2D supracrystals
The supracrystals are defined as the supra atomic periodic structure where atoms in the nodes of a structure are represented by their symmetric complexes.
2DEG
Two dimensional electron gas, typically realised in GaAs / AlGaAs heterostructures or Si/SiO2
AFM
Atomic force microscopy
ALD
Atomic layer deposition
AlN
Aluminium nitride compound
Annealing Oven
Oven for, e.g., Rapid Thermal Annealing (RTA) or Rapid Thermal Processing (RTA) processes, ohmic contact formation or diffusion processes. Anneals are usually short in duration whereupon the wafer temperature is accurately measured and controlled. Our Rapid Thermal Annealing systems AO 500 /AO 600 are equipped for sample sizes up to 12 mm x 12 mm and a maximum temperature of 500°C / 600°C.
Antimonides
Compound semiconductors which substantially contain phosphorus
Arsenides
Compound semiconductors which substantially contain arsenic
Bake-out
UHV chambers are baked out at about 200°C for several days to remove weakly bound surface water and hydrocarbon molecules. Both of which have the effect of limiting the ultimate system vacuum pressure. The UHV chamber including the UHV components is wrapped by bakeout panels, which completely jacket the whole system, in order to reach a homogenous temperature in all UHV areas of the system. Without adequate system bakeout the base pressure will not reach levels below 10×10-9 mbar in UHV systems.
Bayard Alpert ion gauge
The BA ion gauge is a hot-cathode ion gauge, with a small ion collector inside a grid for pressure reading down to the low 10-11 mbar range
Beam Flux Monitor
A Bayard Alpert ion gauge which can be brought close to the substrate position in an MBE system. Therefore, it allows direct measurement of beam flux of effusion sources. It is frequently used to adjust Arsenic but also Gallium, Indium and Alumium pressure at the substrate position.
BEP
The Beam Equivalent Pressure BEP is a local pressure of a directional gas beam on a surface, measured by a pressure gauge. The determined value for this pressure beyond others depends on material and temperature. After calibration it is a measure for the deposition rate.
Borophene
Borophene is a proposed crystalline allotrope of boron. One unit consists of 36 atoms arranged in an 2-dimensional sheet with a hexagonal hole in the middle.
Carbon nanotubes
Carbon nanotubes cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to more than 100 mio : 1. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology
CBE
Chemical beam epitaxy. MBE with gas sources instead of solid sources like effusion cells.
CF flange
CF (ConFlat) flanges use a copper gasket and a knife-edge flange to achieve an ultrahigh vacuum seal. The term “ConFlat” is a registered trademark of Varian, Inc.
CIGS
Copper indium gallium di-selenide (CIGS) is a semiconductor material composed of copper, indium, gallium, and selenium. It has a chemical formula of CuInxGa(1-x)Se2. CIGS is tetrahedrally bonded, with the chalcopyrite crystal structure, and a bandgap varying continuously with x from about 1.0 eV (for copper indium selenide) to about 1.7 eV (for copper gallium selenide). It is used as light absorber for thin-film solar cells.
CIS
The material is a solid solution of copper indium selenide (CIS), see also CIGS.
Cold Lip Filament CL
A cold lip filament CL is a shorter version of the standard filament SF. It does not reach up to the orifice part of the crucible. This fact and some additional shielding leave the crucible lip clearly cooler than the lower parts. This is required for Aluminum evaporation for example. Alternative filament types are Standard Filament SF, Tip Filament TF, Hot Lip Filament HL and Dual Filament DF:
Compound semiconductor
Semiconductor material composed of elements from two or more different groups of the periodic table. They can be formed of elements from group III (e.g.: Al, Ga, In) and from group V (N, P, Ar, Sb). The range is quite broad because there can not just be binaries like GaAs, but also , ternary like GaInAs and quaternary (AlInGaP) alloys. Compound semiconductors are particularly important for opto-electronic devices.
Contact alloying
Our Rapid Annealing Systems AO 500 / AO 600 are practical for fabrication of ohmic contacts by heating the sample.
