Effects of surface defects on two-dimensional electron gas at NdAlO3/SrTiO3 interface

Abstract

Density functional theory calculations of NdAlO3/SrTiO3 heterostructure show that two-dimensional electron gas (2-DEG) is produced at the interface with a built-in potential of ~0.3 eV per unit cell. The effects of surface defects on the phase stability and electric field of 2-DEG have been investigated. It is found that oxygen vacancy is easily to form on the NdAlO3(001) surface, with a low threshold displacement energy and a low formation energy. This point defect results in surface reconstruction and the formation of a zigzag -Al-O-Al- chain, which quenches the built-in potential and enhances the carrier density significantly. These results will provide fundamental insights into understanding how surface defects influence the electronic behavior of 2-DEG and tuning their electronic properties through surface modification.

Effect of Nd 3+ ions on phase transformations and microstructure of 0–4 at.% Nd 3+ :Y 3 Al 5 O 12 transparent ceramics

“…Impossibility of unlimited mutual solubility the NdAP and YAP compounds in the solid state due to the difference in their crystalline structure suggests the possible joint of crystal structures of the orthorhombic (Nd 3+ :YAP ≤ 45 at.%) and the rhombohedral (Y 3+ :NdAP ≤20 at.%) modifications [33]. Probable ways of such a joining promote formation of oxygen vacancies on the surface of the 〈001〉 NdAP as the preferred type of point defects [34] like in the NdAlO 3 /SrTiO 3 system. This type of point defects leads to M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 rearrangement of boundaries between Nd 3+ :YAP-Y 3+ :NdAP phases and formation of zigzag chains =Al-O-Al=, which reduce tension that is inherent to the system and greatly increase the density of charge carriers (the structure-forming ions [34]).…”

“…Probable ways of such a joining promote formation of oxygen vacancies on the surface of the 〈001〉 NdAP as the preferred type of point defects [34] like in the NdAlO 3 /SrTiO 3 system. This type of point defects leads to M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 rearrangement of boundaries between Nd 3+ :YAP-Y 3+ :NdAP phases and formation of zigzag chains =Al-O-Al=, which reduce tension that is inherent to the system and greatly increase the density of charge carriers (the structure-forming ions [34]). This facilitates diffusion of neodymium ions through the layer of formed products during Nd 3+ :YAG solid solution synthesis, which is the ratelimiting stage in the solid-state interaction in the system Y 2 O 3 -Nd 2 O 3 -Al 2 O 3 .…”

Structural Behaviour of Solid Solutions in the NdAlO3-SrTiO3 System

“…The interface effects occurred in the R AlO 3 –SrTiO 3 perovskite systems are in the focus of active research in the field of tunable metal-insulator transition, 2D superconductivity, coexistence of superconductivity and ferromagnetism, etc. [8–11]. …”

Electronic transport of titanate heterostructures and their potential as channels on (001) Si

“…The discovery of a two dimensional electron gas (2DEG) at the interface of two epitaxial oxides 1 has stimulated a decade of research effort into its physical properties, origins, and applications. [2][3][4] While research initially focused on the LaAlO 3 -SrTiO 3 (LAO-STO) material system, similar 2DEGs have been discovered on STO when the LAO layer is replaced by oxides such as LaTiO 3 , 5 NdTiO 3 , 6 and NdAlO 3 , 7 as well as amorphous 8,9 and epitaxial c-Al 2 O 3 . 10,11 Among these examples, the rare-earth titanates (RTO) emerge as a prominent candidate with some of the highest reported carrier densities.…”