Controlled Current Transport in Pt/Nb:SrTiO₃ Junctions via Insertion of Uniform Thin Layers of TaO_x

Abstract

Systematic control of electronic transport is demonstrated for Pt/Nb‐doped SrTiO3 (Nb:STO) junctions based on interface engineering with uniform thin layers of TaOx. By inserting TaOx layers fabricated via sputter deposition with different O2–Ar ratios (rO2), the current–voltage characteristics and behavior of resistive switching can be well controlled in Pt/Nb:STO junctions. Reduction of the Schottky barrier is also demonstrated via the insertion, and formation of an ideal ohmic contact with a low contact resistance of <3 Ω is achieved for rO2 = 0%. Structural and chemical characterizations show that the resistivity of the TaOx layers depends significantly on rO2 while maintaining a uniform structure independent of the resistivity. This indicates that the insertion of both insulating and metallic interface layers is possible by sputtering TaOx with no need for epitaxial growth, suggesting TaOx's potential as an interface‐layer material. Even with very thin layers (1.0 nm) of TaOx the interfacial properties can be controlled to enhance both ohmic contact formation and resistive switching. These results demonstrate an easy and reliable way to control the characteristics of Pt/Nb:STO junctions and present new insights for their memory and semiconductor device applications.

(Invited) Nanoscale Probing of Field-Driven Ion Migration in TaOx for Neuromorphic Memristor Applications

“…1(c)). For the c-AFM analysis of the resistive switching, we used Nb-doped SrTiO 3 (Nb:STO) (001) conductive substrates with a Nb-doping concentration of 1.0%, on which high surface flatness is available by chemical mechanical polishing and a low-resistance ohmic contact can form with an a-TaO x film through the interfacial redox reactions (20). We observed that the PLD-deposited a-TaO x /Nb-STO (001) thin films also have very flat surface morphologies with small R rms s of <0.2 nm.…”