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.
ASJC Scopus subject areas