Single and multiphoton absorption induced photoluminescence in pulsed laser deposited Zn1−xAlxO(0 ≤ x ≤ 0.10) thin films

In the present paper, single and multiphoton absorption induced photoluminescence in pulsed laser deposited Zn1−xAlxO (0 ≤ x ≤ 0.10) thin films, is reported. All the films were observed to be preferentially c-axis oriented in the 002 plane as indicated by the X-ray diffraction. A clear emergence of the dominating E2(high) peak in the Raman spectra further confirmed the formation of Wurtzite phase. Single photon induced photoluminescence spectra of all the samples exhibited strong near band edge emission. Multiphoton absorption (MPA) induced photoluminescence (PL) in the thin films was experimentally observed by exciting with a cw He:Ne laser beam operating at a wavelength of 632.8 nm. A blue shift in the UV-PL spectra was observed in the films till x = 0.05 and beyond that it retraced to red-shift. The Intensity of the PL emission was found to be increased in the ZnO film with Al content up-to x = 0.05 due to the improvement in crystalline structure and it decreased with further increase in Al content. Logarithmic plot of the MPA PL intensity and excitation intensity displayed a slope, m, in the range of 1 < m < 2 confirming two photon absorption induced PL emission in these films.