Critical Thickness
Important figure in strained layer epitaxy. A strained SiGe alloy grown on Si grows latterally compresssed without misfit dislocations up to a certain “critical thickness”. Misfit dislocations appear, and the epi-layer starts to relax, if the layer thickness increases bejond the critical thickness.
Cryopump
A cryopump (cryogenic pump) is a vacuum pump that traps gases and vapours by condensing them on a cold (typically 10K) surface. Cryopumps are applied in ultra high vacuum systems to reach base pressures down to 10E-12 mbar.
Crystallites
Crystallites are small, micrometer or nanometer size crystals, often held together through highly defective boundaries to form a polycristalline solid material.
CZTS
Copper zinc tin sulfide (CZTS) is a quaternary semiconducting compound with kesterite structure, which has received increasing interest for applications in solar cells. The class of related materials includes other I-II-IV-VI such as copper zinc tin selenide (CZTSe) and the sulfur-selenium alloy CZTSSe. CZTS offers properties similar to CIGS making it well suited for use as a thin-film solar cell, but unlike CIGS (or CdTe), CZTS is composed of only abundant and non-toxic elements. Solar cell efficiencies above 10% have recently been demonstrated.
DBR
Distributed Bragg Reflector
Degassing
see " Outgassing "
Diaphragm pump
A diaphragm pump (or Membrane pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic or teflon diaphragm and suitable non-return check valves to pump. They are also used as low-grade vacuum pumps. These pumps are quiet, cheap and have no moving parts in the airstream. This allows them to be used without added lubrication in contact with the air.
Dilute nitrides
GaAsN, InGaAsN componds with only a small percentage of nitrogen incorporated on substitutional sites. The Nitrogen introduces strain and allows to tune the band gap.
Doping
Intentionally introduction of impurities into a high pure (intrinsic) semiconductor for the purpose of defining or modulating its electrical properties. P- or N-type dopants provide free holes or electrons in the semiconductor crystal, respectively.
Droplet epitaxy
Mechanism for the growth of one-dimensional structures, such as nanowires, from vapor deposition. The growth of a crystal through direct adsorption of a gas phase on to a solid surface is generally very slow. The VLS mechanism circumvents this by introducing a catalytic liquid alloy phase which can rapidly adsorb a vapor to supersaturation levels, and from which crystal growth can subsequently occur from nucleated seeds at the liquid–solid interface It is also called “vapor–liquid–solid method” (VLS).
Dual Filament DF
A dual filament is composed of two heaters that can be independently operated by two PID controlled power supplies. Dual filament design provides several operation possibilities depending on which operation mode is chosen. Independent operation of the filaments is possible as well as hot lip, top heated or cold lip operation.
The dual filament is being built of a short top filament, which heats the crucible top and the lip area. It is more densely wired than the bottom filament. Its length is about 1/4 of the crucible’s length from the orifice. A thermocouple measures the temperature near the top filament. (TC1)
About 3/4 of the crucible’s height is heated by the bottom filament. The main thermocouple is the bottom thermocouple, which measures the temperature at the bottom of the crucible. (TC2) In case you want the upper part of the crucible to be hotter than the lower part you can use both filaments in series. Then you have got a simple hot-lipped filament type, by the filament geometry. At higher temperatures the heat loss through radiation from the crucible’s orifice gets higher and the filament geometry on its own is not sufficient for heating the crucible’s top to higher temperature than the temperature at the bottom. If higher temperatures are required at the crucible lip, the top filament has to be heated separately. In case you want a cooler lip (e.g. Al evaporation) you can use the bottom filament only and have simple cold lip filament type by the filament geometry. For the optimum adoption of the dual filament effusion cell application the dual filament power supply PS302-C2 or any similar power supply/controller configuration with two independent PID controllers offers the possibility to adjust the temperatures in the top and in the bottom area in a given range. The range is given by the dual filament design and the heat loss due to radiation from the crucible’s orifice and the heat loss due to radiation from the shielding.
