| 1. |
- Abom, A.E., et al.
(författare)
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Influence of gate metal film growth parameters on the properties of gas sensitive field-effect devices
- 2002
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 409:2, s. 233-242
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of Pt have been grown as gate metals on the oxide surface of gas sensitive field-effect devices. Both electron beam evaporation and dc magnetron sputtering has been used. The energy of the impinging Pt atoms, the substrate temperature and the thickness of the Pt film were used as parameters in this study. The influence of the growth parameters on the gas response has been investigated and compared with the properties of the films, studied by transmission electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The conditions during growth of the Pt film are found to have a large impact on the properties of the device. As expected, crystallinity, morphology and the metal/substrate interfacial structure are also affected by processing parameters. Three different growth processes stand out as the most promising from gas sensor considerations, namely room temperature evaporation, sputtering at high pressures and sputtering at high temperatures. The correlation between gas responses and properties of the gas sensitive layer is discussed. © 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Almer, J, et al.
(författare)
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Microstructure, stress and mechanical properties of arc-evaporated Cr-C-N coatings
- 2001
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 385:1-2, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- The relationships between coating microstructure and properties in the Cr-C-N system have been investigated as a function of composition and post-deposition annealing. Coatings of varying compositions were grown using arc-evaporation, by varying the reactive gas flow ratio fR = f(C2H4)/f(N2) from 0 to 0.2, and were found to consist primarily of the cubic d-Cr(C,N) phase. Changes in both the unstressed lattice parameter, ao, and X-ray diffraction background intensity indicate that both the carbon concentration within the d-phase and amorphous/crystalline content increases with fR. Increasing fR also decreases the magnitude of the compressive biaxial residual stress, from approximately 6 to 1 GPa, while increasing both the inhomogeneous stress and thermal stability. The elastic modulus and hardness of as-deposited coatings were determined from nanoindentation to be 320 and 23 GPa, respectively, for moderate carbon concentrations (fR=0.05). Concurrent variations in microstructure and hardness with post-deposition annealing indicate that the as-deposited hardness is significantly enhanced by the microstructure, primarily by lattice defects and related stresses (microstresses) rather than average stresses (macrostresses).
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| 3. |
- Arias, A.C., et al.
(författare)
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Use of tin oxide thin films as a transparent electrode in PPV based light-emitting diodes
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 371:1, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- Tin oxide (TO) thin films, nominally undoped, have been used as electrodes in poly(p-phenylene vinylene) (PPV) based organic electroluminescent devices. The evolution of the crystallinity and the electrical resistance of TO films submitted to the PPV thermal conversion conditions, have been investigated. It has been found that the electrical resistance is decreased whereas the crystallinity of the film is increased. It is shown in this work, that the photoluminescence of PPV converted on top of TO substrates is not as quenched as it is when converted on top of indium-tin oxide (ITO) substrates. The quantum efficiency of light-emitting diode is 0.07% at 17 V forward bias. It is also shown that the work function of TO films is very stable to different cleaning procedures, in contrast with previous results obtained for ITO films.
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| 4. |
- Arwin, Hans
(författare)
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Ellipsometry on thin organic layers of biological interest : Characterization and applications
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 377-378, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- The thickness resolution and in situ advantage of ellipsometry make this optical technique particularly suitable for studies of thin organic layers of biological interest. Early ellipsometric studies in this area mainly provided thickness quantification, often expressed in terms of surface mass. However, today it is possible to perform monolayer spectroscopy, e.g. of a protein layer at a solid/liquid interface, and also to resolve details in the kinetics of layer formation. Furthermore, complicated microstructures, like porous silicon layers, can be modeled and protein adsorption can be monitored in such layers providing information about pore filling and penetration depths of protein molecules of different size and type. Quantification of adsorption and microstructural parameters of thin organic layers on planar surfaces and in porous layers is of high interest, especially in areas like biomaterials and surface-based biointeraction. Furthermore, by combining ellipsometric readout and biospecificity, possibilities to develop biosensor concepts are emerging. In this report we review the use of ellipsometry in various forms for studies of organic layers with special emphasis on biologically-related issues including in situ monitoring of protein adsorption on planar surfaces and in porous layers, protein monolayer spectroscopy and ellipsometric imaging for determination of thickness distributions. Included is also a discussion about recent developments of biosensor systems and possibilities for in situ monitoring of engineering of multilayer systems based on macromolecules.
