In the last few years there has been a growing interest in nanoparticles and nanophase materials. Nanoparticles are considered to be a new state of the condensed matter due to the high relation of atoms in the surface respect to the number of atoms in the volume, and their properties are neither those of atoms nor those of bulk materials.

There are many interesting questions still to be answered and processes to be understood, from nucleation and growth processes to properties

In the present work we report the results of the fabrication of Mo, MoW and MoNi, particles by d.c. sputtering, under different pressures, from 0.2 torr to 0.8 torr. Their morphology, size distribution, aggregation and structure has been studied by Transmission Electron Microscopy.

We analyzed our results contrasting them with those of Chow 1,2 and Birringer 3 and try to explain with a new perspective the formation mechanism of the particles, and the dependence of particle size with Ar pressure.