Multidimensionality of the Contact Potential Difference at the Nanoscale in Inorganic Oxides

Inorganic-oxide-based sample systems are popular for applications in catalysis, sensing, renewable energy, and fuel cells, in which electronic properties play important roles. Environmental conditions, e.g., temperature, can greatly impact the electronic properties and thereby the performance. The lack of basic knowledge of the local variation of electronic properties as a function of temperature limits the fundamental understanding of systems and hampers their robustness. Here, we present temperature-dependent scanning probe microscopy experiments to reveal the variation of contact potential difference (CPD) across different length scales. Our measurements demonstrate that the CPD of inorganic perovskites (e.g., SrTiO3) and metal-oxide semiconductors (e.g., TiO2) evolves significantly with temperature. We show that CPD variation depends on the locality of the measurement and originates from a thermodynamically driven intrinsic doping state. These results will facilitate a fundamental understanding of the electronic properties of oxides and thus ease emerging technologies, rationalized by engineering temperature-dependent electronic properties.