Comparative studies of ZnO thin films grown by electron beam evaporation, pulsed laser and RF sputtering technique for o
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Comparative studies of ZnO thin films grown by electron beam evaporation, pulsed laser and RF sputtering technique for optoelectronics applications Rashmi Ranjan Kumar1 · Muddam Raja Sekhar2 · Raghvendra1 · Ranjit Laha2 · Saurabh Kumar Pandey1 Received: 9 June 2020 / Accepted: 1 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract ZnO thin films are most promising materials for various emerging applications. In this report, we have compared the physical properties of ZnO thin films deposited at room temperature by three frequently used physical vapor deposition methods, namely, electron beam evaporation, pulsed laser deposition (PLD), and radio frequency (RF) sputtering. The structural, morphological, optical and electrical properties of the deposited ZnO thin films were compared systematically using X-ray diffraction, scanning electron microscopy, atomic force microscopy and UV–visible spectrophotometry. All the films showed polycrystalline nature, with the film deposited using PLD being found to be of highest crystalline quality. Uniformly distributed and densely packed particles were realized throughout the film for all the techniques. The films show notable transparent nature in the visible range of the electromagnetic spectrum. Distinctly visible UV emission was observed for the PLD and RF technique, indicating the suitability for making light-emitting diode and photodiode. E-beam-deposited films showed high porosity which is ideal for designing gas sensors. Keywords Electron beam evaporation · Pulsed laser deposition · Thin film · RF sputtering · ZnO
1 Introduction Zinc oxide (ZnO) is a very suitable material for fabricating various optoelectronic devices such as a light-emitting diode, photo detector, solar cell, liquid crystal displays and touch screen. It also covers various other applications in the field of spintronics, designing gas sensors, and developing transparent electrodes [1–5]. ZnO is an II–VI group direct wide band gap semiconductor material with a band gap of 3.37 eV [6]. It has a large exciton binding energy of 60 meV at room temperature [7]. Like GaN which is also a wide band gap semiconductor, ZnO also crystallizes in wurtzite
* Rashmi Ranjan Kumar [email protected] * Saurabh Kumar Pandey [email protected] 1
Sensors and Optoelectronics Research Group (SORG), Department of Electrical Engineering, Indian Institute of Technology Patna, Bihar 801106, India
Discipline of Physics, Indian Institute of Technology Patna, Bihar 801106, India
2
structure. The ZnO-based devices can operate at higher temperature unlike silicon (Si) which mainly operates at room temperature [8]. ZnO is chemically stable, non-toxic, easy to prepare, and is very easily wet etched in the process of fabrication. Undoped ZnO is found to be n-type as a result of the formation of native point defects [9, 10]. Thin film growth parameters are largely affected by the deposition techniques and the process parameters used therein. There are various deposition techniques available f
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