Naslov
Metal Nanoclusters Formed by Ultrafast Cooling in Laser-mater Interactions

Autori
Lugomer, Stjepan ; Radić, Nikola ; Peto, Gabor ; Toth, Attila ; Horvath, Eniko'

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of Abstracts / AAA - Stockholm, 2005, 63-63

Skup
ICTF 13/ACSIN 8 ; "13th International Congress on Thin Films & 8th International Conference on Atomically Controlled Surfaces, Interfaces , and Nanostructures

Mjesto i datum
Stockholm, Švedska, 19.06.2005. - 23.06.2005

Vrsta sudjelovanja
Poster

Vrsta recenzije
Domaća recenzija

Ključne riječi
Laser ablation; Ultrafast condenstaiomn; Nanovclusters; Diffusion limited aggregation; Cascade aggregation

Sažetak
Growth of thin films, formation of nanoscale systems by pulsed laser interaction, critically depends on the characteristics of nanocluster formation, and therefore on the material and laser properties. The study of nanocluster growth has been performed under special conditions of very high pressure, of a high vapor density, and ultrafast cooling and condensation. Comparative study of nanocluster formation of various metals and alloys formed by vapour redeposition and cooling at the rate ~ 109 &#8211; 1010 K/s, has been studied in the semiconfined configuration of laser-matter interaction (LMI). Redeposition of material on the surface occurs from the monoatomic vapour and of very small particles, that are reflected from the transparent cover plate. Various types of growth mechanisms have been identified on materials like Ni and Fe (film on glass substrate), on the plates of Mo, Ta, and In, as well as on the plate of Wood's alloy, after irradiation by Nd:YAG laser at E ~ 0.5J, 0.8J, 1.2J and 1.5J, at the pulse duration of 40ns. It has been found that the shape, size and the nanocluster distribution strongly depend on the type of metal, but also on the laser energy. The clusters of Ni appear as irregular particles of ~10 nm in size ; at E ~ 0.5J, the cluster size distribution has a wide shoulder at ~ 40 nm. Latter on, a strong peak appears at ~ 30 nm indicating the transition of the slow agregation of 4 clusters, into the fast one of 3 clusters. Finally, some clusters start to grow faster than others and reach ~ 1000 &#8211; 1500 nm in size as the 3D lace type fractals. The clusters of Mo appear as spheroidal particles of ~ 20 nm in size, and at E ~ 1.5J grow preserving the spheroidal shape. A strong peak at 40 nm appears on the distribution curve indicating fast growth by aggregation of two smaller clusters. The clusters of Fe grow in different ways depending on the laser energy. At E ~ 0.5J, they appear as small cotton-like lace fractals. At E ~ 0.8J they grow as quasispherical clusters with a wide maximum of the size distribution at ~ 45nm. Latter on, two additional peaks appear at ~ 90nm and 180nm corresponding to the aggregation of 2, and 4 clusters, respectivelly, into globular cluster. Large globular clusters start to organize into a cell of the hcp symmetry. Clusters formed at E ~ 1.2J appear as spheroidal particles with a wide shoulder in the size distribution between 80 and 100 nm. Therefore, clusters generated at E < 0.8J grow as small lace fractals from the very beginning, while for E > 0.8J, nanoclusters become rounded during their growth, and resemble the globular aggregates. Nanoparticles of BiCdPbSn generated by recondenstion and supercooling of the molten layer of the Wood's alloy randomly grow as threefold icosahedral quasicrystals of ~50 nm in size. Aggregation of quasicrystals results in the formation of a large icosahedral quasicrystal of ~ 500 nm in size, with 3D Penrose lattice ; The icosahedral quasicrystal changes into smoothered spheroide with time. Its round shape is caused by the &laquo ; ; radial raining&raquo ; ; of vapour particles, and nonpreferential growth during vapour condensation Thus, with time, the icosahedral quasicrystal is transformed into spheroidal supercluster.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA