A class of semiconductors demonstrating magnetic properties at room temperature could one day be the basis for innovative computing and storage media in the computers of the future. The electronic and magnetic properties of these so-called dilute semiconductors are altered in useful ways by the deliberate and targeted introduction of impurities in the form of foreign atoms. It is now easier to examine exactly what happens during this process, known as doping, and how desired characteristics can be produced, for an international team of scientists has discovered that a method based on angle resolution photoemission spectroscopy can read information directly from the electronic structure of materials, information that previously could only be interpreted using complex analyses involving theoretical predictions.
Using the so-called "Bragg reflection standing-wave hard X-ray angle-resolved photoemission spectroscopy", scientists succeeded in separating element-specific and momentum-specific information from the valence bands of the semiconductors. In the valence bands, there are electrons that are, for example, responsible for conductivity or the magnetic characteristics. "We can now for the first time directly differentiate between the valence bands of the various different elements", explains Dr. Slavomir Nemšák, a scientist conducting part of his research at the Peter Grünberg Institute, Electronic Properties (PGI-6) in Jülich. "This means that we can identify exactly what kind of influence doping with an element has on the characteristics of the materials."
The researchers employed a combination of methods established separately decades ago, but used much higher energy X-rays from a synchrotron as their light source, which was crucial for this experiment. The method can be used not only for semiconductors, but also to study metallic alloys and superconductors.
Slavomír Nemšák, et al.; Element- and momentum-resolved electronic structure of the dilute magnetic semiconductor manganese doped gallium arsenide; Nature Communications 9, Article number: 3306 (2018), DOI: 10.1038/s41467-018-05823-z