Roles of Point Defects in Thermally Enhanced Generation and Transfer of Electrons and Holes in LaAlO₃

Abstract

Thermal annealing was given to single crystal LaAlO3 and its effects were examined by measuring electron spin resonance (ESR) and optical absorption. When LaAlO3 was annealed at temperatures above 500 °C in an oxidizing atmosphere, the intensities of ESR signals due to transition metal, likely ascribable to Fe3+, decreased. Concurrently with this, two optical absorption bands at 2.7 and 3.5 eV, attributable to a combination of a hole and a La3+ (or Al3+) vacancy, increased. These results indicate that thermal electron–hole generation is induced by oxidizing annealing and that the generated electrons and holes are then captured by Fe3+ ions and La3+ or Al3+ vacancies, respectively. It is also assumed that captured electrons and holes are released and recombine with each other by reducing annealing.

Structural change induced in LaAlO3 by ion implantation

“…When Al 2 O 3 contains Cr, it is called ruby, and when Al 2 O 3 contains small amounts of Fe, it is sapphire. As indicated by these typical examples, Cr is generally present in materials containing aluminum, such as LaAlO 3 and YAlO 3 . We have confirmed the presence of Cr 3+ in single crystals LaAlO 3 and YAlO 3 by electron spin resonance .…”

“…As indicated by these typical examples, Cr is generally present in materials containing aluminum, such as LaAlO 3 and YAlO 3 [23]. We have confirmed the presence of Cr 3+ in single crystals LaAlO 3 and YAlO 3 by electron spin resonance [23,24]. It is known that LaAlO 3 is a perovskite crystal with a structure shown in Fig.…”