Abstract
Using ab initio molecular dynamics, we show that a recently discovered form of 2D Ga—gallenene—exhibits highly variable thickness dependent properties. Here, 2D Ga of four, five and six atomic layers thick are found to be thermally stable to 457 K, 350 K and 433 K, respectively; all well above that of bulk Ga. Analysis of the liquid structure of 2D Ga shows a thickness dependent ordering both parallel and perpendicular to the Ga/vacuum interface. Furthermore, ground state optimisations of 2D Ga to 12 atomic layers thick shows a return to a bulk-like bonding structure at 10 atoms thick, therefore we anticipate that up to this thickness 2D Ga structures will each exhibit novel properties as discrete 2D materials. Gallenene has exciting potential applications in plasmonics, sensors and electrical contacts however, for the potential of 2D Ga to be fully realised an in depth understanding of its thickness dependent properties is required.
Highlights
Gallium (Ga) has an array of applications in the current technological age, being used as a component in light emitting diodes,[1] reversible light-induced switching,[2] phase-change nonlinear systems,[3] active plasmonics,[4] chemical sensing,[5] molecular sensing,[6] and for drug delivery.[7]
We extend the previous work by our group on the thermal stability of 2D Ga by using ab initio molecular dynamics (AIMD) simulations to determine the Tmelt of 2D Ga as the thickness is increased from four, to ve and six atomic layers
The thermal stability of 2D Ga four, ve and six atomic layers thick is considerably greater than the bulk thermal stability
Summary
Gallium (Ga) has an array of applications in the current technological age, being used as a component in light emitting diodes,[1] reversible light-induced switching,[2] phase-change nonlinear systems,[3] active plasmonics,[4] chemical sensing,[5] molecular sensing,[6] and for drug delivery.[7] Ga is considered a technology-critical element.[8]. Despite Ga's use in a wide variety of everyday technologies, Ga is an unusual element because it is highly polymorphic. A-Ga is the standard phase and is stable at atmospheric pressure and room temperature, a range of other phases (b, g, d) are accessible at a variety of temperatures, while Ga(I), Ga(II) and Ga(III) exist under different pressures.[9] Ga has a hugely complex phase diagram with one of the largest liquid temperature ranges of all the elements.[10]. Each Ga has one nearest neighbour at approximately 2.44 Aforming covalently bound dimers, while the remaining 6 nearest neighbours are metallically bound in a strongly buckled plane perpendicular to the average alignment of the dimers.[12,13,14] Bulk a-Ga has a low melting temperature (Tmelt) of 303 K, putting Ga in a select group of low-melting temperature metals (where “low-temperature” is de ned as Tmelt < 303 K) which
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