Effects of in situ vacuum annealing on the surface and luminescent properties of ZnS nanowires

We have monitored the changes that occur in the x-ray-excited optical luminescence, absorption, and photoemission spectra as a function of vacuum annealing time and temperature for ZnS nanowires. All measurements were done in situ. Initial heating causes desorption of surface oxides and a concurrent reduction in the intensity of all the luminescence peaks, which we attribute to the creation of surface states that quench the luminescence. Extended annealing causes diffusion of Au from the particle used to nucleate the wire growth, which results in an increase in intensity of its associated luminescent band at $520\mathrm{nm}$ . Changes were also observed in the $\mathrm{Zn}L$ - and $\mathrm{S}K$ -edge x-ray absorption spectra, which are consistent with this interpretation.