Effect of thermal treatment on points defects of Al-N codoped ZnO films

Abstract

The effect of annealing temperature on the structural properties of Al-N codoped ZnO films were studied by X-ray diffraction, photoluminescence and Raman spectroscopy. ZnO films were deposited by sputtering technique on silicon substrates at 20 ºC, Al-concentration was kept constant and N-flow was changed to 6, 12 and 15 sccm. A thermal treatment was performed by annealing the sample during 30 minutes at 300, 400, 500, 600 and 700 °C. Before annealing, Raman spectra shows two vibration modes located at 275 and 580 cm-1 associated to the nitrogen incorporation and the presence of point defects. Both Raman intensities of modes I275 and I580 decreases when the nitrogen flow increases from 6 to 12 and 15 sccm, which is originated by a decreasing interstitial defects density. The improving of the crystal quality was confirmed by x-ray diffraction and room temperature photoluminescence measurements. After annealing, in the Raman spectra it was observed that I275 increases as the temperature increase, reaches a maximum intensity between 500 and 600 °C, and decreases for higher temperatures. X-ray diffraction measurements show that after annealing the compressive stress decrease progressively as the annealing temperature increase. This study suggests that 275 Raman mode could be used to estimate the optimal thermal treatment in order to achieve pdoping ZnO.