IBS scientists constructed a two terminal tunnelling random access memory (TRAM), in which two electrodes – drain and source – resemble the two communicating neurons in a synapse. The advantage of a two terminal device is that it does not need a rigid oxide layer. “Flash memory is more reliable and has better performance, but TRAM is more flexible and can be scalable,” said IBS Professor Yu Woo Jong.
TRAM is made up of a stack of 2D crystal layers – one layer of molybdenum disulphide with drain and source, an insulating layer of hexagonal boron nitride (h-BN) and a graphene layer. According to the researchers, TRAM performs better than phase change RAM and resistive RAM.
TRAM stores data by keeping electrons on its graphene layer. By applying different voltages between the electrodes, electrons flow from the drain to the graphene layer tunnelling through the h-BN layer. The graphene layer becomes negatively charged and memory is written and stored. When positive charges are introduced in the graphene layer, memory is erased.
IBS scientists determined that a 7.5nm thick h-BN layer allows the electrons to tunnel from the drain electrode to the graphene layer without leakage or the loss of flexibility.
When TRAM was fabricated on flexible plastic and stretachable silicone materials, it could be strained by up to 0.5% and 20% respectively. TRAM could find application in smartphones, smart surgical gloves and body attachable biomedical devices.