Abstract

We present results of structural (XPS) and magnetic resonance (EPR) studies of single-crystal plates of strontium titanate (SrTiO₃) 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 (Cr⁰ or Cr³⁺) and the depth profiles of its distribution in the SrTiO₃ 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 ⁵³Cr isotope, A = 16.2 × 10^–4 cm^–1. From a comparison of these data with parameters for the cubic Cr³⁺ impurity center in the SrTiO₃ single crystal, it was concluded that this center is localized in the structural positions of titanium. Upon implantation of a chromium impurity in SrTiO₃ at room temperature of the substrate, in addition to cubic Cr³⁺ 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 SrTiO₃ samples obtained as a result of hot implantation and then subjected to high-temperature thermal annealing.

中文翻译：

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注入铬离子的钛酸锶（SrTiO 3）中Cr 3+顺磁性中心的形成特征

摘要

我们介绍了利用离子注入技术重掺杂铬的钛酸锶（SrTiO ₃）单晶板的结构（XPS）和磁共振（EPR）研究结果。结果表明，在离子注入过程中（300或900 K），氧化物基体的温度会显着影响注入的铬杂质（Cr ⁰或Cr ³⁺）的价态及其在SrTiO _3中分布的深度分布。矩阵。使用EPR方法可以确定，由于在辐照过程中在较高的衬底温度下注入了铬杂质，表面注入的氧化物层中的主要色心在立方环境中以三价铬离子的形式出现，且因子g = 1.976以及与⁵³ Cr同位素的磁核的超精细耦合常数，A = 16.2×10 ^–4 cm ^–1。通过将这些数据与SrTiO _3中立方Cr ³⁺杂质中心的参数进行比较单晶，可以得出结论，这个中心位于钛的结构位置。在衬底的室温下在SrTiO ₃中注入铬杂质后，除了立方Cr ³⁺中心外，在EPR光谱中还检测到新的信号，这显然与所注入的氧化物中氧空位的形成有关。但是，即使在高达900 K的空气中对样品进行高温热处理之后，这些附加中心的数量也不会显着变化。应注意，这种类型的信号也出现在以SrTiO _3形式获得的SrTiO ₃样品的光谱中。热注入的结果，然后进行高温热退火。