In this research, CuGaO2 thin films were prepared on quartz substrates by a radio frequency magnetron sputtering technique at 400℃ followed by subsequent annealing in N2 ambience. The effects of annealing temperature on structural, morphological, optical, and electrical properties of CuGaO2 thin films is reported. X-ray Diffraction (XRD) analysis confirmed the presence of single phase CuGaO2 in the film annealed at 900℃. Near stoichiometric composition ratio of Cu:Ga (1:1.08) was identified in the film annealed at 900℃. Field emission scanning electron microscopy showed an increase in the grain size with increase in annealing temperature. A UV-Vis spectrophotometer was used to perform optical studies in the 200-800nm wavelength region on all films. The optical bandgap was calculated from the transmission studies and was found to be in the range of 2.77 to 3.43 eV. The films annealed at temperatures 800℃ and above were found to be p-type. The lowest resistivity value of 230 Ω-cm was achieved for the film annealed at 900℃.
Electrical and optical properties of transparent conducting Indium Oxide (In2O3) thin films were studied. These films were deposited by reactive RF sputtering process using Indium target in the presence of oxygen as reactive gas with argon. The pressure and the oxygen gas flow ratios during sputtering were varied to investigate their effect on the resistivity, optical transmission, refractive index, and optical bandgap of In2O3 thin films. The lowest reported resistivity in this study is 2 × 10−3 Ω-cm. The optical transmission was more than 80% in the wavelength range of 400 nm to 800 nm. The optical study revealed the wide optical bandgap of 3.712 eV and 3.875 eV of the deposited In2O3 films. The films showed refractive indices in the range of 1.99 to 2.22. The elemental composition of In2O3 films has been studied through X-ray Photoelectron Spectroscopy (XPS).
For the first time, this research focuses on the deposition and characterization of radio frequency (RF) sputtered p-type CuGaO2 thin films using the dual-target sputtering technique with Cu and Ga2O3 targets. The sputtering power to the Cu target was varied from 5W to 50W while having the Ga2O3 sputtering power constant at 200W. The deposited films were subsequently annealed at two different annealing temperatures of 800℃ and 900℃ in N2 ambiance. The effects of variation in Cu sputtering power and annealing temperature on structural, optical, and electrical properties of CuGaO2 thin films are reported in this work. Single-phase CuGaO2 was confirmed in films deposited with Cu sputtering power of 25W by XRD analysis. XPS analysis revealed a stoichiometric composition ratio of Cu:Ga in films deposited with Cu sputtering power of 25W. The optical studies were performed in 200 nm - 800 nm wavelengths on all the post-deposition annealed films. The optical transmission was found to decrease with increase in Cu sputtering power. The optical bandgap was found to be between 3.3 and 4.6 eV. Single-phase CuGaO2 film was p-type with a resistivity of 60 Ω-cm. This resistivity value is one of the lowest ever reported values identified from CuGaO2 thin films.
Thin films of CuGa2O4 were deposited using an RF magnetron-sputtering technique for the first time. The sputtered CuGa2O4 thin films were post-deposition annealed at temperatures varying from 100 to 900 °C in a constant O2 ambience for 1.5 h. Structural and morphological studies were performed on the films using X-ray diffraction analysis (XRD) and a Field Emission Scanning Electron Microscope (FESEM). The presence of CuGa2O4 phases along with the CuO phases was confirmed from the XRD analysis. The minimum critical temperature required to promote the crystal growth in the films was identified to be 500 °C using XRD analysis. The FESEM images showed an increase in the grain size with an increase in the annealing temperature. The resistivity values of the films were calculated to range between 6.47 × 103 and 2.5 × 108 Ωcm. Optical studies were performed on all of the films using a UV-Vis spectrophotometer. The optical transmission in the 200–800 nm wavelength region was noted to decrease with an increase in the annealing temperature. The optical bandgap value was recorded to range between 3.59 and 4.5 eV and showed an increasing trend with an increase in the annealing temperature.
Synthesis of Cu2In2O5 thin films using intermixing of Cu and In layers deposited using radio-frequency magnetron sputtering technique has been utilized for the first time. The layered structure was subjected to post-deposition annealing at temperatures varying from 700 to 1000°C in a constant oxygen ambiance for five hours. X-ray diffraction analysis confirmed the formation of single-phase Cu2In2O5 thin films at 900°C. An increase in the grain size with an increase in the annealing temperature was noticed from the field emission scanning electron microscopy images. Optical studies were performed on all the annealed films in the 200-2000 nm wavelength range. The bandgap was in the range of 2.88 to 3.46 eV for the films annealed between 700 and 900°C.
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