Characteristics of ultrafine tungsten particles produced by Nd:YAG laser irradiation

Ultrafine particles of tungsten were synthesized by the synchronized irradiation of a substrate in low He gas pressure with two pulsed Nd:YAG lasers. The primary particles have diameters of several nm as measured by transmission electron microscopy (TEM). An agglomeration of the primary particles was generated under high pressure and high laser power conditions. An electron diffraction analysis of the particles indicates that there exist two types of material structure: crystalline and amorphous-like. The size distribution was measured by a low-pressure differential mobility analyzer (LP-DMA). The peak of the size distribution was shifted from several nm to the tens of nm level with increasing pressure.