Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
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Magnetic nanostructures produced by electron beam patterning of direct write transition metal fluoride resists Transition metal (TM) fluoride electron beam sensitive resists suitable for the in situ fabrication of arbitrarily shaped nanometer scale magnetic structures have been developed. 20 nm thick TM fluoride films are prepared by thermal evaporation onto thin carbon films. Nanopatterns are written directly into the TM fluoride film in a scanning transmission electron microscope using a 0.5 nm diameter electron probe. Electron energy loss spectroscopy measurements indicate that as fluorine is released, the TM coalesces. Electron micrographs of exposed patterns show that the resist resolution is on the order of nanometers. Exposure of broad areas leads to coalescent TM layers which cap the remaining fluoride and decrease the rate of fluorine removal. The cross section for the removal of a fluorine atom and the cross section for the same process in the presence of an arbitrarily thick capping layer were measured. An electron dose of 1000 C/cm2 at 100 keV will remove 90% of the fluorine from a 20 nm thick CoF2 film.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 16 Số 3 - Trang 1374-1379 - 1998
Deposition of carbon, deuterium, and metals on the wall and limiters of the Tokamak Fusion Test Reactor Following a two-year operational period the Tokamak Fusion Test Reactor (TFTR) graphite fixed bumper limiter has been examined by a variety of methods. The areal density of metals was mapped in situ by beta backscattering. Several tiles were examined in detail by nuclear-reaction analysis, Rutherford backscattering, and proton-induced x-ray emission to measure areal densities of deuterium and impurities. Some areas of the limiter were found to be covered by deposited material several microns thick. Other areas where the incident plasma flux is higher were much cleaner. Long-term collection coupons were also examined to characterize deposition on the wall. From these results the total amount of deuterium on the limiter and wall in TFTR is estimated to be ∼1.3×1024 atoms. The implications of this for wall-pumping effects and future tritium inventory are discussed.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 6 Số 3 - Trang 2111-2115 - 1988
The nuclear microprobe and its applications to controlled fusion research A nuclear microprobe analysis system attached to Sandia’s EN tandem Van de Graaff accelerator is described. A magnetic quadrupole doublet lens is used for the final focus to obtain beams of 2 μm diameter. Several illustrative applications of the microprobe involving its use in the 1D, 2D, and 3D profiling analysis of fusion reactor components are given.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 3 Số 3 - Trang 1374-1379 - 1985
Summary Abstract: Characterization of CO chemisorption on Fe(100)
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 6 Số 3 - Trang 796-797 - 1988
A fully automated hot-wall multiplasma-monochamber reactor for thin film deposition We present a study on the development and the evaluation of a fully automated radio-frequency glow discharge system devoted to the deposition of amorphous thin film semiconductors and insulators. The following aspects were carefully addressed in the design of the reactor: (1) cross contamination by dopants and unstable gases, (2) capability of a fully automated operation, (3) precise control of the discharge parameters, particularly the substrate temperature, and (4) high chemical purity. The new reactor, named ARCAM, is a multiplasma-monochamber system consisting of three separated plasma chambers located inside the same isothermal vacuum vessel. Thus, the system benefits from the advantages of multichamber systems but keeps the simplicity and low cost of monochamber systems. The evaluation of the reactor performances showed that the oven-like structure combined with a differential dynamic pumping provides a high chemical purity in the deposition chamber. Moreover, the studies of the effects associated with the plasma recycling of material from the walls and of the thermal decomposition of diborane showed that the multiplasma-monochamber design is efficient for the production of abrupt interfaces in hydrogenated amorphous silicon (a-Si:H) based devices. Also, special attention was paid to the optimization of plasma conditions for the deposition of low density of states a-Si:H. Hence, we also present the results concerning the effects of the geometry, the substrate temperature, the radio frequency power and the silane pressure on the properties of the a-Si:H films. In particular, we found that a low density of states a-Si:H can be deposited at a wide range of substrate temperatures (100 °C≤Ts≤300 °C).
