Probing surface electronic properties of a patterned conductive STO by reactive ion etching

SrTiO ₃ (STO) is a highly attractive oxide material due to its flexible tunability of electrical properties. It can be designed to exhibit a high mobility with a tunable carrier concentration by creating oxygen vacancies, or by doping with Nb or La, which substitute the Ti and Sr sites, respectively. Here we show a micro-patterned surface doping of STO by using reactive ion etching (RIE). The creation and pattering of a conductive STO surface were achieved by sequential treatments with Ar and O ₂ plasma. The patterned conductive surface edge was well defined as confirmed by an electrostatic force microscopy. The electronic characteristics of the RIE treated STO surface were probed by a synchrotron radiation photoemission spectroscopy, which shows the emergence of Ti ³⁺ , Ti ²⁺ , Ti ¹⁺ states and metallic states near the Fermi level. The electrical mobility of the conductive STO surface can be increased up to 12000 cm/V s with a typical sheet carrier concentration around 10 ¹³ –10 ¹⁴ cm ⁻² . Increasing Ar plasma time elongate the depth of the conductive surface, which reflects the change of magnetoresistance behavior at low temperature. The demonstrated control of the STO surface conductivity along with a large area and high precision patterning method can be widely used for a variety of oxide electronic and spintronic devices.