A Ferroelectric Oxide Made Directly on Silicon

Abstract

Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives to silicon dioxide are being pursued to enable new functionality and device architectures. We achieved ferroelectric functionality in intimate contact with silicon by growing coherently strained strontium titanate (SrTiO3) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. We observed ferroelectricity in these ultrathin SrTiO3 layers by means of piezoresponse force microscopy. Stable ferroelectric nanodomains created in SrTiO3 were observed at temperatures as high as 400 kelvin.

Materials science: Enter the oxides

“…This can be avoided only by carefully adjusting growth temperatures and supplying just the right amount of oxygen at precisely the right time. Still, progress has been made and the quality of oxide films on silicon has been improving steadily 11 . "Even advanced oxide films such as LaAlO 3 /SrTiO 3 heterostructures have now been grown on silicon, " says Mannhart.…”

Giant flexoelectric effect through interfacial strain relaxation

“…Recently, thin-film deposition techniques have been advanced, enabling the growth of epitaxial heterostructures with atomically controlled interfaces, such as multi-layers [23], superlattices [24,25] and ultrathin films [26,27]. Owing to advanced deposition techniques, studies using strain engineering have improved, and it has been shown experimentally and theoretically that such strain can even stabilize systems in novel non-bulk phases [28][29][30][31][32].…”

A strong electro-optically active lead-free ferroelectric integrated on silicon

“…T he presence of functional properties in many perovskite materials 1,2 has pushed the development of integrating such crystals directly on silicon (Si) to realize a variety of new devices 3 . Since the first methods to epitaxially deposit perovskite thin films on Si were established 4 , the growth process has been carefully optimized 5 and single crystalline layers were fabricated even on large-scale 8 00 substrates 6 .…”