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Hexagonal boron nitride: seems to be the material of choice for 5G RF switches

wallpapers Tech 2020-06-30
A thin layer of hexagonal boron nitride (BN)is sandwiched between gold electrodes, which can be used as a switch to transmit 5G or higher frequencies.
 
Texas engineer designed a non-volatile 2D hexagonal boron nitride switch similar to memory.
 

Two-dimensional materials of atomic order are useful in many ways, but until two years ago, no one thought they could make better storage devices. Deji Akinwande, Jack Lee, and their team at UT Austin gave it a try. It turns out that a 2D material like molybdenum disulfide is sandwiched between two electrodes to form a memory-a two-terminal device that stores data by changing resistance. In the research report last week, they have proved a critical potential application of these "atomic resistors"-analog RF switches, suitable for 5G and even 6G radio in the future.

Cellular radio has done many conversions. They must switch between different frequencies to prevent interference, and they must switch between signals of different phases to control the data beam. RF switches are very demanding devices that require a combination of characteristics that are difficult to obtain. Fast switching, low resistance, high impedance, and small leakage are not available in today's switches; they should remain in place without power. If you don't need to turn on the radio switch, the battery-based IoT system may be used longer. This is what the new nanoscale atomic resistor switch can do now, not only for the 5G frequency but also for the possible 6G spectrum in the future.

Memristors are usually composed of two electrodes sandwiched between columns of insulating material (such as oxide materials). The device starts in a high-resistance state, preventing current flow. But if the voltage is raised to a sufficiently high level, oxygen will be extruded from the oxide, forming a conductive channel. In this state, the device can easily pass current. The high voltage in the opposite direction will return oxygen to its original position and restore its resistance.
 
 
Since there is no vertical dimension in a two-dimensional semiconductor to form a conductive path, this will not happen. In contrast, Akinwande's research team found that certain naturally occurring defects in the lattice of two-dimensional materials produce this effect. These defects are missing atoms. Generally, the resistance of a two-dimensional material is high. Still, if there is enough voltage, the gold atoms on the electrode will temporarily move into the gap, making the material conductive. Akinwande introduced: "Basically, it is like Airbnb. They are just renting a house," a robust reverse voltage will push the gold class.

The atomic reaction was initially discovered using molybdenum disulfide as a two-dimensional material. But for RF switches, the signal must be actively blocked when turned off, "What you need is an insulator," So the team and their collaborators at the University of Lille turned to hexagonal boron nitride (hBN), which is A widely studied two-dimensional insulator.

Akinwande: "Usually, when people use hBN, they use several layers." But over time, his team was able to make switches with 0.3-nm-thick material layers. "People are shocked by this result." The key is that when generating hBN, there must not be any defects large enough to allow current to pass through. "It must be almost perfect."

The essential advantage of an RF switch is its cutoff frequency. It is a combination of on-state resistance and off-state capacitance. In the right switch, both should below. The hertz value of the cutoff frequency indicates that the device is an excellent choice for RF switches, and the experimental hBN device score is 129 terahertz. As part of the test, the team used a carrier frequency of 100 GHz to transmit real-time high-definition video at 8.5 GHz per second. They introduced that this frequency is enough to meet the streaming media needs of 5G. At this data rate, several movies can be downloaded in seconds. They published the results of the research in the journal Nature Electronics.

For 5G frequencies, Akinwande is exploring commercialization to develop nanoscale switches further. Although the research equipment was demonstrated using gold electrodes on a diamond substrate, Akinwande said manufacturing these RF switches is compatible with the CMOS process used by factories. He pointed out that several universities and TSMC research have shown that hBN and silicon can be integrated.

For the 6G frequency, which is expected to include rates in the terahertz range (300 to 3000 GHz), the UT Austin team is planning to conduct new laboratory measurements.

Trunnano is one of the world's largest nitride manufacturers. Boron nitride is one of the leading products. If you are interested in boron nitride, please contact Dr. Leo, email:brad@ihpa.net.


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