Coulomb attractive random telegraph signal in a single-walled carbon nanotube

The gate dependence of a Coulomb attractive random telegraph signal is observed in a single-walled carbon nanotube field effect transistor for temperatures varying from 0.32 to $24\mathrm{K}$. The mechanism of the Coulomb attractive random telegraph signal is attributed to the carrier tunneling between the carbon nanotube and the Coulomb attractive defect. The random telegraph signal is also studied under magnetic field over an entire gate bias range and a wide temperature range. The Coulomb attractive random telegraph signal shows weak magnetic dependence, which may be due to the broadening of the Zeeman levels of the defect in the $p$-type carbon nanotube field effect transistor.

Figure 1

(Color online) Band diagrams and schematic drawings of the corresponding $I_{ds}$-$V_g$ relationship of a Coulomb repulsive RTS (a) and a Coulomb attractive RTS (b) in both a $p$-FET and a $n$-FET due to defects located near the carbon nanotubes.

Figure 2

(Color online) (a) Source-drain current with $V_{ds}=-0.5\mathrm{V}$ measured at $2\mathrm{K}$ for the gate bias range of $-7$ to $-9\mathrm{V}$. (b) Noise power spectrum density of the RTS at $V_g=-7.6\mathrm{V}$ obtained by a numerical method shown in the blue solid-dot line. The result deviates from an ideal Lorentzian spectrum due to a large background $1∕f$ noise. The RTS power spectrum density after subtracting the background noise recovers the Lorentzian power spectrum shape with a cutoff frequency of $0.05\mathrm{Hz}$ as shown by the red/gray dashed line. The inset shows the time domain data of the RTS.

Figure 3

(Color online) Emission and capture time constants and their ratios as a function of gate bias. For the gate range from $-7.4$ to $-8.4\mathrm{V}$, there is a lack of exponential dependence on gate bias.

Figure 4

(Color online) Emission and capture time constants $(V_{ds}=-0.5\mathrm{V})$ as a function of gate bias at temperatures of $0.32$, $1.8$, $12$, and $24\mathrm{K}$.

Figure 5

(Color online) (a) The RTS with the magnetic field from 0 to $18\mathrm{T}$ in both perpendicular and parallel directions. The emission and capture time constants of the RTS show weak magnetic dependence. The applied source-drain bias is $-0.5\mathrm{V}$. 5(b) Emission and capture time constants $(V_{ds}=-0.5\mathrm{V})$ at a temperature of $0.32\mathrm{K}$ with parallel magnetic field of 0, 9, $18\mathrm{T}$. (c) Emission / capture time constants $(V_{ds}=-0.5\mathrm{V})$ at a temperature of $24\mathrm{K}$ with the perpendicular magnetic field of 0, 4.5, 9, 13.5, and $18\mathrm{T}$.