Abstract
We report Cr doping-induced structural phase transformation (PT) in sputter-deposited polycrystalline-AlN thin film from wurtzite (w) to rocksalt (r) structure. Rietveld analysis shows that the steady substitution of Al ions by Cr ions in the w-AlN lattice distorts and compresses the wurtzite lattice along the c-axis. The chemical pressure exerted in the w-AlN lattice by the compression from the doped Cr ions causes the PT, similar to the high-pressure-induced PT in AlN. Post the PT, the r-Al1-xCrxN thin film continues to exhibit compressive residual stress, indicating that such sustained stress may also play a role in stabilizing the metastable r-Al1-xCrxN phase. The structural distortion and the PT also affected the optical absorption characteristics of the w-Al1-xCrxN thin films. The w-Al1-xCrxN exhibit a direct inter-band transition and the band gap (Eg) decreases from ∼ 6.06 eV for pure w-AlN to ∼ 4.15 eV for w-Al0.73Cr0.27N. After the PT, the r-Al0.61Cr0.39N thin film, on the other hand, exhibits an indirect inter-band transition with an Eg of ∼ 1.84 eV. In addition to the change in Eg, a prominent defect band appears at ∼ 4 eV at low Cr% and another band appears at ∼ 0.98 eV at higher Cr%.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
