Writing and Reading of Ultrathin Ferroelectric Domains on Commensurate SrTiO$_{3}$ on Silicon*

Ferroelectricity in ultrathin epitaxial SrTiO$_{3}$ grown commensurately by oxide-molecular beam epitaxy (MBE) on silicon substrates was investigated using piezoforce microscopy (PFM). A series of samples containing $n$ molecular layers (ML) of SrTiO$_{3}$ ($n$ = 3, 4, 5, 6, 8, 10, 20) was grown on silicon substrates. Room-temperature ferroelectricity was observed for samples containing $n$ = 5, 6, 8, 10 ML. Temperature-dependent measurements indicate that the sample with $n$ = 5 exhibits a ferroelectric phase transition at T$_{c}\sim $317 K. Sample with $n$ = 6 remains ferroelectric up to at least 393K. Polar domains created on the $n$ = 6 was found to be stable at room temperature for more than 72 hours. The implications of these results for fundamental and device-related applications will be discussed briefly.