Vacancy defects in CdTe thin films

Vacancy defects have been investigated in a series of CdTe thin films grown by close-space sublimation. Variable-energy positron annihilation lifetime spectroscopy measurements, performed with a high-intensity positron beam, were used to profile polycrystalline films with varying grain size. These were obtained by changing the nitrogen pressure used during deposition. Two vacancy defects were detected, with positron lifetimes of 321(7) ps and 450(30) ps, respectively. Density functional theory calculations support the assignment of the first to the Cd vacancy and provide evidence that the second is the divacancy defect.