Temperature-Dependent Thermal Transport of Vertically Stacked Two-Dimensional PtSe₂/PtSe₂ Homo-Structure

Two-dimensional (2D) transition metal dichalcogenide (TMDC) thin films are attracting significant attention as next-generation materials due to their tunable energy band gaps. In particular, 2D PtSe₂ thin films are excellent materials that can adjust their energy band gaps based on thickness. Additionally, a non-ideal thermoelectric effect has been discovered in stacked structures of 2D TMDC thin films. Typically, the Seebeck effect according to thickness is expressed as a parallel conductor model. However, in the case of vertically stacked 2D PtSe₂ thin films, a non-ideal Seebeck effect has been observed. Our research reports that vertically stacked PtSe₂ thin films exhibit an improved Seebeck coefficient compared to 1-stacked PtSe₂ films due to interfacial effects. This enhancement is attributed to the interaction of hot carriers with the interface, which results in properties independent of the general Seebeck coefficient. Measurements using self-manufactured thermoelectric performance equipment (CAU-system, CAU-SYS) show that the Seebeck coefficient increased by approximately 261% in 4-stacked PtSe₂ samples compared to 1-stacked PtSe₂ samples. Additionally, the power factor increased dramatically by about 570% in 5-stacked PtSe₂ samples. Furthermore, temperature-dependent measurements using Quantum Design's physical properties measurement system (PPMS) demonstrate that this phenomenon remains stable even at low temperatures. The decrease in Seebeck coefficient, electrical conductivity, and power factor with decreasing temperature can be explained by the temperature-dependent electronic behavior of p-type PtSe₂ semiconductors. To calculate the figure of merit (ZT), thermal conductivity measurements are being conducted using the heat diffusion imaging method. This research highlights the dramatic improvement in thermoelectric performance due to the interface-induced Seebeck effect in vertically stacked structures. Therefore, it is anticipated that semiconductor and thermoelectric research using stacked structure technology will be actively pursued in the future.