Surface reconstruction refers to the process by which atoms at the surface of a crystal assume a different structure than that of the bulk. Surface reconstructions are important in that they help in the understanding of surface chemistry for various materials, especially in the case where another material is adsorbed onto the surface.
In an ideal infinite crystal, the equilibrium position of each individual atom is determined by the forces exerted by all the other atoms in the crystal, resulting in a periodic structure. If a surface is introduced to the surroundings by terminating the crystal along a given plane, then these forces are altered, changing the equilibrium positions of the remaining atoms. This is most noticeable for the atoms at or near the surface plane, as they now only experience inter-atomic forces from one direction. This imbalance results in the atoms near the surface assuming positions with different spacing and/or symmetry from the bulk atoms, creating a different surface structure. This change in equilibrium positions near the surface can be categorized as either a relaxation or a reconstruction.
Relaxation refers to a change in the position of surface atoms relative to the bulk positions, while the bulk unit cell is preserved at the surface. Often this is a purely normal relaxation: that is, the surface atoms move in a direction normal to the surface plane, usually resulting in a smaller-than-usual inter-layer spacing. This makes intuitive sense, as a surface layer that experiences no forces from the open region can be expected to contract towards the bulk. Most metals experience this type of relaxation. Some surfaces also experience relaxations in the lateral direction as well as the normal, so that the upper layers become shifted relative to layers further in, in order to minimize the positional energy.
Reconstruction refers to a change in the two-dimensional structure of the surface layers, in addition to changes in the position of the entire layer.
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The principles of 3D surface (SEM) reconstruction and its limitations will be explained. 3D volume reconstruction and tomography methods by electron microscopy (SEM/FIB and TEM) will be explained and
Series of lectures covering the use of electron spectroscopy for the study of the electronic and atomic structure of surfaces, nanostructures, and quantum materials. Special attention is given to vari
Low-energy electron diffraction (LEED) is a technique for the determination of the surface structure of single-crystalline materials by bombardment with a collimated beam of low-energy electrons (30–200 eV) and observation of diffracted electrons as spots on a fluorescent screen. LEED may be used in one of two ways: Qualitatively, where the diffraction pattern is recorded and analysis of the spot positions gives information on the symmetry of the surface structure.
A scanning tunneling microscope (STM) is a type of microscope used for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer, then at IBM Zürich, the Nobel Prize in Physics in 1986. STM senses the surface by using an extremely sharp conducting tip that can distinguish features smaller than 0.1 nm with a 0.01 nm (10 pm) depth resolution. This means that individual atoms can routinely be imaged and manipulated.
Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of surface chemistry and surface physics. Some related practical applications are classed as surface engineering. The science encompasses concepts such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, and adhesives.
The electronic structure of surfaces plays a key role in the properties of quantum devices. However, surfaces are also the most challenging to simulate and engineer. Here, the electronic structure of InAs(001), InAs(111), and InSb(110) surfaces is studied ...
WILEY2022
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A microsecond time-resolved version of cryo-electron microscopy (cryo-EM) has recently been introduced to enable observation of the fast conformational motions of proteins. The technique involves locally melting a cryo sample with a laser beam to allow the ...
This thesis investigates the magnetic properties of single atoms and dimers adsorbed on graphene and oxide decoupling layers supported by single crystal metal substrates, using scanning tunneling microscopy (STM) and spin-polarized scanning tunneling micro ...