Structural, optical and magnetic properties of manganese zinc oxide thin films prepared by sol–gel dip coating method
Introduction
For spintronic devices presence of ferromagnetism above room temperature is needed. Doped non-magnetic semiconductors with transition metals can be ferromagnetic and have spin carriers. The ZnO (II–VI semiconductor) is a part of the suitable candidates that have ferromagnetic properties when doped with transition metals [1], [2]. Mn doped ZnO is a promising material for spintronics because it has room temperature ferromagnetism [3], and it has also been used for the fabrication of solar cells, gas sensors, transparent electrodes and piezoelectric transducers due to its properties of dilute magnetic semiconductor (DMS) [4]. DMS materials have magnetic, optical, electrical, and transport properties that are essential for spintronic devices [5]. Of all DMS materials, Mn-doped ZnO is the most suitable candidate because the Mn ion has the highest magnetic moment among 3d transition metals and creates a fully polarized stable state owing to half-filled 3d bands. Mn is antiferromagnetic so that it can develop clean ferromagnetism. Different physical and chemical methods has been adopted to grow Mn:ZnO thin films e.g. magnetron sputtering [6], spray pyrolysis [7], pulsed laser deposition [8], ion plating, chemical vapor deposition, thermal evaporation, molecular beam epitaxy [9]. Chemical techniques are quite simple, inexpensive, easier composition control, good solubility, excellent homogeneity, and lower synthesis temperature. The purpose of this project is to study the effect of Mn doping on the grain growth, structural and the optical properties of thin films prepared by dip coating.
Section snippets
Experimental details
Zinc acetate dihydrate [Zn (CH3COO)2⋅2H2O] was used as precursor, ethanol as solvent and diethanolamine (DEA) as a stabilizer for synthesizing sol. Manganese acetate served as doping material. 5 g Zinc acetate di-hydrate was dissolved in 30 ml of ethanol at 60 °C under constant stirring for one hour. Then manganese acetate, 5 ml (10 drops) di-ethanolamine (DEA) and 10 ml of water was mixed in the sol of zinc acetate di-hydrate. The mixture was stirred at 80 °C for 7 h to obtain the homogenous sol. The
FTIR
To confirm the formation of ZnO:Mn IR spectroscopy was done and the FTIR spectra of ZnO:Mn thin film is shown in Fig. 1. Four dips are noted at 1632.60, 536.47, 497.55 and 434.31 cm−1. The FTIR transmission spectrum Vs wave number is shown in Fig. 1 for Mn:ZnO synthesized by sol–gel technique predicts that the crystal structure was emerged at 500 °C annealing temperature. Also, Zn
O and MnO stretching modes are easily viewed in Fig. 1. The stretching mode of ZnO is observed at 434.31 cm−1 [10], [11]
Conclusions
Mn doped ZnO thin films are grown by sol–gel dip coating technique at varying withdrawal speed of substrate. The films deposited by a sol–gel technique were found to be highly c-axis oriented and the transmittance was decreased in the visible region with increase of withdrawal speed. Thickness of thin films increases with increase in withdrawal speed of substrate. Grain size of thin films increases with the increase of the thickness, which may be attributed to the decrease of strain and band
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