Structural, morphological and optical study of Li doped ZnO thin films on Si (100) substrate deposited by pulsed laser deposition

Abstract

Structural, morphological and optical properties of Zn1−xLixO thin films grown on Si (100) substrates by pulsed laser deposition at different Li doping concentrations (x=0.0, 0.05, 0.07 and 0.09) are reported. The XRD spectra indicate the formation of single crystalline ZnO thin films preferentially grown along (002) crystallographic orientation with c-axis perpendicular to the substrate surface. FESEM analysis shows the average size of Zn1−xLixO nanostructures to decrease from 42 to 30nm and AFM analysis also shows the average size of Zn1−xLixO nanostructures to decrease from 30 to 05nm with increasing lithium concentrations from x=0 to 0.09. Moreover, Raman and Photoluminescence spectra also confirm the single-phase formation of ZnO thin films. A significant enhancement in optical band gap is found from 3.35 to 3.63eV by Li doping from x=0 to 0.09. It may be due to the increased carrier concentrations by Li doping that blocks the lowest states in the conduction band and results in the increase in band gap. The obtained Zn1−xLixO thin films with c-axis oriented along (002) plane are useful for device fabrication in broadband UV photo-detectors for high tunable wavelength resolution.