Richard L. Wallace, Wayne A. Anderson, K. M. Jones
ABSTRACTA deposition process has been developed which allows the growth of large grain (20+μm) polysilicon films on SiO2substrates at a growth temperature of 650° C. A thin layer of liquid Si-metal solution is formed on the substrate surface as the growth medium. This layer is kept saturated by Si flux from a DC magnetron sputter gun. XRD analysis of the deposited films show a strong (111) preferred orientation, with increasing integrated peak intensities with increasing depositon temperature and solution layer thickness. Films deposited using an In-Si solution are p-type, with carrier concentrations in the mid 1016cm−3range. Conductivities of ∼.2 (Ω cm)−1were measured, with activation energies for both carrier generation and conductivity of about 135meV. The hole mobility was found to be ∼ 30 cm2V−1s−1. A wetting layer is used which may have a detrimental effect on the minority carrier lifetime.
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The depth distribution of open-volume defects has been studied in Si(100) crystals grown by molecular beam epitaxy at 300 °C by the variable-energy monoenergetic positron beam technique combined with well-controlled chemical etching. This procedure gave a 10 nm depth resolution which is a significant improvement over the inherent depth resolving power of the positron beam technique. The epitaxial layer was found to grow defect-free up to 80 nm, from the interface, where small vacancy clusters, larger than divacancies, appear. The defect density then sharply increases toward the film surface. The result clearly shows that the nucleation of small open-volume defects is a precursor state to the breakdown of epitaxy and to the evolution of an amorphous film.
Seung-Jin Han, Seong Chan Park, Jong-Gyu Lee
et al.
We examined the adsorption of Cs on a Si(111)-(7×7) surface by reactive ion scattering (RIS) of hyperthermal Cs+ beams. The RIS from a Cs-adsorbed surface gives rise to Cs2+, representing pickup of a surface Cs by a Cs+ projectile. The Cs2+ intensity is proportional to the surface coverage of Cs at a high substrate temperature (473 K), while it varies anomalously with the coverage at low temperatures (130–170 K). This observation indicates that RIS selectively detects metallic Cs on the surface, but discriminates ionic Cs. The transition from an ionic to metallic Cs adlayer is driven by the thermal diffusion of Cs and their clustering process.