab initio density functional calculations are used as a supplement to the experimental techniques, but even then the structural determination usually relies on a simple trial and error procedure, in which conceivable models are first constructed and then tested for their stability in ab initio calculations. An exhaustive search of the configuration space is usually difficult and requires a significant human effort. Solutions to this problem, such as simulated annealing, have long been known, but are usually considered to be too time-consuming in combination with first principles methods. In this work, we show that ab initio density functional codes are now sufficiently fast to perform extensive finite temperature molecular dynamics. The merits of this approach are exemplified for two cases, for a complex two-dimensional surface oxide on Pd(111), and for the oxygen induced c(6 x 2) reconstruction of V(110).

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