The current for each filament must be limited to reasonable maximum values or suitable lower values in case of operating on sub maximal temperatures. This way the temperature cannot exceed maximum values by accident. Only change this limit if it is really needed! Be aware that any change in the power ratio may alter the feedback characteristics for the thermocouple temperature and may thus require a readjustment of PID parameters.
Operation of a dual filament cell
Mode 1: Filaments in series (hot lip operation), Recommended TC for control loop: Bottom TC2, Use TC 1 as reference only, Use PS2 for top and bottom heater.
Mode 2: Top filament only (top heated cell), Recommended TC for control loop: Bottom TC2, Use TC 1 as reference only, Use PS2 for top heater
Mode 3: Bottom filament only (cold lip operation), Recommended TC for control loop: Bottom TC2, Use TC 1 as reference only, Use PS2 for bottom heater
Mode 4: Dual filament operation (independent control of top and bottom temperature, TC1 with power supply PS1 for top heater, TC2 with power supply PS2 for bottom heater, The dual filament mode 4 is the most critical mode, because there are two controllers and the operation of one filament has effects on both thermocouples and feedback loops.,The temperatures cannot be absolutely independent selected. The maximum possible difference between top and bottom temperature can be estimated from its power graph in top heated mode (Mode 2) where only the top filament is connected to voltage and the bottom part (thermocouple TC2) is being heated solely by radiation.
Mode 5: Dual filament operation with one power supply (pre-set of the power of the top heater as a percentage of the power of the bottom heater), TC1 with power supply PS1 for top heater, TC2 for temperature monitoring
Alternative filament types are Standard Filament SF, Cold Lip Filament CL, Tip Filament TF and Hot Lip Filament HL:
E-beam evaporator
Evaporator in which a source material target (anode) is bombarded with an electron beam. The electron beam es provided by a charged tungsten filament under high vacuum. Mainly two different types of e-beam evaporators are used. For very low beam flux applications a thin stick or wire is heated at its tip to sublimate material. The other type uses magnetically bended e-beams from an e-beam gun to melt material in a water cooled crucible resulting in high beam fluxes.
Effusion cell
see also “Knudsen cell” In contrast to a Knudsen cell which has uniform vapor distribution inside the crucible and a very small orifice an effusion cell has a widely open crucible to increase the beam flux for a given cell temperature. Many of the so called “k-cells” are of the effusion cell type, actually.
Epitaxial layer
Crystalline film deposited by MBE or CVD on a crystalline substrate wafer.
Face-down crucible mounting
Effusion cells that are going to be used for face-down operation need a supplementary face-down assembly to prevent evaporation material from falling out of the cell. In case of face-down operation, the downwards pointing cell crucible is equipped with a special face-down insert that holds the smaller, evaporant-containing crucible in upright position within the regular cell crucible.
The following figure shows a schematic of a typical face-down crucible assembly.
Facet passivation
High power GaAs/AlGaAs/InGaAs laser diodes need a passivation layer on the cleaved facets in order to avoid the reaction of oxygen with the AlGaAs surface which causes catastrophical optical mirror damage during operation.
FET
Field Effect Transistor
Filament Types
Depending on specific applications and differing requirements of the evaporants several effusion cells like, e.g., WEZ, NTEZ or PEZ can be equipped with different filament types:
Schematic of filament types Standard Filament SF, Cold Lip Filament CL, Tip Filament TF, Hot Lip Filament HL and Dual Filament DF
Standard Filament SF A standard wire filament SF heats the crucible evenly along its entire length. A thermocouple TC is fixed near the bottom of the crucible.
Cold Lip Filament CL A cold lip filament is a shorter version of the standard filament SF. It does not reach up to the orifice part of the crucible. This fact and some additional shielding leave the crucible lip clearly cooler than the lower parts. This is required for Aluminum evaporation for example.
Tip Filament TF A tip filament practically is the upper filament of a dual filament. Only the topmost part of the crucible is being heated. This design provides the maximum temperature gradient between crucible bottom and lip.
Hot Lip Filament HL A hot lip filament is wired more densely at the upper part than the standard heating assembly. This way a higher temperature near the crucible lip is achieved by using only one power supply for the heating.
