Atomic-scale epitaxial aluminum film on GaAs substrate

Abstract

Atomic-scale metal films exhibit intriguing size-dependent film stability, electrical conductivity, superconductivity, and chemical reactivity. With advancing methods for preparing ultra-thin and atomically smooth metal films, clear evidences of the quantum size effect have been experimentally collected in the past two decades. However, with the problems of small-area fabrication, film oxidation in air, and highly-sensitive interfaces between the metal, substrate, and capping layer, the uses of the quantized metallic films for further ex-situ investigations and applications have been seriously limited. To this end, we develop a large-area fabrication method for continuous atomic-scale aluminum film. The self-limited oxidation of aluminum protects and quantizes the metallic film and enables ex-situ characterizations and device processing in air. Structure analysis and electrical measurements on the prepared films imply the quantum size effect in the atomic-scale aluminum film. Our work opens the way for further physics studies and device applications using the quantized electronic states in metals.

Topological Transition in a 3 nm Thick Al Film Grown by Molecular Beam Epitaxy

“…The quality of the sample in this work is similar to those reported in Ref. [15]. In our earlier work, for a MBE-grown film deposited at room temperature with an intended thickness of 3 nm, the average roughness of the film is about 4.9 nm which is thicker than the deposited thickness and is possibly caused by the Al oxidation after the exposure to air [17].…”

“…Such a highquality two-dimensional (2D) metallic film is an ideal system for probing 2D physics. Interestingly, the critical temperature T c of the studied MBE-grown Al nanofilms (~2.4 K) [15] can be significantly higher than that of bulk Al (1.2 K). In order to obtain a thorough understanding of the physics and the nature of the observed superconductivity in Al nanofilms, we perform detailed transport measurements on a 3 nm thick (as-grown) Al nanofilm.…”

“…The 3 nm thick Al film reported in this paper was prepared in a Varian Gen-II solid-source MBE system [15]. The experimental details can be found in the supplementary information (S1).…”

“…Aluminum (Al) is the most abundant metal on the Earth's crust, and it has already found wide applications in interconnects, coating on graphene, plasmonic devices, and so on [12][13][14]. Recent advances in sample preparation have made it possible to prepare large-area, high-quality Al films [14,15]. In particular, large-area Al films with an atomically smooth surface grown by molecular beam epitaxy (MBE) on a GaAs substrate can be readily accessible [15].…”

“…Recent advances in sample preparation have made it possible to prepare large-area, high-quality Al films [14,15]. In particular, large-area Al films with an atomically smooth surface grown by molecular beam epitaxy (MBE) on a GaAs substrate can be readily accessible [15]. Such a highquality two-dimensional (2D) metallic film is an ideal system for probing 2D physics.…”