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Selective Area Epitaxy
Selective area epitaxy is the local growth of Epitaxy, epitaxial layer through a patterned amorphous dielectric mask (typically Silicon dioxide, SiO2 or Silicon nitride, Si3N4) deposited on a semiconductor substrate. Semiconductor growth conditions are selected to ensure epitaxial growth on the exposed substrate, but not on the dielectric mask. SAE can be executed in various epitaxial growth methods such as Molecular-beam epitaxy, molecular beam epitaxy (MBE), Metalorganic vapour-phase epitaxy, metalorganic vapour phase epitaxy (MOVPE) and chemical beam epitaxy (CBE). By SAE, semiconductor nanostructures such as quantum dots and nanowires can be grown to their designed places. Concepts Mask The mask used in SAE is usually amorphous dielectric such as SiO2 or SiN4 which is deposited on the semiconductor substrate. The patterns (holes) in the mask are fabricated using standard microfabrication techniques lithography and etching. Variety of lithography and etching techniques can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epitaxy
Epitaxy (prefix ''epi-'' means "on top of”) is a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epitaxial film or epitaxial layer. The relative orientation(s) of the epitaxial layer to the seed layer is defined in terms of the orientation of the crystal lattice of each material. For most epitaxial growths, the new layer is usually crystalline and each crystallographic domain of the overlayer must have a well-defined orientation relative to the substrate crystal structure. Epitaxy can involve single-crystal structures, although grain-to-grain epitaxy has been observed in granular films. For most technological applications, single-domain epitaxy, which is the growth of an overlayer crystal with one well-defined orientation with respect to the substrate crystal, is preferred. Epitaxy can also play an important ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microfabrication
Microfabrication is the process of fabricating miniature structures of micrometre scales and smaller. Historically, the earliest microfabrication processes were used for integrated circuit fabrication, also known as "semiconductor manufacturing" or "semiconductor device fabrication". In the last two decades, microelectromechanical systems (MEMS), microsystems (European usage), Micromachinery, micromachines (Japanese terminology) and their subfields have re-used, adapted or extended microfabrication methods. These subfields include microfluidics/lab-on-a-chip, optical MEMS (also called MOEMS), RF MEMS, PowerMEMS, BioMEMS and their extension into nanoscale (for example NEMS, for nano electro mechanical systems). The production of flat-panel displays and solar cells also uses similar techniques. Miniaturization of various devices presents challenges in many areas of science and engineering: physics, chemistry, materials science, computer science, ultra-precision engineering, fabricat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topological Quantum Computer
A topological quantum computer is a type of quantum computer. It utilizes anyons, a type of quasiparticle that occurs in two-dimensional systems. The anyons' world lines intertwine to form braids in a three-dimensional spacetime (one temporal and two spatial dimensions). The braids act as the logic gates of the computer. The primary advantage of using quantum braids over trapped quantum particles is in their stability. While small but cumulative perturbations can cause quantum states to decohere and introduce errors in traditional quantum computations, such perturbations do not alter the topological properties of the braids. This stability is akin to the difference between cutting and reattaching a string to form a different braid versus a ball (representing an ordinary quantum particle in four-dimensional spacetime) colliding with a wall. It was proposed by Russian-American physicist Alexei Kitaev in 1997. While the elements of a topological quantum computer originate in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Dot
Quantum dots (QDs) or semiconductor nanocrystals are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via quantum mechanical effects. They are a central topic in nanotechnology and materials science. When a quantum dot is illuminated by UV light, an electron in the quantum dot can be excited to a state of higher energy. In the case of a semiconducting quantum dot, this process corresponds to the transition of an electron from the valence band to the conduction band. The excited electron can drop back into the valence band releasing its energy as light. This light emission ( photoluminescence) is illustrated in the figure on the right. The color of that light depends on the energy difference between the discrete energy levels of the quantum dot in the conduction band and the valence band. In other words, a quantum dot can be defined as a structure on a semiconductor which is capable of confi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanowire
file:[email protected], upright=1.2, Crystalline 2×2-atom tin selenide nanowire grown inside a single-wall carbon nanotube (tube diameter ≈1 nm). A nanowire is a nanostructure in the form of a wire with the diameter of the order of a nanometre (10−9 m). More generally, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less and an unconstrained length. At these scales, quantum mechanical effects are important—which coined the term "quantum wires". Many different types of nanowires exist, including superconducting (e.g. Yttrium barium copper oxide, YBCO), metallic (e.g. nickel, Ni, platinum, Pt, gold, Au, silver, Ag), semiconducting (e.g. Silicon nanowire, silicon nanowires (SiNWs), indium phosphide, InP, gallium nitride, GaN) and insulating (e.g. Silicon dioxide, SiO2, Titanium dioxide, TiO2). Molecular nanowires are composed of repeating molecular units either organic (e.g. DNA) or inorganic (e.g. Mo6S9−''x'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid Phase Epitaxy
