191. TWO-DIMENSIONAL ELECTRON GAS DRIVEN BY STRAIN-INDUCED POLARIZATION IN NONPOLAR AHFO3/SRTIO3 (001) (A=CA, SR, AND BA) HETEROSTRUCTURE: FIRST-PRINCIPLES ANALYSIS

Department: NanoEngineering
Research Institute Affiliation: Graduate Program in Chemical Engineering
Faculty Advisor(s): Kesong Yang

Primary Student
Name: Jianli Cheng
Email: jic198@ucsd.edu
Phone: 732-640-6737
Grad Year: 2018

Abstract
The two-dimensional electron gas (2DEG) at polar/nonpolar LaAlO3/SrTiO3 heterostructure (HS) has stimulated a tremendous amount of research activities because of its promising applications in next-generation nanoelectronics. Here, we investigated the formation of 2DEG in nonpolar/nonpolar AHfO3/SrTiO3 (AHfO3/SrTiO3, A = Ca, Sr, and Ba) oxide HS-based slab systems via strain-induced polarization (polarization discontinuity) using first-principles electronic structure calculations. Two types of neutral interfaces are modeled, (AO)0/(TiO2)0 and (HfO2)0/(SrO)0, each with AO and HfO2 surface terminations. Our results suggest that as the AHfO3 film thick- ness increases, the lattice mismatch-induced compressive strain leads to a strong polarization in the AHfO3 film and results in an insulating-metallic transition (IMT). The critical thickness of the AHfO3 film to form the interfacial metallic states depends on the magnitude of lattice mismatch and also the surface termination of AHfO3 film in both types of interface models. It is found that the critical thickness of CaHfO3 film in CaHfO3/SrTiO3 HS exists in all four types models, while the SrHfO3/SrTiO3 and BHO/SrTiO3 HSs only exhibit the IMT with HfO2 surface termination. Our study provides a new route to create 2DEG in complex oxide HSs and can also stimulate the corresponding experimental studies.

Industry Application Area(s)
Electronics/Photonics | Materials | Semiconductor

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