Tunable 2D Group‐III Metal Alloys

Abstract

Chemically stable quantum-confined 2D metals are of interest in next-generation nanoscale quantum devices. Bottom-up design and synthesis of such metals could enable the creation of materials with tailored, on-demand, electronic and optical properties for applications that utilize tunable plasmonic coupling, optical non-linearity, epsilon-near-zero behavior, or wavelengthspecific light trapping. In this work, we demonstrate that the electronic, superconducting and optical properties of air-stable two-dimensional metals can be controllably tuned by the formation of alloys. Environmentally robust large-area two-dimensional InxGa1-x alloys are synthesized by Confinement Heteroepitaxy (CHet). Near-complete solid solubility is achieved with no evidence of phase segregation, and the composition is tunable over the full range of x by changing the relative elemental composition of the precursor. The optical and electronic properties directly correlate with alloy composition, wherein the dielectric function, band structure, superconductivity, and charge transfer from the metal to graphene are all controlled by the indium/gallium ratio in the 2D metal layer.

Atomic-Level Structure Determines Electron–Phonon Scattering Rates in 2-D Polar Metal Heterostructures

“…15 This interband transition is sensitive to the choice of metal intercalant, typically exhibiting a 50 nm red shift for indium with respect to gallium (Figure S1). The 2-D alloy interband transition energy can be tuned by the metal composition, 25 and the absorption peak is located between the 2-D In and 2-D Ga peaks (Figure S1).…”

“…Evidence of increased structural disorder was also obtained from high-resolution scanning transmission electron microscopy (STEM) images of the alloy (Figure 7c,d). 25 Previous statistical analysis of HR-STEM images of 2-D In revealed that the first metal layer is aligned directly above the Si, and the second layer exhibits a strong preference to sit directly above the carbon atoms of the top SiC layer. 14 This preference for a particular registry of the metal atoms over the SiC results in the same metal lattice orientation persisting across an entire terrace.…”

“…2-D Ga, In, and alloy were obtained via the confinement heteroepitaxy (CHet) method in a horizontal tube furnace. The alloy precursor was formed by the mixing of gallium and indium powder on a custom-made alumina crucible at 80 °C in an Ar environment, and annealing at 800 °C and 500 Torr for 30 min was the optimized condition for the CHet process …”

“…The alloy precursor was formed by the mixing of gallium and indium powder on a custom-made alumina crucible at 80 °C in an Ar environment, and annealing at 800 °C and 500 Torr for 30 min was the optimized condition for the CHet process. 25 Linear Extinction. Extinction measurements were performed using an Agilent Cary 5000 with a universal measurement accessory.…”

Scalable Characterization of 2D Gallium-Intercalated Epitaxial Graphene

“…1 In this technique, atoms intercalate at the interface of EG and silicon carbide (SiC) substrates, which facilitates large-area, environmentally airstable 2D nitrides, 2,3 2D oxides, 4,5 2D metals, 1,6 and 2D alloys. 7,8 This air stability provided by the graphene cap is the key ingredient for next-generation quantum, high-frequency electronics, optical, and sensing technologies. 9 In addition, the use of EG enables superior heterostructure quality compared to graphene transferred by liquid methods.…”