Plasmaterials, Inc. offers a broad array of materials for thermal evaporation of vacuum deposited thin films. These materials include elemental, alloy, composite, metallic, ceramic, cermet, refractory as well as “special” materials in a variety of purity levels. These materials are typically available in bulk forms ranging from pellets to graduals to cubes. All materials are meticulously produced via Powder Metallurgy (PM) or Vacuum Melting (VM) techniques. Like all Plasmaterials, Inc. materials, these products come with a certificate of analysis indicating the chemical and trace element analysis of the starting material used to produce the finished product.
Plasmaterials, Inc. offers thermal evaporation materials suitable for both resistance evaporation and electron beam deposition. Smaller geometries are generally available for resistance boats and low volume e-beam crucibles. Additionally, most materials are available in either larger pellet or bulk form as well as electron beam starter sources. When materials are heated in a vacuum, the thermal energy activates the atomic structure increasing the internal energy of the material. Once sufficient energy is high enough to break nearest neighbor atomic bonds, individual atoms or molecules are freed from the matrix host material. These particles develop a vapor stream of material that can be collected and condensed onto a suitably placed substrate thus producing a resultant film. A characteristic vapor pressure curve indicates the vapor pressure of a given material at a given temperature at a given pressure. Armed with this information, it is possible to design experimental and production runs for thin film deposition.
Electron Beam
Electron beam processing effectively and efficiently creates useful changes in material properties and performance, such as polymer crosslinking and chain scissioning.
This technology is not entirely new. Pioneering work in electron beam processing began in the 1930s. E-beam sterilization was commercialized in the 1950s; around the same time e-beam crosslinking was first used for processing wire insulation jacketing.
Since then, electron beam processing has expanded to include heat-shrinkable plastics, thermoset composite curing, semiconductor enhancement, food processing and others, while offering decided economic and environmental advantages.
Starter Sources
Plasmaterials, Inc. offers electron beam starter sources for utilization in Thin Film Deposition in both production and research applications. These pre-forms are manufactured to geometrically fit directly into the conically shaped e-beam hearths of all commercially available sources. These solid bulk sources save time and money by allowing the operator the freedom to directly deposit from a solid source without having to “pre-melt” pellets or granules into a solid geometry prior to deposition. As the pre-forms erode during subsequent deposition and use, additional material or “Make-Up Material” can be added or filled into the erosion cavity and easily liquefied and formed back into the solid.
To properly condition a new charge of material placed in an electron beam hearth, it is generally necessary to carefully control the rise and soak times of the power supply while suitable controlling the beam positioning by rastoring the beam source to gradually heat all pieces of material located within the hearth. In doing so, heat must be transferred via conduction from those individual pieces located on top of the charge to those pieces located beneath them or below the surface. For most materials, this heat transfer is time consuming and inefficient, creating large thermal gradients within the charge. This either leads to non-uniform deposition and resultant films or to the characteristic “splatter” of material onto the substrate. This “splatter” typically results in large amounts of material condensing on the substrate from the vapor stream in a concentrated area. When these globules of material contract while condensing on the substrate, they form non-uniform thickness variations and often cause pin-holes.
Electron beam starter sources alleviate the problem of non-uniform heating, splattering, thickness fluctuations and pin-hole formation by allowing heat to dissipate throughout the source in a controlled uniform manner. With proper heat rise and soak cycles, the uniform deposition of resultant films can typically be performed from the initial run of the source to the last utilization of the material. This helps resolve the usual run-to-run variations and fluctuations within a single process cycle.
Please contact us for further information on electron beam starter sources and other related products.
Crucible Liners
Electron beam deposition sources are equipped with hot element filaments for electron emission, electro magnets for shaping and positioning the stream of electrons and suitable designed water cooled copper hearths to contain the source material to be deposited. Many materials can destructively react with these copper hearths at the temperatures typically encountered during vacuum deposition. In most cases, the material to be deposited is elevated in temperature to some level above the liquidus, making the copper hearth all that much more vulnerable to interaction with the molten material. Even for those materials that sublimate, the likelihood of some chemical interaction with the copper hearth is great. Additionally, by design, the water cooled hearth dissipates heat from the material being deposited at a rapid rate. This necessitates the use of more power and creates differential thermal gradients throughout the material being deposited.
To prevent thermally created interaction with the copper hearth and insure uniform distribution of heat within the source material, it is often beneficial to utilize a hearth liner during electron beam deposition. These liners can be fabricated in all shapes and sizes to fit all commercially available electron beam sources. The composition of the liner is carefully matched to the material being deposited to minimize thermally created chemical interaction and maximize the thermal stability of the evaporation process. Visit our Materials Listing for a list of electron beam hearth liner material compositions, or contact us for further assistance.
For more information on which crucible liner to use, please refer to the Thin Film Evaporation Material Source Reference.
