IBM came up with an ionic liquid transistor

IBM experts have designed a new type of transistor that is suitable for creating a new class of non-volatile memory. This transistor does not use silicon as a semiconductor, but vanadium dioxide (VO ₂ ). Under the influence of a positively charged ionic liquid, it makes a phase transition to the metallic state, and in a negative field again turns into an insulator.

The diagram above shows the device with a drop of ionic liquid over the gold contacts of the integrated circuit. Large golden squares on the left side of the diagram are pads for fixing contacts. The transistor channel (darkened yellow area) is shown on the enlarged area on the right. The gold contacts on the left and right are the source and drain of the transistor, through which a controlled current flows through the channel. The four remaining contacts are used to measure resistance and Hall voltage.

The value of the IBM discovery is that they managed to find a material that causes vanadium dioxide to reliably transition into the metallic state and retain it until it comes into contact with a negatively charged ionic liquid. In this case, the oxygen returns to its place - and instead of the metal, the insulator VO ₂ appears again. A drop of ionic liquid with a volume of about 0.1 µL should be used in each IBM transistor . During the experiments, the standard industrial ionic liquid HMIM-TFSI was used , after its preliminary dehydration in high vacuum (10 ^-7 mm Hg) at a temperature of 120 ° C for several days.

Scientists previously knew the ability of vanadium dioxide to quickly change the phase state from an insulator to a conductor. For example, it performs it when heated to 68 ° C or under pressure. However, IBM scientists have found a more practical way to provoke a phase transition by changing the direction of the field, which is much better suited for industrial use of the material in electronics. They published the results of their work in the journal Science.

The advantage of memory cells of this type is non-volatility. They save charge without supplying power, which can significantly reduce the power consumption of integrated circuits. The disadvantage is the relatively low speed.