Regulation and mechanism of graphene electrode bending onnegative differential resistance of 2-phenylpyridinemolecular devices br

Combining non-equilibrium Green' s function with density functional theory, we study the electronictransport 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 areanalyzed, and the results show that the negative differential resistance (NDR) is effectively adjusted by thebending of ZGNR electrode, which reduces the peak voltage (Vp) and increases the peak-valley ratio (PVR) ofthe device. When the electrode bending angle is 15 degrees, the PVR of device M2 is a maximum value of 12.84 and Vpis 0.1 V, which is low enough for practical applications. The transmission spectra, the density of states and thereal-space scattering state distribution at Efof device under zero bias explain that the weaker coupling betweenthe molecules and the electrodes is caused by the bending of the ZGNR electrode, which might be responsiblefor the adjustability of NDR. The analysis shows that the bending of the electrode changes the electronicstructure between the 2-phenylpyridine molecule and the ZGNR electrode, and then changes the wave functionsoverlap between them, the coupling between the molecule and the electrodes gets weaker. An external bias caninduce the level to shift. The transmission coefficient for the weaker coupling between the molecules. Theelectrodes can fluctuate wildly from level to level, and large NDR effect under very low bias is obtained with thevariation of external bias. Therefore, for highly symmetric molecular devices, the electronic transport propertiescan be effectively adjusted by changing the coupling between the central molecule and the electrodes. Ourinvestigations indicate that the 2-phenylpyridine molecular device with ZGNR electrodes may have potentialapplications in the field of low-power dissipation molecules device