Performance
Measurements taken on SiO₂ films whose thickness was established with a commercial spectroscopic ellipsometer. Every value is measured data.
Against a commercial instrument
| Sample | Commercial | Initial | Mean | STD |
|---|---|---|---|---|
| 1472.3 nm SiO₂ | 1472.3 | 1472.4 | 1471.8 | 0.4 |
| 496 nm SiO₂ | 496.0 | 496.7 | 496.5 | 0.2 |
Values in nm
Long-term stability
Twenty minutes of continuous measurement using offset fitting alone, with no compensation channel. The mean is 1472.66 nm with a standard deviation of 0.27 nm, matching the commercial reading of 1472.3 nm.
- Mean
- 1472.66nm
- STD
- 0.27nm
Acquisition conditions
- Integration time
- 23ms
- Averaging
- 20×
- Wavelength range
- 493.81 – 679.63 nm
- Δ measurement interval
- 3s
Real-time measurement and fitting
Thickness and angle of incidence are fitted together during measurement. The angle is estimated as well because sample mounting and optical alignment can shift the actual angle of incidence slightly.
Running on an edge device
Measurement and monitoring have been confirmed on a Linux edge device as well as a Windows laptop, showing that the system can be developed into an embedded configuration.
About these conditions
The data above was taken on SiO₂ over Si, across 493.8 – 679.6 nm at a fixed 45° angle of incidence. The 400 – 500 nm region is not used because the extinction ratio of the polarizers is low there, which makes accurate Δ difficult to obtain. Validation on other materials and thickness ranges is ongoing.