PECVD法制备氢化纳米晶硅薄膜及其晶化特性的研究

发布时间：2018-06-06 01:12

本文选题：PECVD + nc-Si:H薄膜　；参考：《浙江师范大学》2015年硕士论文

【摘要】：氢化纳米晶硅(hydrogenated nanocrystalline silicon, nc-Si:H)薄膜是硅的纳米晶粒镶嵌在氢化非晶硅(hydrogenated amorphous silicon, a-Si:H)网络里的一种硅纳米结构材料。它具有高电导率、宽带隙、高吸收系数、光致发光等光电特性,已经引起了学术界的广泛关注和研究。一方面,nc-Si:H薄膜材料具有量子限制效应,因此可以通过控制薄膜中的晶粒尺寸等来调节薄膜的带隙,以应用于对不同波段的光的吸收。另一方面,nc-Si:H薄膜材料具有良好的光照稳定性,无明显的光致衰退效应,有望应用于薄膜太阳能电池工业化生产中。然而,nc-Si:H薄膜材料的结构、电学等性质强烈地依赖于其所制备的工艺参数。因此,本文利用等离子体增强化学气相沉积(plasma-enhanced chemical vapor deposition, PECVD)法系统地研究了工艺参数(射频功率、氢稀释比、沉积温度、磷或硼掺杂比)对本征及掺杂nc-Si:H薄膜晶化特性、电导率及生长速率的影响。研究结果表明：(1)在一定范围内,随着射频功率的增加,本征和掺杂nc-Si:H薄膜的晶化率、晶粒大小、沉积速率及电导率都在提高,但是过高的射频功率会使得薄膜表面被大量的原子轰击,导电性下降；(2)提高氢稀释比是制备nc-Si:H薄膜最有效的方法。随着氢稀释比的增加,薄膜逐渐由非晶转变为纳米晶,而且氢稀释比越大,晶化程度越高,但是会显著降低薄膜的沉积速率；(3)在一定范围内,提高沉积温度可以提高n型和本征nc-Si:H薄膜的晶化程度和导电性,但是对p型nc-Si:H薄膜刚好相反,主要是因为掺硼的nc-Si:H薄膜在高温下更容易脱氢所致；(4)随着磷或硼掺杂比的增加,薄膜晶化程度在降低,而沉积速率在增加。在一定范围内,磷掺杂比越高,薄膜导电性越好。而硼掺杂比越高,薄膜导电性越差,且超过0.5%的硼掺杂比就会导致薄膜的非晶化。最后,选取最优的工艺参数,初步探索了nc-Si:H薄膜在p-i-n型薄膜电池上的应用,获得的最高光电转换效率为4.97%。金属诱导晶化(metal induced crystallization, AIC)也是制备纳米晶硅或硅纳米线(SiNWs)的常见方法之一,本文利用PECVD法和磁控溅射(magnetron sputtering deposition, MSD)法制备了锡诱导硅纳米线(Sn-SiNWs).通过扫描电镜拍摄的图片(SEM图)可以看出,PECVD法所制备的Sn-SiNWs的密度、均匀性都要远远高于MSD所制备的。最后,结合实验数据讨论了SiNWs的生长机制。需要指出的是这是首次利用MSD制备出Sn-SiNWs,这在纳米级传感器、存储器等微电子器件中有潜在的应用前景。另外,如何有效地控制生长取向一致的SiNWs还有待于进一步的研究。
[Abstract]:Hydrogenated nanocrystalline silicon (hydrogenated nanocrystalline silicon, nc-Si:H) thin films are silicon nanocrystals embedded in the hydrogenated amorphous silicon (hydrogenated amorphous silicon, a-Si:H) networks. It has high conductivity, wide band gap, high absorption coefficient, photoluminescence and other photoelectric properties, which have already caused the academic circle. On the one hand, nc-Si:H film materials have quantum confinement effect. Therefore, the band gap can be adjusted by controlling the size of the grain in the thin film, so as to apply to the absorption of light in different bands. On the other hand, the nc-Si:H thin film material has good illumination stability and no obvious photoinduced decay effect. It is used in the industrial production of thin film solar cells. However, the structure and electrical properties of nc-Si:H thin film materials strongly depend on the process parameters prepared. Therefore, the process parameters (RF power, hydrogen) are systematically studied by plasma enhanced chemical vapor deposition (plasma-enhanced chemical vapor deposition, PECVD). The effect of dilution ratio, deposition temperature, phosphorus or boron doping ratio on the crystallization properties, electrical conductivity and growth rate of doped nc-Si:H films. The results show that: (1) in a certain range, with the increase of radio frequency power, the crystallization rate, grain size, deposition rate and electrical conductivity of the intrinsic and doped nc-Si:H films are increasing, but too high. Radio frequency power can make the surface of the film bombarded by a large number of atoms and decrease the conductivity. (2) increasing the ratio of hydrogen dilution is the most effective method to prepare the nc-Si:H thin film. With the increase of the hydrogen dilution ratio, the film gradually transforms from amorphous to nanocrystalline, and the greater the ratio of hydrogen dilution and the higher the degree of crystallization, the deposition rate of the film will be significantly reduced; (3) In a certain range, increasing the deposition temperature can improve the crystallization degree and conductivity of the N and the intrinsic nc-Si:H films, but the P type nc-Si:H thin film is the opposite, mainly because the nc-Si:H film doped with boron is more likely to dehydrogenate at high temperature. (4) the crystallization degree of the thin film is reduced with the increase of the doping ratio of phosphorus or boron, and the deposition rate is at the rate of deposition. In a certain range, the higher the phosphorus doping ratio, the better the conductivity of the film, the higher the boron doping ratio, the worse the conductivity of the thin film, and more than 0.5% of the boron doping ratio will lead to the amorphous film. Finally, the optimum process parameters are selected, and the application of the nc-Si:H film on the p-i-n thin film battery is preliminarily explored, and the highest photoelectric conversion efficiency obtained. 4.97%. metal induced crystallization (metal induced crystallization, AIC) is also one of the common methods to prepare nanocrystalline silicon or silicon nanowires (SiNWs). In this paper, the tin induced silicon nanowires (Sn-SiNWs) are prepared by PECVD method and magnetron sputtering (magnetron sputtering deposition, MSD). It is shown that the density and uniformity of Sn-SiNWs prepared by PECVD method is much higher than that of MSD. Finally, the growth mechanism of SiNWs is discussed with the experimental data. It is necessary to point out that this is the first time to make use of MSD to prepare Sn-SiNWs, which has potential application prospects in nanoscale sensors, memory and other micro devices. SiNWs, which controls the growth orientation uniformly, needs further study.
【学位授予单位】：浙江师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

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