Gas adsorption on a nanographite ribbon: Hybridization model and simulations

We propose a hybridization model to simulate the gas molecules adsorbed on a single sheet of nanographite ribbon resulting in a conductivity change. In this study, two energy parameters, the chemical and hybridization energies, are employed to simulate and individualize the adsorbed gas. We propose two competing mechanisms, carrier localization and charge distribution, that coexist in the gas adsorption process, which provide a qualitative explanation for the current increase or decrease in gas adsorption experiments. This study gives qualitative information on nanographite ribbons for gas sensor applications.

Figure 1

Ribbon and electrode contact configurations, with the armchair and zigzag configurations on the left and right, respectively.

Figure 2

Current-bias curves for different chemical potentials under a small constant hybridization interaction $V∕t=0.4$. Each current-bias profile shows a stepwise change at a specific applied voltage equal to the energy difference between the potential $E_p$ and $E_0$.

Figure 3

At small hybridization interactions $V∕t$, the current is enhanced compared with no molecular adsorption $(V∕t=0)$ and the current amplitude first increases slightly then drops dramatically as $E_p$ increases. In contrast to high $V∕t$, the current is depressed, yet the current increases with the $E_p$ increase.

Figure 4

At small hybridization interaction $V∕t$, the conducting property is metallic. On the contrary, at high $V∕t$ the conducting property appears to be semiconducting.

Figure 5

The current amplitude is compared with free molecule adsorption at $E_P∕t=0$. Small $V∕t$ produces an increase in current. Contrastingly, the current decreases when $V∕t$ is large.