Epitaxy (prefix ''epi-'' means "on top of”) is a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epitaxial film or epitaxial layer. The relative orientation(s) of the epitaxial layer to the seed layer is defined in terms of the orientation of the crystal lattice of each material. For most epitaxial growths, the new layer is usually crystalline and each crystallographic domain of the overlayer must have a well-defined orientation relative to the substrate crystal structure. Epitaxy can involve single-crystal structures, although grain-to-grain epitaxy has been observed in granular films. For most technological applications, single-domain epitaxy, which is the growth of an overlayer crystal with one well-defined orientation with respect to the substrate crystal, is preferred. Epitaxy can also play an important ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Beam Epitaxy
Chemical beam epitaxy (CBE) forms an important class of deposition techniques for semiconductor layer systems, especially III-V semiconductor systems. This form of epitaxial growth is performed in an ultrahigh vacuum system. The reactants are in the form of molecular beams of reactive gases, typically as the hydride or a metalorganic. The term CBE is often used interchangeably with metal-organic molecular beam epitaxy (MOMBE). The nomenclature does differentiate between the two (slightly different) processes, however. When used in the strictest sense, CBE refers to the technique in which both components are obtained from gaseous sources, while MOMBE refers to the technique in which the group III component is obtained from a gaseous source and the group V component from a solid source. Basic principles Chemical beam epitaxy was first demonstrated by W.T. Tsang in 1984. This technique was then described as a hybrid of metal-organic chemical vapor deposition (MOCVD) and molecular b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sticking Coefficient
Sticking coefficient is the term used in surface physics to describe the ratio of the number of adsorbate atoms (or molecules) that Adsorption, adsorb, or "stick", to a surface to the total number of atoms that impinge upon that surface during the same period of time. Sometimes the symbol Sc is used to denote this coefficient, and its value is between 1 (all impinging atoms stick) and 0 (no atoms stick). The coefficient is a function of surface temperature, surface coverage (θ) and Structure, structural details as well as the kinetic energy of the impinging particles. The original formulation was for molecules adsorbing from the gas phase and the equation was later extended to adsorption from the liquid phase by comparison with molecular dynamics simulations. For use in adsorption from liquids the equation is expressed based on solute density (molecules per volume) rather than the pressure. Derivation When arriving at a site of a surface, an Adatoms, adatom has three option ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron-beam Lithography
Electron-beam lithography (often abbreviated as e-beam lithography or EBL) is the practice of scanning a focused beam of electrons to draw custom shapes on a surface covered with an electron-sensitive film called a resist (exposing). The electron beam changes the solubility of the resist, enabling selective removal of either the exposed or non-exposed regions of the resist by immersing it in a solvent (developing). The purpose, as with photolithography, is to create very small structures in the resist that can subsequently be transferred to the substrate material, often by Etching (microfabrication), etching. The primary advantage of electron-beam lithography is that it can draw custom patterns (direct-write) with sub-10 Nanometre, nm resolution. This form of maskless lithography has high resolution but low throughput, limiting its usage to photomask fabrication, low-volume production of Semiconductor device, semiconductor devices, and research and development. Systems Electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanowire
file:[email protected], upright=1.2, Crystalline 2×2-atom tin selenide nanowire grown inside a single-wall carbon nanotube (tube diameter ≈1 nm). A nanowire is a nanostructure in the form of a wire with the diameter of the order of a nanometre (10−9 m). More generally, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less and an unconstrained length. At these scales, quantum mechanical effects are important—which coined the term "quantum wires". Many different types of nanowires exist, including superconducting (e.g. Yttrium barium copper oxide, YBCO), metallic (e.g. nickel, Ni, platinum, Pt, gold, Au, silver, Ag), semiconducting (e.g. Silicon nanowire, silicon nanowires (SiNWs), indium phosphide, InP, gallium nitride, GaN) and insulating (e.g. Silicon dioxide, SiO2, Titanium dioxide, TiO2). Molecular nanowires are composed of repeating molecular units either organic (e.g. DNA) or inorganic (e.g. Mo6S9−''x'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an Insulator (electricity), electrical insulator that can be Polarisability, polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of Polarisation density, dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly Chemical bond, bonded molecules, those molecules not only become polarised, but also reorient so that their Symmetry axis, symmetry axes a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Dot
Quantum dots (QDs) or semiconductor nanocrystals are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via quantum mechanical effects. They are a central topic in nanotechnology and materials science. When a quantum dot is illuminated by UV light, an electron in the quantum dot can be excited to a state of higher energy. In the case of a semiconducting quantum dot, this process corresponds to the transition of an electron from the valence band to the conduction band. The excited electron can drop back into the valence band releasing its energy as light. This light emission ( photoluminescence) is illustrated in the figure on the right. The color of that light depends on the energy difference between the discrete energy levels of the quantum dot in the conduction band and the valence band. In other words, a quantum dot can be defined as a structure on a semiconductor which is capable of confi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
