For industrial and manufacturing applications, the use of chemicals is essential to ensure the production of quality materials. With advances in scientific and technical research, chemical engineers have come up with several methods to dissolve and form materials using various chemical processes. One such process is metal organic vapour phase epitaxy, which is also called metal vapour phase epitaxy or monomeric vapour phase epitaxy. This process has many advantages and hence it is widely used.
MOCVD is a process of forming metals using colloidal chemicals that include salts, sugars, alcohols, and a few alkalis or acids. The term ‘MOCVD’ is an abbreviation for metal organic vapor phase epitaxy. Metal organic vapour phase epitaxy is used in various processes to deposit diverse materials on metal surfaces including stainless steel, aluminium, copper, brass, graphite, and other alloys. It is a versatile technique and various processes can be used to achieve the desired results. Some chemicals can even be prepared from simpler raw materials to serve as MOCVD precursors.
MOCVD is an abbreviation for multi-step gas crystallization chamber. A gas crystallization chamber is an arrangement of chambers where a mixture of chemicals are placed. The chambers are made of transparent material so that the gases cannot be monitored. Initially, a gas-filled chamber is used. The gases are monitored and used in the process.
A variety of equipment are required for the functioning of MOCVD. A complete set of equipment is present, which includes: a mixing console, gas chromatography and bead collar, gas sensors, bead separators, temperature controller, and non-metallic valves. Apart from these, some additional equipments are: inhibitors, titration fittings, temperature calibration and other valves. These chemicals need to be stirred at regular intervals during their storage.
The most important part of a MOCVD is its reaction chamber. This chamber is the place where the different chemicals are mixed with helium gas to precipitate them. An MOCVD cycle requires around three to five hours to complete. This cycle needs to be started by connecting the first chamber to the adjacent -offering and by connecting the third to the first or second -offering in the same manner.
Sometimes, MOCVD is performed using the aid of a catalyst. The substances to be mixed with the gas do not need to be mixed together immediately. A small amount of each substance is mixed together first. The amount should be such that the concentration of the substances can reach within the limit of 100ug/cm. The mixture of the substances should be done in the appropriate manner so as to avoid equipments becoming overheated.
In order to control the temperature of the chemicals, the gas can be reheated in a controlled area. The temperature can be increased or decreased depending upon the level of the chemicals present in the MOCVD. It is also possible to mix in non-hazardous chemicals with the noble gas in the MOCVD. These chemicals can react with the noble gas and cause it to react. This reaction causes the gases to ignite and produces heat which raises the temperature of the MOCVD.
There are two ways in which the MOCVDs can be controlled. The first is the self-adjustment setting where in the user can adjust the temperature of the gases to that which is needed for a specific reaction. The second way in which the MOCVDs can be controlled is by use of inert gas mixtures. The inert gases do not react with the compound semiconductors and thus can be used to ensure that there is no chemical reaction and hence no danger of fires.
There are many MOCVD processes which use a MOCVD catalyst. Some of these processes are the so called ‘stretch’ and the heat treat process. The stretch process uses the MOCVD as thickeners in order to increase the thickness of the metal organic chemical vapour deposition on the steel surface. The heat treat process also uses the MOCVD as a catalyst in order to increase the properties of the metal thin films.
Another MOCVD process called the Ald precursor conversion uses the MOCVD as a catalyst in order to form the cvd. The cvd is a sheet which has the same physical properties of the MOCVD and is capable of conducting electricity when a current is passed through. The cvd is then fused onto the steel surface using an electric arc. The process of a cvd formation is similar to the strem process and hence the term strem.
When the cvd material is exposed to the atmosphere it will produce the MOCVD effects which are also known as Ald (Aux) Precursors. These are the substances which are produced as a result of the MOCVD process. As mentioned before MOCVD can be either a Stretching or a melting process but the one which is referred to as a melting process is a direct consequence of the cvd becoming wet. The use of such vapour deposition as part of a coating, such as on aluminium alloys and stainless steels for example has now grown in popularity because of the ease of producing the desired metals and the MOCVD catalyst.
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