Solution Synthesis of Germanium Nanocrystals:  Success and Open Challenges

• Published in: Nano letters 2004-04, Vol.4 (4), p.597-602
• Main Authors: Gerion, Daniele, Zaitseva, Natalia, Saw, Cheng, Casula, Maria Francesca, Fakra, Sirine, Van Buuren, Tony, Galli, Giulia
• Format: Article
• Language: English
• Subjects: Chemical synthesis methods; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of nanofabrication; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Physics
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl035231t

We present a two-step synthesis route that yields nanometer-size crystalline germanium in the form of a black powder. It relies on high temperature decomposition of tetraethylgermane (TEG) in organic solvents. The presence of pure germanium with diamond structure is unambiguously attested by powder XRD measurements. Low-resolution TEM indicates that the particles are between ∼5 to 30 nm in size, depending on the synthesis conditions. The as-synthesized Ge powders can be stored in air for months and no oxidation occurs. The Ge powders are sparingly soluble in conventional solvents because Ge nanocrystals are likely embedded in a matrix composed mainly of CC, C−C, and C−H bonds. The presence of residual organic byproducts impedes probing of the optical properties of the dots. Also, we discuss drawbacks and open challenges in high-temperature solution synthesis of Ge nanocrystals that could also be faced in the synthesis of Si nanocrystals. Overall, our results call for a cautious interpretation of reported optical properties of Ge and Si nanocrystals obtained by high-temperature solution methods.