Mechanism for Black Particle Formation on Gold Coatings Deposited by Electron Beam Evaporation:A Theoretical and Experimental Study

Herein, we theoretically addressed the mechanism for the black particle formation, irregular shaped impurity grains (100 nm~1 μm in size), on gold coatings deposited by electron beam evaporation.We proposed that the localized strong field emission from the impurity cusp (or Tayler-cone) possibly formed on liquid gold surfaces because of carbon surface segregation or residue gas contamination, may account for the tip-discharge, resulting in high temperature evaporation and/or deposition of impurity cusp-apex on the gold coatings.The influence of the deposition conditions, including the evaporation power, shape and bombarding spot position of e-beam, on black-particle deposition was investigated.The experimental results show that the formation/discharge/evaporation/deposition of the cusps formed on liquid gold surfaces are responsible for the black particle formed on gold coatings grown by e-beam evaporation.The experimental and analytical results were found to be in good agreement.