Analysis of the (100)Si/LaAlO3 structure by electron spin resonance: nature of the interface

Abstract

Electron spin resonance of paramagnetic point defects was used to probe (100)Si/LaAlO3 structures with nm-thick amorphous high-dielectric constant (κ) LaAlO3 layers deposited directly on clean (100)Si by molecular beam deposition at ∼100 °C. Unlike common high-κ metal oxide/Si entities, no Pb-type interface defects could be observed in the as-grown state, revealing the absence of an Si/SiO2-type interface in terms of these archetypal Si-dangling bond-type Si/SiO2 interface defects (Pb0, Pb1). This state is found to persist during subsequent thermal treatment (5% O2/N2 mixture) up to T an ∼ 800 °C, indicating a thermally stable abrupt Si/LaAlO3 interface. However, in the range T an ∼ 800–860 °C, a Si/SiO2-type interface starts forming as evidenced by the appearance of Pb0 defects and, with some retardation in terms of T an, the EX center—an SiO2 associated defect, attesting to significant structural/compositional adaptation. Monitoring the defect density versus T an indicates the SiO x nature of the interlayer to disintegrate again upon heating at T an ≥ 930 °C, possibly related to intensifying crystallization and silicate formation. Despite intensive search, no LaAlO3-specific point defects could be revealed.