Fabrication of nanocrystalline silicon thin films utilized for optoelectronic devices prepared by thermal vacuum evaporation

Abstract

Metal-induced crystallization of amorphous silicon is a promising technique for developing high-quality and cheap optoelectronic devices. Many attempts tried to enhance the crystal growth of polycrystalline silicon via aluminum-induced crystallization at different annealing times and temperatures. In this research, thin films of aluminum/silicon (Al/Si) and aluminum/ silicon/tin (Al/Si/Sn) layers were fabricated using the thermal evaporation technique with a designed wire tungsten boat. MIC of a:Si was detected at annealing temperature of 500 °C using X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopy. The crystallinity of the films is enhanced by increasing the annealing time. In the three-layer thin films, MIC occurs because of the existence of both Al and Sn metals forming highly oriented (111) silicon. Nanocrystalline silicon with dimensions ranged from 5 to 300 nm is produced depending on the structure and time duration. Low surface reflection and the variation of the optical energy gap were detected using UV−vis spectroscopy. Higher conductivities of Al/Si/Sn films than Al/Si films were observed because of the presence of both metals. Highly rectifying ideal diode manufactured from Al/Si/Sn on the FTO layer annealed for 24 h indicates that this device has a great opportunity for the optoelectronic device applications.