Dual Filament DF A dual filament is composed of two heaters that can be independently operated by two PID controlled power supplies.
Dual filament design provides several operation possibilities depending on which operation mode is chosen. Independent operation of the filaments is possible as well as hot lip, top heated or cold lip operation.
Fullerenes
A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid or tube. Spherical fullerenes are also called buckyballs. Cylindrical ones are called carbon nanotubes or buckytubes.
Germanane
Germanane is a single-layer crystal composed of germanium with one hydrogen bonded in the z-direction for each atom. Germanane’s structure is similar to graphane.
Graphane
Graphane is a polymer of carbon and hydrogen with the formula unit (CH)n where n is large. Graphane is a form of fully hydrogenated (on both sides) graphene.
Graphane’s carbon bonds are in sp3 configuration, as opposed to graphene’s sp2 bond configuration. Thus graphane is a two-dimensional analog of cubic diamond.
Graphene
Graphene is a substance made of carbon, with atoms arranged in a regular hexagonal pattern similar to graphite, but in a one-atom thick sheet. It is a single planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice.
Graphyne
Graphyne is another 2-dimensional carbon allotrope whose structure is similar to graphene’s. It can be seen as a lattice of benzene rings connected by acetylene bonds.
Growth model
Theoretical models of crystal surfaces provide insights into the crystal growth process. The effects of adsoption, desorption, step flow, surface roughening and impurities have been assessed.
GSMBE
Gas Source Molecular Beam Epitaxy
HBT
Hetero-Bipolar Transistor
HEMT
High Electron Mobility Transistor
Heterojunction
A heterojunction or heterostructure is the interface that occurs between two layers or regions of dissimilar crystalline semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. It is often advantageous to engineer the electronic energy bands in many solid state device applications including semiconductor lasers, solar cells and transistors.
Heterostructure
See heterojunction
Heusler alloy (or Heusler compound)
Heusler alloy (or Heusler compound) is a ferromagnetic metal alloy with special composition like X2YZ and face-centered cubic crystal structure. Examples are: Cu2MnAl, Cu2MnIn, Ni2MnAl, etc.
High mobility electrons
High mobility in the context of MBE means frequently high mobility electrons or holes in modulation doped heterostructures.
Hot Lip Filament HL
A hot lip filament HL is wired more densely at the upper part than the standard heating assembly. This way a higher temperature near the crucible lip is achieved by using only one power supply for the heating.
II-IV semiconductor
Semiconductor material which contains elements out of group II and VI, as for example ZnSe
III-V semiconductor
Semiconductor material which contains elements out of group III and V, as for example GaAs and InP
Interface
Interface that occurs between two layers or regions of dissimilar crystalline semiconductors. E.g. GaAs / AlGaAs interface
Intersubband transition
E.g.: Transition from an electron in a higher subband state to a lower subband state by emission of a photon.
Ion getter pump
An ion getter pump is a ultra-high vacuum pump capable of reaching pressures as low as 10−11 mbar. It ionizes gas within the ultra-high vaccum chamber and employs a strong electrical potential, typically up to 10kV, which allows the ions to accelerate and be captured by a solid electrode.
Kesterides
Kesterites are sulfide crystals with a formula Cu2(Zn,Fe)SnS4. In its lattice structure, zinc and iron atoms share the same lattice sites. Kesterite is the Zn-rich variety whereas the Zn-poor form is called ferrokesterite or stannite. They are interesting as solar cell light absorbing material.
KF flange
Klein Flange (KF) flanges are made with a chamferred back surface that attached with a circular clamp and an elastomeric o-ring that is mounted in a metal centering ring. KF flanges are used for vacuum sealing in the vacuum range down to high vakuum.
