One-dimensional screening effects in bulk-modulated carbon nanotube transistors

We report density-functional theory (DFT), atomistic simulations of the screening properties of carbon nanotube (CNT) field-effect transistors (FETs). Our attention has been focused on recently demonstrated [1, 2] bulk-modulated CNTFETs. Our calculations have been intended to explore, at an atomistic level, the effect of the one-dimensional screening properties on the physical mechanisms which govern the channel conductance modulation in these new devices. We find that in order to correctly describe charge response mechanisms in a small-diameter nanotube, a calculation including electron-electron interaction effects is necessary. Many-body effects tied to the attractive nature of the exchange interaction can produce an unconventional charge response which manifests itself in a negative quantum capacitance.