Optical switching of functionalized carbon nanotube transistors

Carbon Nanotube (CNT) transistors can emit or detect photons at wavelengths defined by the CNT chirality. To extend their capabilities in optoelectronics, it is important to be able to tune this wavelength independently of the CNT structure. A way to achieve such a goal is to chemically functionalize the CNT. In the present study, we demonstrate that drastic photo-induced modifications of the electrical characteristics of self-assembled CNT transistors functionalized by photoactive polymers can be achieved. We show that the polymer film acts as a wavelength dependent 'optical gate', which is much more efficient than a conventional electrostatic gate and can induce changes in conductance exceeding four orders of magnitude. The switching mechanism involves the creation and separation of photo-excited charges in the polymer, the spatial distribution and relaxation rates of which are studied taking advantage of the very high charge sensitivity of the CNT transistor.