Optical properties of silicon carbide thin films deposited by atomic substitution on porous silicon

Abstract

Silicon carbide filmsonporous-Si/Sisubstrateshaveattractedconsiderableattentionduetotheir potential use in modernhigh-power electronicdevices.Here,SiC/porous-Si/Siheterostructures fabricated by anatomic substitution method areinvestigated.Scanningelectronmicroscopyshows theformation ofacontinuousabout40nmthickfilmofSiC,withasharpinterfacetotheporousSi sublayer. Energy-dispersive x-rayspectroscopyconfirmedthatSi,C,andOaretheonlyconstituents of the SiCfilmandtheporous-Siunderlayer.Ramanspectroscopyindicated3Cand6Hpolytypesin theSiCfilm.Spectroscopicellipsometryintherangeof0.6–5.1eVwasperformedinorderto determinethe refractive index(n),extinctioncoefficient(k),andbandgap(Eg)oftheSiClayer. Macro-FTIRtransmission spectrashowedtheexpectedabsorption features ofSiC.IRreflectance mapsmeasuredwithnano-resolution reveal lateralinhomogeneities oftheintensity,whichwe attribute to the morphology oftheporous siliconsublayer.Numericalsimulationsofthelocalnear fieldresponsewereperformedforregions,wheretheSiClayerlaydirectlyonsiliconandforregions where it is free-standing overpores.Thesimulationresultsareincloseagreementwiththe experimentalobservations obtainedbynanoFTIRandconfirmthattheporoussubstrateplaysa decisive role in determining the local optical and structural properties of the SiC/porous-Si/Si heterostructures