Structural, optical and phonon properties of hafnium oxynitride thin films synthesized using plasma-enhanced atomic layer deposition

• Published in: Journal of alloys and compounds 2024-05, Vol.983, p.173925, Article 173925
• Main Authors: Pratik, Ayush, Patterson, Robert, Conibeer, Gavin, Shrestha, Santosh
• Format: Article
• Language: English
• Subjects: Absorption coefficient; Acoustic impedance; Atomic layer deposition; Hafnium oxynitride; Hot carrier solar cells; Phonon bottleneck effect
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2024.173925

Hafnium Oxynitride belongs to the group IVB compounds with high permittivity and large acoustic impedance. In this work, hafnium oxynitride films have been synthesized using plasma-enhanced atomic layer deposition on Si and Quartz substrates. XRD results show the presence of mixed cubic and monoclinic phases with an optimum crystallization occurring at 850 °C. The thin films show strong absorption in the UV–visible spectrum suggesting semiconductor behaviour. The optical properties of the spectrophotometer and spectroscopic ellipsometry agree with the XRD observations. We also report the first observation of experimentally derived photoluminescence (PL) from hafnium oxynitride thin films synthesized using plasma-enhanced atomic layer deposition. The PL spectrum is consistent with the XRD results with two absorption peaks around 576 nm and 705 nm, corresponding to cubic and monoclinic phases, respectively. Also, the PL results match very well with the theoretical value of the band gap of cubic and monoclinic phases of Hf2ON2. The Raman spectrum shows a phonon band gap around 242–263 cm−1, consistent with the theoretically reported value for cubic Hf2ON2. [Display omitted] •The as-deposited films of hafnium oxynitride were partially annealed because of N2 plasma exposure for 15 s.•XRD and Photoluminescence spectra suggested the presence of mixed phases: cubic and monoclinic.•The electronic and phononic band gap matched very closely with the theoretical band gaps of cubic and monoclinic Hf2ON2.•XPS data suggested the chemical states of Hf, N, O to be of Hf-N-O bonds in the core and Hf-O-N bonds in the surface of the thin films.•The absorption coefficient calculated using the spectrophotometry data overlapped with that calculated from extinction coefficients.