石墨烯纳米带电极同分异构喹啉分子结电子输运性质

Electron transport properties of isomeric quinoline molecule junction sandwiched between graphene nanoribbon electrodes

基于密度泛函理论与非平衡格林函数相结合的第一性原理计算方法,系统地研究了通过碳原子(C)连接的同分异构喹啉分子(C9H5N)嵌于石墨烯纳米带电极间的分子电子器件输运性质.研究结果表明:器件电流在偏压[–0.3 V,+0.3 V]范围内呈线性变化,电流在[–0.4 V,–0.9 V]和[+0.5 V,+0.8 V]范围内随着偏压的增大而减小,呈现显著的负微分电阻效应;当喹啉分子平面与石墨烯纳米带电极间存在一定夹角时,器件电流呈现明显的负微分电阻效应且与喹啉分子平面旋转方向无关,当喹啉分子平面与石墨烯纳米带电极垂直时,器件电流截止.以上研究结果得到偏压窗内透射系数积分以及零偏压下实空间电荷密度分布等的有力印证,可为设计制作基于同分异构喹啉分子电子开关和负微分电阻器件提供理论依据.

Since graphene was successfully obtained in the end of 2004, the research on graphene and relevant devices has attracted extensive attention. The armchair-and zigzag-edge graphene nanoribbons, as the building blocks,are often used to design the graphene-based molecular electronic devices. Quinoline, an important intermediate between metallurgical dyes and polymers, is an organic conjugated small molecule which is simple in structure and easy to synthesize and modify the chemical structure, and quinoline has become one of the research focuses in the field of molecular electronic devices in recent years. From the physical point of view, the transport properties of the isomeric quinoline molecular electronic devices connected with graphene nanoribbon electrodes can provide a theoretical basis for designing and manufacturing molecular electronic devices with excellent performance. Based on the first-principles calculation method combining the density functional theory and nonequilibrium Green’s function, this paper systematically investigates the transport properties of the carbon-linked isomeric quinoline molecule electronic devices sandwiched between the graphene nanoribbon electrodes. The obtained results show that the device current presents a linear change in a bias voltage range [–0.3 V, +0.3 V],the current decreases with the increase of the absolute bias voltage, separately, in a range of [+0.5 V, +0.8 V]and [ –0.4 V, –0.9 V], demonstrating a strong negative differential resistance effect. On the other hand, the interesting negative differential resistance effect is remained when there is an angle between the quinoline molecular plane and the graphene nanoribbon electrode;the current of the device is found to be independent of the rotation direction of quinoline molecule in the central region;the current of the device should be forbidden when the quinoline molecule plane is rotated to a direction vertical to the graphene nanoribbon electrodes. The obtained results can provide a theoretical basis for designing and manufacturing the molecular switches and negative differential resistance devices based on isomeric quinoline molecular electronic devices.