Wetting layer
Encyclopedia
In experimental physics, a wetting layer is an initial layer of atom
s that is epitaxially grown on a surface upon which self-assembled quantum dot
s or thin film
s are created. The atoms composing a wetting layer can be semimetallic elements/compounds (usually InAs in the case of self-assembled quantum dots) or metallic alloys (for thin films). This article refers to the wetting layer used for quantum dot applications. By spraying a surface with layers of these atoms under high temperature, this wetting layer residue is produced on the surface. Wetting layers control the artificial atomic states of the quantum dot
for uses in quantum information
processing and quantum computation.
(MBE) chamber at high temperatures. The temperatures required for wetting layer growth usually range from 400-500 degrees Celsius
. If a self-assembled quantum dot is to form, an initial layer of atom
s must first be placed on a surface. Due to the high elastic potential energy once a certain critical thickness is achieved, additional atoms group together to form the quantum dot
to reduce this elastic energy
. If further annealing
of the quantum dot/wetting layer system
is necessary, higher temperatures of up to 1100 degrees may be used.
that can change the physics of a quantum dot
. The thickness and composition determine the effect of the wetting layer on the quantum dot
, however the thickness is usually roughly 0.5 nanometers. The electronic structure and strain of the quantum dot change as a result of the wetting layer. Theoretically, due to the lattice mismatch, finite thickness wetting layers are not stable and therefore admit some strain
on the quantum dot
. The theoretical electronic structure of the quantum dot can change significantly with the consideration of the wetting layer.
which can interfere with the quantum dots in order to control their state for quantum computation and other applications of quantum dot
s.
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s that is epitaxially grown on a surface upon which self-assembled quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
s or thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
s are created. The atoms composing a wetting layer can be semimetallic elements/compounds (usually InAs in the case of self-assembled quantum dots) or metallic alloys (for thin films). This article refers to the wetting layer used for quantum dot applications. By spraying a surface with layers of these atoms under high temperature, this wetting layer residue is produced on the surface. Wetting layers control the artificial atomic states of the quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
for uses in quantum information
Quantum information
In quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-level quantum system...
processing and quantum computation.
Process
The wetting layer is epitaxially grown onto a surface using a molecular beam epitaxyMolecular beam epitaxy
Molecular beam epitaxy is one of several methods of depositing single crystals. It was invented in the late 1960s at Bell Telephone Laboratories by J. R. Arthur and Alfred Y. Cho.-Method:...
(MBE) chamber at high temperatures. The temperatures required for wetting layer growth usually range from 400-500 degrees Celsius
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
. If a self-assembled quantum dot is to form, an initial layer of atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s must first be placed on a surface. Due to the high elastic potential energy once a certain critical thickness is achieved, additional atoms group together to form the quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
to reduce this elastic energy
Elastic energy
Elastic energy is the potential mechanical energy stored in the configuration of a material or physical system as work is performed to distort its volume or shape....
. If further annealing
Annealing (metallurgy)
Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...
of the quantum dot/wetting layer system
System
System is a set of interacting or interdependent components forming an integrated whole....
is necessary, higher temperatures of up to 1100 degrees may be used.
Properties
The wetting layer serves as another parameterParameter
Parameter from Ancient Greek παρά also “para” meaning “beside, subsidiary” and μέτρον also “metron” meaning “measure”, can be interpreted in mathematics, logic, linguistics, environmental science and other disciplines....
that can change the physics of a quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
. The thickness and composition determine the effect of the wetting layer on the quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
, however the thickness is usually roughly 0.5 nanometers. The electronic structure and strain of the quantum dot change as a result of the wetting layer. Theoretically, due to the lattice mismatch, finite thickness wetting layers are not stable and therefore admit some strain
Strain
Strain can refer to:* Strain , variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes* Strain , a chemical stress of a molecule...
on the quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
. The theoretical electronic structure of the quantum dot can change significantly with the consideration of the wetting layer.
Applications
The wetting layer serves as another parameterParameter
Parameter from Ancient Greek παρά also “para” meaning “beside, subsidiary” and μέτρον also “metron” meaning “measure”, can be interpreted in mathematics, logic, linguistics, environmental science and other disciplines....
which can interfere with the quantum dots in order to control their state for quantum computation and other applications of quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
s.