Narrow Results

This work presents a comprehensive investigation of the quantum capacitance and the associated effects on the carrier transit delay in armchair-edge graphene nanoribbons (A-GNRs) based on semi-analytical method. We emphasize on the realistic analysis of bandgap with taking edge effects into account by means of modified tight binding (TB) model. The results show that the edge effects have significant influence in defining the bandgap which is a necessary input in the accurate analyses of capacitance. The quantum capacitance is discussed in both nondegenerate (low gate voltage) and degenerate (high gate voltage) regimes. We observe that the classical capacitance limits the total gate (external) capacitance in the degenerate regime, whereas, quantum capacitance limits the external gate capacitance in the nondegenerate regime. The influence of gate capacitances on the gate delay is studied extensively to demonstrate the optimization of switching time. Moreover, the high-field behavior of a GNR is studied in the degenerate and nondegenerate regimes. We find that a smaller intrinsic capacitance appears in the channel due to high velocity carrier, which limits the quantum capacitance and thus limit the gate delay. Such detail analysis of GNRs considering a realistic model would be useful for the optimized design of GNR-based nanoelectronic devices.

The vibration induced by low-frequency elastic wave reduces the working accuracy of precision instruments. The locally resonant phononic crystal provides a feasible measure for low-frequency vibration isolation because of its bandgap characteristics. In this paper, a locally resonant phononic crystal structure with a broad bandgap is proposed, which consists of a periodic phononic crystal plate with double-sided steel stubs coated by rubber layers. Through finite element analysis, it can be found that the proposed structure can produce a bandgap with 355 Hz bandwidth within the range of 0–500 Hz and isolate vibration in the range of bandgap. By analyzing the local resonance modes of the proposed structure, we further propose the equivalent mass–spring model to predict its bandgap range. The predicted bandgap results from equivalent models of the proposed structure agree well with the results from the finite element analysis. These equivalent models provide an effective and simple method for bandgap optimization of the proposed phononic crystal structure.