The ACT device eliminates the need for semiconductors. Instead, it uses two in-plane symmetric metal electrodes (source and drain) separated by an air gap of fewer than 35 nanometers, and a bottom metal gate to tune the field emission. The nanoscale air gap is less than the mean-free path of electrons in the air. Electrons can travel through the air under room temperature without scattering.
Using metal and air in place of semiconductors for the main components of the transistor has some other advantages, says Shruti Nirantar, a PhD candidate in RMIT's Functional Materials and Microsystems Research Group.
This means that fabrication becomes essentially a single-step process of laying down the emitter and collector and defining the air gap. And though standard silicon fabrication processes are employed in producing ACTs, the number of processing steps are far fewer, given that doping, thermal processing, oxidation, and silicide formation are unnecessary.
Consequently, production costs should be cut significantly. Also, replacing silicon with metal means these ACT devices can be fabricated on any dielectric surface, provided the underlying substrate allows effective modulation of emission current from source to drain with a bottom-gate field.
"Devices can be built on ultrathin glass, plastics, and elastomers", Nirantar said. "So they could be used in flexible and wearable technologies."
ACT devices could become important in space exploration since electrons would be unaffected by vacuums, radiation and the acidic breath of aliens (we made the last one up).
Nirantar was the lead author on a new paper published in Nano Letters, and believes that their new approach "means we can stop pursuing miniaturisation, and instead focus on compact 3D architecture, allowing more transistors per unit volume".