the effect of tio2 thin film on ac electrical properties of nano porous silicon substrate

the ac electrical behaviour of nano porous silicon (psi) with tio2 thin films was examined over the range of frequency 102 to 105 hz. porous silicon (psi) layers were obtained by electrochemical etching in hf solution and tio2 thin films were deposited on psi substrates by using electron beam evaporation technique at room temperature. the porosity of psi layer was found by using the gravimetric method and the crystalline properties of the tio2 thin films were obtained by an x-ray diffract meter. the surface morphology and ac electrical properties of samples were investigated by scanning electron microscopy (sem) and electrometery respectively. for ac electrical properties we studied the dependence of capacitance and dissipation factor on frequency at different temperatures. the capacitance decreased with increasing frequency and increased with increasing temperature, and dissipation factor decreased with increasing frequency to a minimum value and after that increased. this behaviour is in good agreement with goswami's theory. also, the ac conductivity of sandwich structure films was studied over the range of frequency 102 to 105 hz. over the range of frequency103hz hopping mechanism is applied in explaining the conductivity process.