Electrical properties of SnO 2 :Sb ultrathin films prepared by colloidal deposition process
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nilson J. Chiquito NanoLab, Department of Physics, Federal University of São Carlos, São Carlos, São Paulo 13565-905, Brazil
Edson R. Leitea),b) LIEC, Department of Chemistry, Federal University of São Carlos, São Carlos, São Paulo 13565-905, Brazil (Received 28 September 2015; accepted 7 December 2015)
In the present work, we are investigating the electronic transport mechanism for antimony-doped tin oxide (ATO) ultrathin films produced by a colloidal deposition process (CDP) of nanocrystals synthesized via a solvothermal route in organic medium. The ATO ultrathin films were prepared from nanoparticles containing 9 mol% of Sb and the observed electrical resistivity at room temperature was 1.55, 1.10 101, and 1.83 103 X cm, respectively, for the 40, 45, and 71 nm films. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were carried out to investigate the films and electrical resistivity measurements taken in the four-probe mode with temperature ranging from 260 to 27 °C (13–300 K 6 0.1 K). Results show a good data fitting on Mott’s two-dimensional (2D) noninteracting variable range hopping for the 45 nm thin film, which is not further observed for the ATO ultrathin films obtained from CDP.
I. INTRODUCTION
Contributing Editor: Sanjay Mathur a) Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/. DOI: 10.1557/jmr.2015.387
the change in electrical conductivity of semiconductor oxides can be strongly affected by the controlled addition of impurities, Sb for the SnO2 system (ATO—antimonydoped tin oxide), for instance.9–23 Nowadays, indium tin oxide (ITO) is widely used in advanced optoelectronic devices and it is well known that its price is very high and ATO has been explored as a potential replacement for ITO, both classified as TCO materials. Luo et al. successfully demonstrated the use of ATO nanocrystals, which is synthesized in organic media, in the production of optoelectronic devices and its potential to replace commercially available ITO transparent electrodes in organic light-emitting diode (OLED) displays.24 TCOs are electricity conductors either due to the intrinsic defects or extrinsic dopants. The extrinsic dopant content ingeneral varies from 1020 to 1021 cm3 and the electrical resistivity is in the order of 104 X cm for TCOs suitable for applications. In addition, the charge carrier concentration (n) is limited by the dopant solubility and the electronic mobility is limited by scattering of the charge carriers in the lattice. Several electron scattering mechanisms could be operative in a TCO such as scattering by ionized impurities, neutral centers, thermal vibrations of the lattice, structural defects, and grain boundaries, depending on the carrier concentration and materials crystal quality.25 Several art
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