Transistor breakthrough paves way for faster electronics

Unlike conventional FETs made from silicon, the devices have been shown to suffer no performance drop-off under high voltages and provide high electron mobility even when scaled to a monolayer in thickness. "Our work represents an important stepping stone towards the realisation of a new class of electronic devices, in which interfaces based on van der Waals interactions rather than covalent bonding provide an unprecedented degree of control in material engineering and device exploration," said lead researcher Ali Javey. To create the FETs, the Berkeley team used the transition metal dichalcogenide molybdenum disulfide as the electron-carrying channel, hexagonal boron nitride as the gate insulator and graphene as the source, drain and gate electrodes. Mechanical exfoliation was used to create the layered components. Javey continued: "In constructing our 2D FETs so that each component is made from layered materials with van der Waals interfaces, we provide a unique device structure in which the thickness of each component is well-defined without any surface roughness, not even at the atomic level. "The van der Waals bonding of the interfaces and the use of a multi-step transfer process present a platform for making complex devices based on crystalline layers without the constraints of lattice parameters that often limit the growth and performance of conventional heterojunction materials." Looking ahead, the researchers are keen to see if they can grow the heterogeneous layers directly on a substrate. They also want to scale down the thickness of individual components to a monolayer and the lengths of the channels to molecular-scale dimensions.