Gold removal from germanium nanowires

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Germanium nanowires (GeNWs) are crucial for nanoelectronic devices.
• Growth of GeNWs often involves gold nanoparticles (AuNPs) as catalysts.
• Residual AuNPs can negatively impact device performance and require removal.

Purpose of the Study:

• To develop a selective and efficient method for removing AuNPs from GeNW tips.
• To ensure the germanium surface remains unoxidized after gold removal.
• To investigate methods for improving the selectivity of GeNW growth on AuNPs.

Main Methods:

• Selective etching of AuNPs using aqueous hydrochloric acid solutions with potassium triiodide or iodine.
• Quantification of residual gold using inductively coupled plasma-mass spectrometry (ICP-MS).
• Surface analysis using photoemission spectroscopy (PES) and Auger electron spectroscopy (AES).

Main Results:

• Achieved 99% removal of residual gold atoms from GeNW tips.
• PES confirmed no significant oxidation of germanium surfaces post-etching.
• AES revealed germanium incorporation in non-yielding AuNPs and enhanced GeNW selectivity with gaseous HCl addition.

Conclusions:

• Aqueous hydrochloric acid solutions with iodide or triiodide are effective etchants for selective gold removal.
• The developed method preserves germanium surface quality, crucial for device fabrication.
• Optimizing precursor gases during chemical vapor deposition enhances the selectivity of germanium nanowire growth.