These challenges were circumvented with the use of room temperature diffusion controlled reactions. The crystals were bathed in a solution that included the dopants, where slow diffusion allowed for impurities to find their way into the nanocrystal.
The researchers used a scanning tunneling microscope (STM), a device that images surfaces at an atomic level, in order to determine the success of their doping procedure. These measurements indicated how the Fermi energy of the nanocrystals changed upon doping, a key feature in controlling the electronic properties of electronic devices. The results, notes Prof. Rabani, indicate that the nanocrystals have been doped with both n-type dopants, indicating the presence of excess electrons in the nanocrystals, and p-type, which contribute positively charged holes to the semiconductors. This will allow for their use in electronics that require a pn junction, such as solar panels, light emitting diodes, and more.
Broadening the nanocrystal spectrum
Not only did Prof. Rabani and his fellow researchers succeed in doping nanocrystals without bleaching their optical properties, but they also were able to control the optical properties, namely, the color range that the nanocrystals produce. Once doped, the nanocrystal particles could change in color, becoming more red or blue. Prof. Rabani and his colleagues were able to develop a theory to explain these observations.
Prof. Rabani says that this technology can go a long way. Doping semiconductors, he explains, has been essential for the development of technology. "Parallel to this, we also know we want to make electrical components very sma
|Contact: George Hunka|
American Friends of Tel Aviv University