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In this paper, we report the effect of growth conditions on the properties of sputtered precursor thin films for CuIn1-xGaxSe2 (CIGS) absorber layers. Specifically, precursor films containing Cu, In, Ga, and Se were deposited via co-sputtering on flexible Mo-coated stainless steel substrates over a wide range of compositions and deposition conditions. The impact on precursor film phase, morphology, and elemental distribution was investigated as a function of precursor Se content, substrate temperature, target type (CIG/CIG vs. In/Cu3Ga), and Na content. Precursor films selenized at high temperature (>500 °C) to form stoichiometric CIGS and completed using a CdS n-type buffer layer and transparent conducting oxide window layers exhibited full-cell efficiencies as high as 11.5%.

Evolved gas analysis (EGA) mass-spectrometry (MS) is used to characterize the solid state pyrolysis decomposition pathways of air- and moisture-sensitive organometallic compounds. In this study, the single-source GaAs compounds (Et2AsGaEt2)3 (1), (t-Bu2AsGaEt2)2 (2), and [t-Bu(H)AsGaEt2]2 (3) were heated in capillary tubes under inert condition and the volatile products were analyzed by MS. In addition, the relative ratios of evolved gases were characterized using gas chromatography (GC), while the solid state pyrolysis products were analyzed by EDS, 1H NMR and XRD. Pyrolysis of GaAs single-source materials in the solid state reveals chemical information on the stability of the Ga As bond, an observation masked in gas-phase analysis of single-source materials during chemical vapor deposition. Information on Ga As bond stability may be elucidated due to the volatility of the by-products formed during Ga-As precursor pyrolysis. Loss of Ga As bond integrity in materials with alkyl substitution on Ga and As leads to formation of mobile and volatile alkyl diarsine species, as was observed for the pyrolysis of 1. An in-situ method to monitor solid-state pyrolysis by mass spectrometry identified the loss of a tetraalkyl-diarsine as the critical factor that drives formation of sub-stoichiometric GaAs products from single-source precursors. Replacing a single alkyl group on the As atom with a H (precursor 3) leads to the loss of an alkane instead of tetraalkyl-diarsine formation. Solid-state pyrolysis precursor 3 results in the formation of polycrystalline GaAs in up to 58% yield with a 52:48 Ga:As stoichiometry.

Polycrystalline, tetragonal ( P42 / nmc ) zinc phosphide (Zn 3 P 2 ) thin films were deposited on borosilicate glass substrates by reactive radio frequency (r.f.) sputtering of zinc (Zn) in the presence of phosphine gas (PH 3 ). Various sputtering parameters, including substrate temperature ( T sub ), gun power, gas flow rates of PH 3 and argon (Ar), and total sputtering pressure ( P Tot ) were varied to optimize crystalline growth. Under optimal growth conditions [ T sub ~ 200–230 °C, PH 3 :(PH 3 + Ar) P Tot : 1.30–2 Pa], films were polycrystalline in nature, with crystallite sizes up to 100–150 nm and orientation along the (004) direction. Lowering the T sub or increasing the PH 3 content resulted in amorphous growth. The stoichiometry of the films was measured by top-down energy dispersive X-ray spectroscopy (EDS), and cross-sectional EDS mapping indicated compositional homogeneity throughout the film depth. The average surface roughness under optimal growth conditions was less than 10 nm. As-grown films were p-type, with high carrier concentrations (~ 10 16 cm − 3 ) but low mobilities ( 2 /V·s). Ex situ annealing of films in nitrogen or argon/hydrogen (Ar/H 2 ) led to an order of magnitude decrease in the film's resistivity. Films exhibited a direct and an indirect optical bandgap of 1.58 and 1.44 eV, respectively, as measured by ellipsometry. Equipment limitations defined the reactive sputtering conditions explored here, but the data suggest that film properties may be further improved with deposition at higher substrate temperatures (> 250 °C) and higher sputtering pressures (> 2 Pa).

Molybdenum disulfide promoted with alkali metals is one of the most studied catalysts for the conversion of synthesis gas to alcohols. In this work, MoS2 was promoted by adding potassium precursors by physical mixing (PM) and incipient wetness impregnation (IWI) and tested in a small scale reactor. The catalysts prepared by impregnation showed poorer performance compared to the sample prepared by physical mixing of K2CO3 and MoS2. The catalysts were characterized by means of X-ray diffraction, TGA–MS, SEM–EDS, TEM and XPS. The characterization results obtained by SEM–EDS and XRD analyses do not show major differences between the catalysts studied here. In contrast, the TGA results indicated that physical mixing leads to catalysts that lose sulfur at temperatures above 330 °C and TEM images showed that randomly oriented small MoS2 crystallites are obtained from PM preparation while IWI preparation gave long MoS2 crystallites.

Nickel oxide (NiO) nanoparticles were synthesized via a solvothermal reaction with nickel(II) acetylacetonate as the metal containing precursor and 2-butanone (methyl ethyl ketone, MEK) as the solvent. The particles were characterized using X-ray diffraction, electron microscopy, Brunauer–Emmett–Teller (BET) surface area measurements and thermal gravimetric analysis (TGA) to determine that the crystal structure, particle size, and the presence of residual organic material upon completion of the reaction. The effect of varying the reaction temperature, time and metal precursor concentration were investigated. A range of optimal reaction conditions; defined here as a high yield, low residual organic content; were determined. A particle size in the range of 5.5–6.5 nm was observed for the optimal reaction conditions. The formation of metallic Ni was also observed for reactions carried out at 225 °C and time durations longer than 24 h. The reaction mechanism for the formation of NiO nanoparticles was investigated using mass spectrometry and a proposed pathway based on a keto-enol tautamerization is presented.

