Morphological and optical properties of low temperature processed SnO₂ :F

Abstract

Thin films of transparent conducting fluorine doped tin oxide (SnO2:F) on soda lime glass and stainless steel substrates are prepared by spray pyrolysis at low temperature ≤250 °C. Optical properties in the form of complex dielectric function (ϵ = ϵ1 + iϵ2) spectra are obtained using spectroscopic ellipsometry from 0.035 to 5.89 eV for SnO2:F on glass and from 0.75 to 5.89 eV for SnO2:F on stainless steel. The absorption coefficient (α) spectra are extracted from spectra in ϵ for the film on soda lime glass from 0.035 to 5.89 eV and on stainless steel from 0.75 to 5.89 eV. Direct band gaps for SnO2:F thin films on soda lime glass and stainless steel substrates are determined to be 3.45 ± 0.01 and 3.60 ± 0.01 eV, respectively. Infrared extended measurement shows an absorption feature at 0.063 eV (508 cm−1) which may be attributed to Sn–O and Sn–F bonding. A broad background phonon absorption feature due to Sn–OH and O–H bonding is also identified at 0.3 eV (2420 cm−1). Resistivity is deduced from ϵ. Improved agreement between optically and electrically determined resistivity is obtained when the infrared range spectrum is analyzed. The morphologies of both the films are studied by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM).

Understanding near infrared absorption in tin doped indium oxide thin films

“…It is noted that the Tauc-gap does not truly represent the actual direct band gap of ITO film here, but should be realistically be considered as an absorption onset. The true band gap is calculated from the Tauc-plot as described elsewhere [53][54][55]. The direct band gap of ITO on soda lime glass and c-Si substrates are determined to be 3.43 ± 0.01 and 3.61 ± 0.01 eV, respectively, and agreed well with reported values near 3.5 eV [7,56].…”

“…Significantly lower 4-point probe ρ compared to opticallyextracted ρ for the film on native oxide coated c-Si, may be due to the fact that the semiconducting c-Si substrate separated by only a 2 nm thick native oxide could contribute somewhat as an additional conducting pathway in the 4-point probe technique. As has been shown previously [21,54,63,64], inclusion of THz range spectra is necessary to achieve good agreement with direct electrical measurements. The values of τ resulting from full range SE analysis for ITO on glass and c-Si substrates presented in table 3 are comparable to the reported value of τ = 6.6 fs for sputtered ITO [7].…”

Optical and electrical properties of H2 plasma-treated ZnO films prepared by atomic layer deposition using supercycles

“…These results corroborate previous findings demonstrating the importance of collecting low photon energy ellipsometric spectra (i.e. into the THz range) in order to achieve good agreement with direct electrical measurements [52,64,65]. The values of optical μ determined here from SE range from 29.5 to 41.5 cm 2 /Vs.…”

Anti-reductive properties of AZO/FTO bilayered transparent conducting films

“…Another issue which mattered is that TCO is inert to hydrogen-rich plasmas because of the a-Si:H layers deposited onto it [5,6]. Light scattering is normally achieved by a textured surface which can be obtained either by chemical etching or direct growth [7][8][9][10]. Direct growth is highly efficient to form a high haze surface and to make the grains present pyramidal or mountain-like morphology at the film surface by controlling the growth process.…”