| 1. |
- Abbondanza, Giuseppe, 1991, et al.
(författare)
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Hydride formation and dynamic phase changes during template-assisted Pd electrodeposition
- 2023
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Ingår i: Nanotechnology. - 1361-6528 .- 0957-4484. ; 34:50
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the structural evolution of electrochemically fabricated Pd nanowires in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and two-dimensional surface optical reflectance (2D-SOR). This shows how electrodeposition and the hydrogen evolution reaction (HER) compete and interact during Pd electrodepositon. During the bottom-up growth of the nanowires, we show that beta-phase Pd hydride is formed. Suspending the electrodeposition then leads to a phase transition from beta-phase Pd hydride to alpha-phase Pd. Additionally, we find that grain coalescence later hinders the incorporation of hydrogen in the Pd unit cell. GTSAXS and 2D-SOR provide complementary information on the volume fraction of the pores occupied by Pd, while XRF was used to monitor the amount of Pd electrodeposited.
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| 2. |
- D'Antuono, M., et al.
(författare)
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Nanopatterning of oxide 2-dimensional electron systems using low-temperature ion milling
- 2022
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 33:8
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Tidskriftsartikel (refereegranskat)abstract
- We present a 'top-down' patterning technique based on ion milling performed at low-temperature, for the realization of oxide two-dimensional electron system devices with dimensions down to 160 nm. Using electrical transport and scanning Superconducting QUantum Interference Device measurements we demonstrate that the low-temperature ion milling process does not damage the 2DES properties nor creates oxygen vacancies-related conducting paths in the STO substrate. As opposed to other procedures used to realize oxide 2DES devices, the one we propose gives lateral access to the 2DES along the in-plane directions, finally opening the way to coupling with other materials, including superconductors.
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| 3. |
- Rehammar, Robert, 1980, et al.
(författare)
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Optical properties of carbon nanofiber photonic crystals
- 2010
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Ingår i: NANOTECHNOLOGY. - : Institute of Physics; 1999. - 0957-4484 .- 1361-6528. ; 21:46, s. 465203-
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n(CNF) = 4.1.
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| 4. |
- Bouravleuv, A. D., et al.
(författare)
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Electronic structure of (In, Mn) As quantum dots buried in GaAs investigated by soft-x-ray ARPES
- 2016
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 27:42
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Tidskriftsartikel (refereegranskat)abstract
- Electronic structure of a molecular beam epitaxy-grown system of (In, Mn) As quantum dots (QDs) buried in GaAs is explored with soft-x-ray angle-resolved photoelectron spectroscopy (ARPES) using photon energies around 1 keV. This technique, ideally suited for buried systems, extends the momentum-resolving capabilities of conventional ARPES with enhanced probing depth as well as elemental and chemical state specificity achieved with resonant photoexcitation. The experimental results resolve the dispersive energy bands of the GaAs substrate buried in similar to 2 nm below the surface, and the impurity states (ISs) derived from the substitutional Mn atoms in the (In, Mn) As QDs and oxidized Mn atoms distributed near the surface. An energy shift of the Mn ISs in the QDs compared to (In, Mn) As DMS is attributed to the band offset and proximity effect at the interface with the surrounding GaAs. The absence of any ISs in the vicinity of the VBM relates the electron transport in (In, Mn) As QDs to the prototype (In, Mn) As diluted magnetic semiconductor. The SX-ARPES results are supported by measurements of the shallow core levels under variation of probing depth through photon energy. X-ray absorption measurements identify significant diffusion of interstitial Mn atoms out of the QDs towards the surface, and the role of magnetic circular dichroism is to block the ferromagnetic response of the (In, Mn) As QDs. Possible routes are drawn to tune the growth procedure aiming at practical applications of the (In, Mn) As based systems.
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| 5. |
- Chen, Si, 1985, et al.
(författare)
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Ultrahigh sensitivity made simple : nanoplasmonic label-free biosensing with an extremely low limit-of-detection for bacterial and cancer diagnostics.
- 2009
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Ingår i: Nanotechnology. - : Institute of Physics (IOP). - 0957-4484 .- 1361-6528. ; 20:43
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple and robust scheme for biosensing with an ultralow limit-of-detection down to several pg cm(-2) (or several tens of attomoles cm(-2)) based on optical label-free biodetection with localized surface plasmon resonances. The scheme utilizes cost-effective optical components and comprises a white light source, a properly functionalized sensor surface enclosed in a simple fluidics chip, and a spectral analyzer. The sensor surface is produced by a bottom-up nanofabrication technique with hole mask colloidal lithography. Despite its simplicity, the method is able to reliably detect protein-protein binding events at low picomolar and femtomolar concentrations, which is exemplified by the label-free detection of the extracellular adherence protein (EAP) found on the outer surface of the bacterium Staphylococcus aureus and of prostate-specific antigen (PSA), which is believed to be a prostate cancer marker. These experiments pave the way towards an ultra-sensitive yet compact biodetection platform for point-of-care diagnostics applications.
