Role of ion milling angle in determining conducting and insulating states on SrTiO3 surfaces

SrTiO3 (STO), a promising wide-bandgap semiconductor for high-k capacitors and photocatalysis, requires precise surface control for device fabrication. This study investigates the impact of ion milling on STO’s surface conductivity. We find that ion milling at incident angles below 10° preserves the insulating state, while ion milling at larger angles induces a conducting surface with high electron mobility (5000–11 000 cm²/Vs). This transition is attributed to the milling penetration depth exceeding the STO lattice constant (3.905 Å). Our results provide valuable insights for optimizing STO-based device fabrication, enabling precise control over surface properties while maintaining the desired insulating characteristics.