Laser ablated SiC nanorods for optoelectronics applications

SiC thin films (undoped and doped with SnO₂ at 1 at.%, 5 at.% and 10 at.% concentrations) are prepared using pulsed laser deposition on quartz substrates kept at room temperature. The XRD patterns show a crystalline cubic phase for the undoped and 10 at.% SnO₂ doped SiC thin films while 1 at.% and 5 at.% SnO₂ doped SiC thin films exhibit an amorphous nature. The formation of nanorods with a non-uniform distribution of nanoparticles are studied using various microscopic techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Non-uniform distribution of particles with an average diameter 50 nm is seen in SEM micrographs of undoped SiC. On doping with 10 at.% SnO₂, nanorods of average length of 1 micron are formed which is evidenced from the SEM image. TEM images also supports the formation of nanorods of average diameter of 20 nm in the 10 at.% SnO₂ doped SiC thin films. TEM images also suggest the formation of nano particles of size ~ 5 nm in 10 at.% SnO₂ doped SiC thin films. A low surface roughness of 3.6 and 1.69 nm is obtained for the undoped SiC and 10 at.% SnO₂ doped SiC thin films from the AFM analysis. The presence of Raman bands in the region 500- 600 cm^-1 for all the samples indicates the disorder prevailing in the films. It is seen that with higher dopant concentrations, this band becomes more well-defined and appear with more intensities at higher wave numbers which suggests that SnO₂ doping increases disorder in the crystallites in the films. Optical band gaps of the films are estimated from the UV-Vis absorption spectra. Variation in band gap observed with doping concentration may be due to broadening of the absorption edge occurred by the impurity levels. A near interface trap induced blue photoluminescence is observed in the undoped, 5 at.% and 10 at.% SnO₂ doped SiC thin- - films. The open aperture Z-scan measurements revealed strong absorptive nonlinearities. The Z scan curves suggest that the films are good saturable absorbers with saturation intensity I_s being 6 × 1012 and 5.9 × 1012 W/m², respectively for the 1 at.% and 10 at.% SnO₂ doped SiC films.