Knudsen Cell
The original Knudsen type evaporation source is an evaporation cell with small orifice. It has been described by Martin Knudsen in 1909 and was used to measure vapor pressure data. Many people use the name Knudsen cell or k-cell for large opening effusion cells despite the fact, that the orifice is open or conical shaped. Effusion Cells are used as evaporator in MBE for materials like Ga, In, Al, As etc.. It is a thermal evaporator with a crucible. The flux of the source is controlled by careful temperature regulation. A typical effusion cell contains a crucible (made of pyrolytic boron nitride, quartz, tungsten or graphite), heating filaments (often made of metal tantalum), water cooling system, heat shields and orifice shutter.
Laser diodes
A laser diode is a laser whose active medium is formed by a p-n junction of a semiconductor similar to that found in a light-emitting diode, but with a resonator for enhanced stimulated emission.
LEED
Low Energy Electron Diffraction
Magnetic semiconductors
Magnetic semiconductors are materials that exhibit both ferromagnetism and semiconductor properties. Whereas traditional electronics are based on control of charge carriers (n- or p-type), magnetic semiconductors can also provide control of quantum spin state. Applications are for examples spin transistors.
MBE
MBE (molecular beam epitaxy) is a method of depositing layers of materials with atomic thicknesses on to substrates. A gaseous ‘beam’ of particles, i.e. molecules or single atoms, of a material is created by means of evaporation sources (effusion cells, sublimation sources, etc.). This beam impinges on to a substrate resulting in layers that take on a lattice structure and orientation identical to those of the substrate (’epitaxial growth’ of monocrystalline films). These so called ‘superlattices’ have a number of technologically important uses including quantum well lasers for semiconducting systems, and giant magneto-resistance for metallic systems
Micro-cavity
An optical microcavity is a structure formed by reflecting faces on the two sides of a spacer layer or optical medium. The optical cavity is only a few micrometers thick. The spacer layers are in the nanometer range. As with common lasers this forms an optical resonator which allows only one standing optical wave to form inside the spacer layers. Micro cavities are often used in vertical cavity surface emitting laser diodes.
Migration enhanced MBE
MBE process but, with alternate deposition of the constituent elements (i.e. with monolayer by monolayer growth interruptions). The interruped deposition allows surface migration, which results in planarization during epitaxial growth.
Misfit Dislocation
Misfit dislocations are basically where there is a missing or dangling bond in the lattice between two layers with different lattice constant. In Si/SiGe heterostructures, when SiGe is grown on Si above the critical thickness 60˚ misfit dislocations result due to the smaller silicon lattice as compared to SiGe.
MOCVD
Metal organic chemical vapor deposition
Modulation doping
Semiconductor heterostructure where doping layer is separated from the charged carriers
Molybdenum disulfide
Molybdenum disulfide is the inorganic compound (MoS2). Molybdenum disulfide is similar to graphite. It is widely used as a solid lubricant because of its low friction properties and robustness. As a transition metal di-chalcogenide, MoS2 possesses some of graphene’s desirable qualities (such as mechanical strength and electrical conductivity), and can emit light, opening possible applications such as photodetectors
MOMBE
Metal Organic Molecular Beam Epitaxy
MOVPE
Metal Organic Vapor Phase Epitaxy
Nanostructure
A nanostructure is an crystal or material with a size in the nanometer scale.
Nanowire
A nanowire can be defined as structure that has a thickness or diameter constrained to few nanometers and an unconstrained length
Nitrides
GaInAlN compound semiconductors and heterostructures used for LEDs, laser diodes or transistors
Nucleation
Adsorption of atoms in MBE on a substrate surface, and subsequent growth of a crystaline layer or island structure
OLED
Organic Light Emitting Diode
Outgassing
(sometimes also called degassing) Initial thermal outgassing of UHV components like effusion cells or heated stages is required to remove tightly bound species and the hydrogen diffusing from the bulk. During the outgassing procedure, the local heaters are operated well above subsequent operation temperatures. This means, for example, that the crucible heater of an effusion cell is heated to maximum temperatures as high as 1400 to 1500°C prior to crucible loading with source material.
PBN
Pyrolytic Boron Nitride. In the form of pyrolytic BN it is used for crucibles in MBE.
