An atomically thin layer of hexagonal boron nitride is sandwiched between gold and electricity, which can be used as a switch for transmitting 5G or even higher frequencies. Monomer boron

Engineers in Texas designed a memory-like non-volatile 2D hexagonal boron nitride switch.

Atomic-level two-dimensional materials 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 tried it out. Facts have proved that sandwiching a 2D material like molybdenum disulfide between two electricity forms a memory-a double-ended device that stores data by changing its resistance. In the research report last week, they have demonstrated a very important potential application of these "atomic resistors"-analog radio frequency switches, suitable for 5G and even future 6G radios.

Cellular radio has done a lot of conversions. They switch between different frequencies to prevent interference, and switch between signals of different phases to control the data beam. The RF switch is a very demanding device and requires a combination of features that are difficult to obtain. Fast switching, low resistance, high isolation resistance, and small leakage are what today's switches do not have. They should remain in place without power. If you don’t have to turn on the radio switch, a battery-based IoT system may last longer. This is what the new nanoscale atomic resistor switch can do now, not for 5G frequencies, but also for possible 6G frequencies in the future.

A memristor is usually composed of two electrically sandwiched pillars of edge material (such as oxide material). The device starts in a high-resistance state and prevents the flow of current. But if the voltage is increased to a high level, oxygen will be squeezed out of the oxide to form a conductive path. In this state, the device can now easily pass current. A high voltage in the opposite direction will put the oxygen back in place, restoring its resistance.

A layer of hexagonal boron nitride forms a nanoscale switch.

Since there is no vertical dimension to form a conductive path in a two-dimensional semiconductor, 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 the lack of atoms. Generally, the resistance of two-dimensional materials is very high, but if there is a voltage, the gold atoms on the electricity will temporarily move into the gap, making the material conductive. Akinwande said: "Basically, it's like Airbnb. They are just renting a house," a strong reverse voltage will push gold out.

The atomic reaction was first discovered using molybdenum disulfide as a two-dimensional material. But for the RF switch, when it is off, the signal is strongly blocked, "What you really need is a conditional body." Therefore, the team and their collaborators in Lille turned to hexagonal boron nitride (hBN), which is one A two-dimensional marginal body that has been widely studied.

Akinwande: "Usually when people use hBN, they use several layers." But over time, his team was able to make switches with layers of material 0.3 nanometers thick. "People are shocked by this result." The key is that hBN cannot be produced with any defects large enough to allow current to pass. "It's almost perfect."

The key advantage of the RF switch is its cut-off frequency. It is a combination of on-state resistance and off-state capacitance. In a good switch, both should be low. The Hertz value of the cutoff frequency indicates that the device is a good choice for RF switches, and the experimental hBN device scored 129 Terahertz. As part of the test, the team used a 100 gigahertz carrier frequency to transmit real-time high-definition video at a speed of 8.5 gigahertz per second. They introduced that this frequency meets the 5G streaming media requirements. At this data rate, several movies can be downloaded in a few seconds. They published their findings in the journal Nature Electronics.

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

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