Abstract
The Cu (3 to 15 at%) is incorporated into ZnO thin film by atomic beam co-sputtering has been investigated for enhancement in room temperature ferromagnetism and green photo-luminance. These Cu-ZnO thin films examined with Raman spectroscopy, X-Ray Diffraction (XRD), UV-Visible spectroscopy, Hall measurement, magnetic force microscopy (MFM) and magnetic hysteresis. Raman spectroscopy, XRD confirms wurtzite structure and improvement in the crystallinity of ZnO upto 7% Cu. Further increase in Cu concentration results in growth in Cu nanoparticles. On increasing Cu concentration, there is decrement in transparency and increase in band gap with increase in n-type carrier concentration as confirmed from UV-Visible and Hall measurement studies. Magnetic measurement exhibited unique feature of room temperature ferromagnetic ordering in undoped and doped sample upto 3% Cu. The enhancement in magnetic moment as well as green emission in photoluminescence response with increase in Cu doping indicates that generation of large defects in ZnO by Cu doping, which can be attributed to combined effect of the presence of oxygen vacancies and/or structural inhomogeneity as well as formation of bound magnetic polarons. Importantly, synthesised Cu doped ZnO thin films can be used as spin LEDs and switchable spin-laser diodes.
Highlights
Metal oxides give an opportunity to extend the performance of today’s semiconductor devices which are widely used in high frequency, high power and high temperature applications
Photoluminescence properties of zinc oxide (ZnO) can be tailored by doping of foreign elements in ZnO12–14 and green emission, is reported on Cu doping in ZnO, its mechanism is the part of focused discussion[15,16]
Bound magnetic polarons (BMP) model[29,30,31] is used to explain ferromagnetic ordering in transition metal doped ZnO, in this polarons is a collections of electrons or holes which are bound to impurity atoms through exchange interactions with in an orbit
Summary
Metal oxides give an opportunity to extend the performance of today’s semiconductor devices which are widely used in high frequency, high power and high temperature applications. Doping of various impurity elements in ZnO shows different functions and improved properties of semiconductor compounds such as electrical, optical and mechanical, which facilitate the development of many electronic and optoelectronic devices[7,8,9]. Mechanism of double exchange model is given by Zener[27] based on the hopping of electrons between two neighbor transition metal ions i.e. describes a system of localized spins interacting with spins of conducting electrons, to explain the strong correlation between movement of charge and spin polarization of the magnetic lattice ions. Bound magnetic polarons (BMP) model[29,30,31] is used to explain ferromagnetic ordering in transition metal doped ZnO, in this polarons is a collections of electrons or holes which are bound to impurity atoms through exchange interactions with in an orbit. The efforts have been made to correlate all the physical properties of Cu doped ZnO and the basic mechanism for observation of RTFM, and green luminescence in ZnO thin films is explained comprehensively
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