The use of hybrid integration schemes is investigated using a combination of a SiOC film at the via level and a porous SiLK Y film at the trench level. Sequential finite element analysis is used to determine the mechanics and, subsequently, a hybrid damascene interconnect is built to demonstrate the approach.

Barrier integrity of Ta-films deposited using the enhanced coverage by re-sputtering (EnCoRe) barrier was investigated on untreated surfaces of blanket porous SiLK semiconductor dielectric (developmental version 7, hereinafter v7). Barrier integrity of a bi-layer EnCoRe Ta(N)/Ta film was studied on single damascene lines using v7 and porous SiLK semiconductor dielectric (developmental version 9, hereinafter v9). On blanket wafers more than 30 nm barrier thickness is necessary to achieve complete pore sealing. Analysis of the sheet resistance showed that when tantalum is deposited, a low resistivity α-phase is nucleated on the low-k surface. When deposited onto single damascene structures, EnCoRe Ta(N)/Ta is successful in providing a continuous metallic barrier layer over v7 and v9 semiconductor dielectric lines.

The microstructures of YBCO/N/YBCO ramp-edge junctions have been studied by transmission electron microscopy and related to supercurrent transport properties which depend on the barrier layer N, the interfacial structures and defect structures in the multilayer epitaxial devices. Three different types of junction materials were investigated: Metallic oxide barriers, CaRuO{sub 3} and SrRuO{sub 3}; barriers isostructural to YBCO, Co-doped YBCO and Co-doped PrBa{sub 2}Cu{sub 3}O{sub 7}; and 'interface engineered' barriers, formed by plasma treatment of the YBCO ramp-edge. Metallic oxide barriers are characterized by high steps and strong variations in local barrier width. The observed topologies are consistent with an island growth mode for both CaRuO{sub 3} and SrRuO{sub 3}. The metallic oxide barriers are associated with interfacial strain fields that are believed to be the cause for interfacial oxygen depletion in YBCO and the observed excess normal-state resistance. A number of structural defects and deviations from perfect epitaxy have been observed. Most disruptive to the integrity of the multilayer structures and transport properties is the nucleation of a-axis YBCO grains at steep barrier steps and within the YBCO layers. The barrier layers in isostructural junctions are well structured with a high degree of interfacial coherence and for the most part,more » Cu-O planes are continuous across the interfaces. In contrast to heterostructured metallic oxide barriers, isostructural junctions contain few extraneous defects, such as a-axis grains at the barrier layer, moreover, the second YBCO layer is of good quality due to the perfect epitaxy between the materials. Among the junctions investigated the interface engineered junctions have shown the best electromagnetic properties. Their structure is characterized by narrow (2-3 nm) barriers that are continuous and crystalline. No significant interfacial strains and structural disorder were observed. This and a constant barrier thickness appear responsible for obtaining good uniformity of electric transport properties. The narrow pinhole-free barrier, coupled with excellent epitaxy and few defects, yields good reproducibility and a range of properties suitable for practical applications.« less

Disordered boron carbide coatings with their high hardness, high lubricity, and low surface friction have become the coatings of choice to enhance the wear performance of many existing products. These coatings have been successfully commercialized using a magnetron sputtering process. In this paper, the effects of one of the critical process parameters, bias voltage, on the chemistry, microstructure, and the properties of the coatings are discussed. In combination with microstructure examination, special emphasis was made on nanoscopic level chemical analyses in order to explain the effects of this process parameter. The substrate bias was found to have strong effects on the hardness and the stress of the coating, but it has little influence on the frictional characteristics of the coating. The results of the examination and the analyses of the coating using FTIR, XPS, TEM, PEELS, and SIMS revealed that the morphology of the coating changed from a columnar structure to a continuous solid structure as the substrate bias voltage increased from 0 to 200 V. Oxide species were found in between the columns, while the columns mainly consisted of boron carbide with a boron to carbon atomic ratio of about 4. The atomic ratio of boron to carbon appeared to be independent of the substrate bias.

Superconductor-normal-superconductor (SNS) edge junctions consisting of YBa 2 Cu 3 O 7 /CaRuO 3 /YBa 2 Cu 3 O 7 were fabricated on (001) LaAlO 3 substrates using laser deposition. These devices display an excess resistance which may be related to the SN interface and normal layer structure or composition. High-resolution and conventional transmission electron microscopy were employed to investigate the SN interface structure to determine the degree of interface matching and possible interfacial defects. Energy-loss spectroscopy and energy dispersive X-ray analysis were performed on the CaRuO 3 film and near interface regions to determine the normal layer composition and to quantify the extent of interdiffusion between the CaRuO 3 and YBCO films. Results are compared to recent investigations of SNS edge junctions consisting of YBa 2 Cu 3 O 7− x /YBa 2 Cu 2.79 Co 0.21 O 7− x /YBa 2 Cu 3 O 7− x .

Residual strains were introduced into an Al SiC w composite by in situ cooling a thin foil from room temperature to -160°C. A detailed analysis was conducted using convergent-beam electron diffraction (CBED) to quantify the elastic residual stresses and strains in the matrix near the end and side of a SiC whisker. Large hydrostatic and effective stresses were measured in the matrix near the side of the whisker; the maximum stresses were located near the Al/SiC w interface and decreased to zero approximately 1 μm (∼2 whisker diameters) from the interface. Residual strains were also observed in the matrix near the whisker end, but these strains could not be measured due to the complexity of the strain field. At the whisker end, the largest residual strains were located near the Al/SiC w interface and decreased to zero approximately 0.5 μm (∼1 whisker diameter) from the interface. Finite element techniques were used to predict the residual strains in the composite material and these results were compared to experimental measurements.