Effect of chloride on the photoluminescence of ZnS:Mn thin films

ZnS:Mn thin films at various substrate temperature are grown by halide transport chemical vapor deposition. These films show blue and red photoluminescence (PL) in addition to the typical yellow-orange emission. The manganese crystal environment is characterized by electron spin resonance (ESR) spectroscopy. A computer simulation of the ESR spectra is used to quantify the number of isolated manganese and the number of clustered manganese in the crystal lattice. These data reveal that the red emission occurs in films with low manganese concentration, and, therefore, occurs from a mechanism different than those previously posed. The activation energy for Mn incorporation is measured to be $E_a\text{=137\hspace{0.17em}}\mathrm{kJ/mol}.$ From these data, a Mn–Cl defect pair is proposed as the red emission center. Self-activated blue emission in intentionally Cl-doped ZnS films is also demonstrated. Thus both red and blue PL in ZnS thin films result from chloride impurities.