Dataset: Growth of Ta₂SnO₆ Films, a Candidate Wide-Band-Gap p-Type Oxide

Matthew Barone¹, Michael Foody², Yaoqiao Hu³, Jiaxin Sun¹, Bailey Frye^4,5, S. Sameera Perera⁶, Biwas Subedi^4,5, Hanjong Paik¹, Jonathan Hollin⁷, Myoungho Jeong⁸, Kiyoung Lee⁸, Charles H. Winter⁷, Nikolas J. Podraza^4,5, Kyeongjae Cho³, Adam Hock², and Darrell G. Schlom^1,9,10

1. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
2.Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
3.Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States
4. Department of Physics and Astronomy, The University of Toledo, Toledo, Ohio 43606, United States
5. Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606, United States
6.Lumigen Instrument Center, Department of Chemistry, Wayne State University, Detroit, Michigan, 48202, United States
7.Department of Chemistry, Wayne State University, Detroit, Michigan 48202,United States
8.Nano Electronics Laboratory, Samsung Advanced Institute of Technology (SAIT), Samsung Electronics, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16678, South Korea
9.Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, United States
10.Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany

In an effort to discover a high-mobility p-type oxide, recent computational studies have focused on Sn²⁺-based ternary oxides. Ta₂SnO₆ has been suggested as a potentially useful p-type material based on the prediction of simultaneously high hole mobility and a wide range of synthesis conditions over which it is the energetically favored phase. In this study, we synthesized this material epitaxially for the first time and evaluated its properties experimentally. We measured the band gap to be 2.4 eV and attempted to substitutionally dope titanium for tantalum (Ti_Ta^’) and potassium for tin (K_Sn^’) but found that both doped and undoped films were insulating. Amorphous Ta₂SnO₆ films were also grown via thermal atomic layer deposition (ALD) at 175 °C. Electrical characterization of the ALD-fabricated amorphous films found them to be insulating with an optical band gap of 2.24 eV. Density functional theory calculations indicate that, under MBE growth conditions, oxygen vacancies have a negative energy of formation in crystalline Ta₂SnO₆ when the Fermi energy lies near the valence band edge. These oxygen vacancies would lead to compensation of holes generated by Ti_Ta^’ or K_Sn^’ dopants, which is consistent with our observations. We conclude that the direct growth of epitaxial p-type Ta₂SnO₆ films using MBE-accessible growth conditions is thwarted by the spontaneous formation of oxygen vacancies. While our growth conditions do not yield p-type films, we calculate that there are conditions under which Ta₂SnO₆ is the thermodynamically stable phase and spontaneous formation of compensating defects does not occur, motivating further studies with different synthesis techniques.