Spatial inhomogeneity and temporal dynamics of a 2D electron gas in interaction with a 2D adatom gas

TL;DR

This study explores how a 2D electron gas interacts with a 2D adatom gas on a surface, revealing spatial inhomogeneities and temporal fluctuations influenced by temperature, adatom concentration, and surface structures.

Contribution

It provides new insights into the spatial and temporal dynamics of 2DEG in the presence of adatom gases, including temperature-dependent structural effects and charge transfer behavior.

Findings

Linear surface work function change with adatom concentration

Breakdown of linearity due to superstructure formation below room temperature

Observation of charge transfer fluctuations linked to adatom dynamics

Abstract

Fundamental interest for 2D electron gas (2DEG) systems has been recently renewed with the advent of 2D materials and their potential high-impact applications in optoelectronics. Here, we investigate a 2DEG created by the electron transfer from a Ag adatom gas deposited on a Si(111)$\sqrt{3}\times\sqrt{3}$-Ag surface to an electronic surface state. Using low-energy electron microscopy (LEEM), we measure the Ag adatom gas concentration and the 2DEG-induced charge transfer. We demonstrate a linear dependence of the surface work function change on the Ag adatom gas concentration. A breakdown of the linear relationship is induced by the occurrence of the Ag adatom gas superstructure identified as Si(111)$\sqrt{21}\times\sqrt{21}$-Ag only observed below room temperature. We evidence below room temperature a confinement of the 2DEG on atomic terraces characterised by spatial inhomogeneities of the 2DEG-induced charge transfer along with temporal fluctuations. These variations mirror the Ag adatom gas concentration changes induced by the growth of 3D Ag islands and the occurrence of an Ehrlich-Schwoebel diffusion barrier of 155$\pm$10meV.