Product Code: ICAL07_N405

Nano-particle Generation by Femto Second Laser Ablation
Authors:
N Semaltianos, The University of Liverpool; Liverpool Great Britain
C Williams, The University of Liverpool; Liverpool Great Britain
Martin Sharp, The University of Liverpool; Liverpool Great Britain
Walter Perrie, The University of Liverpool; Liverpool Great Britain
Stuart Edwardson, The University of Liverpool; Liverpool Great Britain
Geoff Dearden, The University of Liverpool; Liverpool Great Britain
Ken G Watkins, The University of Liverpool; Liverpool Great Britain
Presented at ICALEO 2007

Ultrashort laser pulse ablation leads to the generation of intense plasmas expanding from a substrate surface. This highly ionised material, initially at almost solid state density, expands well after the pulse has been absorbed. and is collisionally cooled by the ambient gas. The resulting debris returning to the surface consists mainly of spherical nano-particles whose size distribution depends strongly on the ambient gas composition and pressure. We present results on the study of nano-particle size distribution and their physical properties (eg crystalline structure) with Ti6Al4V, Si, Alumina and fused silica ablated at 775nm with 180fs pulselength. For example, in Silicon, the particle size distribution is broad and peaks around 100nm in air while under liquid, the size distribution reduces dramatically with most particles < 50nm size.