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 9 Số 4 - Trang 2331-2341 - 1991
X-ray fluorescence measurements of x-ray absorption near edge structure at the Si, P, and S <i>L</i> edges High-resolution (≤0.2 eV) x-ray absorption near edge structure (XANES) spectra have been recorded at the Si, P, and S 2p edges of several compounds using microchannel plates to detect the ultrasoft x-ray fluorescence after 2p excitation or ionization. The fluorescence yield (FY) XANES of SiO2, Si, InP, FeS2, and Na2S2O3 are of at least as good quality as the XANES recorded using total electron yield (TEY), despite the extremely small fluorescence yield. The FY spectra obtained show two significant advantages over the TEY spectra. First, the FY XANES is much more bulk sensitive; and second the resolution of the FY spectra is usually considerably better.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 11 Số 5 - Trang 2694-2699 - 1993
Effect of nitric-phosphoric acid etches on material properties and back-contact formation of CdTe-based solar cells Forming a low-resistance contact to p-type CdTe is a critical issue for successful commercialization of CdTe-based photovoltaic devices. One solution to this problem has been to incorporate surface pretreatments to facilitate contact formation. In this article, the effects of a nitric–phosphoric (NP) acid pretreatment on material properties and device performance are investigated for polycrystalline CdTe-based devices. We demonstrate that the NP acid pretreatment, when applied to CdTe thin films, forms a thick, highly conductive Te layer on the back surface of the film and on exposed grain boundaries. When etched under optimal conditions, this results in CdS/CdTe devices with reduced series resistance and enhanced performance. On the other hand, we find that the NP etch preferentially etches grain boundaries. Overetching can result in complete device failure by forming shunt paths that extend to the heterointerface. Therefore, carefully controlling the etch concentration and duration is critical to optimizing device performance.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 17 Số 3 - Trang 805-809 - 1999
Nondestructive analysis of Hg1−<i>x</i>Cd<i>x</i>Te (<i>x</i>=0.00, 0.20, 0.29, and 1.00) by spectroscopic ellipsometry. I. Chemical oxidation and etching Chemical oxidation and etching reactions are studied using the real-time analytic capabilities of spectroscopic ellipsometry to avoid ambiguities arising from air exposure or delays between processing and measurement. We show that bromine–methanol treatments leave the surfaces of these materials covered with an optically identifiable Te layer about 7 Å thick. Previous XPS measurements indicating TeO2 as a reaction by-product of Br exposure can be understood as an artifact of air oxidation and the inability to resolve the 3d core-level signal of metallic surface Te from that of semiconductor substrate Te. The Te layer can be removed from the Hg-containing compounds by oxidizing and stripping freshly polished samples with HNO3 or by reducing them with NaBH4. The Te layer cannot be completely removed in this way from CdTe. Chemical oxidations of these materials with H2O2 solutions of different pH values show that the oxide on CdTe is a single stoichiometric compound, probably the tellurite CdTeO3, while that formed on HgTe is a physical mixture of TeO2 and probably HgTeO3. The H2O2-grown oxides can be removed with HCl, but a Te residue remains. No evidence is found for chemically induced bulk damage in any of the compounds studied.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 2 Số 3 - Trang 1309-1315 - 1984
Phase behavior in the CdTe–CdS pseudobinary system Polycrystalline thin films deposited by coevaporation of CdTe and CdS form metastable single-phase CdTe–CdS alloys. Subsequent heating in a kinetic-enhancing ambient segregates CdTe1−xSx and CdS1−yTey phases from the original alloy phase. The equilibrium miscibility gap between the resulting CdTe1−xSx and CdS1−yTey alloy phases is determined for CdTe1−xSx films with initial x ∼ 0.4 treated from 360 to 700 °C. At 625 °C, the equilibrium compositions correspond to published results for mixed crystals. Below 625 °C the miscibility gap widens asymmetrically due to different mixing free energies for S in CdTe and Te in CdS. The solubility thermodynamics are modeled with an excess mixing free energy to account for nonideal mixing behavior.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 20 Số 4 - Trang 1462-1467 - 2002
Dependence of microstructure and thermochromism on substrate temperature for sputter-deposited VO2 epitaxial films A systematic study on the epitaxial growth of VO2 films deposited on sapphire by sputtering at various substrate temperatures (Ts) was carried out. The deposited films were characterized by x-ray diffraction, high energy electron diffraction, Rutherford backscattering spectrometry, atomic force microscopy, and spectrophotometry. Epitaxial VO2 was obtained from a Ts of 300 °C which is the lowest reported yet. Two epitaxial relationships, i.e., a dominant VO2(010)//sapphire (110), (001)//(001) and a secondary VO2(100)//sapphire (110), (010)//(001), were confirmed. The epitaxial films show strong dependence of the morphology and thermochromism on Ts. Films deposited at above 400 °C exhibit changes in resistivity of ΔR>104 upon switching, while those deposited at Ts=300 °C have reduced ΔR of 102. The film obtained at Ts=300 °C exhibits novel transition properties, i.e., a largely reduced τc (45 °C) even without any doping, and very little thermal hysteresis.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films - Tập 15 Số 3 - Trang 1113-1117 - 1997
Tổng số: 190
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