Tailoring of stoichiometry and band-tail emission in PLD a-SiC thin films by varying He deposition pressure

Abstract

The present work focuses on the effect of He pressure (vacuum, 10 −2 -5 mbar) on structural and optical properties of amorphous silicon carbide (a-SiC) thin films, deposited by pulsed laser deposition (PLD) technique onto fused silica. A stoichiometric change occurs in PLD a-SiC film, with increasing He deposition pressure, transforming a near stoichiometric SiC material to C-rich SiC films till 1 mbar of He pressure followed by drastic decrease in carbon (C) content at 5 mbar. The optical band gap of the films estimated using Tauc plot from UV-Vis-NIR transmittance spectra showed initial increase from 2.09 to 2.61 eV with increasing He pressure from 10 −6 to 1 mbar, then decrease to 2.11 eV at 5 mbar. A broad band photoluminescence (PL) peak featured in each of the a-SiC films at room temperature. The PL spectra exhibited blue shift in peak energy from 1.8 to 2.2 eV with increase in atomic percentage of C from 49.4 to 62.4%. The origin of the PL exhibited in these films is clearly due to band tail emissions from amorphous SiC structures which has been explained by the observed variation of PL intensity and corresponding FWHM with band gap as well as Urbach energy.

Design, Construction and Programming of a Low-Cost Pulsed High-Voltage Direct Current Power Supply for the Electrophoretic Deposition of Silicon Carbide Mixed with Graphite and/or Alumina for Thermoelectric Applications

“…Furthermore, modes at 827 cm −1 and 921 cm −1 were identified as the transverse and longitudinal optical phonons of 3C-SiC, respectively (Figure 19). The wide bands between 700 and 1000 cm −1 indicate the presence of high structural disorder in SiC bonds and are therefore attributed to the optical Raman modes of 6H-SiC [38]. The 1607 cm −1 signal is related to C−C vibrations in amorphous carbon [39].…”