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| 5. |
- Baudin, M., et al.
(författare)
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Molecular dynamics simulations of an Al2O3(0001 +/-, 0-10(II))/CeO2 (011 +/-,01-1(II)) interface system
- 2001
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 401:02-jan, s. 159-164
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Tidskriftsartikel (refereegranskat)abstract
- Constant stress, constant temperature (10 K, 300 K) molecular dynamics simulations were carried out with shell-model potentials for an infinite composite ceria-alumina slab with two free surfaces [alpha -Al2O3 (0001) and CeO2(011) and their opposite counterparts]. The interface introduces considerable structural and dynamical changes, both at the slab surfaces and in the center of the slab. Structurally, both oxide surfaces become effectively oxygen-terminated and the surface structures become disordered close to the interface. Dynamically, in the region near the 'alumina surface/ceria surface/alumina-ceria interface' 3-phase junction the ionic motion is considerably enhanced. Thus, in the interface region, the ionic mean-square displacements increase 2-3 times compared to the pure slabs. Moreover, the ions at the interface participate in a new kind of motion, not present in the pure oxide slabs: large occasional, but frequently reoccurring, back-and-forth ionic motions take place with square-amplitudes as large as similar to0.70 Angstrom (2).
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| 6. |
- Chen, Weimin
(författare)
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Applications of optically detected magnetic resonance in semiconductor layered structures
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 364:1, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- A short introduction is given on the physics, method, capabilities and limitations of the optically detected magnetic resonance (ODMR) technique. The advantages of the optical detection method in terms of sensitivity and of its direct probe in recombination processes, as compared with the traditional spin resonance technique, will be demonstrated. The importance of these advantages for the ODMR applications in semiconductor layered and quantum structures will be emphasized. The ability of the ODMR technique to provide important information on physical properties of semiconductor layered structures will be highlighted. These include chemical identification, electronic and geometric structure of both radiative and non-radiative defects, carrier recombination mechanism, electronic excitation, etc. Representative cases from CVD-SiC and MBE-Si/SiGe based layered structures will be discussed as examples. The most recent progress, on-going efforts and prospects in achieving unprecedentedly high spectral, time and spatial resolution of the ODMR technique will also be outlined.
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| 7. |
- Chirita, Valeriu, et al.
(författare)
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Cluster diffusion and surface morphological transitions on Pt (111) via reptation and concerted motion
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 370:1, s. 179-185
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Tidskriftsartikel (refereegranskat)abstract
- Embedded-atom molecular dynamics simulations were used to follow the diffusion dynamics of compact Pt clusters with up to 19 atoms on Pt (111) surfaces. The results reveal a novel cluster diffusion mechanism, involving successive shear translations of adjacent subcluster regions, which give rise to reptation, a snake-like gliding motion. We show that for compact clusters with 4 to 6 atoms, this mechanism competes energetically with that of island diffusion through concerted motion. However, as the cluster size increases from > 7 to ? 20 atoms, reptation becomes the energetically favored diffusion mechanism. The concerted shear motion of subcluster regions, leading to reptation, is also shown to play a significant role in dendritic-to-compact morphological transitions of Pt island.
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| 8. |
- Cobet, C., et al.
(författare)
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Optical properties of SiC investigated by spectroscopic ellipsometry from 3.5 to 10 eV
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 364:1, s. 111-113
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present the dielectric function of hexagonal 4H- and 6H-SiC polytypes as well as the cubic 3C-SiC polytype in the energy range from 3.5 to 10 eV measured by spectroscopic ellipsometry. We operated with synchrotron radiation at the Berlin electron storage ring BESSY I. Additionally the samples were investigated by atomic force microscopy to correct the measured dielectric function for the influence of surface roughness. The experimental results are compared to theoretical calculations.
