Thermodynamic criterion for searching high mobility two-dimensional electron gas at KTaO_(3)interface

Two-dimensional electron gases(2 DEGs)formed at the interface between two oxide insulators present a promising platform for the exploration of emergent phenomena.While most of the previous works focused on SrTiO_(3-)based 2 DEGs,here we took the amorphous-ABO_(3)/KTaO_(3)system as the research object to study the relationship between the interface conductivity and the redox property of B-site metal in the amorphous film.The criterion of oxide-oxide interface redox reactions for the B-site metals,Zr,Al,Ti,Ta,and Nb in conductive interfaces was revealed:the formation heat of metal oxide,ⅢH_(f)^(o),is lower than-350 kJ/(mol O)and the work function of the metalΦis in the range of 3.75 eV<Φ<4.4 eV.Furthermore,we found that the smaller absolute value ofⅢH_(f)^(o)and the larger value ofΦof the B-site metal would result in higher mobility of the two-dimensional electron gas that formed at the corresponding amorphous-ABO_(3)/KTaO_(3)interface.This finding paves the way for the design of high-mobility all-oxide electronic devices.

Electric gating of the multichannel conduction in LaAlO_(3)/SrTiO_(3) superlattices

The electric gating on the transport properties of two-dimensional electron gas(2DEG) at the interface of LaAlO_(3)/SrTiO_(3)(LAO/STO) heterostructure has attracted great research interest due to its potential application in fieldeffect devices. Most of previous works of gate effect were focused on the LAO/STO heterostructure containing only one conductive interface. Here, we systematically investigated the gate effect on high-quality LAO/STO superlattices(SLs)fabricated on the TiO_(2)-terminated(001) STO substrates. In addition to the good metallicity of all SLs, we found that there are two types of charge carriers, the majority carriers and the minority carriers, coexisting in the SLs. The sheet resistance of the SLs with a fixed thickness of the LAO layer increases monotonically as the thickness of the STO layer increases. This is derived from the dependence of the minority carrier density on the thickness of STO. Unlike the LAO/STO heterostructure in which minority and majority carriers are simultaneously modulated by the gate effect, the minority carriers in the SLs can be tuned more significantly by the electric gating while the density of majority carriers is almost invariable. Thus, we consider that the minority carriers may mainly exist in the first interface near the STO substrate that is more sensitive to the back-gate voltage, and the majority carriers exist in the post-deposited STO layers. The SL structure provides the space separation for the multichannel conduction in the 2 DEG, which opens an avenue for the design of field-effect devices based on LAO/STO heterostructure.