IBM has come up with an ionic transistor

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



The diagram above shows a device with a drop of ionic liquid over the gold contacts of an integrated circuit. Large golden squares on the left side of the scheme are platforms for fixing contacts. The enlarged portion on the right shows the transistor channel (darkened yellow area). The gold contacts on the left and the 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 the resistance and Hall voltage.



The value of IBM's discovery lies in the fact that they managed to find such a material that causes vanadium dioxide to reliably pass into a metallic state and preserve 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. Each IBM transistor should use a drop of ionic liquid with a volume of about 0.1 µL . During the experiments, 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.

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Scientists have previously known the ability of vanadium dioxide to quickly change the phase state from insulator to conductor. For example, he 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 the industrial use of material in electronics. The results of their work, they published in the journal Science .



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