Comparison the optical properties for Bi2O3 and NiO ultrathin films deposited on different substrates by DC sputtering technique for transparent e

📝 Abstract

Bismuth and Nickel transparent oxides thin films were grown on glass and flexible polythelene terephalate (PET) substrates by DC sputtering technique at room temperature 300 K. The structures of Bi2O3 and NiO films were analyzed by X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM). A profilometry is used to measure the thicknesses of the ultrathin films. These values were established by a spectro-ellipsometry technique with a new amorphous dispersion model in the range of 200 nm to 2200 nm with one nm increment. In addition, the optical constants of these films were investigated using a double beam UV-Vis-NIR spectrometer and a spectro-ellipsometry and compared using the same wavelength range. They present an excellent agreement. According to the optical transmittance spectra of the films a high average transmittance in the visible region of each sample deposited onto different substrates is measured. Moreover, the absorption coefficients and the optical energy gaps for four types of optical transitions (allowed direct, forbidden direct, allowed indirect, forbidden indirect) of the films were determined and compared with the two different techniques. Finally, the nature of the structure and morphology of Bi2O3 and NiO ultrathin films has been analyzed and compared.

💡 Analysis

Bismuth and Nickel transparent oxides thin films were grown on glass and flexible polythelene terephalate (PET) substrates by DC sputtering technique at room temperature 300 K. The structures of Bi2O3 and NiO films were analyzed by X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM). A profilometry is used to measure the thicknesses of the ultrathin films. These values were established by a spectro-ellipsometry technique with a new amorphous dispersion model in the range of 200 nm to 2200 nm with one nm increment. In addition, the optical constants of these films were investigated using a double beam UV-Vis-NIR spectrometer and a spectro-ellipsometry and compared using the same wavelength range. They present an excellent agreement. According to the optical transmittance spectra of the films a high average transmittance in the visible region of each sample deposited onto different substrates is measured. Moreover, the absorption coefficients and the optical energy gaps for four types of optical transitions (allowed direct, forbidden direct, allowed indirect, forbidden indirect) of the films were determined and compared with the two different techniques. Finally, the nature of the structure and morphology of Bi2O3 and NiO ultrathin films has been analyzed and compared.

📄 Content

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Comparison the optical properties for Bi2O3 and NiO ultrathin films deposited on different substrates by DC sputtering technique for transparent electronics. M. RASHEED, R. BARILLÉ MOLTECH-Anjou, Université d’Angers/UMR CNRS 6200,
2 Bd Lavoisier, 49045 Angers, (France) Corresponding author: rasheed.mohammed40@yahoo.com

Abstract Bismuth and Nickel transparent oxides thin films were grown on glass and flexible polythelene terephalate (PET) substrates by DC sputtering technique at room temperature 300 K. The structures of Bi2O3 and NiO films were analyzed by X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM).
A profilometry is used to measure the thicknesses of the ultrathin films. These values were established by a spectro-ellipsometry technique with a new amorphous dispersion model in the range of 200 nm to 2200 nm with one nm increment. In addition, the optical constants of these films were investigated using a double beam UV-Vis-NIR spectrometer and a spectro-ellipsometry and compared using the same wavelength range. They present an excellent agreement. According to the optical transmittance spectra of the films a high average transmittance in the visible region of each sample deposited onto different substrates is measured. Moreover, the absorption coefficients and the optical energy gaps for four types of optical transitions (allowed direct, forbidden direct, allowed indirect, forbidden indirect) of the films were determined and compared with the two different techniques. Finally, the nature of the structure and morphology of Bi2O3 and NiO ultrathin films has been analyzed and compared.

Keywords Bismuth and nickel oxides films, DC sputtering, different substrates, spectrophotometer, ellipsometry.

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1. Introduction Bismuth oxide (Bi2O3) and nickel oxide (NiO), (metal oxides thin films) are P- type semiconductor [1, 2], antiferromagnetic [3, 4], and are interesting for their excellent optical and electrical properties, high chemical thermal stability, low resistivity, high transparency in the visible region, and a wide optical energy gap [5, 6]. These films exhibit an extremely wide range of physical and chemical properties used in a variety of technical applications that includes the uses in photoelectrochemical or photocatalysis [7, 8], smart windows [9, 10], electrochromic devices [11, 12], transparent electronic devices [13, 14], gas sensing [15], metal-insulator [16, 17], fuel cells [18, 19], and heat mirror [20].
   The surface and interface properties of metal oxides play an important role in all these applications, and sometimes even dominate device performances.
   Among them Bismuth oxide and Nickel oxide play an important role due to their high melting points (817ºC, 1955ºC) respectively remaining until this reached temperature point with a high corrosion resistance. Bi2O3 and NiO are also good candidates as electrodes for thin film solar cell applications because of high thermal expansion coefficients representing large dimensional variations under heating and cooling, which would limit the performance of an electrolyte. NiO (octahedral) is commonly known as the rock salt structure, and is often non-stochiometric. The stoichiometric NiO is green and the non- stoichiometric NiO is black. There are various techniques for the growth of these films such as molecular beam epitaxy [21, 22], chemical vapor deposition (CVD), thermal evaporation [23, 24], spray pyrolysis [25, 26], sol gel [27, 28], pulsed laser deposition [29, 30], RF reactive sputtering [31, 32], induced self- assembly [33, 34], DC sputtering [35, 36]. However, DC sputtering has become an attractive method for nanomaterials. In this way, the increasing of substrate temperatures was not used, which is very important with flexible Polyethylene terephthalate (PET) substrate to prevent it from damages.
   Until now, we did not find any studies for the Bi2O3 and NiO thin films prepared by DC sputtering method and deposited on different substrate like glass and PET. The optical properties of these thin films were investigated using spectrophotometry and spectroscopic ellipsometry methods with a comparison between them. The aim of the present work is to synthesis and studies the optical constants of Bi2O3 and NiO ultrathin films deposited on different substrates at room temperature by a DC sputtering method. The optical properties of the deposited films were determined using spectrophotometry (UV) and spectroscopic ellipsometry (SE) in the spectral range 200 - 2200 nm. The objective of the present work paper is to investigate the optical properties of Bi2O3 and NiO thin films that are candidate for future of transparent conducting oxide (TCOs). The DC sputtering technique was used to prepare the films in the same deposition conditions at 300 K. The optical constants were calculated with a new amorp

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