High‐Temperature and High‐Speed Atomic Force Microscopy Using a qPlus Sensor in Liquid via Quadpod Scanner and Hybrid‐Loop Frequency Demodulation

Atomic‐resolution imaging on molten metal/solid interfaces at temperatures above was achieved using a high‐temperature, high‐speed atomic force microscope (AFM) equipped with a qPlus sensor. A tip‐scanning high‐speed Quadpod scanner for a large mass load of qPlus sensor () was developed to enhance thermal drift tolerance by high‐speed scanning and thermal insulation from the heated specimen. This scanner has dominant resonant frequencies of (lateral) / (vertical) without a load. In addition, the Hybrid‐Loop frequency demodulation technique for low‐resonant‐frequency () sensors with a wider bandwidth than conventional phase‐locked loop was also established, providing a demodulation bandwidth of without exceeding the theoretical noise of the input deflection signal. Combining these techniques enabled atomic‐resolution imaging on the molten Ga/ interface at . The topographic images obtained at showed a relatively low‐symmetry surface with an oblique lattice with a superstructure, which differed from the primitive rectangular lattice observed in the non‐heated sample left at room temperature for . This demonstrates that the developed high‐temperature, high‐speed AFM techniques for qPlus sensors enable visualization of non‐aqueous liquid/solid interfaces above at atomic resolution, which has various potential applications, such as injection modeling, soldering, and the fabrication of liquid‐metal‐based catalysts.