Scientists reveal Germanium telluride's hidden properties at the nanoscale
The material could allow data processing with significantly less energy input
Germanium Telluride is an interesting candidate material for spintronic devices. In a comprehensive study at BESSY II, a Helmholtz-RSF Joint Research Group has now revealed how the spin texture switches by ferroelectric polarization within individual nanodomains.
Germanium telluride (GeTe) is known as a ferrolectric Rashba semiconductor with a number of interesting properties. The crystals consist of nanodomains, whose ferrolectric polarization can be switched by external electric fields. Because of the so-called Rashba effect, this ferroelectricity can also be used to switch electron spins within each domain. Germanium telluride is therefore an interesting material for spintronic devices, which allow data processing with significantly less energy input.
Russian German Cooperation
Now a team from HZB and the Lomonosov Moscow State University, which has established a Helmholtz-RSF Joint Research Group, has provided comprehensive insights into this material at the nanoscale. The group is headed by physical chemist Dr. Lada Yashina (Lomonosov State University) and HZB physicist Dr. Jaime Sánchez-Barriga. “We have examined the material using a variety of state-of-the-art methods to not only determine its atomic structure, but also the internal correlation between its atomic and electronic structure at the nanoscale,” says Lada Yashina, who produced the high-quality crystalline samples in her laboratory.
Nanodomains observed in detail
Their microscopy investigations showed that the crystals possess two distinct types of boundaries surrounding ferroelectric nanodomains with sizes between 10 to 100 nanometres. At BESSY II, the team was able to observe two surface terminations with opposite ferroelectric polarization, and to analyse how these terminations correspond to nanodomains with either Ge or Te atoms at the topmost surface layer.
Ferroelectric polarization and spin texture
“At BESSY II, we were able to precisely analyze the intrincate relationship between the spin polarization in the bulk or at the surface and the opposite configurations of the ferroelectric polarization”, explains Jaime Sánchez-Barriga. The scientists also determined how the spin texture switches by ferroelectric polarization within individual nanodomains. “Our results are important for potential applications of ferroelectric Rashba semiconductors in non-volatile spintronic devices with extended memory and computing capabilities at the nanoscale,” emphasizes Sánchez-Barriga.
Publication
ACS Nano 2020: Atomic and Electronic Structure of a Multidomain GeTe Crystal
Alexander S. Frolov, Jaime Sánchez-Barriga, Carolien Callaert, Joke Hadermann, Alexander V. Fedorov, Dmitry Yu. Usachov, Alexander N. Chaika, Brian C. Walls, Kuanysh Zhussupbekov, Igor V. Shvets, Matthias Muntwiler, Matteo Amati, Luca Gregoratti, Andrei Yu. Varykhalov, Oliver Rader, and Lada V. Yashina
DOI: 10.1021/acsnano.0c05851
Further information:
Helmholtz-Zentrum Berlin für Materialien und Energie
Department Materials for green spintronics
Dr. Jaime Sánchez-Barriga
Phone +49 30 8062-15695
Email: jaime.sanchez-barriga(at)helmholtz-berlin.de
Lomonosov Moscow State University
Faculty of Chemistry
Dr. Lada Yashina
Email: yashina(at)inorg.chem.msu.ru
Press release HZB, 5 November 2020