Junction Properties and Gap States in Nb-Doped TiO2Thin Films

Abstract
Nb-doped TiO2thin films were successfully prepared on p-type crystalline Si substrates using the sol-gel process. The current-voltage (I-V) characteristics of the heterojunctions between TiO2and Si show a rectification and the capacitance-voltage (C-V) characteristics an approximate linearC-2-Vrelationship in the reverse-bias condition. By application of an isothermal capacitance transient spectroscopy (ICTS) method on these junction diodes, it is found that two gap states are located at 0.027 eV and 0.22 eV below the conduction band edge (Ec).