a-Si∶O∶H薄膜微结构及其高温退火行为研究

THE MICROSTRUCTURE AND ITS HIGH-TEMPERATURE ANNEALING BEHAVIOURS OF a-Si∶O∶H FILM

以微区Raman散射、X射线光电子能谱和红外吸收对等离子体增强化学气相沉积 (PECVD)法制备的氢化非晶硅氧 (a Si∶O∶H)薄膜微结构及其退火行为进行了细致研究 .结果表明a Si∶O∶H薄膜具有明显的相分离结构 ,富Si相镶嵌于富O相之中 ,其中富Si相为非氢化四面体结构形式的非晶硅 (a Si) ,富O相为Si,O ,H三种原子随机键合形成的SiOx∶H(x≈ 1.35 ) .经 115 0℃高温退火 ,薄膜中的H全部释出 ;SiOx∶H (x≈ 1.35 )介质在析出部分Si原子的同时发生结构相变 ,形成稳定的SiO2 和SiOx(x≈ 0 .6 4) ;在析出的Si原子参与下 ,薄膜中a Si颗粒固相晶化的成核和生长过程得以进行 ,形成纳米晶硅 (nc Si) .研究发现此时的薄膜具有典型的壳层结构 ,在nc Si颗粒表面和外围SiO2 介质之间存在着纳米厚度的SiOx(x≈ 0 .6 4)

The microstructure and its annealing behaviours of a-Si:O:H film prepared by PECVD are investigated in detail using micro-Raman spectroscopy, X-ray photoelectron spectroscopy and Infrared absorption spectroscopy. The results indicate that the as-deposited a-Si:O:H film is structural inhomogeneous, with Si-riched phases surrounded by O-riched phases. The Si-riched phases are found to be nonhydrogenated amorphous silicon (a-Si) clusters, and the O-riched phases SiOx:H (x approximate to 1. 35) are formed by random bonding of Si, O and H atoms. By high-temperature annealing at 1150 degreesC, the SiOx:H (x approximate to 1.35) matrix is shown to be transformed into SiO2 and SiOx ( x approximate to 0.64), during which all of the hydrogen atoms in the film escape and some of silicon atoms are separated from the SiOx:H ( x approximate to 1.35) matrix; The separated silicon atoms are found to be participated in the nucleation and growth processes of solid-phase crystallization of the a-Si clusters, nano-crystalline silicon (ne-Si) is then formed. The microstructure of the annealed film is thereby described with a multi-shell model, in which the ne-Si clusters are embedded in SiOx (x = 0.64) and SiO2. The former is located at the boundaries of the nc-Si clusters, with a thickness comparable with the scale of nc-Si clusters, and forms the transition oxide layer between the ne-Si and the SiO2 matrix.