Two-dimensional (2D) superconductors have intriguing physical properties and abundant potential applications. Recently, 2D superconducting α-Mo 2 C and facecentered cubic Mo 2 C have been controllably prepared and they bring new viewpoints to carbon-based superconductivity. Although molybdenum carbides (Mo-Cs) have multiple crystalline stacking orders, there are still few structures reported for the lack of higher energy supply during growth. In this study, we report a two-step vapor deposition method to grow superconducting η-Mo 3 C 2 films with different thicknesses, with the assistance of controllable plasma power. The grown η-Mo 3 C 2 films show polycrystalline characteristics, but they still present superior superconductivity. The 3.0-nm-thick film has the superconducting transition temperature of 5.38 K, and its electrical performances follow truly 2D superconducting transitions. This study will not only exhibit a robust superconducting η-Mo 3 C 2 ultrathin film, but also provides a convenient growth way to realize more carbide-based heterostructures for future device applications.

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Understanding the high-temperature behaviors of two-dimensional (2D) transition metal dichalcogenides under different environments will provide a directive guide for the fabrication and application of their nanoelectronic devices. In this study, we investigate the high-temperature properties of chemical vapor deposition grown molybdenum disulfide (MoS2) in different atmospheres through the ex situ and in situ morphological and spectroscopical characterizations. When the MoS2 is exposed to Ar, dry O2, and wet O2 at the temperature of 500, 350, and 300 °C, the etching process starts at the edge and inner regions simultaneously, and the etched trenches are opposite to the outline of the MoS2 triangular shape. We observe a clear redshift of MoS2 in the Raman peak position and the photoluminescence peak position by in situ spectroscopical characterizations as the temperature increases. Moreover, a strong photoluminescence enhancement of 24-fold of MoS2 is observed when exposing to O2 at 300 °C . This should be due to the chemical and physical adsorbed oxygen on the MoS2 surface. Moreover, we find that physical adsorption can be eliminated after vacuum annealing. This study provides a real-time strategy to study the morphology and property evolution of 2D materials at high temperature in different atmospheres. These results will contribute to the applications in future electronic and optoelectronic functional devices of 2D materials.