Evidence of new 2D material: Cu₂Te

Abstract

The number of two-dimensional (2D) materials has grown steadily since the discovery of graphene. Each new 2D material demonstrated unusual physical properties offering a large flexibility in their tailoring for high-tech applications. Here, we report on the formation and characterization of an uncharted 2D material: ‘Cu2Te alloy monolayer on Cu(111) surface’. We have successfully grown a 2D binary Te-Cu alloy using a straightforward approach based on chemical deposition method. Low electron energy diffraction (LEED) and scanning tunneling microscopy (STM) results reveal the existence of a well-ordered alloy monolayer characterized by (√3 × √3)R30° superstructure, while the x-ray photoemission spectroscopy (XPS) measurements indicate the presence of single chemical environment of the Te atoms associated with the Te-Cu bonding. Analysis of the valence band properties by angle resolved photoemission spectroscopy (ARPES); in particular the electronic states close to the Fermi level suggests a strong hybridization between Te and Cu electronic states leading to an appearance of new dispersive bands localized at the surface alloy, which is confirmed by first-principles calculations. These bands are strongly influenced by the surface reconstruction and undergo a back-folding at the boundaries of the reduced surface Brillouin zone (SBZ). More interesting, a band gap of about 0.91 eV and a Rashba splitting in the conduction band are obtained. These findings taken together clearly prove the presence of 2D-type electron system within the Cu2Te alloy layer, which is promising for spintronic application.

CuTe chains on Cu(111) by deposition of 1/3 ML Te: atomic and electronic structure

“…Our results contradict the findings of others who claim that the deposition of 1 /3 ML Te leads to the formation of a Cu 2 Te-surface alloy with a √ 3 × √ 3 R30 • supercell [18][19][20] . Only one early investigation reported a 2 √ 3 × √ 3 R30 • structure for this coverage 17 .…”

“…To understand the nucleation and the formation of interfaces one needs to start with a low Te coverage Θ. For the particular case of Θ = 1 /3 ML of Te on Cu(111) attempts have been made over the years [16][17][18][19][20] but a true reliable structural analysis is still missing. Seemingly, there is an agreement on a √ 3 × √ 3 R30 • superstructure, but from our work we can infer that such a structure only occurs at much higher Te coverage or under the influence of some contaminant.…”

In Situ Dynamics during Heating of Copper-Intercalated Bismuth Telluride

“…In addition to these interesting dynamics, this transformation is also a potential synthetic pathway for producing flat platelets of single-crystal Cu 2 Te, which has only been synthesized in a few nanostructured form factors to date. [63][64][65][66] As mentioned previously, the details of the transformation process are specific to the high vacuum conditions used here. However, to verify the applicability of these results to other conditions, Cu-intercalated Bi 2 Te 3 platelets were heated to 650 C in a 200-Torr Ar environment as shown in Figure S4A.…”

Atomic Level Insights into Metal Halide Perovskite Materials by Scanning Tunneling Microscopy and Spectroscopy

“…It also allows in situ real-time monitoring and characterization of material growth and evolution processes,s urface dynamics,a nd surface chemistry.Scanning tunneling spectroscopy can precisely reveal the electronic structures of the surface at the atomic scale.F urthermore,S TM can be combined with many other ultrahigh vacuum (UHV) techniques to provide comprehensive characterization of the sample surface.C ompared with transmission electron microscopy (another powerful technique with the capability of atomic-resolution imaging), STM experiments can be considered non-invasive and the sample preparation is relatively straightforward. However,S TM requires an atomically smooth and conductive surface and asharp metallic tip.Although STM can offer crucial insights into the fundamental understanding of materials ultimately at the atomic scale, [15] STM studies on perovskite materials are still relatively rare,p resumably because of the technical difficulty in obtaining an immaculate and atomically flat sample surface. [13a, 16] Recent findings indicate that the surface trap states in the perovskite layer can strongly influence the performance of the solar cell devices; [7b,17] however, the chemical and physical properties of atomic-scale defects and surface and interface properties are not well-understood.…”