Synthesis of GeSn particles with high substitutional Sn concentration by pulsed laser depositon

We have proposed that germanium-tin (GeSn) particles with high substitutional Sn concentrations can be synthesized by pulsed laser deposition (PLD) in ambient Ar at low pressure (similar to 100 Pa). In this method, a Ge0.9Sn0.1 target is ablated by KrF excimer laser irradiation. At low Ar pressure (similar to 100 Pa), the agglomeration of Ge and Sn atoms occurs easily in ambient Ar, and the agglomerated particles are rapidly cooled by collision with Ar atoms. An Si-receiving substrate was placed in front of the target. Various GeSn particles from several 100 nm to approximately 20 mu m with spherical, disk, and irregular shapes were deposited on the Si-receiving substrate. In Raman spectra, the Ge-Ge vibration peaks of all the particles were shifted to lower wavenumbers compared with those of the Ge(100) crystal. The Raman peak position reportedly shifts to lower wavenumbers with increased substitutional Sn concentration in crystalline Ge. Thus, GeSn crystal particles with over 10% substituted Sn atoms can be synthesized by low-pressure PLD.