New research could lead to improved semiconductor nanocrystals

Semiconductor nanocrystals consist of tens to thousands of atoms and the tiny particles have the potential uses in the semiconductor industry. However, the semiconductors are poor electrical conductors, and in order to use them in electronic circuits the conductivity must be tuned by the addition of impurities. In this process foreign atoms called impurities are introduced into the semiconductor, causing an improvement in its electrical conductivity. The semiconductor industry annually spends billions of dollars in efforts to intentionally add impurities into semiconductor products, which is a major step in the manufacturing of numerous electronic products, including computer chips, LEDs and solar cells. Researchers worldwide have made continuing attempts at doping nanocrystals in order to achieve ever greater miniaturisation and to improve production methods for electronic devices. However, the tiny crystals are resistant to doping, as their small size causes the impurities to be expelled. An additional problem is the lack of analytical techniques available to study small amounts of dopants in nanocrystals. Due to this limitation, most of the research in this area has focused on introducing magnetic impurities, which can be analysed more easily – although the magnetic impurities don't really improve the conductivity of the nanocrystal. Professor Uri Banin, pictured, and David Mocatta from the Hebrew University Center for Nanoscience and Nanotechnology, have achieved a breakthrough in the development of a straightforward, room temperature chemical reaction to introduce impurity atoms of metals into the semiconductor nanocrystals. They claim that the new effects have not previously been reported. The researchers built up a comprehensive picture of how the impurities affect the properties of nanocrystals and they discovered that the impurity affects the nanocrystal in unexpected ways, resulting in new physics. "We had to use a combination of many techniques that when taken together make it obvious that we managed to dope the nanocrystals. It took five years but we got there in the end," said Mocatta. This breakthrough was reported recently in journal Science and could lead to the development of potential applications with nanocrystals, ranging from electronics to optics, from sensing to alternative energy solutions.