Performance analysis of carbon nanotube and graphene nanoribbon based biochemical sensors at atomic scale

Abstract

Advancements in fabrication technologies have led to the possibility for synthesizing atomic scale structures of graphene nanoribbon (GNR) and carbon nanotube (CNT) based nanodevices. The purpose of this study is to model the electronic properties and electrical characteristics of these devices by atomistic modelling using density functional theory (DFT) and non-equilibrium Green’s function (NEGF) and compare the effects of molecular functionalization and sensing. Potential profile of the device is computed using three dimensional Poisson’s equation for smaller applied bias within 1 voltage range. Simulation showed a bandgap of 1eV for armchair GNR (AGNR), which exhibited insensitive behaviour to functionalized amine molecule resulting in lesser alteration in the density of states (DoS), transmission spectra and the device current (ΔI). The bandgap further increased to 2eV on rolling the GNR to armchair CNT (ACNT) which further deteriorated the sensitivity. However, changing the configuration of AGNR to zigzag GNR (ZGNR) shows remarkable alteration in the DoS and transmission spectra and significant improvement in sensitivity. This further improves to 1.5 - 2 times as the ZGNR is rolled to zigzag CNT (ZCNT). Thus, at lower dimensions in atomic scale, we found the alteration in device current of the carbon structures which is directly proportional to the sensitivity in the following order: ΔIACNT < ΔIAGNR < ΔIZGNR < ΔIZCNT. However, the same is found to fall for ZGNR and ZCNT with increase in width to length (W/L) ratio. This specifies the importance of smaller atomic structures and the work provides a guideline for effectively utilization these structures for biochemical sensing.