Crystallization of hydrogenated amorphous silicon thin film on glass by using ns-pulsed fiber laser operating at 1064 nm

Salman H. S., BACIOĞLU A., Eken S. K.

MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, vol.95, pp.20-27, 2019 (SCI-Expanded) identifier identifier


A nanosecond pulsed, Ytterbium doped optical fiber laser, operating at 1064 nm, has been used for laser induced crystallization (LIC) of a standard recipe-hydrogenated amorphous silicon (a-Si: H) thin film, deposited in a radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) reactor. Despite relatively lower photon energy of 1.165 eV, the crystallization of the a-Si: H sample with the Tauc gap of 1.70 eV was succeeded. The optical energy density impinging on the sample surface was adjusted by the treatment parameters: average output power, repetition frequency and scanning speed. The laser spot energy density was varied mainly from 7.1 to 49.5 J/cm(2). By using Raman scattering, scanning electron microscopy (SEM) and Fourier-Transform infrared (FTIR) spectroscopy, the LIC of the sample was investigated both quantitatively and qualitatively. Depending on the magnitude of the spot energy density, the crystal fraction of the sample could be adjusted between 16% and 99%. We have suggested a threshold spot energy density of 21.2 J/cm(2), for a large crystal volume fraction of 60%. For smaller energy densities, sub-micrometer sized crystal structures were formed. The nano-scaled silicon grains of 3.05 nm has been reached by decreasing the laser energy density to 7.1 J/cm(2). Since the crystallization of large fractions, as much as 99%, is possible with the increase of the laser spot energy density, the nanosecond pulsed 1064 nm laser is a possible candidate to produce crystal silicon on glass (CSG), for photovoltaic applications.