Triggering one dimensional phase transition with defects at the graphene zigzag edge

TL;DR

This study demonstrates that artificially introduced defects can induce a well-defined one-dimensional phase transition at graphene zigzag edges, combining experimental microscopy with simulations to understand the atomic-scale dynamics and enabling new GNR fabrication methods.

Contribution

It introduces a novel method to induce and analyze 1D phase transitions in graphene edges using defects, supported by combined experimental and computational approaches.

Findings

Defects induce a clear 1D phase transition at graphene zigzag edges.

Atomic-scale dynamics of the transition are elucidated through microscopy and simulations.

GNRs with different edge symmetries exhibit a metal-insulator-semiconductor transition.

Abstract

One well-known argument about one dimensional(1D) system is that 1D phase transition at finite temperature cannot exist, despite this concept depends on conditions such as range of interaction, external fields and periodicity. Therefore 1D systems usually have random fluctuations with intrinsic domain walls arising which naturally bring disorder during transition. Herein we introduce a real 1D system in which artificially created defects can induce a well-defined 1D phase transition. The dynamics of structural reconstructions at graphene zigzag edges are examined by in situ aberration corrected transmission electron microscopy (ACTEM). Combined with an in-depth analysis by ab-initio simulations and quantum chemical molecular dynamics (QM/MD), the complete defect induced 1D phase transition dynamics at graphene zigzag edge is clearly demonstrated and understood on the atomic scale. Further, following this phase transition scheme, graphene nanoribbons (GNR) with different edge symmetries can be fabricated, and according to our electronic structure and quantum transport calculations, a metal-insulator-semiconductor transition for ultrathin GNRs is proposed.