Thermal evaporation and oxidation for synthesising nanostructured Al doped Zn thin films and their optical characteristics

This study explores the synthesis of zinc oxide (ZnO) via direct thermal oxidation of Al/Zn multilayer films, targeting optimised structural and optical properties for optoelectronic applications. The in situ layering of aluminium and zinc enabled controlled oxidation kinetics and precise nanostructure formation. Scanning electron microscopy (SEM) revealed that Zn only films formed porous, disordered morphologies, whereas Al containing films exhibited well aligned nanowires and hexagonal crystalline structures. Photoluminescence (PL) spectroscopy identified two dominant emission bands: a near band edge ultraviolet (UV) peak at 3.295 eV and a defect related green emission around 2.5 eV. Al doping significantly enhanced UV emission while suppressing green luminescence, indicating effective reduction of oxygen vacancies and other deep level defects. The Al/Zn/Al configuration demonstrated the highest UV to green intensity ratio and the narrowest FWHM, highlighting superior optical quality. Temperature dependent PL measurements showed UV quenching with increasing temperature, whereas green emission remained stable, confirming its origin in deep level defect states. These results underscore the critical role of aluminium doping and multilayer architecture in tailoring ZnO nanostructures, demonstrating their potential for advanced optoelectronic devices, including UV LEDs and photodetectors.