Graphyne- and Graphdiyne-based Nanoribbons: Density Functional Theory Calculations of Electronic Structures (1211.4310v1)

Abstract: We report on the configurations and electronic properties of graphyne and graphdiyne nanoribbons with armchair and zigzag edges investigated with first principles calculations. Our results show that all the nanoribbons are semiconductors with suitable band gaps similar to silicon. And their band gaps decrease as widths of nanoribbons increase. We also find that the band gap is at the Gamma point for all graphdiyne ribbons and it is at the X point for all graphyne ribbons. Of particular interest, the band gap of zigzag graphyne nanoribbons show a unique step effect as the width increases. This property is good for tuning of the energy band gap, as in a certain range of the ribbon width, the energy gap remains constant and in reality the edge cannot be as neat as that in a theoretic model.

• The paper demonstrates that both graphyne and graphdiyne nanoribbons are semiconductors with tunable band gaps ranging from 0.54 to 1.65 eV.
• The paper details a unique 'step effect' in zigzag graphyne nanoribbons and distinct gap positions at the Γ and X points, underpinning precise electronic tunability.
• The paper employs DFT with a PAW method in VASP, ensuring accurate structure optimization and establishing these nanoribbons as potential semiconductor materials.

Electronic Properties of Graphyne- and Graphdiyne-based Nanoribbons: A DFT Study

This paper examines the electronic structures and properties of nanoribbons based on graphyne and graphdiyne, using density functional theory (DFT) calculations. With a focus on nanoribbons featuring armchair and zigzag edge configurations, the research provides a comprehensive assessment of their band gap characteristics and potential applicability in semiconductor technologies.

Main Findings

The paper's principal finding is that both graphyne and graphdiyne nanoribbons are semiconductors with tunable band gaps. Specifically, these band gaps range from 0.59 to 1.32 eV for graphyne nanoribbons, depending on whether they possess armchair or zigzag edges, while for graphdiyne nanoribbons, the range is from 0.54 to 1.65 eV. Notably, the band gaps of graphyne nanoribbons are larger than those of graphene nanoribbons with comparable widths, assuming values similar to silicon's.

Importantly, the paper reveals a unique "step effect" in the band gap variation of zigzag graphyne nanoribbons with increasing width, unlike the smoother decrease observed in other ribbons. This effect underscores the differences in band structure behavior between edge configurations and offers potential avenues for precise band gap tuning, critical for applications in electronic devices.

Another pivotal finding is the distinct behavior of band gaps in reciprocal space: for graphdiyne nanoribbons, the band gap emerges at the Γ point, while for graphyne nanoribbons, it appears at the X point. The dependence of this phenomenon on the number of acetylenic linkages provides an insightful rule that may help predict electronic properties in related carbon nanostructures.

Methodological Approach

The researchers used DFT with local density approximation (LDA) to perform simulations, implementing the Vienna ab-initio simulation package (VASP). The paper deployed a projector augmented wave (PAW) approach to achieve accurate electronic wave function representations. The optimization of nanoribbon structures was meticulous, ensuring the geometric stability requisite for reliable electronic property predictions.

Implications and Future Directions

The findings offer substantial implications for the future of nanoscale electronic devices. The ability to engineer band gaps similar to those of silicon positions graphyne and graphdiyne nanoribbons as potential alternatives in semiconductor applications. The width-dependent tunability of band gaps, coupled with the observed "step effect," enables a new dimension of electronic property control, which is particularly advantageous in designing devices that require specific electronic characteristics.

Theoretically, this research enriches the understanding of electronic behavior in quasi-one-dimensional nanocarbon systems, a domain gaining increasing prominence. Future explorations could explore the interaction of these structures with other materials and potential composite formations. Additionally, examining the environmental stability and manufacturability of these ribbons will be crucial for transitioning from theoretical exploration to practical application.

In summary, this paper methodically expands the knowledge on graphyne and graphdiyne nanoribbons, presenting them as viable candidates for future electronic materials. The presence of tunable band gaps and unique band structure properties sets a promising foundation for further exploration in material science and electronic engineering.