Figure 1

Conductance for realistic FET geometries. (a) Device geometry, with metal contacts on the left and right, a ground plane, and a top gate. Contour lines show the electrostatic potential for a top gate voltage of 2 V. (b) Corresponding conductance versus gate voltage at room temperature, for different SBs. The SB height for electrons is indicated for each curve. (c) NT conduction-band energy near the contact, for gate voltages of 4 and 10 V.Reuse & Permissions

Figure 2

Influence of the FET geometry on the device characteristics. The four right-most curves correspond to different thicknesses of the oxide above the NT, as labeled, with all other parameters as in Fig. 1. (The curve for 100 nm is the same as that in Fig. 1b for a SB height of 0.3 eV.) The dot-dashed curve shows the conductance when the contact thickness is reduced to 5 nm. The curve at the left corresponds to a needlelike metal electrode and cylindrical gate, see text. Open circles are calculated as for the other curves, solid curve uses the exact electrostatic kernel. All calculations are at room temperature. The inset shows the same curves, but for each curve the gate voltage is rescaled by the voltage at which the conductance is ${10}^{-8}\mathrm{S}$. (The five rightmost curves cannot be distinguished on this scale, forming a single line.)Reuse & Permissions

Figure 3

Calculated conductance vs gate voltage at room temperature, varying (a) the work function of the metal electrode, and (b) doping of the NT. In (a) the work function of the metal electrode is changed by $-0.2\mathrm{e}\mathrm{V}$ (red dashed), $-0.1\mathrm{e}\mathrm{V}$ (orange dashed), $0\mathrm{e}\mathrm{V}$ (green), $+0.1\mathrm{e}\mathrm{V}$ (light blue), and $+0.2\mathrm{e}\mathrm{V}$ (blue), from left to right, respectively. In (b) the doping atomic fraction is $n$-type ${10}^{-3}$ (red), $5\times {10}^{-4}$ (orange), and ${10}^{-4}$ (green), and $p$-type ${10}^{-4}$ (blue dashed), from left to right, respectively.Reuse & Permissions

Figure 4

The experimentally measured effect of (a) oxygen adsorption and (b) potassium doping on NT-FETs. In (a) the annealed ($n$-type) FET has been exposed to oxygen for 2 min at $P=0$ Torr (red), $P={10}^{-4}$ Torr (orange), $P=5\times {10}^{-4}$ Torr (light green), $P=5\times {10}^{-3}$ Torr (dark green), $P={10}^{-1}$ Torr (light blue), and in ambient (blue), from left to right respectively. Details are given in Ref. 7. In (b) the curves from right to left (blue, dark and light green, light and dark orange, red) correspond to increasing deposited amounts of potassium.Reuse & Permissions

Figure 5

Bending of NT valence and conduction bands at room temperature in the case of (a) metal electrode work function increased by $0.2\mathrm{e}\mathrm{V}$ and (b) $n$-type doping of the NT at atomic fraction $5\times {10}^{-4}$. The solid lines correspond to zero gate voltage. The dashed lines are for $-500\mathrm{m}\mathrm{V}$ in (a) and $+500\mathrm{m}\mathrm{V}$ in (b). All energies are with respect to the Fermi energy.Reuse & Permissions