摘要
采用非平衡格林函数结合密度泛函理论探讨了以锯齿型石墨烯纳米带为电极、2-苯基吡啶分子为中心区的分子器件电子输运性质.分析I-V特性及透射谱随偏压的变化表明,电极弯折能够调控器件负微分电阻特性,使器件峰值电压(V_(p))减小、电流峰谷比(PVR)增大,当电极弯折角度为15°时,器件获得低峰值电压(0.1 V)、高电流峰谷比(12.84)的负阻特性.平衡态下器件的透射谱、态密度、散射态实空间分布图及投影态密度解释了器件负阻特性被调控源于电极弯折使器件中心分子与电极间的波函数交叠发生变化,导致两者间耦合减弱.弱耦合下外加偏压后,器件的透射系数因能级移动和偏压的变化而产生大幅波动,使器件在低偏置电压处即出现大的透射系数,产生峰值电流Ip,降低了器件的V_(p),且增大了PVR值,其所获得的低V_(p)、高PVR的负阻特性在低功耗分子电子领域具有潜在的应用前景.
Combining non-equilibrium Green’s function with density functional theory,we study the electronic transport properties of the molecular devices comprised of 2-phenylpyridine and zigzag graphene nanoribbon(ZGNR)electrodes.The I-V characteristics and transmission coefficients under external voltage biases are analyzed,and the results show that the negative differential resistance(NDR)is effectively adjusted by the bending of ZGNR electrode,which reduces the peak voltage(V_(p))and increases the peak-valley ratio(PVR)of the device.When the electrode bending angle is 15°,the PVR of device M2 is a maximum value of 12.84 and V_(p)is 0.1 V,which is low enough for practical applications.The transmission spectra,the density of states and the real-space scattering state distribution at Efof device under zero bias explain that the weaker coupling between the molecules and the electrodes is caused by the bending of the ZGNR electrode,which might be responsible for the adjustability of NDR.The analysis shows that the bending of the electrode changes the electronic structure between the 2-phenylpyridine molecule and the ZGNR electrode,and then changes the wave functions overlap between them,the coupling between the molecule and the electrodes gets weaker.An external bias can induce the level to shift.The transmission coefficient for the weaker coupling between the molecules.The electrodes can fluctuate wildly from level to level,and large NDR effect under very low bias is obtained with the variation of external bias.Therefore,for highly symmetric molecular devices,the electronic transport properties can be effectively adjusted by changing the coupling between the central molecule and the electrodes.Our investigations indicate that the 2-phenylpyridine molecular device with ZGNR electrodes may have potential applications in the field of low-power dissipation molecules device.
作者
邢海英
张子涵
吴文静
郭志英
茹金豆
Xing Hai-Ying;Zhang Zi-Han;Wu Wen-Jing;Guo Zhi-Ying;Ru Jin-Dou(School of Electronic and Information Engineering,Tiangong University,Tianjin 300387,China;Multi-discipline Research Center,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China;Engineering Research Center of High Power Solid State Lighting Application System,Tianjin 300387,China;Hongzhiwei Technology(Shanghai)Co.Ltd.,Shanghai 200120,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第3期355-363,共9页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11475212,11505211,61204008)资助的课题。
关键词
负微分电阻特性
电极弯折
非平衡格林函数
密度泛函理论
negative differential resistance
electrode bending
non-equilibrium Green’s function
density functional theory
