Electrical creation of spin polarization in silicon at room temperature Eventual commercialization will mean faster electronics that is far more energy efficient.
The control and manipulation of the electron spin in semiconductors is central to spintronics which aims to represent digital information using spin orientation rather than electron charge. Such spin-based technologies may have a profound impact on nanoelectronics, data storage, and logic and computer architectures. Recently it has become possible to induce and detect spin polarization in otherwise non-magnetic semiconductors (gallium arsenide and silicon) using all-electrical structures but so far only at temperatures below 150 K and in n-type materials, which limits further development. Here we demonstrate room-temperature electrical injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect and the electrical detection of the induced spin accumulation. A spin splitting as large as 2.9 meV is created in n-type silicon, corresponding to an electron spin polarization of 4.6%. The extracted spin lifetime is greater than 140 ps for conduction electrons in heavily doped n-type silicon at 300 K and greater than 270 ps for holes in heavily doped p-type silicon at the same temperature. The spin diffusion length is greater than 230 nm for electrons and 310 nm for holes in the corresponding materials. These results open the way to the implementation of spin functionality in complementary silicon devices and electronic circuits operating at ambient temperature, and to the exploration of their prospects and the fundamental rules that govern their behaviour.
Digital electronics is almost universally based on the detection and control of the movement of electrons through the electrical charge associated with them. However electrons also have the property of spin and transistors that function by controlling an electron’s spin orientation, instead of its charge, would use less energy, generate less heat and operate at higher speeds. That theory has resulted in a field of research called spintronics. However, until now this has required low temperatures for operation.
Indeed, as the University of Twente authors comment, the ability to detect spin polarization in otherwise non-magnetic semiconductors — including gallium arsenide and silicon — using all-electrical structures has only been achieved at temperatures below 150 K and in n-type materials, which has limited further development.
The authors state that they have demonstrated room-temperature electrical injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect and the electrical detection of the induced spin accumulation.
The spin splitting has a life time of greater than 140-ps for conduction electrons in heavily doped n-type silicon at 300 K and greater than 270-ps for holes in heavily doped p-type silicon at the same temperature.
Nonetheless, the results open up the possibility of embedding spintronic operation in complementary silicon operating at ambient temperature.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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