Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11664010, 11264013), the Hunan Provincial Natural Science Foundation of China (Grant Nos. 2017JJ2217, 12JJ4003), the Scientific Research Fund of Hunan Provincial Education Department of China (Grant No. 18A293), and the Research Program of Jishou University, China (Grant Nos. JGY201851, Jdy1849, Jdy19039)
Received Date:27 July 2019
Accepted Date:23 September 2019
Available Online:26 November 2019
Published Online:05 December 2019
Abstract: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 non-equilibrium 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. Keywords:isomeric quinoline molecule/ graphene nanoribbon/ first-principles calculation/ electron transport
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2.模型与方法半无限长锯齿型石墨烯纳米带-喹啉C9H5N分子-半无限长锯齿型石墨烯纳米带构成的分子电子器件如图1所示, 器件分为左电极、中心散射区(图1中的红色虚线框区域所示)和右电极三个部分, 喹啉C9H5N分子中氮原子N的位置编号如图1(a)所示. 喹啉C9H5N分子中氮原子N分别处于编号2, 3和5处时的模型称为M1, M2和M3, 如图1(a)—图1(c)所示. 将喹啉C9H5N分子平面垂直纸面向里旋转方向定义为正, 如图1(d)和图1(e)给出喹啉C9H5N分子平面与石墨烯纳米带电极平面成0°和90°时的模型. 图 1 由半无限长锯齿型石墨烯纳米带左电极/中心散射区/半无限长锯齿型石墨烯纳米带右电极组成的ZGNR/C9H5N/ZGNR分子电子器件结构示意图, 红色方框区域表示中心散射区 (a)—(c)分别对应喹啉C9H5N分子中氮原子N处于编号2, 3和5处; (d)和(e)给出喹啉C9H5N分子平面与石墨烯纳米带电极平面成0°和90°时的模型 Figure1. ZGNR/C9H5N/ZGNR molecular electronic device schematic diagram consisted of a semi-infinite ZGNR left electrode/a central scattering region/a semi-infinite right ZGNR electrode, the red dashed line area represents the central scattering region. (a)?(c) denotes the marked 2nd, 3rd and 5th N atom of the C9H5N molecular; (d) and (e) illustrates the model of the 0° and 90° angle between the C9H5N molecule and graphene nanoribbon electrodes, respectively.