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| 9. |
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| 10. |
- Donchev, V., et al.
(författare)
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Photoluminescence study of AlAs/GaAs superlattices containing enlarged wells
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 364:1, s. 224-227
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Tidskriftsartikel (refereegranskat)abstract
- Photoluminescence (PL) spectra of MBE grown short-period AlAs/GaAs superlattices with one or two enlarged wells (5 and 12 nm) have been measured at 2 K. Sharp PL peaks corresponding to excitonic transitions between the lowest electron and heavy-hole states in the enlarged wells are observed. The excitonic transition energies are calculated by means of an envelope function based model, taking into account the exciton binding energies. The model incorporates a smooth potential at the interfaces, which is represented by a diffusion potential, the diffusion length being a parameter. The calculated and experimentally observed excitonic transition energies agree well if diffusion lengths of 3.5 and 4.5 monolayers are considered in the samples with and without a buffer layer, respectively. These values are consistent with the complicated nature of the growth kinetics and mechanisms of quantum heterostructures. The PL spectra reveal also complicated structures connected with the superlattice. Their qualitative discussion confirms the smooth potential model. Thus, an attempt is made to extend the analysis of complicated AlAs/GaAs heterostructures towards real interfaces, which is essential for advanced device fabrication.
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| 11. |
- Edwards, N.V., et al.
(författare)
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Optical characterization of wide bandgap semiconductors
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 364:1, s. 98-106
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Tidskriftsartikel (refereegranskat)abstract
- Our work primarily concerns the characterization of wide-gap III-V nitride semiconductors, nondestructively and at variable temperature, with spectroscopic ellipsometry (SE) and reflectometry in the spectral range from 1.5 to 6 eV. In the case of GaN, there are three main concerns associated with such data: (a) the quantification of the dispersion of the index of refraction with energy, (b) the removal of surface overlayers in real-time, and (c) the determination of the variation of valence bands with biaxial stress and the quantification of residual stress in thin films. The SE and reflectance capabilities provide (1) broadband spectra from 1.5 to 6 eV, which yield information about (a) below the bandgap and (b) above it, and (2) high resolution spectra (less than 1 meV at 3.4 eV) in the vicinity of the gap (3.3-3.6 eV), which enables (c). Here we will discuss issues concerning the relation of (c) to GaN material and growth parameters, though similar data for other wide bandgap materials will be discussed where relevant. Specifically, optimal heterostructure design for potential valence band engineering applications will be discussed in the context of trends in residual stress as a function of film thickness, growth temperature and substrate orientation for GaN/AlN/6H-SiC heterostructures. Standard heterostructures are mostly compressive for samples less than about 0.7 µm thick, are tensile up to about 2 µm and then abruptly become less tensile with stress values near 1 kbar thereafter. Additionally, these trends can be circumvented for moderately thick (approximately 2 µm) GaN layers (normally>2 kbar, tensile) by the introduction of a `buried interface' approach, namely, a strain mediating layer (SML) above the standard high-temperature AlN buffer layer designed to yield a range of compressive stresses from 0 to 2 kbar. The strain characteristics but also the growth rates of subsequently deposited nitride layers can be modulated by changing the growth parameters of the SML. This is achieved by in situ techniques during crystal growth without degrading the optical and structural properties of the deposited layer, as confirmed by XRD, SEM, PL, and AFM data taken on the overlying GaN layers. These results are interpreted in terms of coefficient of thermal expansion data for the layers and data concerning the planarization of GaN layers and growth behavior in non-(0001) directions.
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| 12. |
- Greczynski, G., et al.
