Structural, optical and magnetic properties of cobalt-doped ZnTe dilute magnetic semiconductors
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Structural, optical and magnetic properties of cobalt‑doped ZnTe dilute magnetic semiconductors M. Shobana1 · S. R. Meher1 Received: 15 May 2020 / Accepted: 22 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Cobalt-doped ZnTe (Co:ZnTe) polycrystalline powders with different Co concentrations (0%, 3%, 5% and 8%) are prepared by solid state reaction method with an aim to study their dilute magnetic semiconducting behaviour. The effect of Co doping on the structural, optical and magnetic properties of the synthesized samples are investigated. The phase and crystallinity of Co:ZnTe powders are studied through X-ray diffraction and Raman spectroscopy. The surface morphology has been analysed through scanning electron microscopy. The chemical environment of the dopant in the host lattice is analysed through X-ray photoelectron spectroscopy. The optoelectronic properties of Co:ZnTe powder samples are evaluated through diffuse reflectance spectroscopy and photoluminescence spectroscopy. The ferromagnetic behaviour of the samples has been investigated at room temperature by the vibrating sample magnetometer. The origin of magnetism in ideal Co:ZnTe bulk system has been analysed through ab initio density functional theory.
1 Introduction ZnTe is a group II-VI semiconductor with a direct bandgap of ~ 2.26 eV [1]. It has potential applications in visible light optoelectronic devices. It crystallizes predominantly in the cubic zinc blende phase. ZnTe doped with suitable elements has attracted substantial interest amongst the scientific community in fundamental research as well as in technological applications. In the literature, several dopants, e.g. In, Cu, Ni, Cr, Bi, Mn, Ag, V, Gd, etc. have been reported to tune the properties of ZnTe host lattice [2–4]. ZnTe is a natural hole dominant semiconductor owing to the low formation energy of Zn vacancies [5]. But Al doping has been reported to induce electron dominant conductivity in ZnTe [6]. On the other hand, Cu and Sb doping leads to hole dominant degenerate behaviour in ZnTe [7, 8]. Similarly, the change in the optoelectronic properties of ZnTe with respect to the dopant concentration has been studied by many researchers. Most of the studies on the dopant induced optoelectronic properties of ZnTe are limited to thin films. Mahmood et al. [9] have studied the structural and optical properties of Z n1−xNixTe thin films grown by e-beam evaporation. They have reported * S. R. Meher [email protected] 1
Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore 632014, India
a linear decrease in the optical bandgap with increase in the Ni concentration. Z n1−xCrxTe thin films are reported to be grown using thermal evaporation technique [10]. A linear decrease in the optical bandgap with increase in the dopant concentration is observed for these films. Pattar et al. [11] have studied the effects of In doping in ZnTe thin films. They have achieved successful In doping by immersing the ZnTe thin
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