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Introduction to Silicon Carbide Color Centers
To understand Silicon Carbide Color Centers, the material Silicon Carbide (SiC) must first be introduced. SiC belongs to a group of materials called complementary metal-oxide semiconductor compatible materials (CMOS). These materials are used in a broad range of electronic devices, especially in integrated chips and circuits. Silicon Carbide Color Centers are point defects in the crystal lattice of SiC, which are known as color centers.

Fabrication of defects in Silicon Carbide Color Centers
There are mainly three methods to fabricating Silicon Carbide Color Centers. The three methods are electronic irradiation, ion injection, and femtosecond laser writing.

Electronic Irradiation
This technique works from exposing the material to an electron beam that is highly ionizing. This knocks of electrons in the material itself, which generates color centers (or defects). This process however, requires a large amount of energy, having 9MeV normally being the lower limit of energy in most materials.

Ion Injection
Ion injection is normally used to dope semiconductors, but it can also be used to create color centers. An ion if first accelerated to certain energy, normally in the MeV range. This ion is then accelerated into the material, which then implants the ion into the material, changing the material composition, which can create a color center.

Femtosecond Laser Writing
Utilizing a nonlinear laser writing process, along with the appropriate aberration correction, defects can be generated at any depth in the crystal. This process preserves spin and optical coherence properties. The way it works is from multiphoton ionization from the femtosecond laser process. This method of fabricating defects does not only work for SiC, but can also work for other materials.

Currently, new methods of fabrication are also being experimented with to try and reduce the energy used, or the complication of the process. One of the new methods is a new method of utilizing a laser writing method with a nanosecond laser.

Types of Defects in SiC
There are multiple types of defects in SiC, some of which are listed below:


 * Vsi(-) (TV1-TV3)


 * DV(0)
 * Ky5
 * CAV (Carbon anti-site-vacancy pair)
 * SiC(D1)
 * NCVSi(-)
 * TM Color Centers
 * TI(0)
 * Cr3+
 * V(-), V(0)
 * Mo(0)
 * Er3+

More details are available in the article Silicon carbide color center for quantum applications by Stefania Castelletto and Alberto Boretti.

Photonics
Recently, these color centers in SiC have shown promise in becoming one of the best single-photon emitters for non-classical light sources. Traditionally, attenuated lasers have been the substitute for single-photon sources (SPS). This works for quantum cryptography, but they are a partial substitute, and in the end this was not a true substitute for SPS. Normally, there are two main methods of generating single-photons: spontaneous parametric down-conversion and epitaxial quantum dots.

In spontaneous parametric down-conversion, single photons can be produced up to a rate of 106 photons per second. The drawback to this approach is that there is no way to generate single photons on demand. This makes this type of generation hard to use practically.

Epitaxial quantum dots are shown to generate single photons exceptionally when put under electrical pumping. This however works under very low temperatures, which also makes this applications harder to do practically in experiments.

Color centers in SiC, diamonds, and other related materials would be more practical that the two other traditional approaches due to the higher temperature that they can operate at when under optical and electrical pumping.

Semiconductors
SiC is currently being used in the semiconductor industry already, due to the reliable fabrication of high-quality single crystal wafers. Since Semiconductors be definition already have point defects, some may be used for purposes like SPS.

Quantum Properties of Silicon Carbide Color Centers
When studied at the single defect level, single emitters could be isolated. As the result of this, Silicon Carbide Color Centers can be used for applications in quantum cryptography protocols.

It is also important to note that quantum entanglement between the electron spin state and the single photon quantum state when two conditions are met:


 * 1) The quantum state of a single photon can be correlated to the electron spin state of the Silicon Carbide Color Centers
 * 2) This correlation is able to be stored in nearby nuclear spins in the Color Centers

This quantum entanglement allows there to be a creation of quantum networks, which leads to quantum communications, quantum memory, and Metrology.

One example of this was a study on nitrogen-vacancy centers in diamond in 2014 that showcased novel results on how in diamonds, the nitrogen-vacancy were color centers, which also are fluorescent impurities that have many applications

Quantum Sensing
When the color centers are first brought to an excited state, a photon can be emitted from the decay from the excited state to the ground states. This photon can then interact with other sources of static and variable magnetic fields. As the result of this, the spin transition frequency and the coherence time is altered, which this effected is used in Quantum Sensing.