Introduction to Molecular Beam Epitaxy Technology
Molecular beam epitaxy (MBE) is a newly developed epitaxial film-making method and a special vacuum coating process. Epitaxy is a new technology for preparing single crystal thin films. It is a method of growing thin films layer by layer along the crystal axis of the substrate material under appropriate substrates and conditions. The advantages of this technology are: the substrate temperature used is low, the film growth rate is slow, the beam intensity is easy to accurately control, and the film composition and doping concentration can be quickly adjusted as the source changes. This technology can be used to prepare single crystal films as thin as dozens of atomic layers, as well as ultra-thin layer quantum microstructure materials formed by alternately growing films of different compositions and dopings. principle The abbreviation of molecular beam epitaxy is MBE, which is a new technology for growing high-quality crystal films on crystal substrates. Under ultra-high vacuum conditions, the vapor generated by heating in a furnace containing various required components is collimated through small holes to form a molecular beam or atomic beam, which is directly sprayed onto a single crystal substrate at an appropriate temperature. By controlling the molecular beam to scan the substrate, molecules or atoms can be "grown" layer by layer in a crystalline arrangement to form a thin film on the substrate. Features (2) The temperature of epitaxial growth is low, thus reducing the lattice mismatch effect caused by thermal expansion at the interface and the self-doping diffusion effect of substrate impurities on the epitaxial layer. (3) Since the growth is carried out in ultra-high vacuum, the substrate surface can be completely clean after treatment, and contamination can be avoided during the epitaxy process, so an epitaxial layer of excellent quality can be grown. Molecular beam epitaxy devices are generally equipped with instruments for detecting surface structure, composition and vacuum residual gas, which can monitor the composition and structural integrity of the epitaxial layer at any time, which is beneficial to scientific research. (4) MBE is a kinetic process, in which incident neutral particles (atoms or molecules) are accumulated one by one on the substrate for growth, rather than a thermodynamic process, so it can grow materials that are difficult to grow according to ordinary thermal equilibrium growth methods. film. (5) MBE is an ultra-high vacuum physical deposition process that neither needs to consider intermediate chemical reactions nor is affected by mass transmission, and the shutter can be used to instantaneously control growth and interruption. Therefore, the composition and doping concentration of the film can be rapidly adjusted as the source changes. application
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