Ultrafast pulsed laser ablation for synthesis of nanocrystals

Abstract

We have performed a systematic study of nanoparticle generation using near infrared ultrafast pulsed laser ablation. The materials we have studied include metal, metal alloy, and metal oxide. We find that by optimizing the ablation conditions, as a direct result of ultrafast pulsed laser ablation, polycrystalline and single-crystalline nanoparticles can be abundantly produced without intermediate nucleation and growth processes. Combining with different background gases, versatile structural forms have been obtained for the nanocrystals. Using metal nickel as a sample material, we have produced Ni/NiO core/shell nano-spheres and NiO nano-cubes. In the study of generation of alloy nanoparticles, which has been challenging in fabrication, we demonstrate production of binary alloy NiFe nanoparticles that have the same composition as the target material. Metal alloy nanoparticles containing up to three elements are also produced. For metal oxide nanoparticles, two important oxide materials are studied, including TiO₂ and ZnO. All nanoparticle samples are examined using high resolution transmission electron microscopy for morphological, structural, and chemical analysis. An ion probe is used <i>in situ</i> to study the laser ablation process in real-time.