Electronic transport in CrN and related alloys

Authors
McGahay, Mary
ORCID
Loading...
Thumbnail Image
Other Contributors
Gall, Daniel
Dutta, Partha S.
Shi, Jian
Ullal, Chaitanya
Issue Date
2020-12
Keywords
Materials engineering
Degree
PhD
Terms of Use
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
Full Citation
Abstract
Further exploration of the effects of O in bulk CrN was achieved through substitutional replacement of N with O in epitaxial CrN(001) layers by growing samples in a mixed N2 and Ar+O2 atmosphere. O incorporation facilitates Cr vacancies, yielding a rocksalt-structure solid solution Cr1 x/2N1 xOx with a single compositional parameter x and a measured lattice constant that decreases from a = 0.4175 to 0.4116 nm for x = 0 to 0.59. First-principles calculations predict da/dx = +0.0200, -0.0018, and -0.0087 nm for CrN1-xOx, Cr1-x/3N1-xOx, and Cr1-x/2N1-xOx, respectively. Thus, they confirm, in combination with ion beam compositional analyses and x-ray diffraction results, a vacancy concentration of x/2 per cation site. The room temperature resistivity decreases by over two orders of magnitudes from ρ = 1.5×10-3 to 7.7×10-6 Ω m for x = 0-0.26. This is accompanied by a transition from a negative to a positive temperature coefficient of resistivity, an increase in the Hall mobility from μH = 0.37 to 2.4 cm2/Vs, and an increase in the carrier concentration n = 1.1×1020 to 4.9×1021 cm-3. However, ρ increases again to 6.9×10-5 Ω m for x = 0.34 and to > 10 Ω m for x ≥ 0.59 with a corresponding drop in μH. These results indicate insulator-to-metal and subsequent metal-to-insulator transitions at x = 0.04 ± 0.03 and 0.30 ± 0.03, respectively. The transition to metallic conduction and the measured n for x = 0.01-0.26 are due to substitutional O on anion sites acting as donors and cation vacancies as compensating acceptors. The insulating properties at large x are attributed to increased electron correlation effects.
Description
December 2020
School of Engineering
Department
Dept. of Materials Science and Engineering
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Relationships
Rensselaer Theses and Dissertations Online Collection
Access
Restricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.