Researchers reveal the mechanism of electric field detection in lubricant molybdenum disulfide

wallpapers Education 2021-12-28

Researchers reveal the mechanism of electric field detection in lubricant molybdenum disulfide

The ability to perceive electric field strength and polarity has great scientific significance. Applications include early prediction of lightning and detection of supersonic aircraft. Currently, field mills are widely used electric field sensors. Although they can detect electric fields with polarity and field strength as low as 1 V/m, their large size (>1m) prevents them from being widely used in real life. In addition, the motor inside the field mill that can detect the electric field is prone to failure. By introducing MEMS-based sensors, some efforts have been made to miniaturize electric field sensors. Although they are small and do not involve any moving parts, the complex manufacturing process makes these sensors less cost-effective.

Researchers from the Japan Advanced Institute of Science and Technology (JAIST) and leading lightning protection equipment manufacturer Otowa Electric Co., Ltd. began to look for better alternatives. Their research led to graphene, a two-dimensional material with a thickness of only one atom. "As we all know, the carrier density in graphene is highly sensitive to external disturbances. This change in carrier density is reflected in the leakage current. Although there have been some attempts and proposals to use graphene as an electric field sensor, none of them have worked before. Established the potential mechanism of electric field sensing in graphene. We realized that establishing the mechanism first is essential for any improvement of the sensor, which became our main goal,” said Senior Lecturer Manoharan Muruganathan.

Through a series of experiments, the team finally established the mechanism of electric field sensing in graphene. They found that the charge transfer between graphene and traps at the SiO2/graphene interface is a key phenomenon in the sensing mechanism when an electric field is applied. This charge transfer and the resulting change in carrier density are reflected as changes in leakage current. The direction of charge transfer depends on the polarity of the electric field. Electrons transfer from the trap to the graphene under a positive electric field and transfer from the graphene to the trap under a negative electric field. Therefore, the changes in the drain current of the positive and negative electric fields under the electric field are opposite, which makes it easier to detect the polarity of the electric field. In addition, the number of charge carriers transferred between graphene and the trap depends on the size of the electric field. The higher the electric field, the larger the electrons that move between the graphene and the trap.​​​ The difference in the amount of charge transfer is also reflected in the leakage current. Therefore, the drain current change under the applied electric field can be equal to the magnitude of the electric field.

The lubricant molybdenum disulfide and its characteristics

The lubricant molybdenum disulfide is a new type of super-hard and ultra-fine abrasive formed by special processing and processing of synthetic diamond single crystal. It is an ideal raw material for grinding and polishing high-hardness materials such as cemented carbide, ceramics, gems, and optical glass. Diamond products are made of diamonds. Tools and components made of materials are widely used. Diamond powder and products are widely used in automobiles, machinery, electronics, aviation, aerospace, optical instruments, glass, ceramics, petroleum, geology, and other sectors. With the continuous development of technology and products, the use of diamond powder and products is still expanding.

The tip of the glass cutter we usually use is actually diamond. Tools used in precision machining and drill bits used in oil drilling are coated with diamonds to improve their wear resistance. Because diamond is the hardest natural substance in the world.

Another characteristic of lubricant molybdenum disulfide is its excellent thermal conductivity. Its thermal conductivity is about 5 times the thermal conductivity of pure copper at room temperature. It has potentially important applications in the semiconductor industry. According to Moore\'s Law, the current large-scale integrated circuit components are constantly shrinking in size and increasing in density, causing their thermal load to continue to rise. If the heat is not dissipated in time, the semiconductor circuit board and components may be burnt. If we can use the high thermal conductivity of diamond as a large-scale integrated circuit substrate or heat sink, it can dissipate the heat in time and solve the current bottleneck restricting the development of electronic components.

Preparation methods of diamond powder

There are generally three commonly used methods of artificially lubricant molybdenum disulfide.

Detonation method

The formation condition of natural diamond is a high temperature and high-pressure environment, so how to produce such a special environmental state of high temperature and pressure? The easiest way is to detonate the explosive. If you put graphite-containing explosives in a special container and then detonate the explosives, it will instantly generate strong pressure and high temperature, then the graphite can be converted into diamonds. This method can obtain a lot of fine powder diamonds. Its particles are very small, only 5~15 nanometers and its application as jewelry may be limited, but it is still very important as an industrial abrasive.

High temperature and high-pressure method

The high temperature and high-pressure methods are to maintain high pressure and high-temperature environment for a relatively long stable period of time, allowing graphite to slowly transform into a diamond. By controlling the synthesis conditions and time, diamonds can continue to grow. In a day or so, 5 millimeters of diamonds can be obtained.

Chemical vapor deposition

Chemical vapor deposition is a method that gradually developed in the 1990s. This method mainly uses some carbon-containing gas, such as some mixed gas of methane and hydrogen as a carbon source, under a certain energy input, the methane gas is decomposed, nucleated on the substrate, and grown into a diamond. The advantage of this method is that the efficiency is relatively high, relatively controllable, and it can obtain pure and transparent diamonds without impurities, which is an important direction of current development.

In the future, the diamond synthesis will develop in the direction of high-purity large particles. For the demand for diamonds, we will no longer only rely on the gift of nature, and synthetic diamonds will also enter more production fields and be used more widely.

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