Superconductivity Behavior in Epitaxial $\mathrm{Ti}\mathrm{N}$ Films Points to Surface Magnetic Disorder

Superconductivity Behavior in Epitaxial $Ti N$ Films Points to Surface Magnetic Disorder

N.A. Saveskul, N.A. Titova, E.M. Baeva, A.V. Semenov, A.V. Lubenchenko, S. Saha, H. Reddy, S.I. Bogdanov, E.E. Marinero, V.M. Shalaev, A. Boltasseva, V.S. Khrapai, A.I. Kardakova, and G.N. Goltsman

Phys. Rev. Applied 12, 054001 – Published 1 November 2019

Abstract

We analyze the evolution of the normal and superconducting properties of epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of the residual resistivity, that becomes dominated by diffusive surface scattering for $d \leq 20 nm$ . At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk $Ti N$ value. In such high-quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of approximately $10^{12} {cm}^{- 2}$ . Our results suggest that surface magnetic disorder is generally present in oxidized $Ti N$ films.

Received 14 March 2019
Revised 15 July 2019

DOI:https://doi.org/10.1103/PhysRevApplied.12.054001

Physics Subject Headings (PhySH)

Impurities in superconductors Magnetism Point defects Superconductivity Surface & interfacial phenomena

Nitrides Ultrathin films

Resistivity measurements

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

N.A. Saveskul¹, N.A. Titova¹, E.M. Baeva^1,2, A.V. Semenov¹, A.V. Lubenchenko³, S. Saha^4,5, H. Reddy^4,5, S.I. Bogdanov^4,5, E.E. Marinero^4,6, V.M. Shalaev^4,5, A. Boltasseva^4,5, V.S. Khrapai^1,2,7, A.I. Kardakova ^1,2,*, and G.N. Goltsman^1,2

¹Moscow State University of Education, 29 Malaya Pirogovskaya Street, Moscow 119435, Russia
²National Research University Higher School of Economics, 20 Myasnitskaya Street, Moscow 101000, Russia
³National Research University MPEI, Krasnokazarmennaya Street, 14, Moscow 111250, Russia
⁴School of Electrical & Computer Engineering and Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907-2057, USA
⁵Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, USA
⁶School of Materials Engineering, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907-2057, USA
⁷Institute of Solid State Physics, 2 Ak. Osipyana Street, Chernogolovka 142432, Russia