Growth and crystallographic feature-dependent characterization of spinel zinc ferrite thin films by RF sputtering
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NANO EXPRESS
Open Access
Growth and crystallographic feature-dependent characterization of spinel zinc ferrite thin films by RF sputtering Yuan-Chang Liang* and Hao-Yuan Hsia
Abstract ZnFe2O4 (ZFO) thin films exhibiting varying crystallographic features ((222)-epitaxially, (400)-epitaxially, and randomly oriented films) were grown on various substrates by radio-frequency magnetron sputtering. The type of substrate used profoundly affected the surface topography of the resulting ZFO films. The surface of the ZFO (222) epilayer was dense and exhibited small rectangular surface grains; however, the ZFO (400) epilayer exhibited small grooves. The surface of the randomly oriented ZFO thin film exhibited distinct three-dimensional island-like grains that demonstrated considerable surface roughness. Magnetization-temperature curves revealed that the ZFO thin films exhibited a spin-glass transition temperature of approximately 40 K. The crystallographic orientation of the ZFO thin films strongly affected magnetic anisotropy. The ZFO (222) epitaxy exhibited the strongest magnetic anisotropy, whereas the randomly oriented ZFO thin film exhibited no clear magnetic anisotropy. Keywords: Spinel; Oxide; Crystallographic feature; Sputtering; Surface morphology; Magnetic property
Background Recently, spinel-structured ferrite oxides have been intensively investigated because of their versatile physical and chemical properties as well as technological applications in magnetic sensors, biosensors, and photocatalysts [1,2]. ZnFe2O4 (ZFO) is one of the major ferrite oxides with a spinel structure, and it has remarkable magnetic and electromagnetic properties regarding its state of chemical order and cation site occupancy in lattices [3]. Moreover, it is also a semiconductor, processes light response, has photochemical characteristics, and can be used as a material for supercapacitors [4,5]. ZFO in various forms, such as powders, films, and various nanostructures, prepared using different methodologies have been reported [6-8]. Many ZFO nanostructures can be used as versatile building blocks for fabricating functional nanodevices; however, integrating the reported methodologies for preparing nanostructured ZFO into Si-based semiconductor device processes remains a challenge. ZFO in thin-film form is promising and is compatible in the fabrication of devices with Si * Correspondence: [email protected] Institute of Materials Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan
semiconductors. Yamamoto et al. prepared ZFO thin films on a single-crystal sapphire substrate by using pulsed laser deposition and examined the effect of the deposition rate on its magnetic properties [9]. ZFO thin films with a microlevel scale were grown on glass substrates by radio-frequency (RF) sputtering at room temperature, and the magnetic properties of the films were investigated [10]. Ogale et al. used a pulsed laser evaporation method to synthesize ZnO and ZnxFe3−xO4 mixed-phase thin films on sapphire substrates using ZnFe2O4 pell
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