Penning gauge
Cold-cathode ionization gauge. A DC potential of about 4 kV is used for operation. Axially symmetric magnetic field is applied to create path lengths in the range of meters for electrons. The electrode tapered to facilitate the field emission of electrons. Pressure reading ranges down to E-11 mbar.
Perovskite solar cell
This is a type of solar cell which includes an active compound with a perovskite crystal structure. Often this compound is a hybrid organic–inorganic, lead or tin halide-based material as the light absorbing layer. Perovskite materials, such as methylammonium lead halides and all-inorganic cesium lead halide, are cheap to produce and simple to manufacture. Perovskite solar cells are expected to commercially attractive especially as tandem type cells combined with Si solar cells. Such tandem junction solar cells have show efficiencies of more then 30%, but long term reliability is still an issue.
Phosphorene
Phosphorene is a 2-dimensional, crystalline allotrope of phosphorus. Its mono-atomic hexagonal structure makes it conceptually similar to graphene. However, phosphorene has substantially different electronic properties; in particular it possesses a nonzero band gap. This property potentially makes it a better semiconductor than graphene.
Phosphoros compounds
Compound semiconductors which substantially contain phosphoros, like InP, GaP or GaInP.
Photodiodes
A photodiode is capable of converting light into either current or voltage.
Pirani gauge
A Pirani gauge consist of a metal wire in the pressure being measured. The wire is heated by a current flowing through it and cooled by the gas surrounding it. If the gas pressure is reduced, the cooling effect will decrease. The resistance of the wire is a function of its temperature: by measuring the voltage across the wire and the current flowing through it, the resistance (and so the gas pressure) can be determined. The operating range is: 10-3mbar - 10 mbar.
Point Source
A point source is an evaporation source or effusion cell which has a single localized opening for material evaporation, distinguishing it from other source geometries like from linear evaporation sources. The actual source opening needs not to be physically small.
Product Code
Our product code gives information about the product configuration itself.
Example for Standard Effusion Cell WEZ product code:
WEZ 40-10-22-KS-HL-C-P-L220D36
For further product code abbreviations please have a look at the descriptions on the particular product websites.
Pseudo-morphic growth
Planar epitaxial layer growth in straind layer epitaxy. In the pseudo-morphic growth regime the epitaxial layer latterally strained (extended or compressed) in order to matched the lattice of the crystalline substrate. E.g.: GaInAs on GaAs substrate. Above a critical film thickness misfit dislocations are introduced which allow strain relaxation.
PVD
Physical Vapor Deposition
QMA Quadrupole Mass Analyzer
Inside a Quadrupole Mass Analyzer four parallel rods with applied oscillating electric field filter and separate sample ions due to their mass-to-charge ratio.
Quantum cascade laser
Unlike normal interband semiconductor lasers, QCLs are unipolar and laser emission is achieved through the use of intersubband transitions in a repeated stack of semiconductor multiple quantum well heterostructures. Quantum cascade lasers emit light in the mid- to far-infrared electromagnetic spectrum. In the QCL, once an electron has undergone an intersubband transition and emitted a photon in one period of the superlattice, it can tunnel into the next period where another photon can be emitted. This process of a single electron causing the emission of multiple photons as it traverses through the QCL structure gives rise to the name cascade.
Quantum computer
A quantum computer makes use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. A classical computer has a memory made up of bits, where each bit represents either a one or a zero. A quantum computer maintains a sequence of qubits. A single qubit can represent a one, a zero, or any quantum superposition of these two qubit states. Quantum computers will be able to solve certain problems much faster by using the best currently known algorithms, like integer factorization or the simulation of quantum many-body systems
Quantum dot
Quantum dots are nanometer scale semiconductors structures whose carriers are confined in all three spatial dimensions. Therefore, they have discrete electronic states similar to atoms.
Quantum well
A quantum well is a potential well in one crytalographic direction with only discrete energy values. They are formed in semiconductor heterostructures by having a material, like GaAs sandwiched between two layers of a material with a wider bandgap, like AlGaAs. These structures can be grown by molecular beam epitaxy with control of the layer thickness down to monolayers. Charged carries are confined in one direction but free in the perpendicular plane.
