Unexpected Huge Dimerization Ratio in One-Dimensional Carbon Atomic Chains

Abstract

Peierls theory predicted atomic distortion in one-dimensional (1D) crystal due to its intrinsic instability in 1930. Free-standing carbon atomic chains created in situ in transmission electron microscope (TEM)1-3 are an ideal example to experimentally observe the dimerization behavior of carbon atomic chain within a finite length. We report here a surprisingly huge distortion found in the free-standing carbon atomic chains at 773 K, which is 10 times larger than the value expected in the system. Such an abnormally distorted phase only dominates at the elevated temperatures, while two distinct phases, distorted and undistorted, coexist at lower or ambient temperatures. Atom-by-atom spectroscopy indeed shows considerable variations in the carbon 1s spectra at each atomic site but commonly observes a slightly downshifted π* peak, which proves its sp bonding feature. These results suggest that the simple model, relaxed and straight, is not fully adequate to describe the realistic 1D structure, which is extremely sensitive to perturbations such as external force or boundary conditions.

Engineering and modifying two-dimensional materials by electron beams

“…The different arrangements are reflected in varied C-C bond length, and a recent study finds an unexpectedly high dimerization ratio in such 1D carbon atomic chains (i.e., the polyyne structure) created under the e-beam at elevated temperatures. 35 One-dimensional atomic chains with alternating B-N-B-N arrangement have also been produced in h-BN under e-beam ( Figure 5b), and they remain insulating as suggested by theory. 36 The stability of heteroatomic chains is significantly enhanced once they are supported by an h-BN layer.…”

“…32 In addition, novel nanostructures, which might not be grown by conventional methods, can be controllably fabricated under e-beam irradiation. Examples include the selective sculpting of 1D atomic chains 8,[33][34][35][36] and subnanometer nanowires [37][38][39][40][41] in a monolayer matrix using a focused e-beam and the formation of new atomically thin 2D materials (monolayer Fe 42 and monolayer copper oxide 43,44 ) via self-assembly of adatoms on a graphene surface (or in graphene nanopores) under e-beam irradiation.…”

A single-molecule porphyrin-based switch for graphene nano-gaps

“…25 Interestingly, TEM images of such graphene junctions show that linear carbon chains can form at a variety of angles to the graphene edges, including the almost 90°bond angle assumed here. 39…”

The Sub‐Nanometer Scale as a New Focus in Nanoscience

“…However, from the perspective of thermodynamics, pure atomic chains must be very unstable, because they contain extremely large amounts of surface atoms and perhaps many dangling bonds. Only a few kinds of metals or carbon materials have been identified to experimentally have the form of single‐atom chains with lengths of several to several tens of atoms, and they showed very short lifetimes (less than 2 min) under ambient conditions. To stabilize single‐atom chains, the surrounding chemical environment had to be engineered; then, hollow materials with 1D pores began to be studied.…”