Direct mapping of temperature-difference-induced potential variation under non-thermal equilibrium

It is expected to develop the measurement system to obtain physical/chemical information with nanoscale space resolution related to the non-thermal equilibrium phenomena. In this study, we developed controlled temperature-gradient kelvin force microscopy (T-KFM) to measure the temperature difference (ΔT)-induced vacuum level variation under non-thermal equilibrium. Therein, the biggest issue, difficulty in applying the large ΔT in narrow space (∼100 μm), was solved by introducing “heating and cooling systems” in T-KFM; one sample side is heated using a ceramic heater and the other side is cooled using liquid nitrogen. Using T-KFM, the space distribution of ΔT-induced vacuum level variation was well observed on the scale of hundreds of nanometers in a polycrystalline ZnO film with nanostructures. The obtained image of the ΔT-induced vacuum level variation can reflect a distribution of the thermal properties such as the thermal resistance and thermoelectromotive force. This pronounced technique for obtaining surface potential under T-gradient helps us to comprehend the non-thermal equilibrium phenomena.