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| 6. |
- Fu, Yifeng, 1984, et al.
(författare)
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A complete carbon-nanotube-based on-chip cooling solution with very high heat dissipation capacity
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- Heat dissipation is one of the factors limiting the continuous miniaturization of electronics. In the study presented in this paper, we designed an ultra-thin heat sink using carbon nanotubes (CNTs) as micro cooling fins attached directly onto a chip. A metal-enhanced CNT transfer technique was utilized to improve the interface between the CNTs and the chip surface by minimizing the thermal contact resistance and promoting the mechanical strength of the microfins. In order to optimize the geometrical design of the CNT microfin structure, multi-scale modeling was performed. A molecular dynamics simulation (MDS) was carried out to investigate the interaction between water and CNTs at the nanoscale and a finite element method (FEM) modeling was executed to analyze the fluid field and temperature distribution at the macroscale. Experimental results show that water is much more efficient than air as a cooling medium due to its three orders-of-magnitude higher heat capacity. For a hotspot with a high power density of 5000 W cm(-2), the CNT microfins can cool down its temperature by more than 40 degrees C. The large heat dissipation capacity could make this cooling solution meet the thermal management requirement of the hottest electronic systems up to date.
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| 7. |
- Grant, Ann W., 1964, et al.
(författare)
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Transmission electron microscopy "windows" for nanofabricated structures
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 15:9, s. 1175-1181
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Tidskriftsartikel (refereegranskat)abstract
- We present the microfabrication of silicon nitride membrane supports ('windows') for transmission electron microscopy (TEM) and illustrate their usefulness for direct preparation and studies of nanostructures. These membrane 'windows' enable TEM to be incorporated as an affordable diagnostic tool in nanostructure fabrication and applications thereof, in an iterative fashion, both during and after preparation as well as subsequent experimental steps with the nanostructures, and even for real time in situ TEM observations. Several examples are shown, including protein adsorption and nanofabrication for applications in heterogeneous catalysis.
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| 8. |
- Kabir, Mohammad, 1974, et al.
(författare)
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Fabrication of individual, vertically aligned carbon nanofibres on metal substrates from prefabricated catalyst dots
- 2006
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 17:3, s. 790-794
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nanofibres (CNFs) of controlled diameter and length were grown on different metal substrates using plasma-enhanced chemical vapour deposition (PECVD). The diameter control of catalyst dots (and hence CNF diameter) was obtained by using the shot modulation technique in electron beam lithography. Catalyst dots of different sizes within arrays of different pitch were prepared and the dependence of the growth of vertically aligned CNFs on these parameters was studied for different metal underlayers. Good quality vertically aligned CNFs with a narrow length distribution were grown on Mo and W substrates. The structures grown on Nb substrates were significantly shorter for identical growth conditions and showed a lower nucleation rate. We demonstrate that through the shot modulation technique it is possible to control the diameter variation of CNFs from a single design geometry for the catalyst deposition. Individual VACNFs can be grown down to a pitch within the range 100–500 nm.
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| 9. |
- Kabir, Mohammad, 1974, et al.
(författare)
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Plasma-enhanced chemical vapour deposition growth of carbon nanotubes on different metal underlayers
- 2005
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 16, s. 458-466
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Tidskriftsartikel (refereegranskat)abstract
- One important requirement for future applications of carbon nanotube electronic devices is the ability to controllably grow carbon nanotubes on metal electrodes. Here we show that it is possible to grow small diameter (<10 nm) vertically aligned carbon nanotubes on different metal underlayers using plasma-enhanced chemical vapour deposition. A crucial component is the insertion of a thin silicon layer between the metal and the catalyst particle. The electrical integrity of the metal electrode layer after plasma treatment and the quality of the metals as interconnects are also investigated.
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| 10. |
- Kalem, S., et al.
(författare)
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Black silicon with high density and high aspect ratio nanowhiskers
- 2011
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 22:23
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Tidskriftsartikel (refereegranskat)abstract
- The physical properties of black silicon (b-Si) formed on Si wafers by reactive ion etching in chlorine plasma are reported in an attempt to clarify the formation mechanism and the origin of the observed optical and electrical phenomena, which are promising for a variety of applications. The b-Si consisting of high density and high aspect ratio sub-micron length whiskers or pillars with tip diameters of well under 3 nm exhibits strong photoluminescence (PL) both in the visible and the infrared, which is interpreted in conjunction with defects, confinement effects and near band-edge emission. Structural analysis indicates that the whiskers are all crystalline and encapsulated by a thin Si oxide layer. The infrared vibrational spectrum of Si-O-Si bondings in terms of transverse-optic (TO) and longitudinal-optic (LO) phonons indicates that disorder induced LO-TO optical mode coupling can be an effective tool in assessing the structural quality of the b-Si. The same phonons are likely coupled to electrons in visible region PL transitions. Field emission properties of these nanoscopic features are demonstrated indicating the influence of the tip shape on the emission. Overall properties are discussed in terms of the surface morphology of the nanowhiskers.
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