Mechanisms of quasi-van der Waals epitaxy of 3D metallic nanoislands on suspended 2D materials

TL;DR

This paper investigates the formation and structure of 3D metallic nanoislands on suspended 2D materials, revealing how interface energies and growth conditions influence morphology, and introduces a new method for fabricating 3D/2D heterostructures.

Contribution

It provides a detailed analysis of the interface structures and growth mechanisms of metallic nanoislands on 2D materials, including a novel fabrication approach for heterostructures.

Findings

Interface energies quantified for Au on graphene and TMDs.

Transition from dendritic to facetted islands with temperature.

Suspended 2D materials enable new 3D/2D/3D heterostructures.

Abstract

Understanding structure at the interface between two-dimensional (2D) materials and 3D metals is crucial for designing novel 2D/3D heterostructures and improving the performance of many 2D material devices. Here, we quantify and discuss the 2D/3D interface structure and the 3D morphology in several materials systems. We first deposit facetted Au nanoislands on graphene and transition metal dichalcogenides, using measurements of the equilibrium island shape to determine values for the 2D/Au interface energies and examining the role of surface reconstructions, chemical identity, and defects on the grown structures. We then deposit the technologically relevant metals Ti and Nb under conditions where kinetic rather than thermodynamic factors govern growth. We describe a transition from dendritic to facetted islands as a function of growth temperature and discuss the factors determining island shape in these materials systems. Finally, we show that suspended 2D materials enable the fabrication of a novel type of 3D/2D/3D heterostructure and discuss the growth mechanism. We suggest that emerging nanodevices will utilize such versatile fabrication of 2D/3D heterostructures with well-characterized interfaces and morphologies.