Soultati Anastasia, Aidinis Konstantinos, Chroneos Alexander, Vasilopoulou Maria, Davazoglou Dimitris
Institute of Nanoscience and Nanotechnology, NCSR "Demokritos", POB 60228, 153 10, Agia Paraskevi, Attiki, Greece.
Department of Electrical and Computer Engineering, Ajman University, P.O. Box 346, Ajman, United Arab Emirates.
Sci Rep. 2023 Nov 30;13(1):21166. doi: 10.1038/s41598-023-48060-1.
The surface electric conduction in amorphous and crystallized molybdenum oxide films was studied as a function of electronic structure by current-voltage and simultaneous spectroscopic ellipsometry measurements on structures of the kind Al/Molybdenum oxide (MoO)/Al, at temperatures up to 400 °C and in ambient air. At room temperature, both amorphous and crystalline MoO samples were found to be sub-stoichiometric in oxygen. The random distribution of oxygen vacancies and the imperfect atomic ordering induced the creation of an intermediate band (IB) located near the valence band and of individual electronic gap states. At temperatures below 300 °C, the conduction was found to exhibit ambipolar character in which electrons and holes participated, the former moving in the conduction band and the latter in the IB and though gap states. Above 300 °C, due to samples gradual oxidation and improvement of atomic ordering (samples crystallization), the density of states in the IB and the gap gradually decreased. The above in their turn resulted in the gradual suppression of the ambipolar character of the conduction, which at 400 °C was completely suppressed and became similar to that of ordinary n-type semiconductor. The above phenomena were found to be reversible, so as the semiconducting MoO samples were returning to room temperature the ambipolarity of the conduction was gradually re-appearing giving rise to an unusual phenomenon of "metallic" temperature variation of electrical resistance when electrons were injected.
通过对Al/氧化钼（MoO）/Al结构进行电流-电压和同步光谱椭偏测量，研究了非晶态和晶态氧化钼薄膜的表面电导与电子结构的关系，测量温度高达400°C，环境为空气。在室温下，发现非晶态和晶态MoO样品的氧含量均低于化学计量比。氧空位的随机分布和不完美的原子有序性导致在价带附近形成一个中间带（IB）和单个电子能隙态。在300°C以下的温度下，发现传导表现出双极性特征，电子和空穴都参与其中，前者在导带中移动，后者在IB中并通过能隙态移动。在300°C以上，由于样品逐渐氧化和原子有序性的改善（样品结晶），IB和能隙中的态密度逐渐降低。上述情况进而导致传导的双极性特征逐渐受到抑制，在400°C时完全被抑制，变得类似于普通n型半导体。发现上述现象是可逆的，因此当半导体MoO样品回到室温时，传导的双极性逐渐重新出现，当注入电子时会产生电阻“金属性”温度变化的异常现象。