(författare)
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Polymer interfaces studied by photoelectron spectroscopy : Li on polydioctylfluorene and Alq3
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 363:1, s. 322-326
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of lithium atoms deposited on the surfaces of ultra-thin spin-coated films of poly(dioctylfluorene), and of condensed molecular solid films of tris(8-hydroxyquinoline) aluminum, have been studied through a combined experimental-theoretical approach. The Li-atoms donate charges to the organic systems, leading to doping-induced electronic states in the otherwise forbidden energy gap. The changes in the electronic structure induced by charge transfer from the Li-atoms are different in the two materials studied, and depend upon the localization of the electronic states to which the electrons are transferred. In the case of the delocalized wave functions of the p-system of poly(dioctylfluorene), at low doping levels, the added charges lead to the formation of polaron states, while at higher doping concentrations, bipolaron states are formed. In the case of the tris(8-hydroxyquinoline) aluminum, however, up to a level of three added electrons per molecule, the added electrons reside in states localized on each of the three ligands.
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| 13. |
- Grivickas, V., et al.
(författare)
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Spatially and time-resolved infrared absorption for optical and electrical characterization of indirect band gap semiconductors
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 364:02-jan, s. 181-185
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Tidskriftsartikel (refereegranskat)abstract
- The current status of the spatially and time-resolved free-carrier absorption (FCA) method is provided. The FCA technique allows monitoring carrier dynamics in a time scale from nanoseconds to miliseconds by employing either collinear or orthogonal geometry between pump and probe beams. A high spatial resolution is achieved allowing in-depth carrier profiles to be extracted. The method is particularly suited for investigation of injection-dependent optical and recombination phenomena: band gap optical absorption, Shockley-Read-Hall (SRH) lifetime, Auger recombination coefficient, and the injection-dependent surface (interface) recombination velocity. We summarize important aspects of the technique demonstrating numerous measurements that have been implemented in studies of bulk Si, epilaxial 4H-SiC and porous silicon.
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| 14. |
- Hellgren, N., et al.
(författare)
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Effect of chemical sputtering on the growth and structural evolution of magnetron sputtered CNx thin films
- 2001
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 382:1-2, s. 146-152
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Tidskriftsartikel (refereegranskat)abstract
- The growth and microstructure evolution of carbon nitride CNx (0=x=0.35) films, deposited by reactive d.c. magnetron sputtering in Ar/N2 discharges has been studied. The substrate temperature TS varied between 100 and 550 °C, and the N2 fraction in the discharge gas varied from 0 to 100%. It is found that the deposition rate and film morphology show strong dependence on TS and nitrogen fraction. For growth temperature of 100 °C, the films are amorphous, and essentially unaffected by the nitrogen fraction. For TS>200 °C, however, the nitrogen fraction has more significant effect on the growth and structural evolution of the films. The pure carbon films appear porous and have a high surface roughness. For increasing nitrogen fraction the films become denser and the roughness decreases by one order of magnitude. It is suggested that a chemical sputtering process, during which desorption of volatile N2 and CN-species, predominantly C2N2, is important not only for the deposition rate and the nitrogen incorporation, but also for the resulting film structure. The chemical sputtering process becomes more pronounced at elevated temperatures with higher nitrogen fractions.
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| 15. |
- Hultaker, A., et al.
(författare)
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Electrical and optical properties of sputter deposited tin doped indium oxide thin films with silver additive
- 2001
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 392:2, s. 305-310
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Tin doped indium oxide (ITO) films with a few mol% of silver were prepared by reactive DC magnetron sputtering. The purpose of adding silver is to boost conductivity. The real part of the refractive index of ITO was determined from ellipsometry data, applying a model combining a Drude and a Lorentz term. The imaginary part was calculated from the absorptance, which was derived from transmittance and reflectance data. We found that up to 6 mol% of silver additive enhanced the conductivity by as much as a factor of two for layers post-treated at 200 and 300°C in reducing gas consisting of 93% N2 and 7% H2. For samples with 1 mol% silver, which was post-treated at 100 and 200°C, we observed an increase in the luminous transmittance. The transmittance decreased with increased silver content. © 2001 Elsevier Science B.V.
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| 16. |
- Jin, P., et al.
