Cathodic needle growth from Mo(CO)6 vapors at higher electric fields

It is shown that metallic needle crystals grow on electron emitting areas of field emission cathodes working in Mo(CO)₆ vapor. The growth is driven by ions impinging from a field emission arc plasma, and the products are classified into two categories depending on the thermal energy supplied externally to the substrate: 1) Mo particles are agglomerated in dendritic shapes at 300-1300 K, and 2) whisker-like crystals with an unknown structure are obtained at 1300-1500 K. The high-temperature needles are capped with Taylor cones during the growth, and it is shown that they are a metastable phase of Mo.