Finding the Distribution of Dopants in Semiconductor Nanocrystals
As important as the use of semiconductors in modern technology, has been the use of dopants to modify the properties of the semiconductors. Sometimes the semiconductor lacks the specific characteristics needed, such as conductivity or transparency, but by replacing a few atoms, this can be changed. Researchers at Berkeley Lab have delved into doped semiconductor nanocrystals to analyze how the distribution of dopants contributes to their impact on the larger material.
Normally when a material is doped, one is concerned with how much of the dopant is present, and not where the doping atoms are located. While this has been working well for some time, the Berkeley researchers wanted to look deeper and started with ITO. Indium tin oxide is a transparent semiconductor found in many technologies, including displays, solar cells, and smart windows that can selectively block certain frequencies of light. Tuning the amount of tin, the dopant, enables control of what frequency of light is absorbed, but the researchers wanted to see if the distribution of tin mattered, so they turned to X-ray photoelectron spectroscopy to study some samples. By collecting electrons emitted by the samples under X-ray beams of different energies, the researchers could determine the dopant distribution through the material.
The researchers found that indeed the position of the dopants does impact how the material interacts with light. This knowledge could be applied to achieve the same tuning we have now but with less doping, or to design materials with new properties and new applications in mind.
Source: Berkeley Lab