Epitaxial ferroelectric oxides on silicon with perspectives for future device applications

Abstract

Functional oxides on silicon have been the subject of in-depth research for more than 20 years. Much of this research has been focused on the quality of the integration of materials due to their intrinsic thermodynamic incompatibility, which has hindered the flourishing of the field of research. Nevertheless, growth of epitaxial transition metal oxides on silicon with a sharp interface has been achieved by elaborated kinetically controlled sequential deposition while the crystalline quality of different functional oxides has been considerably improved. In this Research Update, we focus on three applications in which epitaxial ferroelectric oxides on silicon are at the forefront, and in each of these applications, other aspects of the integration of materials play an important role. These are the fields of piezoelectric microelectromechanical system devices, electro-optical components, and catalysis. The overview is supported by a brief analysis of the synthesis processes that enable epitaxial growth of oxides on silicon. This Research Update concludes with a theoretical description of the interfaces and the possibility of manipulating their electronic structure to achieve the desired coupling between (ferroelectric) oxides and semiconductors, which opens up a remarkable perspective for many advanced applications.

Epitaxial ferroelectric interfacial devices

“…3(b). 218,220 The growth of complex oxides on semiconducting substrates, particularly Si, has been intensively investigated, with the aim of integrating complex oxides in semiconductor platforms to realize multifunctional electronic and electro-optic devices 167,[251][252][253][254][255][256][257][258][259][260] and for using high-κ dielectric oxides as alternatives to SiO for gate dielectrics in MOSFET transistors. 170,[261][262][263] The challenge is to achieve epitaxial growth and a sharp interface without the formation of an interfacial oxide amorphous layer that may be formed by exposure of the clean semiconducting surface to the oxygen species required for the metal oxide growth or due to reaction with the oxide layer, that could degrade device performance.…”

Chaos at Interface Brings Order into Oxide/Silicon Structure

“…The structure and stoichiometry (1/2 monolayer) of the passivating Eu reconstruction have been studied by diffraction and microscopy techniques; [ 31–33 ] this reconstruction is isostructural to 1 × 2 Sr/Si(001), [ 33 ] a template commonly employed for synthesis of oxides on Si. [ 5–11 ] The formation of 1 × 2 Eu/Si(001) is ensured by the substrate temperature, metal flux, and deposition time. We would like to notice that this type of Si surface protection is not limited to MBE.…”

“…However, looking back at the decades of oxide/Si research we are left with only a handful of crystalline oxides directly coupled with Si. [ 5,9 ] For many complex oxides, the only option is to be grown on a buffer layer such as SrTiO 3 . [ 9–11 ] Moreover, a sharp oxide/Si interface, a major factor controlling the functional properties of the heterostructure, [ 9,12,13 ] is often difficult to achieve.…”

“…[ 5,9 ] For many complex oxides, the only option is to be grown on a buffer layer such as SrTiO 3 . [ 9–11 ] Moreover, a sharp oxide/Si interface, a major factor controlling the functional properties of the heterostructure, [ 9,12,13 ] is often difficult to achieve. [ 14,15 ] Therefore, it is only natural to wonder whether a regular metal reconstruction presents the optimal route to oxide/Si integration.…”

Switchable Electric Dipole from Polaron Localization in Dielectric Crystals

“…The field has evolved with the development of hybrid improper ferroelectrics and multi-ferroelectrics [4][5][6][7][8]. These non-conventional cases exhibit different interactions with other physical quantities, notably the strain field, and are thus anticipated to overcome existing performance bottlenecks [9,10].…”