Paramagnetic point defects in $(100)Si∕LaAlO3$ structures: Nature and stability of the interface

The atomic nature of the interface in $(100)Si∕LaAlO3$ structures with nanometer-thin amorphous $LaAlO3$ layers of high dielectric constant $(κ)$⁠, deposited directly on clean (100)Si by molecular beam deposition at $∼100°C$⁠, was assessed through probing of paramagnetic point defects. On the as-grown samples $K$-band electron spin resonance indicated the absence of a $Si∕SiO2$-type interface in terms of the archetypal Si-dangling bond-type $Si∕SiO2$ interface defects (⁠$Pb0$⁠, $Pb1$⁠). With no $Pb$-type defects observed, this state is found to persist during subsequent annealing (⁠$1atm$ $N2$ or 5% $O2$ in $N2$ ambient) up to the temperature $Tan∼800°C$⁠, referring to a thermally stable abrupt $Si∕LaAlO3$ interface, quite in contrast with other high-$κ$ metal oxide∕Si structures. However, in the range $Tan∼800–860°C$ a $Si∕SiO2$-type interface starts forming as evidenced by the appearance of $Pb0$ defects and, with some delay in $Tan$⁠, the $EX$ center—a $SiO2$ associated defect, attesting to significant structural∕compositional modification. The peaking of the defect density versus $Tan$ curves indicates the $SiOx$ nature of the interlayer to break up again upon annealing at $Tan⩾930°C$⁠, possibly related to crystallization and∕or degrading silicate formation. No specific $LaAlO3$-specific point defects could be traced.