Publications

(Embargo/in-progress) Characterization of the Chemical and Electrical Properties of defects at the Niobium-Silicon Interface.

Published in , 2020

The concentration of electrically active defects at Nb-Si interfaces can be minimized by optimizing the Si surface preperation, using an HF etch and an Ar ion mill. The dominant electrically-active defect is a Nb atom on a Si site.

Recommended citation: (Manuscript in progress) Low microwave loss in deposited Si and Ge thin-film dielectrics at near single-photon power and low temperatures. C. Kopas, J. Gonzales, S. Zhang, D. Queen, B. Wagner, N. Newman

(Manuscript in-progress) Ge dielectric resonators with tantalum diffusion-barriers for use in Nb-based superconductor technology.

Published in , 2020

Tantalum interdiffusion barrier layers are used to decrease intermixing and microwave loss in Nb-Ge superconducting microwave resonators.

Recommended citation: (Manuscript in progress) Tantalum Ge thin-films with tantalum diffusion-barriers for use in Nb-based superconductor technology. C. Kopas, S. Zhang, J. Gonzales, D. Queen, B. Wagner, R. Carpenter, N. Newman

(In review) Integrated High-Temperature YBa2Cu3O7-δ Superconductor-High-Performance Microwave Dielectric Thin Film Structures.

Published in , 2020

tri-layer Superconductor/dielectric/superconductor structures of high-Tc superconductor YBCO and low-loss high-performance microwave dielectrics BZT and BCT were fabricarted by introducing a SrTiO3 barrier layer between the YBCO and dielectric layers.

Recommended citation: (In Review) Integrated High-Temperature YBa 2 Cu 3 O7-δ Superconductor-High-Performance Microwave Dielectric Thin Film Structures. C. Kopas, J. Park, P. Balaji, K. Zhang, S. Gajare, N. Newman </p> </article> </div>

Low-temperature synthesis of 2D anisotropic MoTe2 using a high-pressure soft sputtering technique

Published in Nanoscale Advances, 2020

This paper documents a soft-sputtering technique for deposition of 2-D MoTe2 films.

Recommended citation: Low-temperature synthesis of 2D anisotropic MoTe2 using a high-pressure soft sputtering technique. Kentaro Yumigeta+, Cameron Kopas+, Mark Blei, Debarati Hajra, Yuxia Shen, Dipesh Trivedi, Pranvera Kolari, Nathan Newman, Sefaattin Tongay. Nanoscale Advances (2020) DOI: 10.1039/D0NA00066C https://pubs.rsc.org/en/content/articlehtml/2020/na/d0na00066c

The influence of substrate temperature on the properties of pyrite thin films deposited using a sequential coevaporation technique

Published in Thin Solid Films, 2019

This paper documents a new sequential co-evaporation method for fabrication of FeS2 (iron pyrite) thin films, and the substrate temperature dependence on the film properties.

Recommended citation: The influence of substrate temperature on the properties of pyrite thin films deposited using a sequential coevaporation technique. A. Walimbe, A. Wertheim, A. Ravi, C. Kopas, et. al. Thin Solid Films 669, pp 49-5 (2019). DOI: 10.1016/j.tsf.2018.10.022 https://www.sciencedirect.com/science/article/pii/S0040609018306916

Magnetic properties of chromium-doped Ni80Fe20 thin films

Published in Journal of Magnetism and Magnetic Materials, 2018

This paper is about the magnetic properties of Cr-doped NiFe (permalloy) films.

Recommended citation: Magnetic properties of chromium-doped Ni80Fe20 thin films. Alex Devonport, Alena Vishina, RK Singh, Matthew Edwards, Kaiwen Zheng, John Domenico, ND Rizzo, Cameron Kopas, Mark van Schilfgaarde, Nathan Newman. Journal of Magnetism and Magnetic Materials 460 pp. 193-202 (2018). DOI: 10.1016/j.jmmm.2018.03.054 https://www.sciencedirect.com/science/article/pii/S0304885317335382

In-situ electron paramagnetic resonance studies of paramagnetic point defects in superconducting microwave resonators

Published in Applied Physics Letters, 2016

We developed an in-situ technique to measure paramagnetic loss in dielectric resonator structures.

Recommended citation: In-situ electron paramagnetic resonance studies of paramagnetic point defects in superconducting microwave resonators. S Zhang, C Kopas, B Wagner, D Queen, N Newman. Applied Physics Letters 109 (12), 122602 (2016). DOI: 10.1063/1.4962953 https://aip.scitation.org/doi/abs/10.1063/1.4962953

Growth and characterization of Ba(Cd1/3Ta2/3)O3 thin films

Published in Journal of Crystal Growth, 2014

This paper establishes growth conditions for high-quality Ba(Co,Zn)1/3Nb2/3O3 thin films using pulsed laser deposition (PLD).

Recommended citation: Growth and characterization of epitaxial Ba(Co, Zn)1/3 Nb2/3O3 thin films. Y Li, C Kopas, M Huang, K Bunish, N Newman. Journal of Crystal Growth 387, 81-85 (2014) DOI: 10.1016/j.jcrysgro.2013.10.047 https://www.sciencedirect.com/science/article/pii/S002202481300729X

Effect of Helium Ion Irradiation on the Tunneling Behavior in Niobium/Aluminum–Aluminum Oxide/Niobium Josephson Junctions

Published in IEEE Transactions on Applied Superconductivity, 2013

This paper measures the effects of helium-ion irradation on Nb/Al-AlOx/Nb Josephson Junctions.

Recommended citation: Effect of Helium Ion Irradiation on the Tunneling Behavior in Niobium/Aluminum–Aluminum Oxide/Niobium Josephson Junctions. Tiantian Zhang, Cameron Kopas, Lei Yu, Ray W Carpenter, Makram A Qader, Mengchu Huang, Rakesh K Singh, John Mardinly, Robin Cantor, John M Rowell, Nathan Newman IEEE Transactions on Applied Superconductivity 23 (4), 1101610-1101610 (2014) DOI: 10.1109/TASC.2013.2256358. https://ieeexplore.ieee.org/document/6522170

Experimental study of the kinetically-limited decomposition of ZnGeAs2 and its role in determining optimal conditions for thin film growth

Published in Journal of Crystal Growth, 2012

Recommended citation: Experimental study of the kinetically-limited decomposition of ZnGeAs2 and its role in determining optimal conditions for thin film growth. M Vahidi, ZZ Tang, J Tucker, TJ Peshek, L Zhang, C Kopas, RK Singh, M Van Schilfgaarde, N Newman. Journal of Crystal Growth 338 (1), 267-271 (2012) DOI: 10.1016/j.jcrysgro.2011.11.004 https://www.sciencedirect.com/science/article/pii/S0022024811009171