Quantum magnetoconductivity characterization of interface disorder in indium-tin-oxide films on fused silica

• Published in: Communications materials 2021-03, Vol.2 (1), p.1-7, Article 33
• Main Authors: Look, David C., Leedy, Kevin D., Santia, Marco D., Badescu, Stefan C.
• Format: Article
• Language: English
• Subjects: 639/301/119/1000; 639/301/930/12; 639/766/483/3924; Chemistry and Materials Science; Conductivity; Figure of merit; Film thickness; Fused silica; Indium oxides; Indium tin oxides; Interference; Low temperature; Magnetic fields; Magnetic properties; Material properties; Materials Science; Oxide coatings; Pulsed laser deposition; Pulsed lasers; Silicon dioxide; Substrates; Thin films; Tin; Upper bounds
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-021-00137-y

Disorder arising from random locations of charged donors and acceptors introduces localization and diffusive motion that can lead to constructive electron interference and positive magnetoconductivity. At very low temperatures, 3D theory predicts that the magnetoconductivity is independent of temperature or material properties, as verified for many combinations of thin-films and substrates. Here, we find that this prediction is apparently violated if the film thickness d is less than about 300 nm. To investigate the origin of this apparent violation, the magnetoconductivity was measured at temperatures T  = 15 – 150 K in ten, Sn-doped In 2 O 3 films with d  = 13 – 292 nm, grown by pulsed laser deposition on fused silica. We observe a very strong thickness dependence which we explain by introducing a theory that postulates a second source of disorder, namely, non-uniform interface-induced defects whose number decreases exponentially with the interface distance. This theory obeys the 3D limit for the thickest samples and yields a natural figure of merit for interface disorder. It can be applied to any degenerate semiconductor film on any semi-insulating substrate. Disorder in semiconductors may lead to quantum interference and positive magnetoconductivity, whose maximum value in 3D is independent of material properties. Here, an apparent violation of this upper bound, in Sn-doped In 2 O 3 films on fused silica, is explained by a model that accounts for additional disorder close to the interface.