Photoluminescent properties of oxidized stochiometric and carbon-rich amorphous Si1-xCx:H films

Abstract

Abstract. Near-stochiometric and carbon-rich a-Si 1−x C x :H thin films were deposited using the magnetron sputtering of Si target in Ar/CH 4 gas mixture. As-deposited nearstochimetric (x = 0.5) sample showed weak blue photoluminescence (PL), while PL of as-deposited carbon-rich (x = 0.7) sample was 20 times stronger and white in color. The films were annealed in pure argon, wet argon, and dry oxygen at 450 °C for 30 min. The intensity of PL in a-Si 1−x C x :H layers were enhanced by the factor from 2 to 12 after annealing in dependence on the annealing atmosphere. The strongest oxidation and strongest light emission were observed in carbon-rich series (x = 0.7) after annealing in oxidizing atmosphere. Structural properties of the films were characterized by infra-red absorption spectroscopy, ellipsometry and electron paramagnetic resonance. The effect of carbon enrichment of a-Si 1−x C x :H films and annealing atmosphere on the evolution of photoluminescence and local interatomic bonding structure in annealed material were studied and analyzed. It has been found that main effects of thermal treatments is strong enhancement of photoluminescence accompanied by formation of Si:C-H n and Si-O x C y bonding. The strongest oxidation effect as well as strongest photoluminescence were observed in carbon-rich a-SiC:H films.

Enhanced Photoluminescence of Hydrogenated Amorphous Silicon Carbide Thin Films by Means of a Fast Thermal Annealing Process

“…For example, the hydrogenated amorphous phase of silicon carbide (a-SiC:H) has been demonstrated to be a good candidate for the development of large-area optoelectronic devices due to its light emission and absorption properties. Different methods for obtaining a-SiC:H thin films have been used, such as electron cyclotron resonance (ECR), magnetron sputtering, and Plasma Enhanced Chemical Vapor Deposition (PECVD) [1][2][3];…”

“…These important processes have been used to improve the spectral response, external/internal quantum efficiency, and efficiency of solar cells [4][5][6]. For this purpose, several authors have reported photoluminescence in a-SiC:H. Vasin et al [2] reported the strong PL of a-SiC:H films deposited by sputtering with an annealing process at 450 • C for 30 min in dry oxygen, with values in the range of 1.91-3.26 eV with a peak at 2.66 eV. Li et al [7] obtained luminescence values from 1.75 to 3.1 eV with a peak at 2.48 eV of a-SiC:H using a PECVD system with high power densities (289-520 mW/cm 2 ).…”

“…Therefore, the research works on a-SiC:H have reported different bands of light emission, some of which have associated the PL to quantum confinement effects (if there are silicon nanocrystals in the amorphous matrix [1,8]) and others to radiative recombination in the band gap [7,9,10]; however, the majority have related the intensity and position of PL to the carbon content [2,11,12]. Nevertheless, there are few studies in which thermal annealing has been performed to study its effect on light emission.…”