Papers by Author: Vladimir Lysenko

Abstract: Photoluminescence properties of a freestanding nanoporous SiC layer obtained from bulk 6H-SiC substrate as well as SiC nanopowder consisting of numerous separated nanoparticles has been investigated. The nanoporous SiC layer is obtained by UV radiation assisted electrochemical etching of the 6H-SiC wafer and the SiC nanopowder is formed by mechanical grinding of the nanoporous SiC free layer. A comparison of low temperature PL spectra of the SiC nanostructures and initial SiC bulk substrate has been performed. The evolution of PL spectra of the SiC nanostructures with respect to their surface states and excitation laser power has been studied. In particular, the well pronounced high energy tail above the excitonic bandgap in the PL spectra of the nanostructured SiC is attributed to quantum confinement effects. The strong PL signal obtained below the bandgap is explained by radiative transitions involving surface states, N-Al donoracceptor recombination levels and deep levels corresponding to volume defects in the SiC nanocrystallites.

Abstract: SiC nanopowder has been formed using an original technological approach based on grinding of bulk porous SiC nanostructures. The initial porous SiC nanostructures were obtained by anodization of n+-type 4H-SiC substrate in HF/Ethanol solution under UV illumination. Large single SiC nanoparticles (~ 30 nm in diameter) constituting the nanopowder have a porous structure which can be clearly visible. On the other hand, small single SiC nanoparticles (~ 4 nm in diameter) exhibit a clear crystalline structure. A broad and very intense luminescence band (400 – 900 nm) provided from the nanopowder corresponds to the radiative processes involving nanoparticle surface states. A smaller photoluminescence peak centred at 358 nm may correspond to radiative recombination of the photogenerated excitons confined in the individual and spatially separated 4HSiC nanoparticles.