Effect of Annealing on Optical, Electrical and Charge Trapping Properties of TiO2 NPs Arrays

Glancing angle deposition technique has been carried out to synthesize TiO2 nanoparticles over SiO x thin film. The samples were annealed at different temperatures 550 degrees C and 950 degrees C. The average grain sizes and surface RMS roughness have been increased from 9 nm, 0.62 nm (as deposited); 21 nm, 2.47 nm (550 degrees C annealed) to 37 nm, 4.2 nm (950 degrees C annealed). Fivefold maximum increase in optical absorption has been recorded for the 950 degrees C annealed sample as compared to that of the as grown. The absorption and photoluminescence peaks show the red shift with an increase in annealing temperature and grain sizes. Transmission electron microscopy (TEM) has been used to investigate phases of nanoparticles. The junction capacitance of the Au/TiO2 NPs device was observed to decrease with an increase in frequency. A minimum change in junction capacitance of 1 pF was calculated for 950 degrees C annealed device for the variation of frequency from 500 Hz to 1 MHz. The results are used to simulate the capacitance as a function of frequency and voltage characteristic of TiO2 NPs based device in different temperature. Simulated results are exceptionally close to experimental results. The TiO2 NPs based device annealed at 950 degrees C possessed higher impedance and lower conductance among all three type of devices. The sample annealed at 950 degrees C showed the maximum capacitance (0.09 pF at 0 V) as well as charge (-0.6 Coulomb at + 8 V) retention compared to that of the 550 degrees C annealed and as deposited samples.