Ballistic electron emission microscopy and spectroscopy: Recent results and related techniques

Abstract

Interfaces play a central role in determining properties of optical and electronic devices. Many mature techniques exist for surface characterization, providing a great deal of detailed, local information. Interface methods with equivalent capabilities have not developed as fully, due primarily to the inaccessibility of buried interfaces to traditional surface sensitive probes. Ballistic electron emission microscopy (BEEM) is a class of microscopies and spectroscopies that uses energetic electrons injected by a scanning tunneling microscopy tip as a probe of subsurface electronic structure. This article reviews the growth of BEEM methods and summarizes recent areas of investigation using these techniques. Research areas span a range of materials, such as metals, semiconductors, insulators, magnetic materials, and organic layers, as well as a variety of physical properties that include interface barrier height, hot-carrier scattering, interface heterogeneity, magnetic domain structure, and electronic band structure.

Internal Photoemission Metrology of Inhomogeneous Interface Barriers

“…In vacuum, evaluation of the WF lateral non‐uniformity can be done by a variety of techniques ranging from scanning‐probe methods (Kelvin probe, ballistic electron microscopy, BEEM,) to electron emission imaging methods such as photoelectron emission microscopy (PEEM), surface ionization methods and photoemission from adsorbed probe‐atoms . However, in the case of interface barriers, detection of lateral non‐uniformity represents a considerable challenge.…”

“…Similarly, the lateral resolution of the CV method is determined by the Debye length of chosen semiconductor and is usually of the order of 0.1 μm . Significantly better lateral resolution of interface barrier quantification can be achieved by BEEM . However, in order to achieve a sufficiently high electrode transparency, most of these works focus on relatively low metal/semiconductor barriers.…”

Effective Metal Top Contact on the Organic Layer via Buffer-Layer-Assisted Growth: A Multiscale Characterization of Au/Hexadecanethiol/n-GaAs(100) Junctions

“…16 For a detailed review on the BEEM technique, the reader might refer to the excellent recent work published by L. Douglas Bell. 17 Briefly, the BEEM technique is derived from the STM one. In the case of a Schottky contact (Au/GaAs), hot electrons are injected from the STM tip to the metallic surface, and a small fraction of them (only a few percent) reaches the Au/GaAs interface with no energy loss.…”

Visualization of Plasmon-Induced Hot Electrons by Scanning Electron Microscopy

“…Hot electrons can be characterized by spectroscopic methods such as incident photon current efficiency (IPCE), which measures the electric current followed by illumination, , and laser raster scanning integrated by photocurrent measurements. , Hot-electron formation can be estimated qualitatively as well as indirectly by cathodoluminescence (CL). , Another important technique for the visualization and imaging of energetic carriers is scanning tunneling microscopy (STM), which is also implemented using a technique known as ballistic electron emission microscopy (BEEM). − …”