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Apparent Barrier Height and Barrier-Height Imaging of Surfaces
Summary Tunneling barrier height is one of the most fundamental parameters in STM. It is this barrier height that leads to the exponential gap dependence of the tunneling current and hence enables STM to probe surfaces with atomic resolution. In a simple one-dimensional model of electron tunneling in STM, the barrier height has a definite meaning and its relation to the tunneling current and to the work functions of the tip and sample are both firmly established. In real STM, however, the barrier height derived experimentally from the gap dependence of the tunneling current cannot be simply interpreted as a potential barrier height since it contains complicated contributions from the electronic and atomic structures of the tip and sample. Because of this difficulty in analyzing barrier-height data, STM barrier-height imaging has long remained an auxiliary imaging technique, although it was invented in the early days of STM. However, in recent experiments, barrier-height imaging has been revived to procure unique information which cannot be obtained by other imaging methods. In these experiments, the sensitivity of the barrier height to the sample work function has been utilized for elemental identification on surfaces and for probing local changes in work function induced by adsorption and defect formation. In this article, we will present a brief review of experimental and theoretical studies of the barrier height in STM, together with some recent applications of barrier-height imaging to clean and adsorbed surfaces.
Apparent Barrier Height and Barrier-Height Imaging of Surfaces
Summary Tunneling barrier height is one of the most fundamental parameters in STM. It is this barrier height that leads to the exponential gap dependence of the tunneling current and hence enables STM to probe surfaces with atomic resolution. In a simple one-dimensional model of electron tunneling in STM, the barrier height has a definite meaning and its relation to the tunneling current and to the work functions of the tip and sample are both firmly established. In real STM, however, the barrier height derived experimentally from the gap dependence of the tunneling current cannot be simply interpreted as a potential barrier height since it contains complicated contributions from the electronic and atomic structures of the tip and sample. Because of this difficulty in analyzing barrier-height data, STM barrier-height imaging has long remained an auxiliary imaging technique, although it was invented in the early days of STM. However, in recent experiments, barrier-height imaging has been revived to procure unique information which cannot be obtained by other imaging methods. In these experiments, the sensitivity of the barrier height to the sample work function has been utilized for elemental identification on surfaces and for probing local changes in work function induced by adsorption and defect formation. In this article, we will present a brief review of experimental and theoretical studies of the barrier height in STM, together with some recent applications of barrier-height imaging to clean and adsorbed surfaces.
Apparent Barrier Height and Barrier-Height Imaging of Surfaces
Sakai, Akira (author)
2000-01-01
23 pages
Article/Chapter (Book)
Electronic Resource
English
Barrier Height , Tunneling Current , Scan Tunneling Spectroscopy , Bias Dependence , Surface Work Function Engineering , Electronics and Microelectronics, Instrumentation , Science, general , Materials Science, general , Surfaces and Interfaces, Thin Films , Optical and Electronic Materials , Solid State Physics
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