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Semiconductor research at ISIS

Temperature dependence of the muonium shallow donor fraction in nano

Temperature dependence of the muonium shallow donor fraction in nanocrystalline CdTe compared with bulk material. Inset – nanocrystalline CdTe.
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Semiconductors are present in forms of modern technology ranging from computers to solar cells.

Electronic devices rely on being able to control the flow of electrons around microscopic circuits. Achieving this requires careful control of the properties of the semiconducting material, producing materials with exceptionally high purity, and harnessing new materials. Research at ISIS in this area includes:

  • Determining how structural changes affect the properties of semiconductors
  • Finding new ways to use the properties of electrons in semiconductors to convey information
  • Developing advanced materials processing 
  • Showing the effects of cosmic rays on semiconductor devices.

One of the principal challenges in harnessing the energy of the sun is producing cheap, large area devices that can collect useful amounts of the sun’s energy. A potential route to such devices uses polymers that can be printed onto a surface and assemble themselves into the structure required to capture light effectively. Scientists have used ISIS to investigate how this process of self-assembly works and how these materials arrange themselves on surfaces. Work to understand how electronic charges move through these materials has used muons to examine the upper limit for intrinsic mobility.

Many semiconductor devices are grown by deposition from hydride gases and this can lead to hydrogen defects that trap conduction electrons. It can be difficult to determine the form that these defects take, but muons can impersonate hydrogen in semiconductors and give an easier way to examine this sort of defect. This has been done for a wide range of semiconductors, an example being zinc oxide, which is transparent and suitable for white light applications.

Pairing magnetic and semiconducting materials offers the possibility of using the magnetic moment of electrons to carry information, rather than just their electrical charge. This would offer new ways of making computers and is referred to as spintronics. ISIS neutrons have shown how potential materials for such applications function at the microscopic level and how fine-tuning can optimise their properties.

Chipir is a new instrument currently being built at ISIS that will irradiate electronic devices with neutrons to learn how they respond to cosmic rays. A cosmic ray hitting a semiconductor device can change the information stored in a device’s memory or damage the electronics more permanently. By using the intense neutron beam available at ISIS, an hour of testing can simulate hundreds of years of flying time in an aircraft. This will lead to a better understanding of how different device designs mitigate the effects of cosmic rays.

More detailed descriptions of semiconductor research carried out at ISIS are listed on the following pages.

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