Natural defects and defects created by ionic implantation in zinc tellurium

Various defects have been studied in ZnTe crystals by transmission electron microscope and by scanning electron microscope in cathodo-luminescence mode: grain boundaries, sub-grain boundaries, twins. Ionic implants of boron (100 keV - 2x1014 and 1015 ions cm-2) were made on these crystals followed by isochrone annealing (30 minutes) of zinc under partial pressure at 550, 650 and 7500C. The nature of the defects was determined by transmission electron microscope: these are interstitial loops (b=1/3<111>) the size of which varies between 20 A (non-annealed sample) and 180A (annealed at 7500C). The transmission electron microscope was also used to make concentration profiles of defects depending on depth. It is found that for the same implant (2x1014 ions.cm-2), the defect peak moves towards the exterior of the crystal as the annealing temperature rises (400 - 1000 and 7000 A for the three annealings). These results are explained from a model which allows for the coalescence of defects and considers the surface of the sample as being the principal source of vacancies. During the annealings, the migration of vacancies brings about the gradual annihilation of the implant defects. The adjustment of certain calculation parameters on the computer result in giving 2 eV as energy value for the formation of vacancies