Vacuum Metal Deposition for Development of fingerprints: Influence of Quantities of Gold on Size and Density of Clusters

Vacuum metal deposition (VMD) is well recognised as a very effective method of developing latent fingerprints on non-porous surfaces. The technique consists of the evaporation and deposition, under high vacuum, of gold and then zinc. A previously identified difficulty with the development of latent fingerprints on low-density polyethylene (LDPE) by vacuum metal deposition (VMD) is that excess gold deposition prevents effective zinc deposition and so inhibits latent print development. The size of the gold clusters formed on the surface of the polymer plays a critical role. The aim of this study was to visualise gold clusters by transmission electron microscopy (TEM) and study the density and growth of gold clusters on a polymer surface with an increasing amount of evaporating gold. As a result, initially, new incoming gold forms new clusters, so cluster density increases significantly. As the clusters reach a certain size, no new clusters are formed, but existing clusters continue to increase in size.