ABSTRACT The powder-like ZnS:Cu grown by self-propagating high temperature synthesis from the mix... more ABSTRACT The powder-like ZnS:Cu grown by self-propagating high temperature synthesis from the mixture of Zn, S and CuCl is investigated before and after annealing at 800 °C by photoluminescence (PL) and X-ray diffraction (XRD) techniques. It is found that after synthesis the ZnS:Cu powder consists of a mixture of cubic and hexagonal ZnS phases as well as crystalline CuxZn1-x solid solution. PL spectrum shows a wide PL band which is the superposition of green and blue Cu-related bands as well as self-activated one. It is shown that annealing at 800°C gives rise to three processes, controlled by the heating time to annealing temperature: i) phase transformation of ZnS hexagonal phase to cubic one; ii) oxidation processes resulting in ZnO formation; iii) the non-monotonic changes of CuxZn1-x phase composition and decrease of its content. These changes are accompanied by the non-monotonic variation of the blue to green Cu-related PL band intensities ratio which correlates with the variation of CuxZn1-x phase composition. The model that explains the changes of ZnS:Cu PL characteristics by indiffusion of Zn and Cu from CuxZn1-x phase is proposed. The anisotropic character of ZnS phase transformation and oxidation process is found.
ABSTRACT The fabrication procedure of transparent and conducting ZnO films yielding ohmic contact... more ABSTRACT The fabrication procedure of transparent and conducting ZnO films yielding ohmic contacts to p-GaN has been developed. The microstructure and electronic properties of p-GaN/ZnO interface were studied using atomic force and electron transmission microscopies, and X-ray photoelectron spectrometry. The observed ohmic behaviour is explained in terms of formation of a tunnelling p-GaN/ n+-ZnO junction.
ABSTRACT The powder-like ZnS:Cu grown by self-propagating high temperature synthesis from the mix... more ABSTRACT The powder-like ZnS:Cu grown by self-propagating high temperature synthesis from the mixture of Zn, S and CuCl is investigated before and after annealing at 800 °C by photoluminescence (PL) and X-ray diffraction (XRD) techniques. It is found that after synthesis the ZnS:Cu powder consists of a mixture of cubic and hexagonal ZnS phases as well as crystalline CuxZn1-x solid solution. PL spectrum shows a wide PL band which is the superposition of green and blue Cu-related bands as well as self-activated one. It is shown that annealing at 800°C gives rise to three processes, controlled by the heating time to annealing temperature: i) phase transformation of ZnS hexagonal phase to cubic one; ii) oxidation processes resulting in ZnO formation; iii) the non-monotonic changes of CuxZn1-x phase composition and decrease of its content. These changes are accompanied by the non-monotonic variation of the blue to green Cu-related PL band intensities ratio which correlates with the variation of CuxZn1-x phase composition. The model that explains the changes of ZnS:Cu PL characteristics by indiffusion of Zn and Cu from CuxZn1-x phase is proposed. The anisotropic character of ZnS phase transformation and oxidation process is found.
ABSTRACT The fabrication procedure of transparent and conducting ZnO films yielding ohmic contact... more ABSTRACT The fabrication procedure of transparent and conducting ZnO films yielding ohmic contacts to p-GaN has been developed. The microstructure and electronic properties of p-GaN/ZnO interface were studied using atomic force and electron transmission microscopies, and X-ray photoelectron spectrometry. The observed ohmic behaviour is explained in terms of formation of a tunnelling p-GaN/ n+-ZnO junction.
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