(författare)
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Epitaxial growth of W-doped VO2/V2O3 multilayer on a-Al2O3(110) by reactive magnetron sputtering
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 375:1-2, s. 128-131
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Tidskriftsartikel (refereegranskat)abstract
- Multilayer epitaxy with a W-VO2 top layer over a bottom layer of which the crystal phase depends on the starting oxygen flow, was done on a-Al2O3(110) by reactively sputtering a V-W (1.6 at.% wt.) alloy target at linearly increasing oxygen flow without interrupting film growth. For the film deposited in the oxygen flow from 10 to 26 sccm, a W-VO2/W-V2O3 multilayer was formed on a-Al2O3(110) with the epitaxial relationship being (001)f?(110)s, (110)f?(001)s for W-V2O3, and (010)f?(110)s, (100)f?(001)s for W-VO2 where f and s denote the film and substrate, respectively. The formation of a triple domain structure was confirmed in the W-VO2 top layer due to the strong influence from the symmetry of the substrate. The multilayer shows phase transition behavior differing from the single layer film, which was presumably due to the effects of W-doping, compositional gradient, and strain.
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| 17. |
- Johansson, M P, et al.
(författare)
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Growth of CNx/BN : C multilayer films by magnetron sputtering
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 360:1-2, s. 17-23
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Tidskriftsartikel (refereegranskat)abstract
- Symmetric CNx/BN:C multilayer thin films, with nominal compositional modulation periods of ? = 2.5, 5, and 9 nm were deposited by unbalanced dual cathode magnetron sputtering from C (graphite) and B4C targets in an Ar/N2 (60/40) discharge. The multilayers and single-layer of the constituent CNx and BN:C compounds were grown to a total thickness of 0.5 µm onto Si(001) substrates held at 225°C and a negative floating potential of approx. 30 V (Ei = 24 eV). Layer characterizations were performed by TEM, X-ray reflectivity, RBS, and nanoindentation measurements. Results show that CN0.33 and BN:C (35, 50, and 15 at.% of B, N, and C, respectively) layers were prepared at the above conditions. It is suggested that all films exhibit a three-dimensional interlocked structure with a cylindrical texture in the film growth direction. The structure was continuous over relatively well defined and smooth CNx/BN:C interfaces. All coatings exhibit extreme elasticity with elastic recoveries as high as 85-90% (10 mN maximum load) attributed to the observed structure. However, the multilayers were stiffer and more elastic compared to that of the single-layers and thus shows promise for improved protective properties.
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| 18. |
- Karlsson, L., et al.
(författare)
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Influence of residual stresses on the mechanical properties of TiCxN1-x (x = 0, 0.15, 0.45) thin films deposited by arc evaporation
- 2000
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 371:1, s. 167-177
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Tidskriftsartikel (refereegranskat)abstract
- The influence of residual stress state and composition on the mechanical properties of arc evaporated TiCxN1-x thin films been investigated. By controlling the flow ratios of the reactive gases, N2 and CH4, films with compositions x = 0 (TIN), x to approximately 0.15, and x to approximately 0.45 have been grown on cemented carbide substrates. The residual stress state was altered through variations in the negative substrate bias over the range 20 V=Vs=820 V. The intrinsic stress, sint, measured by the X-ray diffraction (XRD) sin2? method was compressive and increased with decreasing Vs and increasing x. The latter behavior is suggested to be due to increased effective stability of defect complexes when the carbon content increases. Maximum stress level was between -6 and -7 GPa and limited by interior cracking of the films. The increase in intrinsic stress was accompanied by an increase in XRD peak broadening due to inhomogeneous strains. The hardness, H, and Young's modulus, E, of as-deposited films were measured using the nanoindentation technique. Apparently linear correlations between sint and H were found for each film composition where H increased with x. The maximum H, 44 GPa, was thus obtained for the x to approximately 0.45 film with sint = -5.5 GPa. The lowest hardness for this composition was 35 GPa for a film with sint = -2.7 GPa. For the TiN films, a similar variation in hardness of 33 GPa at sint = -5.8 to 26 GPa at sint = -1.2 GPa was obtained. E was constant at approximately 610 GPa for most of the films, with a slight decrease in the films with the lowest sint values.
