Nanoindentation and nanoscratch behavior of ZnO:Pr thin films deposited by DC sputtering
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ARTICLE Nanoindentation and nanoscratch behavior of ZnO:Pr thin films deposited by DC sputtering Vipul Bhardwaj Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, India
Ashwani Kumar Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee-247667, India
Rajib Chowdhury Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, India
Rengaswamy Jayaganthana) Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, India; and Department of Engineering Design, Indian Institute of Technology Madras, Chennai-600036, India (Received 19 December 2017; accepted 2 May 2018)
Mechanical properties of Pr (praseodymium)-doped ZnO thin films, deposited on a corning glass substrate and fused quartz at different deposition pressures using DC sputtering were investigated. Crystalline growth in Pr-doped ZnO thin films is more pronounced and improves at 10 mtorr deposition pressure. However, lower sputtering deposition pressure evoked deposition rates to the formation of polycrystalline films emerged in several crystal planes. Pr ions incorporated in the ZnO host lattice was examined by X-ray photoelectron spectroscopy (XPS), AFM, and FESEM. XPS spectroscopy revealed the presence of Pr31 and Pr41 at the ZnO surface layer and it was in tandem with EDS mapping. Nanoindentation prior to scratch testing is used for analyzing deformation characteristics. Pr-doped ZnO thin films exhibit better hardness (9.89 6 0.14 GPa) and Young’s modulus (112.12 6 3.45 GPa) on the glass substrate. The crack propagation resistance parameter of the films was evaluated using initial critical load, Lc1 ; 2250.5 lN for the crack initiation and upper critical load Lc2 ; 2754.5 lN for film failure. Better crack propagation resistance was observed for films deposited at 10 mtorr sputtering pressure on both substrates, attributed to better crystalline nature of the films.
I. INTRODUCTION
Technological upgradation is possible by manufacturing nanodevices with the miniaturization mechanism for semiconducting materials. However, during the miniaturization process, the materials should exhibit functional properties and also mechanically robust to sustain higher resistance to damage. In recent decades, versatility and diverse properties as well as facile synthesis of zinc oxide (ZnO) nanostructures are gaining significant technological importance among all compound semiconductors. Its direct band gap of 3.37 eV at room temperature, high electromechanical coupling constant, high exciton binding energy of ;60 meV, and excellent optoelectrical properties make it suitable candidate for nanodevice applications.1 Nanostructured ZnO can be synthesized using several physical and chemical techniques along with the microstructure manipulations.2 Doping in ZnO also enhances various electrical and optical properties of a)
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