Choosing an evaporation material involves two separate decisions: which chemical composition the coating requires, and which physical form the source can use. A specification that says only “high-purity copper” leaves the second decision unresolved.
Pellets, granules, irregular pieces, and wire are useful purchasing categories, but none is a universal quality ranking. The practical choice starts with the evaporation source, its loading geometry, and the condition of the material supplied. This guide connects those purchasing questions to manufacturing and illustrates the differences with aluminum, gold, and copper.
Start with the source, not the shape
A useful RFQ identifies whether the material will be used in a resistively heated source or an electron-beam source, together with the boat, filament, crucible, or liner involved. These are equipment constraints rather than interchangeable names for the feedstock.
For example, Lesker documents aluminum wire forms used with tungsten filaments, as well as pellet-based aluminum evaporation approaches. That is a material-and-source-specific example—not a rule that wire always means thermal evaporation and pellets always mean electron-beam evaporation. [1]
Before comparing prices, establish the source opening, usable cavity dimensions, charge arrangement, and the equipment supplier's loading requirements. A product that fits a quotation category may still be the wrong geometry for a particular source.
Compare the forms by the information they require
| Feedstock form | Useful feature to evaluate | What to specify |
|---|---|---|
| Pellets | Defined individual geometry can make loading easier to reproduce | Diameter, length, allowable size variation, and quantity |
| Granules or shot | A size distribution rather than one nominal piece dimension | Size interval, oversize limit, fines requirement, and supplied mass |
| Irregular pieces | Fit depends on the largest dimensions and shape of each piece | Maximum piece dimensions and any restrictions on sharp or elongated pieces |
| Wire | The source may require a particular diameter or loading shape | Diameter, diameter tolerance, cut length or spool format, and surface condition |
These are selection questions, not claims that one form provides a higher deposition rate or cleaner film than another. A well-defined specification is more useful than an unsupported label such as “premium pellets.”
What the manufacturing description should tell you
The word pellet describes a supplied shape, not a unique production process. Do not infer from that word alone whether the material was cut from stock, formed from a melt, or consolidated from powder. Similarly, a granule size range does not identify how the granules were made.
When manufacturing history matters to the experiment, ask how the final geometry was produced and what cleaning or finishing followed it. For cut material, useful questions concern cut faces, burrs, and surface residues. For a powder-consolidated product, ask whether density or residual processing aids are relevant. A binder concern applies only where a binder was actually used; it is not a characteristic of every pellet.
These questions turn manufacturing information into inspectable purchase requirements. “Provide the agreed piece-size interval and describe the supplied surface condition” is more actionable than “use the best production technology.”
Example 1: Aluminum—source compatibility matters more than a convenient shape
Aluminum illustrates why a high melting point does not, by itself, establish that a boat or liner is compatible. Lesker's aluminum guidance describes alloying with tungsten, molybdenum, and tantalum and associated source damage. [1]
For the buyer, the consequence is straightforward: do not order aluminum wire or pellets independently of the source arrangement. State the intended source and ask for a compatible feedstock geometry. Changing from a pellet to a piece does not automatically resolve a chemical interaction at the source interface.
This is also why a materials article should not prescribe one universal current, beam power, crucible fill percentage, or replacement interval. Those settings belong to the validated material-and-equipment process.
Example 2: Gold—high purity is not a complete explanation of spitting
A researcher observing droplets during gold evaporation may first suspect the charge material. Feedstock condition should be checked, but the investigation should not stop there. Lesker's gold guidance identifies heating behavior, power delivery, cleanliness, and liner-related heat transfer among relevant considerations. [2]
For a repeatable comparison, record the charge form, supplied lot, loading arrangement, source condition, and operating sequence. If all of these change together, a better coating result cannot confidently be attributed to pellet geometry alone.
The purchasing lesson is to specify consistent material and loading inputs, then evaluate them within a controlled deposition process. Neither “5N” nor “pellet” is a guarantee of droplet-free operation.
Example 3: Copper—film mass is not the source charge
Consider a calculation for a uniform copper film over 100 cm², with a thickness of 100 nm, using a reference density of 8.96 g/cm³. The density is a bulk-material reference, not a measured density of the deposited film. [3]
The calculation is:
Film mass = density × coated area × film thickness
Since 100 nm = 0.00001 cm:
8.96 × 100 × 0.00001 = 0.00896 g = 8.96 mg
This is an illustrative mass calculation, not a recommendation to load 8.96 mg into an evaporation source. It contains no allowance for material deposited elsewhere, conditioning losses, or material remaining in the source. Actual film density and thickness uniformity also affect the estimate.
The Thin Film Material Calculator is useful for this planning step. Keep its film-mass result separate from the source-charge specification and purchasing quantity. [4]
A geometry example: maximum size can matter more than average size
Suppose a source has a restricted loading opening. Two hypothetical lots have the same material, purity, total mass, and average piece size. One lot also contains a few elongated pieces that cannot pass through the opening.
The average size does not resolve that problem. The relevant RFQ detail is a maximum acceptable piece dimension or an explicitly bounded size interval. This is an illustrative geometric example, not a measured comparison of Basis products.
Likewise, equal loose-fill heights should not be treated as proof of equal charge mass. Weigh the charge or use an appropriate validated loading procedure rather than assuming that different shapes occupy a cavity identically.
Put cleanliness and documentation into the order specification
For a repeat purchase, define what must remain consistent: composition, purity basis, feedstock geometry, surface condition, packaging, and lot identification. Ask whether the documentation describes the finished material or an upstream raw-material sample.
Avoid adding requirements that cannot be inspected. If a particular surface residue or trace contaminant matters, name it and discuss an appropriate verification method. “Clean for our process” is less precise than an agreed surface preparation and packaging requirement.
Do not adopt an improvised cleaning, baking, or handling recipe from a generic blog. Use the material-specific SDS, equipment guidance, and the laboratory's validated procedures.
What to specify when requesting a quote
A useful starting request is:
Please quote the required metal in a form compatible with our evaporation source. We will provide the source or liner details, usable loading dimensions, purity requirement, piece-size or wire-diameter requirement, total quantity, and any documentation or surface-condition requirements.
Where those details are not yet fixed, send a drawing or photograph of the empty source and identify the equipment model. The discussion can then focus on the missing dimensions instead of guessing a standard pellet size.
Frequently asked questions
Are pellets always better than pieces?
No. Compare the specified geometry and supplied condition against the source requirements. The name of the form does not establish a universal performance advantage.
Can wire be used as a heating element?
An evaporation wire is a feedstock product, not automatically a qualified heater filament. A heating element needs its own material, electrical, mechanical, and operating specification.
Does the calculated film mass tell me how much material to buy?
Not by itself. Treat it as one input alongside the source charge, process losses, residual material, number of runs, and planned development work.
Specify the material and the source together
The most useful evaporation-material specification combines chemistry, geometry, supplied condition, and source compatibility. It does not need to prescribe every manufacturing step, but it should make the important final requirements clear.
Explore Basis Materials evaporation materials, including gold pellets, copper pellets, and aluminum wire. For a source-specific configuration, request a quote with your material, loading geometry, and quantity.
Final material and configuration requirements are confirmed during quotation.
Related guides
- High-Purity Metal Foil and Wire: How Rolling, Drawing, and Annealing Affect Performance
- Metal Purity Explained: 3N, 4N, 5N, and How to Read a Certificate of Analysis