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| 19. |
- Lu, J., et al.
(författare)
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Chemical vapour deposition of molybdenum carbides : aspects of phase stability
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 370:02-jan, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of different molybdenum carbides (delta-MoC1-x, gamma'-MoC1-x and Mo2C) have been deposited from a gas mixture of MoCl5/H-2/C2H4 at 800 degrees C by CVD. The H-2 content in the vapour has a strong influence on the phase composition and microstructure. Typically, high H-2 contents lead to the formation of nanocrystalline delta-MoC1-x films while coarse-grained gamma'-MoC1-x, is formed with an H-2-free gas mixture. This phase has previously only been synthesized by carburization of Mo in a CO atmosphere and it has therefore been considered as an oxycarbide phase stabilized by the presence of oxygen in the lattice. Our results, however, show that gamma'-MoC1-x films containing only trace amounts of oxygen can be deposited by CVD. Stability calculations using a FP-LMTO method confirmed that the gamma'-MoC1-x phase is stabilized by oxygen but that the difference in energy between e.g. delta-MoC0.75 and oxygen-free gamma'-MoC0.75 is Small enough to allow the synthesis of the latter phase in the absence of kinetic constraints. Annealing experiments of metastable delta-MoC1-x and gamma'-MoC1-x films showed two different reaction products suggesting that kinetic effects play an important role in the decomposition of these phases.
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| 20. |
- Lu, J, et al.
(författare)
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Chemical vapour deposition of molybdenum carbides: aspects of phase stability
- 2000
-
Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 370:1-2, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of different molybdenum carbides (δ-MoC1−x, γ′-MoC1−x and Mo2C) have been deposited from a gas mixture of MoCl5/H2/C2H4 at 800°C by CVD. The H2 content in the vapour has a strong influence on the phase composition and microstructure. Typically, high H2 contents lead to the formation of nanocrystalline δ-MoC1−x films while coarse-grained γ′-MoC1−x is formed with an H2-free gas mixture. This phase has previously only been synthesized by carburization of Mo in a CO atmosphere and it has therefore been considered as an oxycarbide phase stabilized by the presence of oxygen in the lattice. Our results, however, show that γ′-MoC1−x films containing only trace amounts of oxygen can be deposited by CVD. Stability calculations using a FP-LMTO method confirmed that the γ′-MoC1−x phase is stabilized by oxygen but that the difference in energy between e.g. δ-MoC0.75 and oxygen-free γ′-MoC0.75 is small enough to allow the synthesis of the latter phase in the absence of kinetic constraints. Annealing experiments of metastable δ-MoC1−x and γ′-MoC1−x films showed two different reaction products suggesting that kinetic effects play an important role in the decomposition of these phases.
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| 21. |
- Ni, Wei-Xin, et al.
(författare)
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Light emitting SiGe/i-Si/Si : Er
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 369:1, s. 414-418
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Tidskriftsartikel (refereegranskat)abstract
- p+-SiGe/i-Si/n-Si:Er:O/n+-Si tunneling diodes have been processed using layer structures prepared by molecular beam epitaxy (MBE). Electroluminescence has been observed at room temperature from these devices at reverse bias. The devices have been used for characterizing the optical activation of Er3+ ions in MBE Si:Er:O layers grown at different conditions. In the range of 400-575 °C, a high substrate temperature is favored for formation of Er emission centers, but this is limited by the silicidation process occurring above 600 °C. Several important device parameters such as the impact excitation cross section and various EL decay processes have been carefully studied. A fast decay (approximately 4 µs) due to the Auger carrier transfer process is observed.
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| 22. |
- Niklasson, Gunnar A., et al.