Quartz crystal microbalance
A quartz crystal microbalance (QCM) measures a mass per unit area by measuring the change in frequency of a quartz crystal resonator. The QCM is frequently used in vacuum deposition processes for monitoring the rate of deposition in thin film deposition systems.
Qubit
In standard computing the information is encoded in bits. A bit can have the value zero or one. In quantum computing the information is encoded in qubits. A qubit is a two-level quantum state, where the two qubit states are written as ∣0⟩ and ∣1⟩. A qubit can be a linear combination (superposition) of both states. It is written as: ψ=α∣0⟩+β∣1⟩ In other words, a qubit can be in a ∣0⟩, a ∣1⟩ or a superposition of both, called a quantum state. This is fundamental to the operation of quantum computers.
RDS
Reflectance Difference Spectroscopy. It is a spectroscopic technique which measures the difference in reflectance of two beams of light in normal incident on a surface with different linear polarizations. It allow to monitor crucial stages on the surface of the thin film growth.
RHEED
Reflection high energy electron diffraction. RHEED is used in MBE systems to check surface reconstructions and to calibrate deposition rates.
RHEED oscillations
Intensity oscillations observed during layer by layer growth in MBE. RHEED oscillations allow to count the number of atomic planes deposited during the MBE growth process.
Roughing pump
Vacuum pump used to initially evacuate a vacuum system, as a first stage towards achieving high vacuum or ultra high vacuum. It is used in the rough vacuum range above 1x10-3 mbar. Roughing pumps are mechanical pumps or diaphram pumps.
RTA Rapid Thermal Annealing
Rapid Thermal Annealing (RTA) is a process in which a wafer is heated in order to affect its electrical properties. Anneals are usually short in duration whereupon the wafer temperature is accurately measured and controlled. Our Rapid Thermal Annealing systems AO 500 /AO 600 are equipped for sample sizes up to 12 mm x 12 mm and a maximum temperature of 500°C / 600°C.
RTP Rapid Thermal Processing
For Rapid Thermal Processing (RTP) wafers are rapidly heated to high temperatures. These processes are used for a wide variety of applications in semiconductor manufacturing including dopant activation, thermal oxidation, metal reflow and chemical vapor deposition. Our systems AO 500 /AO 600 for Rapid Thermal Processing are equipped for sample sizes up to 12 mm x 12 mm and a maximum temperature of 500°C / 600°C.
sccm
Sccm is an abbreviation of standard cubic centimeters per minute indicating a flow rate which is equivalent to a flow of 1cm³ under normal conditions (1013 hPa ambient pressure and 0°C) per minute. 1 sccm = 1013 hPa * 0,001 l / 60 s = 0.0169 mbar l /s
(1 hPa = 1 mbar)
Scroll pump
A scroll compressor uses two interleaving scrolls (spirals) to pump, compress liquids and gases. It is used as an oil-free rough pump followed by a turbo molecular pump on an UHV chamber.
Selective area epitaxy
Selective area epitaxy is the local growth of epitaxial layer through a patterned dielectric mask (typically SiO2) deposited on a substrate and patterned by lithography prior to the epitaxy process.
Self-assembling quantum dots
Quantum dots or nanometer small semiconductor island created in strained layer epitaxie by Stranski–Krastanov growth. For example, few nanometer small InAs island are formed when deposited on a GaAs substrate.
Silicene
Silicene is a two-dimensional allotrope of silicon, with a hexagonal honeycomb structure similar to that of graphene.
Solar cell
A solar cell is an electronic device that converts the energy of light directly into electricity. The absorption of light in the P-N junction of a semiconductor diode generates electron-hole pairs which result in electrical current in a circuit.
Spintronics
Spintronics (spin transport electronics), also known as magnetoelectronics, is an emerging technology exploiting both the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-state devices. Examples of applications are: Read heads of modern hard drives. They are based on the giant magnetoresistance effect. Non-volatile spin-logic devices to enable scaling beyond the year 2025 are being studied.
