Empirical transport model of strained CNT transistors used for sensor applications

摘要

We present an empirical model for the near-ballistic transport in carbon nanotube (CNT) transistors used as strain sensors. This model describes the intrinsic effect of strain on the transport in CNTs by taking into account phonon scattering and thermally activated charge carriers. As this model relies on a semiempirical description of the electronic bands, different levels of electronic structure calculations can be used as input. The results show that the electronic structure of strained single-walled CNTs with a radius larger than 0.7 nm can be described by a fully analytical model in the sensing regime. For CNTs with smaller diameter, parameterized data from electronic structure calculations can be used for the model. Depending on the type of CNTs, the conductance can vary by several orders of magnitude when strain is applied, which is consistent with the current literature. Further, we demonstrate the tuning of the sensor by an external gate which allows shifting the signal amplitude. These parameters have to be balanced to get good sensing properties. The impact of (semi-)metallic CNTs on the sensor performance is evaluated, too. Metallic CNTs have to be avoided in order to construct working sensing devices. Due to its basically analytical nature, the transport model can be evolved towards a compact model for circuit simulations.