Synthesis and analysis of surface defect induced tuning of band bending and work function of ZnO nanoparticles

ZnO is a potential material for future applications in transparent electronics, photo-catalysis, and gas sensing. These applications require enhanced surface sensitivity and tailoring of surface-related properties. In the present work, we report on the enhancement of potential fluctuation, band tail energy, and reduction of work function and surface band bending of ZnO nanoparticles by tailoring the surface defects by solvent strength and interfacial energy . Spectral width of photoluminescence reveals an increment of mean potential fluctuation from 0.750 eV to 0.917 eV, and conduction band tail energy from 0.9 eV to 1 eV, respectively. Photoluminescence excitation spectra show quenching of band-to-band transition, breakdown of emission selection rules, and transfer of photo-excited electrons to the oxygen vacancies . Electron spin resonance measurement shows the presence of two ionic surface defects at g = 1.964 and 1.962 with thermal activation energies of 97.2 meV, and 250 meV. These defects are frozen and non-interacting in nature. UV photoelectron emission shows a decrease in work function, and surface band bending by 0.5 eV, and 0.634 eV, respectively, with enhanced valence band tail energy by 1 eV due to random distribution of surface defects .