High Resolution Replication of Metallic Microcrystals

Bradley's well known direct carbon replication technique with Pt-C shadowing offers the best resolution of any method currently in use. In the present study variations of this technique were applied to a system of gold microcrystals in an effort to obtain replicas of the highest possible resolution. Crystals with diameter on the order of 1000Å and thickness ∼100 Å have been examined for surface defects which might effect the growth process. This requires replication with higher resolution than is normally obtained.The basic technique consists of evaporating a suspension of the particles onto a clean glass slide, depositing 100-200 angstroms of carbon by vacuum evaporation, floating the carbon film on a solvent to remove the particles, and mounting the replica on support grids for shadowing. The factors limiting the resolution of the replica are:The accuracy in the reproduction of the surface topography by the carbon film.“Pile-up” effects due to the physical thickness of the carbon and Pt-C in the shadowing direction.Contamination of the specimen and replica surfaces by a layer of hydrocarbons.Granularity of the shadowing material.

Electron Microscopic Techniques for Fluorescent Lamp Phosphor Studies by Single Stage Replication

Electron Microscopy has long been utilized in the lamp industry for the study of tungsten and other lamp components. Little information has been published regarding the use of electron microscopy in the study of phosphors, a main component in fluorescent lamps. This study concerns calcium halophosphate phosphors, a primary component of fluorescent lamps.A modified single stage replica method similar to that of Munch has been adapted for use in the study of phosphors. The samples to be replicated were prepared by depositing the phosphor powder on a clean glass slide. Deposition was accomplished by a dry spray technique using low pressure Freon. A commercially available spray mounter can be utilized for this purpose. The critical parameter in the operation is pressure control, which when properly regulated promotes an even distribution of particles, and appears to facilitate subsequent removal of the evaporated film from the glass slide.