Sputtering
Sputtering is a process where atoms are ejected from a solid target (source material) by bombardment of the target with energetic particles like Argon. It happens when the kinetic energy of the incoming particles is high enough. It is commonly used for thin-film deposition or etching.
Standard Filament SF
A standard wire filament SF heats the crucible evenly along its entire length. A thermocouple TC is fixed near the bottom of the crucible.
Stanene
Stanene is a 2 dimensional material. It is composed of tin (Sn) atoms arranged in a single atomic layer. It has a hexagonal structure similar to graphene. It is also expected to be a 2 dimensional topological insulator. Stanene is one of the possible candidates which my exhibit dissipationless currents in edge channels at room temperature.
STM
Scanning Tunneling Microscopy
Strain layer epitaxy
Epitaxial deposition of strained heterostructures. For example SiGe deposited on Si substrate. Or GaInAs on GaAs substrate. In these cases the epitaxial layer is laterally strained to match the lattice constant of the substrate. The strained epitaxial layer starts to relax by formation of misfit dislocations if a critical film thickness is exceeded.
Strain relaxation
See strain layer epitaxy
Stranski–Krastanov growth
It is a layer-plus-island crystal growth mode. Initially a planar films of one or more monolayers grows in a layer-by-layer fashion on a planar crystal substrate. Beyond a critical layer thickness, which depends on strain and the chemical potential of the deposited film, growth continues through the nucleation and coalescence of adsorbate islands.
SUMO source
Thermal effusion source from Veeco Inc. for Group III evaporation in MBE with a specially shaped crucible. It exhibits a cylindrical reservoir for large with a small tapered orifice. Our solution to this is a cylindrical reservoir crucible with a removeable beam shaping insert. This offers a low cost crucible and easy material load with otherwise similar characteristics.
Superlattice
Periodic structure of alternating layers of two or more semiconductor materials. Typically, the thickness of one layer is several nanometers. Superlattices are applied in quantum cascade lasers.
Surface reconstruction
Surface reconstruction refers to the process by which atoms at the surface of a crystal form a different structure than that of the bulk. The free dangling bonds of atoms on the surface are re-arrange in order to assume a minimum surface energy.
TEM
Transmission Electron Microscopy
Tip Filament TF
A tip filament TF practically is the upper filament of a dual filament. Only the topmost part of the crucible is being heated. This design provides the maximum temperature gradient between crucible bottom and lip.
Topological Insulator
Material that behaves as an insulator in its interior but whose surface contains conducting states. There are two main classes: three-dimensional (3D) and two-dimensional (2D) material systems. The 2D topological insulators are expected to exhibit one dimensional dissipationless edge channels, while the 2D plane inside is insulating . Materials of special interest are: HgTe, Bi2Se3, Bi2Te3, Sb2Te3, Stanene, Heusler compounds, special oxides and others.
TSP
Titanium Sublimation Pump
Tungsten diselenide
Tungsten diselenide is an inorganic compound (WSe2).
It has a hexagonal crystalline structure. Every tungsten atom is covalently bonded to six selenium ligands in a trigonal prismatic coordination sphere, while each selenium is bonded to three tungsten atoms in a pyramidal geometry. Layers stack together via van der Waals interactions. WSe2 is a stable semiconductor in the group-VI transition metal dichalcogenides.
Turbo-molecular pump
These pumps work on the principle that gas molecules can be given momentum in a desired direction by repeated collision with a moving multiple stages rotors. A rapidly spinning turbine rotor hits gas molecules from the inlet of the pump towards the exhaust in order to create or maintain a high vacuum. They are applied for base pressures down to 10-10 mbar.
UHV
A vacuum regime of a pressure lower than 10 -9 mbar characterizes Ultra High Vacuum (UHV)
Valved cracker source
An evaporation source which comprising a reservoire, a valve for flux control and a thermal cracking zone. The cracking cone breakes the evaporated molecules into atoms or smaller molecules (e.g. As4 to As2).
VCSEL
Vertical Cavity Surface Emitting Laser diode
VPE
Vapor Phase Epitaxy
XRD
X-Ray Diffraction