Ferromagnetic signature in vanadium doped ZnO thin films grown by pulsed laser deposition
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R.S. Rawat, P. Lee, and T.L. Tan Natural Science and Science Education, National Institute of Education, Nanyang Technological University, Singapore 637616, Singapore
C. Ke, R. Chen, and H.D. Sun Division of Physics and Applied Physics, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore (Received 8 March 2016; accepted 25 August 2016)
Dilute magnetic semiconductors are attractive due to their potential in spintronic devices. In this work, vanadium doped ZnO system has been studied to see its future as a dilute magnetic semiconductor. Vanadium doped ZnO thin films where vanadium percentage is 2, 3, and 5% are deposited by pulsed laser technique (PLD). The lattice parameter c derived from the (002) diffraction peak increases as vanadium content increases, suggesting vanadium substitution for Zn in ZnO lattice. Photoluminescence (PL) measurements at low temperature shows the emission peak at 3.30 eV which hint toward p-type doping in ZnO. X-ray photoelectron spectroscopy (XPS) results show that vanadium exists in V21 and V41 valence state, which is in agreement with the XRD and PL results and support the vanadium doped ZnO phase. The ferromagnetic behavior also supports the formation of vanadium doped ZnO phase in thin film samples. I. INTRODUCTION
In 1990s, the research community began to focus their attention on the research and development of ‘spin’ and ‘charge’ of the electrons. The control over these two degrees of freedom is essential for the realization of devices with exceptional functionalities known as ‘Spintronic’ devices. Spintronic, the combination of spin & electronics, is the technology where spin can be used to transform reading and writing information rather than electronic charge.1,2 Currently, the research is actively focusing on spintronic devices like spin transistors, spin light emitting diodes, spin valves etc.3 due to their potential advantages over charge-based electronics. For the realization of these devices, scientists investigated dilute magnetic semiconductors (DMSs) where they can easily manipulate the charge and spin of electrons. The initial studies on III–V semiconductors doped with Mn such as InMnAs4 and GaMnAs1,2 offered promising future for controlling spin and charge. But low Curie temperature (120 K) of these semiconductors, posed a hindrance in the scope of their applications. Theoretically, it was proposed Contributing Editor: Michael E. McHenry a) Address all correspondence to this author. e-mail: [email protected], shumailakaramat@comsats. edu.pk DOI: 10.1557/jmr.2016.328
that ZnO could be a strong contestant in the field of DMSs, if it can be doped by Mn dopants.5 It is easy to dope for higher percentages in II–VI type semiconductors as compare to III–V semiconductors. ZnO is a marvelous material, hugely used in various applications such as UV coatings,6 gas sensors,7 flat panel displays,8 and solar cells9 to name a few. ZnO is known to be an n-type semiconductor,10 but its co-doping makes it a p-type.11 It will be
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