Novel blue-violet photoluminescence from sputtered ZnO thin films

Although wurtzite ZnO has a simple crystal structure, the mechanism of its photoluminescence is still controversial and this topic has attracted numerous research efforts. The polycrystalline ZnO thin films studied here were deposited on Si (1 0 0) substrate by sputtering in pure Ar atmosphere, and then thermally annealed in air at various temperatures ranging from 300 °C to 1050 °C. The photoluminescence spectra of the as-synthesized ZnO thin films exhibited some interesting results: two novel and remarkable blue-violet emission peaks around 415 nm and 440 nm were discovered, while the usual strong green emission peak at 450–550 nm was absent. These two blue-violet peaks might originate from zinc interstitial and zinc vacancy point defects, which were introduced during sputtering in a non-oxygen atmosphere. Strong blue-violet emissions of ZnO are highly desirable and they have great potential in light emitting and biological fluorescence labeling applications.

Research highlights
► Two novel and remarkable blue-violet emission peaks around 415 nm and 440 nm from ZnO thin film are discovered.
► The usual green emission from ZnO at 450–550 nm is absent.
► The origins of these two blue-violet peaks are firstly suggested to zinc interstitial and zinc vacancy point defects.