本文采用磁控溅射法,衬底温度500℃下在硅衬底上分别制备具有Ge填埋层的a-Si/Ge薄膜和a-Si薄膜,并进行后续退火,采用Raman光谱、X射线衍射、原子力显微镜及场发射扫描电镜等对所制薄膜样品进行结构表征.结果表明,Ge有诱导非晶硅晶化的作用,并得出以下重要结论:衬底温度为500℃时生长的a-Si/Ge薄膜,经600℃退火5 h Ge诱导非晶硅薄膜的晶化率为44%,在相同的退火时间下退火温度提高到700℃,晶化率达54%.相同条件下,无Ge填埋层的a-Si薄膜经800℃退火5 h薄膜实现晶化,晶化率为46%.通过Ge填埋层诱导晶化可使在相同的条件下生长的非晶硅晶薄膜的晶化温度降低约200℃.Ge诱导晶化多晶Si薄膜在Si(200)方向具有高度择优取向,且在此方向对应的晶粒尺寸约为76 nm.通过Ge诱导晶化制备多晶Si薄膜有望成为制备高质量多晶Si薄膜的一条有效途径.
Single-crystal samples of type-VIII BasGa16-xCuxSn30 （x = 0, 0.03, 0.06, 0.15） clathrates were prepared using the Sn-flux method. At room temperature the carrier density, n, is 3.5-5 × 10^19 cm^-3 for all the samples, the carrier mobility, μH, increases to more than twice that of BasGa16Sn30 for all the Cu doping samples, and consequently the electrical conductivity is enhanced distinctly from 1.90×10^4 S/m to 4.40 ×10^4 S/m, with the Cu composition increasing from x = 0 to x = 0.15. The Seebeck coefficient,α, decreases slightly with the increases in Cu composition. The values are about 0.72 W/mK at 300 K and are almost invariant with temperature up to 500 K for the samples with x = 0 and x = 0.03. The lattice thermal conductivity, μL, decreases from 0.59 W/InK for x = 0 to 0.50 W/mK for x = 0.03 at 300 K. The figure of merit for x = 0.03 reaches 1.35 at 540 K.
Deng Shu-KangLi De-CongShen Lan-XianHao Rui-TingT.Takabatake
