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

Abstract

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.

The local potential variation mapping including thermoelectromotive force in nanocomposite materials under non-thermal equilibrium

“…39) These microscopic S values measured by T-KFM roughly agreed with the macroscopic ones measured by ZEM-3, a commonly used macroscopic S measurement system. 39) This indicates that T-KFM works correctly. However, in nanocomposite material cases, the inhomogeneous temperature distribution is needed for the estimation of microscopic S.…”

“…39) Using this sample holder, we evaluated the S values of some uniform materials with homogeneous temperature distribution in our previous work. 39) These microscopic S values measured by T-KFM roughly agreed with the macroscopic ones measured by ZEM-3, a commonly used macroscopic S measurement system. 39) This indicates that T-KFM works correctly.…”

“…In 2021, we proposed the controlled T gradient Kelvin force microscopy (T-KFM), which enables us to measure the T difference (ΔT)-induced vacuum level (V vac ) variation, which is ΔT effect, including V TE under non-thermal equilibrium. 39) In the T-KFM measurement for ZnO films without hetero-nanostructures, it was revealed that the impurities bringing a distinguishing ΔT effect were incorporated into ZnO films. This detection of space distribution of ΔT-induced V vac variation on the nanoscale shed light on understanding the physical mechanism of S enhancement.…”

The effect of interdiffusion during formation of epitaxial Ca intercalated layered silicene film on its thermoelectric power factor

“…Therefore, many researchers have attempted to realize high ZT in Earth-abundant Si-based materials. [10][11][12][13][14][15][16][17][18][19][20] Recently, thanks to the development of nanotechnology, 13,[21][22][23][24][25][26][27][28] κ was dramatically reduced by nanoscale interfaces in Si-based materials and low dimensional materials. [10][11][12]18,[29][30][31][32][33] On the other hand, the various methodologies of power factor enhancement have been proposed, which are quantum confinement, [34][35][36] energy filtering, [37][38][39] band convergence, 40,41) and impurity resonance.…”