Features of Formation of Cr3+ Paramagnetic Centers in Strontium Titanate (SrTiO3) Implanted with Chromium Ions

• Published in: Surface investigation, x-ray, synchrotron and neutron techniques Vol. 14; no. 3; pp. 551 - 554
• Main Authors: Sukhanov, A. A., Yanilkin, I. V., Valeev, V. F., Nuzhdin, V. I., Khaibullin, R. I., Tagirov, L. R., Voronkova, V. K.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2020; Springer Nature B.V
• Subjects: Chemistry and Materials Science; Chromium; Chromium plating; Color centers; Crystal structure; Heat treatment; High temperature; Impurities; Ion implantation; Magnetic resonance; Materials Science; Room temperature; Single crystals; Strontium; Strontium titanates; Substrates; Surfaces and Interfaces; Thin Films; Trivalent chromium; Valence; strontium titanate; electron paramagnetic resonance; ion implantation; thermal annealing; XPS; chromium ion; oxygen vacancies
• ISSN: 1027-4510; 1819-7094
• DOI: 10.1134/S1027451020030398

We present results of structural (XPS) and magnetic resonance (EPR) studies of single-crystal plates of strontium titanate (SrTiO 3 ) heavily doped with chromium utilizing ion implantation technique. It was shown that the temperature of the oxide matrix during ion implantation (300 or 900 K) significantly affects the valence state of the implanted chromium impurity (Cr 0 or Cr 3+ ) and the depth profiles of its distribution in the SrTiO 3 matrix. Using the EPR method, it was established that as a result of implantation of chromium impurity at an elevated substrate temperature during irradiation, the dominating color centers in the surface implanted oxide layer appear in the form of trivalent chromium ions in a cubic environment with a g-factor g = 1.976 and the value of the hyperfine coupling constant with the magnetic nucleus of 53 Cr isotope, A = 16.2 × 10 –4 cm –1 . From a comparison of these data with parameters for the cubic Cr 3+ impurity center in the SrTiO 3 single crystal, it was concluded that this center is localized in the structural positions of titanium. Upon implantation of a chromium impurity in SrTiO 3 at room temperature of the substrate, in addition to cubic Cr 3+ centers, new signals were detected in the EPR spectra, apparently associated with the formation of oxygen vacancies in the implanted oxide. However, the number of these additional centers does not change significantly even after high-temperature heat treatment of samples in air at temperatures up to 900 K. It is noted that signals of this type also appear in the spectra of SrTiO 3 samples obtained as a result of hot implantation and then subjected to high-temperature thermal annealing.