Investigation of nanocrystallization of a-Si1-xGex:H thin films diluted with argon in the PECVD system

The structural evolution and nanocrystallization of hydrogenated amorphous silicon germanium (a-Si1-xGex:H) thin films deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) through decomposition of silane and germane diluted with argon gas have been investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy, respectively. The results show that argon dilution gas plays a significant role in the growth of nanocrystalline grains in a-Si1-xGex:H thin films. It is observed that the nanocrystalline grains have been developed in amorphous network when the argon dilution ratio is about 4, a relatively low ratio compared to hydrogen dilution. Moreover, the surface roughness, nano-grain size, crystalline volume fraction and hydrogen content of the thin films increase with the rise of argon dilution ratio. Besides, the electrical and optical properties of the samples with different argon dilution ratios have been also measured. Finally, the effect of germanium content on the nanocrystallization of the thin films with fixed argon dilution ratio has been studied. It is found that the a-Si1-xGex:H thin films with high germanium content are prone to nanocrystallization. (C) 2013 Elsevier B.V. All rights reserved.