(författare)
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Surface roughness of pyrolytic tin dioxide films evaluated by different methods
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 359:2, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- The scaling of surface roughness in thin spray pyrolyzed fluorinated tin dioxide films of different thicknesses was obtained from atomic force microscopy. The data show that, within experimental uncertainties, the effective dimensionality of the surface is 2; hence no evidence of fractal surface roughness was found. Other methods – based upon light scattering and cyclic voltammetry – gave additional information on the surface topography. Cyclic voltammetry measurements show that the reaction sites on the surface are distributed in a fractal structure and may be identified with hillocks seen in surface reliefs.
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| 23. |
- Odén, Magnus, 1965-, et al.
(författare)
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Microstructure-property relationships in arc-evaporated Cr-N coatings
- 2000
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 377-378, s. 407-412
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Tidskriftsartikel (refereegranskat)abstract
- Chromium nitride (Cr-N) coatings have received increased attention for tribological applications due to their favorable properties including wear resistance, toughness and oxidation resistance. These properties, in turn, can be strongly influenced by the coating microstructure and residual stress resulting from deposition and subsequent processing operations. In this study these microstructure-property correlations are investigated in Cr-N coatings grown by arc-evaporation. Prominent as-deposited features include formation of metastable amounts of the cubic d-CrN phase, and high levels of compressive residual stress and defect density. During annealing up to 650 ░C the residual stress and defect density decrease substantially, accompanied by a diffusion-based d-CrN to ▀-Cr2N phase transformation and equiaxed grain formation. The effects of these microstructural modifications on the hardness, fracture and wear properties of the coatings are evaluated using a combination of nanoindentation, scratch and pin-on-disk testing. Appreciable changes in these properties are found after annealing, and are correlated to the Cr-N microstructure. As-deposited coating hardness is enhanced by high levels of lattice defect density, with both decreasing concomitantly during annealing. Scratch results show that resistance to cohesive flaking is increased by annealing, suggesting ductility increases via defect annealing and equiaxed grain formation. Finally, the wear rate under dry sliding generally increased with annealing temperature, although wear rates of all Cr-N coatings significantly outperformed TiN tested under identical conditions.
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| 24. |
- Olsson, M.K., et al.
(författare)
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Mechanisms for reactive DC magnetron sputtering of elements with different atomic masses : Large area coatings of Al oxide and W oxide
- 2000
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 371:1, s. 86-94
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Tidskriftsartikel (refereegranskat)abstract
- Stoichiometric Al and W oxide films are prepared with high stability from the metallic state of the cathodes using conventional reactive DC magnetron sputtering on an industrial prototype scale. While for the Al, increased target power is a trivial way to increase growth rates, W oxide sputtering of optically functional films with sufficiently amorphous structure is severely limited by the effect of gas rarefaction at high powers. Choosing an appropriate working gas pressure and a source-to-substrate distance, which facilitates the gas scattering allows the deposition of homogeneous stoichiometric tungsten oxide films in a stable condition with a relatively high discharge current. Optimization of the process parameters with respect to film properties and efficiency of the deposition process is discussed.
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| 25. |
- Palmquist, J.-P., et al.
(författare)
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Deposition of epitaxial ternary transition metal carbide films
- 2002
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 405, s. 122-128
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Tidskriftsartikel (refereegranskat)abstract
- Thin epitaxial carbide films have been deposited in UHV by co-evaporation of Mo, Nb, Ti and V, with C60 as carbon source. Two separate systems were studied, Ti1-xVxCy on MgO(001) and Nb1-xMoxCy on MgO(111). We demonstrate the possibility to tune the cell parameter of an epitaxial ternary carbide film by control of the composition. Analysis with reciprocal space mapping show that deposition of Ti0.34V0.66C0.81 at 500 °C yields a strain-free film with perfect match towards the MgO(001) substrate. Also, a good manual control of the individual fluxes allows the design of tailor-made compositional gradient structures. An epitaxial linear carbide gradient film going from TiC to VC was deposited at 500 °C. Furthermore, the low deposition temperature allows the deposition of metastable carbide structures. This was shown with epitaxial growth of a Nb1-xMoxCy film at 500 and 600 °C. © 2002 Elsevier Science B.V. All rights reserved.
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