Abstract
We report the effect of air exposure and deposition temperatures,
T
d, on the optical property of nanocrystalline silicon (nc-Si). The nc-Si thin films were investigated by photoluminescence (PL), optical absorption, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) absorption and Raman scattering. Experimental results show the structural change from an amorphous to a nanocrystalline phase at
T
d=80
°C. In addition, it suggests that
T
d low condition leads to the increase in the density of SiH-related bonds and a decrease in the average grain size, 〈
δ〉. The oxygen absorption peak increases with the air-exposure time. The PL exhibited two peaks at around 1.75–1.78 and 2.1–2.3
eV. The PL increases and blue shifts consistently with the decrease of 〈
δ〉 and increase of oxygen content. The first peak may be related to nanocrystallites in nc-Si films and the origin of another one may be due to defect-related oxygen. Thus, by the plasma-enhanced chemical vapor deposition (PECVD) technique at low
T
d, we can produce the nc-Si films with different grain sizes, causing the corresponding luminescent properties. The new method processes advantages of low deposition temperature and effective oxidation of nc-Si on inexpensive substrates, thus making it more suitable for developing low-cost array or flexible nc-Si optoelectronic devices.