Uniform size Y-Ba-Cu-O particles obtained by laser ablation and post-annealing

Thermally induced motion and clustering of single particles obtained by pulsed laser deposition (PLD) from an YBa₂Cu₃O_6+x target having nanosize grains is investigated. As shown by atomic force microscopy the as-deposited particles on SrTiO₃ substrates have average height of 1-3 unit cells and width of 40 nm. When the substrate is post-annealed after deposition in oxygen at a temperature T_a<400°C no changes in the distribution and sizes of the particles are observed. For T_a>400°C the particles start to grow in height and simultaneously their surface density on the substrate decreases. Only when most of the particles have reached the height of 10 nm their width begins to grow, increasing continuously as T _a is risen up to 900°C. The way of coalescence of the particles upon increasing T_a is compared with island growth models of thin films prepared by PLD. It is suggested that these particles could be used for manufacture of nanostructures fusing them together by thermal annealing