Abstract

An analog of the Datta-Das spin field-effect transistor (FET) is investigated, which is all graphene and based on the valley degree of freedom of electrons/holes. The “valley FET” envisioned consists of a quantum wire of gapped graphene (channel) sandwiched between two armchair graphene nanoribbons (source and drain), with the following correspondence to the spin FET: valley (K and $K^{\prime }$) ↔ spin (up and down), armchair graphene nanoribbons ↔ ferromagnetic leads, graphene quantum wire ↔ semiconductor quantum wire, valley-orbit interaction ↔ Rashba spin-orbit interaction. The device works as follows. The source (drain) injects (detects) carriers in a specific valley polarization. A side gate electric field is applied to the channel and modulates the valley polarization of carriers due to the valley-orbit interaction, thus controlling the amount of current collected at the drain. The valley FET is characterized by (i) smooth interfaces between leads and the channel, (ii) strong valley-orbit interaction for electrical control of drain current, and (iii) vanishing interband valley-flip scattering. By its analogy to the spin FET, the valley FET provides a potential framework to develop low-power FETs for graphene-based nanoelectronics.

Net Spin Polarization

A spin field effect transistor (FET) is proposed by utilizing a graphene layer as the channel. Similar to the conventional spin FETs, the device involves spin injection and spin detection by ferromagnetic source and drain. Due to the negligible spin-orbit coupling in the carbon based materials, spin manipulation in the channel is achieved via electrical control of the electron exchange. Spin polarized field effect transistor (Spin FET) was proposed by Datta Das in 1990. This has not been realized yet, but is regarded as one of the most advanced applications of spintoronics in the future. Firstly, the classification of field-effect spin transistors is described. Then, the MOSFET type of spin transistor, i.e., spin-MOSFET, is focused on, and its device structure, operating principle, performance, and device/process technologies are shown.

• Received 27 July 2012

DOI:https://doi.org/10.1103/PhysRevB.86.165411

Boba Fett Spin Off Series

©2012 American Physical Society

Magnetism is a property that had been missingfrom graphene’s impressive list of physical properties – until now. Owing to its unconventional magnetic properties, graphene has been touted as a promising material for spintronics applications. The ambition of the EU-funded SPRING project is to develop an all-graphene platform, where spins can be used for transporting, storing and processing information. Researchers from different disciplines will collaborate to fabricate atomically precise open-shell graphene nanostructures, and manipulate their electron spin and charge, and nuclear spin state. The aim is to test the potential of graphene as a fundamental building block for spintronic devices.

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