Properties of ITO thin films rapid thermally annealed in different exposures of nitrogen gas

Abstract

Indium tin oxide (ITO) thin films were rapid thermal annealed (RTA) for 5 min at a temperature of 550 °C in different exposures of nitrogen gas. Effects of these exposures on the structural, morphological, electrical, and optical properties of these films were investigated using X-ray diffraction, atomic force microscopy and field emission-scanning electron microscopy, four-point probe and hall effect measurements, and ultraviolet-visible-near-infrared (UV-VIS-NIR) spectrophotometer, respectively. The un-exposed RTA ITO films maintained (400) plane preferential orientation similar to the un-annealed sample. However, this plane preferential orientation was reduced relative to (222) plane for exposed RTA sample. The grains and surface roughness parameters were reduced for exposed and enhanced for un-exposed RTA samples as compared to the un-annealed sample. Relatively higher electrical conductivity, average solar transmittance, and bandgap values were observed for ITO films annealed while exposed to nitrogen gas. The exposed RTA ITO films showed sheet resistance of 7.91 Ω sq −1 , average solar transmittance of 83%, and bandgap of 3.93 eV. Findings from this study suggest that RTA exposure have the potential to control ITO thin films properties, hence, extending its potential applications.

Effects of Multilayer Structure on the Microstructure and Optical Properties of the DC Sputtered Chromium Thin Films for Selective Solar Absorber Applications

“…The patterns depict only one diffraction peak at 2ϴ  44.2 for multilayer and 2ϴ  39.3 for single layer film indicating the preferential orientation on ( 210) and ( 200) planes, respectively (PDF No: 19-0323). The observed shift of peak position to lower angles may be associated with residual stress due to the increase in deposition power (Wang et al 2011, Höflich et al 2016, Ollotu et al 2020. The structural transformation of Cr films was also observed by other researchers due to other processing parameters such as substrate temperature, operating pressure, and substrate biasing (Balu et al 2005).…”

“…As seen from Figures 3c-d and 5c, the obtained refractive indices show decreasing trends with wavelength, concurrently the obtained extinction coefficients showed increasing trends with wavelength indicating the metallic behaviour of Cr metal (Khelifa et al 2018). The films' average solar transmittances, T av were determined by Equation (2) using Air Mass 1.5 solar irradiance G() as ascribed by Maghanga et al (2010) and Ollotu et al (2020). Figure 4 shows the reflectance spectra of the deposited chromium thin films.…”

Annealing-free fabrication of high-quality indium tin oxide films for free-carrier-based hybrid metal–semiconductor nanophotonics

“…This is a comparable result to those presented in Refs. 35 , 44 , 46 , given the significantly lower temperature of our process, preserved good electrical properties of ITO films and despite the smaller grain sizes in our samples. Lastly, it is worth noting that the use of oxygen plasma in the range of discharge voltages between 120 and 165 V allows for low resistivity to be maintained, while providing a very wide range of carrier concentration and mobility at the same time.…”

“…In this degenerated semiconductor, the majority carriers are electrons that originate from the partial substitution of indium In 3+ by tin Sn 4+ ions and from the creation of doubly charged oxygen vacancies O 2- in the lattice 2 , 45 . These two mechanisms are strongly correlated with the substrate temperature used in the manufacturing process and the introduction of post-annealing treatment 35 , 46 . Since ITO layers are typically prepared using physical vapor deposition techniques, the deposited films are polycrystalline and have significantly more complex carrier transport mechanisms than those found in single crystals.…”

“…To obtain high carrier concentration and optical transparency simultaneously, it is necessary to introduce high substrate temperatures, typically between 250 and 500 °C, to ensure sufficient recrystallization of the evaporated material 2 , 25 , 26 , 30 – 33 . As an alternative, it is also suggested to use post-process annealing at 550 °C to produce samples of similar quality 15 , 16 , 34 , 35 . Unfortunately, the introduction of elevated temperatures into the manufacturing process can damage other, more temperature-sensitive nanolayers or even entire components of the device in the case of many systems.…”