The effects of adsorption orientations on transport through a nanotube gas sensor*

We calculate the quantum transport of a nanoelectronic gas sensor for various adsorption orentations of the gas molecules. The nanosensor employs electronic transport properties of a carbon nanotube exposed to NO$_2$ molecules. The calculations are based on ab initio electronic structures, combined with the Green's function formulation of Landauer's transport theory. Our results show that different energetically equivalent orientations of the NO$_2$ molecules result in different details of transport characteristics. The main features of transport modulation, however, are the same for all the orientations. Implications for nanotube-based gas sensors are discussed.