Anion Vacancy States in the Insulator-ZnS Interface

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Abstract
The ground state energy of a trapped electron in an anion vacancy near the insulator-ZnS interface is estimated in a point-ion lattice approximation including an interface image potential. Assuming the (111) interface to be the halfly intersected plane of a Zn-S bond growned to the (111) crystal orientation and the insulator as a classical dielectric medium, the interface Madelung constant which can be used in a point-ion lattice approximation is calculated as a function of the position of an anion vacancy from the interface and the permittivity of insulator by the Evjen method. Taking the appropriate value 1.033 for the effective charge, the estimation shows the ground state energy levels of anion vacancies whose positions are in the 1st and 3rd atomic layers from the interface arise in the range of 1.18±0.3∼1.55±0.3 eV below the lowest conduction band whereas, in the 2nd and 4th atomic layers, of 1.51±0.3∼2.46±0.3 eV.