Blue shift of photoluminescence from a-Si: H nanoball films

Hydrogenated amorphous silicon (a-Si:H) nanoball films which include Si nanocrystals, are fabricated by the double-tubed coaxial-line-type microwave plasma chemical vapor deposition (DTCL-MPCVD) system. Photoluminescence (PL) is observed at room temperature after the a-Si:H nanoball films are oxidized at high temperature in air and/or pure oxygen atmosphere. In this study, the HF treatment is performed to a-Si: H nanoball. By the HFtreatment, the photoluminescence wavelength has shifted from about 740 nm to 590 nm. We have measured the diameter of Si nanocrystal using the X-Ray Diffraction (XRD) and the Transmission Electron Microscope (TEM). It is found that the diameter of the Si nanocrystal decreases from about 5.0 nm to 3.0 nm, by the HF treatment. After changing the conditions of oxidation, PL peak wavelengths are shifted from about 740 nni to 500 nm. We have determined the diameter of Si nanocrystal contained in the a-Si:H nanoball using XRD and TEM. Consequently, it is found that the diameter of Si nanocrystal becomes small from about 5.1 nm to 3.4 nm.