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Investigation of Ferromagnetism in<br/>Ge-Based Diluted Magnetic Semiconductors

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Spin-based electronics made by chemistry

Ferromagnetic semiconductors were the focus of EU-funded research because of their unusual physical properties as well as potential applications in spin-based computing.

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In conventional computing devices, charge and spin are used separately. Charge, on the one hand, is used for computing. Transistors operate by controlling with electric fields the flow of charge carriers through a semiconducting material. On the other hand, spin is used for magnetic data storage. Encoding information with the spin state of electrons in addition to their charge could dramatically improve the computational speed and reduce power consumption. Diluted ferromagnetic semiconductors (DMSs) are the most well understood and promising materials for such spintronics devices. The EU-funded project IFMGEDMS (Investigation of ferromagnetism in Ge-based diluted magnetic semiconductors) focused on DMSs based on germanium. Scientists synthesised thin films of manganese-doped germanium that exhibited ferromagnetic properties, allowing spin injection. These DMSs were grown on suitable silicon substrates by molecular beam epitaxy with atomic-scale precision. X-ray photoelectron spectroscopy enabled detailed structural and magnetic characterisation of manganese-doped germanium films synthesised under various conditions. Scientists were thus able to identify the optimal growth conditions to incorporate the highest concentration of diluted manganese. Moreover, they found that magnetic ordering and Curie temperature could be controlled by carefully adjusting the distance between manganese atoms in the germanium spacer layer. Research performed in IFMGEDMS led to high-quality films of manganese-doped germanium. In this type of new semiconducting material, spin becomes another information carrier together with charge, with numerous advantages when incorporated into silicon-based spintronic devices.

Keywords

Semiconductors, diluted ferromagnetic semiconductors, spintronics, IFMGEDMS, molecular beam epitaxy

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