Blue Shift in Ultraviolet Absorption Spectra of Oxygen Doped Titanium Nitride Thin Films

Abstract

The objective of this study is to investigate the effect of film thickness on the bandgap of oxygen (O2)-doped titanium nitride (TiN) thin films. To accomplish this, high-quality two-dimensional O2-doped TiN films have been prepared on single-crystal sapphire substrates using a pulsed laser deposition method. The film thicknesses were varied from 3 to 100 nm by varying the number of laser pulses, while other deposition parameters are kept constant. X-ray diffraction (XRD) patterns have shown that the films grow in (111) orientation on the sapphire substrate. The increase in the intensity of the XRD (111) peak also demonstrates a better orientational alignment of the TiN films with substrate as the film thickness increases. The x-ray rocking curve has been used to measure the full width half maxima (FWHM) for each film. The FWHM values has been found to vary from 0.07 to 0.2° as the film thickness decreases. This is taken to indicate that the grain size decreases with a decrease in film thickness. Ultraviolet visible spectroscopy measurements in the wavelength range (200–800 nm) have been performed as well, which indicates an increase in the bandgap of O2-doped TiN films with a decrease in film thickness. The decrease in the film thickness leads to a blue shift of the peak in the ultraviolet-visible absorption (UV-A) region; this blueshift is accompanied by an increase in the bandgap of O2-doped TiN from 3.2 to 3.8 eV. The change in the bandgap due to a change in film thickness has been explained using the quantum confinement effect.

Modulation of Structural, Electronic, and Optical Properties of Titanium Nitride Thin Films by Regulated In Situ Oxidation

“…The XPS data on our samples have indicated the presence of TiO 2 , TiNO, and TiN. false( α h υ false) 1 / 2 ∝ ( h υ − E g ) where h is Planck’s constant, υ is the photon’s frequency, α is the absorption coefficient, and E g is the bandgap. By plotting (α h υ) 1/2 against photon energy ( h υ) and through extrapolating the linear part of the (α h υ) 1/2 curve to zero, the optical bandgaps of TiN films were obtained according to the Tauc plot. , A representative plot of (α h υ) 1/2 vs h υ is displayed in the Figure inset for the sample made using 750 laser pulses.…”

“…The terminal compounds (TiN with x = 0 and TiO with x = 1) as well as all the intermediate compounds with x between 0 and 1 have a rock-salt structure (Figure ), but they possess wide-ranging physicochemical properties . One of the terminal compounds of the family, TiN ( x = 0), has been known for its well-established properties for decades. − A controlled variation of oxygen in TiNO can be used in the fabrication of multijunction solar cells, electrocatalysts, photoelectrocatalysts, − photodetectors, , and plasmonic , and metamaterial devices. − Our success in producing semiconducting TiNO with room-temperature conductivity (∼158–6493 Ω –1 cm –1 ) significantly higher than that of carbon (∼1 Ω –1 cm –1 ) may open up the door for the development of carbon-free support materials as an electrocatalyst/photoelectrocatalyst in water-splitting research.…”