Laser Annealing of Hydrogenated Amorphous Silicon Thick Films

Abstract

Hydrogenated amorphous silicon thick films deposited by dc glow discharge on molybdenum substrates were annealed by a pulsed Nd:glass laser. Mass spectrometry showed hydrogen remaining in all the laser annealed films. The amount of hydrogen remaining decreased with decreasing scan rate. The hydrogen evolved upon heating at 365 °C and mainly at 658 °C before laser annealing, but at 365, 575 (Mainly) and 645 °C after laser annealing, indicating weakening of the silicon-hydrogen bonding after laser annealing. The presence of hydrogen inhibited crystallization, as indicated by Raman scattering. The photo and dark conductivity of the film increased by one and three orders of magnitude respectively with increasing laser energy density up to 12 J/cm2 at a fixed scan rate. This Means that the photoresponse was decreased with laser annealing, in spite of the associated increase in crystallinity. This photoresponse decrease is attributed to the hydrogen evolution.

Effect of Deposition Temperature on the Photoresponse of Crystallized Hydrogenated Amorphous Silicon Films

“…(Table 2). In contrast, for a-Si:H films, only two peaks were observed [14]. The peaks at T 2 and T 3 shifted to higher temperatures with increasing deposition temperature, indicating that the hydrogen was more strongly held to the silicon with increasing deposition temperature for the laser annealed films.…”

“…(There was no effect of hydrogen passivation in these films, since crystallization of a-Si:H by furnace annealing results in the evolution of hydrogen from the film.) In this work, we employed an alternate crystallization technique, namely pulsed laser annealing, whereby the out-diffusion of hydrogen is minimized [14,15] and crystallization occurs in the liquid phase, as opposed to the solid phase crystallization occurring in furnace annealing. The investigation on photoresponse was conducted as a function of a-Si:H deposition temperature through dark and photoconductivity measurements, Fourier transform infrared spectroscopy (FTIR) and evolution gas analysis (EGA), and supplemented by Raman scattering and x-ray diffraction (XRD).…”

Chemical Vapor Deposition of Zirconium Oxide on Aerosolized Silicon Nanoparticles

“…There is a rich literature on the thermal desorption of hydrogen from single-crystal Si and from Si wafers. In general, hydrogen thermally desorbs from Si in the 450−700 °C range, with the desorption temperature depending on the state of the surface and the experimental conditions. − This brackets the range for which the preheating induced effect is most pronounced.…”

“…In general, hydrogen thermally desorbs from Si in the 450-700 °C range, with the desorption temperature depending on the state of the surface and the experimental conditions. [32][33][34][35][36][37][38][39] This brackets the range for which the preheating induced effect is most pronounced.…”