Characterization and in-situ monitoring of sub-stoichiometric adjustable superconducting critical temperature titanium nitride growth

Vissers, M. R., Gao, J., Kline, J. S., Sandberg, M., Weides, M. P. , Wisbey, D. S. and Pappas, D. P. (2013) Characterization and in-situ monitoring of sub-stoichiometric adjustable superconducting critical temperature titanium nitride growth. Thin Solid Films, 548, pp. 485-488. (doi:10.1016/j.tsf.2013.07.046)

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Abstract

The structural and electrical properties of Ti–N films deposited by reactive sputtering depend on their growth parameters, in particular the Ar:N2 gas ratio. We show that the nitrogen percentage changes the crystallographic phase of the film progressively from pure α-Ti, through an α-Ti phase with interstitial nitrogen, to stoichiometric Ti2N, and through a substoichiometric TiNx to stoichiometric TiN. These changes also affect the superconducting transition temperature, TC, allowing, the superconducting properties to be tailored for specific applications. After decreasing from a TC of 0.4 K for pure Ti down to below 50 mK at the Ti2N point, the TC then increases rapidly up to nearly 5 K over a narrow range of nitrogen incorporation. This very sharp increase of TC makes it difficult to control the properties of the film from wafer-to-wafer as well as across a given wafer to within acceptable margins for device fabrication. Here we show that the nitrogen composition and hence the superconductive properties are related to, and can be determined by, spectroscopic ellipsometry. Therefore, this technique may be used for process control and wafer screening prior to investing time in processing devices.

Item Type:Articles
Additional Information:We acknowledge support for this work from DARPA, the Keck Institute for Space Studies, the NIST Quantum Initiative, and NASA under Contract No. NNH11AR83I.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Weides, Professor Martin
Authors: Vissers, M. R., Gao, J., Kline, J. S., Sandberg, M., Weides, M. P., Wisbey, D. S., and Pappas, D. P.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:Thin Solid Films
Publisher:Elsevier
ISSN:0040-6090
ISSN (Online):1879-2731
Published Online:25 July 2013

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