Laser Ablation of Films and Suspended Particles in a Solvent: Formation of Cluster and Colloid Solutions

Abstract

Crystalline silicon particles of cubic structure are formed in the plasma which is initiated in an argon‐silane mixture by a focussed 694 nm Ruby laser flash. Part of the particles can be dissolved as colloid in organic solvents. The solubilization is increased by small amounts of 1,3‐propane‐dithiol. The raw material has a broad size distribution. Centrifugation and filtration methods are applied to obtain samples with narrow size distribution. Small silicon particles have structured absorption spectra. The particles luminesce after etching with HF under air. The larger particles have a red luminescence (peaking at 720 nm) and the smaller particles emit a blue luminesce. The luminescence effects are explained by size quantization of the electronic energy levels in the particles.