Paper OX-TuP1
Electrical and Structural Properties of p-type Transparent Conducting La_2/3Sr_1/3VO₃ Thin Films Grown Using RF Sputtering Deposition

Tuesday, October 22, 2019, 6:30 pm, Room Union Station B

The development of efficient p-type transparent conducting oxides (TCOs) remains a global material challenge. Converting oxides from n-type to p-type via acceptor doping is extremely difficult and these materials exhibit low conductivity due to the localized nature of the O 2p -derived valence band, which leads to difficulty in introducing shallow acceptors and small hole effective masses. High-quality perovskite oxide (ABO₃) thin film p-n junctions have significant potential for electronic devices with multifunctional properties. The p-type perovskites currently in use are not sufficiently transparent in the visible region. Alloying Sr and La at the A-sites of perovskite SrVO₃, i.e. La_2/3Sr_1/3VO₃ (LSVO), can introduce holes at the top of the valence band (VB), resulting in p-type conductivity while maintaining reasonable transparency.

In this work, p-type LSVO thin films were grown on various substrates using RF magnetron co-sputtering deposition with SrVO₃ (actually Sr₂V₂O₇) and La₂O₃ targets between 400 and 500 °C with a mixed gas of H₂ (35%) and Ar. The generator powers were 60 and 30 W, respectively. Film thicknesses varied between 120 and 150 nm. The growth temperature and sputtering gas ambient were optimized and precisely controlled. The chamber pressure was set at . We used LSAT, LaAlO₃, TiO₂/Si, Si, SiO₂/Si as substrates. The structural and morphological properties of LSVO films were studied using grazing angle incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), spectroscopic ellipsometry, and X-ray photoemission spectroscopy (XPS). The electrical properties of all samples were measured using Keithley 4200. Hall effect measurements provided the Hall carrier concentration and Hall mobility as 3.0×10²⁰ cm^-3 and 5.15 cm²/(V·s), respectively. The resistivity was measured to be 4.1 mΩ·cm. In comparison, Hu et al. reported the resistivity, carrier concentration, and mobilities as 1.15 mΩ·cm, 1.69×10²¹ cm⁻³, and 3.2 cm²/(V·s), respectively for LSVO grown by using pulsed layer deposition [1]. GIXRD measurements showed 2Θ = 32.36˚, which arose from (112) plane of tetragonal crystal structure of LSVO films. We discuss the substrate dependence of the electrical and optical properties of LSVO thin films in detail. We plan to develop all perovskite La_2/3Sr_1/3VO₃/SrVO₃ p-n junctions.

[1] L. Hu et al., Adv. Elect. Mater. 4, 1700476 (2018).