Research Areas

 

The Spintronics and Nanodevice Laboratory is particularly interested in nanomaterials and nanodevices, which are directed towards information technology and microelectronics. There are two related research themes; 1) growth and characterisation of spintronic materials and 2) development of nano scale devices for the next generation microelectronics and nanoelectronics. Spintronics is expected to have a major impact on microelectronics, information storage, automotive sensors, communication, and future quantum computing in a way comparable to the development of the transistor 50 years ago.  The group consists of three laboratories including materials growth laboratory, electron transport measurement laboratory, and magneto-optical characterisation Laboratory. Their research has been funded by the EPSRC, the Royal Society, White Rose Network, and CCLRC.

 

 

 

 

Spintronics and Nanomagnetism: Base on the very basic fact that electrons have spin as well as charge, an exciting new field of electronics, spin electronics (spintronics), has attracted great attention recently. Within the context of spin-electronics, the electrons’ spins, not just their electrical charge, are controlled for the operation in information circuits. This emerging field of spin-electronics could largely be viewed as composed of three closely related topics according to the material systems explored: a) magnetic/nonmagnetic multilayers, granular films, and magnetic/oxide tunnelling junctions etc., b) mesoscopic ferromagnets, and c) mesoscopic magnetic/semiconductor heterostructures. The development of spin-electronics is driven partially by scientific curiosity and partially by a great industrial potential. As the conventional solid-state electronic devices are based on semiconductors, the injection and manipulation of spin electrons in mesoscopic ferromagnetic/semiconductor heterostructures may lead to the “marriage” of magnetic storage and semiconductor devices, and the development of next generation spin-electronic devices for data storage and processing at the same time.  One of their current projects on spintronic materials is to synthesise half metallic oxides on semiconductor, and this type of hybrid materials might be one of the most promising systems for spintronics as half metallic oxides has large spin polarisation and large Curie temperatures. They have gown for the first time the half-metallic epitaxial Fe3O4 on GaAs, which was presented as an invited talk at MRS Fall Meeting in Boston, 2005. They are currently developing the high efficient spin-LED devices in collaboration with Toshiba using the high quality material grown in York. For the devices, they are developing vertical hybrid spin-devices for direct electrical spin-injection and detection based on magnetic/semiconductor hybrid materials. His group has demonstrated large direct electric spin-injection and detection from ferromagnetic metals such as Fe and FeNi into III-V semiconductors such as GaAs at room temperature, which is one of the major progresses in hybrid spintronics.

 

       

Nanofabrication and nanodevices: The “designer capability” in the state-of-the-art nanofabrication techniques, such as atomically-precise film growth using molecular beam epitaxy, and advanced electron beam lithography pushing down to about 50nm has opened up a way to explore this fascinating new realm of micromagnetism and nanoelectronics. A major discovery is the giant magneto-resistance effect (GMR) observed in layered magnetic thin-film structures consisting of a stack of alternating layers of magnetic and nonmagnetic atoms. GMR read heads will boost disk drive capacity by 20 times, and the GMR devices might be incorporated into random access memory units (RAM). When the critical structural dimensions of magnetic materials approach or fall below the characteristic lengths such as magnetic domain wall width, exchange length and spin-dependent mean free path, magnetic properties change and new phenomena with dominant quantum effect will occur. However, when the bit size approaches the critical diameter of superparamagnetic clusters (about 100nm for Co for example), the thermal effect will dominate the magnetization process. Both for fundamental studies and applications, the magnetic properties and electron transport should be addressed in submicron and nanometer scale.

 

 

 

 

 

Research Facilities:

 

  • UHV growth chambers with three e-beam sources, two sputtering sources and a sample transfer chamber.
  • In-situ Structural analysis using RHEED
  • In-situ Magnetic and magneto-elastic properties measurements
  • Advanced photolithography (a mask aligner up to 3 inch wafers, a photoresist spinner, and a wet chemical workstation)
  • Advanced e-beam lithography
  • Focused Ion beam for lithography
  • Atomic force microscopy/magnetic force microscopy/scanning tunneling microscopy
  • Plasma Enhanced Chemical Vapour Deposition (PECVD)
  • A plasma reactive ion etcher (RIE)
  • Thermal Oxidation
  • Scanning Electron Microscope.
  • Ex-situ and in-situ MOKE for magnetic characterisation
  • Magneto-resistance, I-V characterisation and spin dependant transport measurements
  • A well equipped class 100 clean room for device fabrications and testing
  • Facilities in central laboratory of research council, Daresbury Synchrotron Radiation Laboratory and Diamond Laboratory

 

 

Technical support:

 

The group research has strong technical supports from both the mechanical and electronic workshops in the department for instrumental development and construction. Senior experimental officers and technical staffs within the group support the running of the laboratory.