Material decision
PSL and silica are not interchangeable optical references
| Attribute | PSL spheres | Silica particles |
|---|---|---|
| Composition | Polymer | Silicon dioxide |
| Density | Current AP PSL pages describe approximately 1.05 g/cm³ | Higher and product-specific |
| Refractive index | Current AP PSL pages describe approximately 1.59 at 589 nm | Different and wavelength dependent |
| Suspension behavior | Low-density aqueous suspension with surfactant-dependent stability | Different settling and surface chemistry |
| Common roles | Particle-counter calibration, count controls, aerosol, wafer deposition | Semiconductor, optical, surface and material-specific applications |
When PSL is favored
Repeatable spherical polymer references
- The method or instrument is calibrated to PSL-equivalent response.
- A narrow, documented spherical population is required.
- The available PSL family covers the required size node.
- The aqueous suspension and certificate fit the procedure.
- Existing historical data is based on PSL.
When silica may be favored
Material and application fit
- The process or inspection response is better represented by silica.
- Semiconductor contamination or UV/DUV response makes material properties important.
- Higher density or different surface chemistry is required.
- The method calls for silica or a closer optical surrogate.
- A dry or specialized silica format is needed.
Decision rule
Choose the reference that supports the interpretation
Do not choose by diameter alone. The instrument may assign different equivalent sizes to PSL and silica of the same geometric diameter because optical and material properties differ.
The future Silica-Nanoparticles.com authority property will own the deeper silica-specific content. Until that site is built, current silica products and specifications remain on AppliedPhysicsUSA.com.
Applied Physics technical pathway
Match the standard to the measurement—not the other way around.
Send the instrument, medium, target size, concentration, certificate and packaging requirements to Applied Physics for a technical recommendation.