Is this the first graphene transistor?
- Autore:Ella Cai
- Rilasciare il:2017-07-06
Researchers in Sweden believe they have created a prototype of a graphene transistor device for future computers.
Spintronics, as it is called, can result in electronics that are significantly faster and more energy efficient.
What the research group at Chalmers University of Technology has demonstrated is that graphene, which is an excellent electrical conductor, also has unsurpassed spintronic properties.
Graphene which is an ultra-thin carbon mesh can convey electrons with coordinated spin over longer distances and preserving the spin for a longer time than any other known material at room temperature, say the researchers.
Although the distance is still on the scale of a few micrometres and the time is still measured in nanoseconds, this in principle opened the door to the possibility of using spin in microelectronic components.
“But, it is not enough to have a good motorway for the spin signal to travel on. You also need traffic lights so the signal can be controlled,” says Associate Professor Saroj Dash, leader of the research group.
“Our new challenge became finding a material that can both convey and control the spin. It is hard, since both tasks normally require completely opposite material properties,” he explains.
The experiment setup, built by André Dankert and Saroj Dash, consists of a graphene conductor mounted on a silicon substrate.
Along with André Dankert, postdoc researcher in the group, Dash designed an experiment where a few layers of molybdenum disulphide were placed on top of a layer of graphene in a type of sandwich, referred to as a heterostructure. With this, they could identify in detail what happens to the spin signal when the electron current reaches the heterostructure.
“Firstly, the magnitude of the spin signal and lifetime in graphene is reduced tenfold just through the close contact with molybdenum disulphide. But, we also show how one can control the signal and lifetime by applying electrical gate voltage across the heterostructure,” says Dash.
This is because the natural energy barrier that exists between the material layers, called the Schottky barrier, reduces when the electrical voltage is applied.
Opening or closing a “valve” in this manner by regulating a voltage is similar to how a transistor works in conventional electronics.
But Dash is a little hesitant to call the device a spin transistor.
“When researchers proposed on future spin transistors, they often imagined something based on semiconductor technology and so called coherent manipulation of electron spin. What we have done works in a completely different way, but performs a similar switching task,” he says.
“This is the first time that anyone has been able to demonstrate that the gate control of spin current and spin lifetime works at room temperature – which naturally increases the possibilities for different applications in the future,” says Saroj Dash.
The discovery is published in the scientific journal Nature Communications.
By combining graphene with another two-dimensional material, researchers at Chalmers University of Technology in Gothenburg have created a prototype of a transistor-like device which uses electron spin as the information carrier.
Spintronics, as it is called, can result in electronics that are significantly faster and more energy efficient.
What the research group at Chalmers University of Technology has demonstrated is that graphene, which is an excellent electrical conductor, also has unsurpassed spintronic properties.
Graphene which is an ultra-thin carbon mesh can convey electrons with coordinated spin over longer distances and preserving the spin for a longer time than any other known material at room temperature, say the researchers.
Although the distance is still on the scale of a few micrometres and the time is still measured in nanoseconds, this in principle opened the door to the possibility of using spin in microelectronic components.
“But, it is not enough to have a good motorway for the spin signal to travel on. You also need traffic lights so the signal can be controlled,” says Associate Professor Saroj Dash, leader of the research group.
“Our new challenge became finding a material that can both convey and control the spin. It is hard, since both tasks normally require completely opposite material properties,” he explains.
The experiment setup, built by André Dankert and Saroj Dash, consists of a graphene conductor mounted on a silicon substrate.
Along with André Dankert, postdoc researcher in the group, Dash designed an experiment where a few layers of molybdenum disulphide were placed on top of a layer of graphene in a type of sandwich, referred to as a heterostructure. With this, they could identify in detail what happens to the spin signal when the electron current reaches the heterostructure.
“Firstly, the magnitude of the spin signal and lifetime in graphene is reduced tenfold just through the close contact with molybdenum disulphide. But, we also show how one can control the signal and lifetime by applying electrical gate voltage across the heterostructure,” says Dash.
This is because the natural energy barrier that exists between the material layers, called the Schottky barrier, reduces when the electrical voltage is applied.
Opening or closing a “valve” in this manner by regulating a voltage is similar to how a transistor works in conventional electronics.
But Dash is a little hesitant to call the device a spin transistor.
“When researchers proposed on future spin transistors, they often imagined something based on semiconductor technology and so called coherent manipulation of electron spin. What we have done works in a completely different way, but performs a similar switching task,” he says.
“This is the first time that anyone has been able to demonstrate that the gate control of spin current and spin lifetime works at room temperature – which naturally increases the possibilities for different applications in the future,” says Saroj Dash.
The discovery is published in the scientific journal Nature Communications.
