BaTiO₃ Integration with Nanostructured Epitaxial (100), (110), and (111) Germanium for Multifunctional Devices

Abstract

Ferroelectric-germanium heterostructures have a strong potential for multifunctional devices. Germanium (Ge) is attractive due to its higher electron and hole mobilities while ferroelectric BaTiO3 is promising due to its high relative permittivity, which can make next-generation low-voltage and low-leakage metal-oxide semiconductor field-effect transistors. Here, we investigate the growth, structural, chemical, and band alignment properties of pulsed laser deposited BaTiO3 on epitaxial (100)Ge, (110)Ge, and (111)Ge layers. Cross-sectional transmission electron microscopy micrographs show the amorphous nature of the BaTiO3 layer and also show a sharp heterointerface between BaTiO3 and Ge. The appearance of strong Pendellösung oscillation fringes from high-resolution X-ray diffraction implies the presence of parallel and sharp heterointerfaces. The valence band offset relation of ΔEV(100) ≥ ΔEV(111) > ΔEV(110) and the conduction band offset relation of ΔE(C)(110) > ΔE(C)(111) ≥ ΔE(C)(100) on crystallographically oriented Ge offer significant advancement for designing new-generation ferroelectric-germanium-based multifunctional devices.

New modalities of strain-control of ferroelectric thin films

“…Building off of this success, researchers experimentally replicated straininduced ferroelectricity in SrTiO 3 [26,[110][111][112] demonstrating the efficacy of this approach in imposing epitaxial strain on ferroelectrics intergraded on silicon [462,463]. Recently, there has been a renewed focus on such systems with demonstrations of ferroelectricity in BaTiO 3 films grown on p-and n-type SrTiO 3 buffer layers and directly on Ge (100), (110), and (111) [464][465][466]. Thus far researchers have produced SrTiO 3 [467,468], BaTiO 3 [469], PbZr 1−x Ti x O 3 [470][471][472][473], BiFeO 3 [474][475][476], and others using these techniques.…”

Ab initio study of the BaTiO3/Ge interface

“…Researchers have reported studies of heterostructures involving BaTiO 3 and Ge [14,24,41] including BaTiO 3 thin films directly grown on Ge [25]. However, a study of the direct epitaxial BTO/Ge interface has only recently been published [1].…”

Functionalization of the Si(1 1 1) 7 × 7 substrate with coronene molecules using simple molecular source

“…For this reason, different semiconductor systems are being intensively investigated to solve specific problems, e.g. formation of the metallic contacts [3,4], monoatomic passivation layers [5][6][7][8] or thin insulating layers [9,10]. On the other hand, local surface defects or adsorbed molecules are considered for the controlled nanostructures growth [11][12][13].…”