Dr. Subhajit Biswas and Jessica Doherty travelled to Daresbury in the UK this week to make use of the SuperSTEM facilities to analyse GeSn nanowires, with the help of Prof. Quentin Ramasse.
The exact distribution of elements within a nanowire is difficult to determine. However, the specific ordering of the atoms will strongly impact the electronic properties of alloy nanowires. Due to the low melting point of Sn and the low solubility of Sn in the Ge host, Sn segregation at the Ge surface and bulk is highly probable.
The atomic resolution mapping of Sn will also convey the local bonding environment, i.e. the lack of Sn-Sn bond and local segregation of Sn, in the nanowire lattice. Aberration-corrected STEM analysis coupled with atomic resolved EELS analysis can help to confirm the local distribution of Sn atom in the Ge nanowire and in the metal catalyst.
Using the SuperSTEM, it is also possible to obtain Low Loss EEL Spectra from nanowires for use in band gap mapping.