Titanium nitride (TiN) thin films have been the subject of intense research due to their exceptional combination of physical, chemical and mechanical properties. As the device dimension is getting smaller and nanofabrication technology is developing rapidly; the study of ultra-low thickness thin films attracting the researcher’s attention. The objective of this study was to investigate the effect of thickness on the bandgap of Oxygen (O~2~) doped TiN thin films. To accomplish the objective high-quality two-dimensional (O~2~) doped TiN films have been prepared on single crystal sapphire substrates using a pulsed laser deposition method. The thickness of TiN films was varied from 2 to 10 nm by varying the number of laser pulses, while other deposition parameters were kept constant. All the TiN films were deposited under 15 mTorr oxygen pressure. Structural properties were studied by using high-resolution X-ray diffraction (XRD). XRD patterns have shown that each film grows in (111) direction on the sapphire substrate, which is located at 2 theta \~ 36 degrees. The intensity of the XRD (111) peak has also shown that the orientational alignment of the TiN films with substrate orientation becomes better with the increase in O~2~ doped TiN film thickness. The x-ray rocking curve was used to measure the full width half maxima (FWHM) for each film. FWHM values varied from 0.07 to 0.2 degrees as the film thickness decreases, which indicates that grain size decreases with decreasing film thickness. Scanning electron microscopy (SEM) have also been used to observe the surface morphology of each film. SEM images indicate that all TiN films surface are smooth. Ultraviolet visible spectroscopy measurements in the wavelength range (200-800 nm) reveal that the bandgap of O~2~-doped TiN films increases as the film thickness decreases. The decrease in film thickness leads to a blue shift of the absorption spectra in the UV-A region (310-400 nm). This blueshift is accompanied by an increase in the bandgap of O~2~ doped TiN from 3.2 to 3.8 eV. The change in bandgap by changing the film thickness can be explained using a size effect in the two-dimensional material system. Since wide bandgap semiconductor is promising materials for optoelectronic and microelectronic devices, especially UV detectors or sensors. Recently UV detectors have received a wide attraction due to their remarkable applications in the military and civilian arena. So, bandgap engineering of O~2~ doped TiN thin films by changing film thickness can open wide application potential in the UV detector industry. 


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

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Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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