a-SiGe:H Deposited by Hot-Wire CVD Using a Tantalum Filament Operated at Low Temperature

We report the deposition of optimum-quality a-SiGe:H and a-Si:H by the hot-wire chemical vapor deposition (HWCVD) technique using a tantalum filament operating at a low temperature. We gauge the material quality of the a-SiGe:H films by comparing infrared, small-angle x-ray scattering, photocapacitance, and conductivity results to those presented elsewhere

Electro-Optical Characterization at NREL

One of the core issues in all of the photovoltaics technologies is relating PV device performance to the methods and materials used to produce them. Due to the nature of PV devices, the electronic and optical properties of the materials are key to device performance. The relationship between materials growth and processing, the resulting electro-optical properties, and device performance can be extremely complex and difficult to determine without direct measurement of these properties. Accurate and timely measurement of the electro-optical properties as a function of device processing provides researchers and manufacturers with the knowledge they need to troubleshoot problems and develop the knowledge base necessary for reducing cost, maximizing efficiency, improving reliability, and enhancing manufacturability. The Electro-optical Characterization Team at NREL provides this support for all internal and external projects funded by the PV Program

Amorphous Transparent Conducting Oxides (TCOs) Deposited at T 100<= ..deg.. C

The summary of this report is that amorphous InZnO (a-IZO) is a very versatile TCO with: (1) low process temperatures ({approx} 100 C); (2) easy to make by sputtering; (3) excellent optical and electronic properties; (4) very smooth etchable films; and (5) remarkable thermal processing stability

Optimization of Conductivity and Transparency in Amorphous In-Zn-O Transparent Conductors: Preprint

Amorphous mixed metal oxide TCOs are of increasing interest due to the excellent opto-electronic properties and smoothness (RRMS < 0.5 nm) obtained for sputtered films deposited at less than 100 ..deg..C. Here, we have investigated the combined materials phase space of oxygen stoichiometry and metals composition (In:Zn ratio) and made two key discoveries

Oxynitride Thin Film Barriers for PV Packaging

Dielectric thin-film barrier and adhesion-promoting layers consisting of silicon oxynitride materials (SiOxNy, with various stoichiometry) were investigated. For process development, films were applied to glass (TCO, conductive SnO2:F; or soda-lime), polymer (PET, polyethylene terephthalate), aluminized soda-lime glass, or PV cell (a-Si, CIGS) substrates. Design strategy employed de-minimus hazard criteria to facilitate industrial adoption and reduce implementation costs for PV manufacturers or suppliers. A restricted process window was explored using dilute compressed gases (3% silane, 14% nitrous oxide, 23% oxygen) in nitrogen (or former mixtures, and 11.45% oxygen mix in helium and/or 99.999% helium dilution) with a worst-case flammable and non-corrosive hazard classification. Method employed low radio frequency (RF) power, less than or equal to 3 milliwatts per cm2, and low substrate temperatures, less than or equal to 100 deg C, over deposition areas less than or equal to 1000 cm2. Select material properties for barrier film thickness (profilometer), composition (XPS/FTIR), optical (refractive index, %T and %R), mechanical peel strength and WVTR barrier performance are presented

Combinatorial Exploration of Novel Transparent Conducting Oxide Materials

High-throughput combinatorial approaches have been used for the discovery and optimization of transparent conducting oxide (TCO) materials for PV applications. We report on current investigations in In-Zn-O, In-Ti-O and In-Mo-O systems. The InZnO system is shown to be amorphous in the best conducting range with a conductivity of ~ 3000 &#937;-cm-1 for 50%-70% In/Zn. The amorphous InZnO films are very smooth (2..ANG.. rms). In-Ti-O is found to be an excellent high-mobility TCO with mobilities of greater than 80 cm2/v-sec and conductivities of more than 6000 &#937;-cm-1 for sputtered thin film materials

SURFACE TOPOGRAPHY ANALYSIS OF WATER VAPOR PLASMA IRRADIATION INDUCED EFFECTS IN Ti FILMS

ABSTRACT In the present work, the changes of surface topography driven by interaction of ions extracted from low-pressure water vapor plasma are studied. Titanium 0.5-1 m thickness films were deposited on silicon wafer substrates using magnetron sputtering technique and immersed in water vapor plasma at pressure 1-10 Pa. The samples were located on the cathode of magnetron and affected by high-flux, low-energy ions extracted by 250-300V bias negative voltage. The used Ti and W cathodes were water cooled. It is shown that the surface roughness of irradiated films changes in dependence of irradiation fluence and intensity. The experimental results are explained on the basis of the analysis of the selective erosion of oxide phases synthesized in the near-surface region. Three sputtering modes are distinguished: (i) metallic, (ii) oxide and (iii) composite: metallic with clusters of oxide

Water Vapor-Plasma-Enhanced Oxidation of Thin Titanium Films

It is shown that the water vapor plasma processing offers modified Ti oxidation thermodynamics and kinetics over conventional, thermal oxidation. The 0.3-0.6 μm thick Ti films were sputter-deposited on silicon substrates and subsequently treated with low-pressure water vapor plasma at room temperature under continuous injection of water cloud vapor into the vacuum chamber from the heated water container. The changes of microstructure, phase composition, elemental composition and surface morphology upon the RF-power dissipated in plasma and treatment duration were investigated. We conclude that oxygen diffusion is enhanced in the presence of water vapor plasma, and deduce that fast $H^+$ transients because of their high mobility may be responsible for oxygen diffusion enhancement. This phenomenon can be explained as the result of two coexisting and competing reactions of oxidation and reduction on the surface. The different plasma reduction/oxidation state on the surface can be maintained by coordinated adjustment of an intensity of plasma radiation. Analysis of the experimental results is used to obtain important insights into the behavior of water molecules adsorbed on the oxidized titanium surfaces exposed to water vapor plasma at room temperature