Overview
Accessories
General
Several accessories are required for metallic ions depositing on substrates during vacuum evaporation process. The accessories are evaporation sources. Aluminum, chromium or nickel is thermally evaporated with some evaporation sources such as filaments, baskets, boats, crucibles, boxes or alumina coated source. Selected sources provide adequate electrical current discharge to melt the metals which then gains enough energy to become ions bombarding on substrates. Proper evaporation sources are selected depend on few factors.
- available transformers powers
- mass of metal to be evaporated
- distances between sources and substrates
- evaporant materials
Filament
It is a coil or rod design available in different lengths, wire and filament diameters. It could be single strand or multiple strands. Filaments are usually made of tungsten, molybdenum and tantalum. Tungsten filaments generally work very well for most evaporation.
Boat
It is a plate like design made of tungsten, molybdenum or tantalum. Capacities are usually few cc. Boat sources could be used for both low and high temperature evaporation materials.
Crucible
Crucible sometimes offers unique advantages to other types of sources. This container like evaporation sources is usually design with larger capacity. Evaporants are easily loaded. Direction of vapor patterns could be controlled and focused. Quartz, alumina, boron nitride, carbon, molybdenum and tantalum are usually major materials of crucibles
Box
Open and close box sources are available in tungsten, molybdenum or tantalum with various thicknesses. Defects such as pinholes could be found with general evaporation sources when materials are silicon monoxide and zinc sulphide. The boxes evaporation sources are shielded and baffled. The shielding eliminates impurities formed in vapor stream.
Alumina Coating
Alumina coated sources have good thermal transfer. Alumina is also inert to most metals. When evaporants melt, evaporants do not wet the alumina which eliminates resistance changes in the boats. Evaporants thus, form spheres when melted resulting in "point source" performance. Alumina coated sources are also more durable than non-coated evaporation sources.
