Research carried out in EPFL’s Laboratory of Nanoscale Electronics and Structures in Switzerland has shown that molybdenite is a very effective semiconductor. The mineral (MoS2), which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants but it had not yet been extensively studied for use in electronics.
‘It’s a two-dimensional material, very thin and easy to use in nanotechnology,’ said EPFL’s Prof Andras Kis. ‘It has real potential in the fabrication of very small transistors, light-emitting diodes and solar cells.’
Kis compared its advantages with two other materials: silicon, currently the primary component used in electronic and computer chips, and graphene.
According to EPFL, one of molybdenite’s advantages is that it is less voluminous than silicon, which is a three-dimensional material.
‘In a 0.65nm sheet of MoS2, the electrons can move around as easily as in a 2nm-thick sheet of silicon,’ said Kis. ‘But it’s not currently possible to fabricate a sheet of silicon as thin as a monolayer sheet of MoS2.’
It is claimed that another advantage of molybdenite is that it can be used to make transistors that consume 100,000 times less energy in standby state than traditional silicon transistors.
A semiconductor with a ‘gap’ must be used to turn a transistor on and off, and molybdenite’s 1.8 electron-volt gap is said to be ideal for this purpose.
In solid-state physics, band theory is a way of representing the energy of electrons in a given material. In semiconductors, electron-free spaces exist between these bands, the so-called ‘band gaps’. If the gap is not too small or too large, certain electrons can hop across the gap. It offers a greater level of control over the electrical behaviour of the material, which can be turned on and off easily.
The existence of this gap in molybdenite also gives it an advantage over graphene. Considered today by many scientists as the electronics material of the future, the ‘semi-metal’ graphene does not have a gap, and it is very difficult to artificially reproduce one in the material.
An article detailing the research has been published online in the journal Nature Nanotechnology.