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{{bf{3}}}{boldsymbol{times }}sqrt{{bf{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{{bf{21}}}{boldsymbol{times }}sqrt{{bf{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 ± 10 meV.
Highlights
IntroductionWe evidence below room temperature a confinement of the 2D electron gas systems (2DEG) on atomic terraces characterised by spatial inhomogeneities of the 2DEGinduced charge transfer along with temporal fluctuations
21 × 21-Ag only observed below room temperature
The occurrence of a conductive 2D phase at the surface of oxides paves the way for the emerging field of functional oxide electronics1. 2D Dirac electron gas observed in graphene has been shown to surpass the long-standing 2D electron gas systems (2DEG) confined at the GaAs/AlGaAs interface to determine the Planck constant h using Quantum Hall resistance measurements2. 2DEG at metal/semiconductor interfaces have pushed the phenomenon of superconductivity downto its very 2D limit[3] and shown intriguing electron localisation and metal-insulator transition[4]
Summary
We evidence below room temperature a confinement of the 2DEG on atomic terraces characterised by spatial inhomogeneities of the 2DEGinduced 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 EhrlichSchwoebel diffusion barrier of 155 ± 10 meV. RT, we evidence the confinement of the 2DEG on atomic terraces upon Ag deposition and after the nucleation of 3D growing Ag islands This regime is characterised by inhomogeneous spatial distributions and temporal fluctuations of the 2DEG charge transfer induced by the Ag-2DAG. Interpreted as the result of the occurrence of an Ehrlich-Schwoebel diffusion barrier of 155 ± 10 meV below RT and of the interaction between the Ag-2DAG and growing 3D Ag islands
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