The device is a ferroelectric tunnel junction (FTJ) that contains a thin layer of aferroelectric material sandwiched between two electrodes. Ferroelectric materials are intrinsically polarized so that negative electrical charge concentrates on one side of the layer and positive charge clusters on the opposite side. Applying an electric field flips this polarization, and the two states can represent the “1”s and “0”s of binary data. The device crucially does not need power to retain this data.
Tom Wu of from the KAUST Material Science and Engineering program and colleagues created an FTJ containing a film of ferroelectric samarium-doped bismuth iron oxide (SBFO) that was just three to nine nanometers thick1. One electrode was made of platinum and the other was niobium-doped strontium titanate (NSTO), a light-sensitive semiconductor.
Electrons can sometimes tunnel through a very thin ferroelectric layer—a quantum mechanical process that allows them to skip across an energy barrier to create a current. In one of its polarization states, SBFO has a low tunneling electroresistance (TER) that allows electrons across. However, in the other polarization state, the team found that its TER is 100,000 times larger, which prevents electron tunneling. This is the largest change in TER ever seen for a FTJ, providing an unambiguous way to read its polarization state.
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