1.    How do I determine which angle to use?

  • In general, a single angle measurement is sufficient for a majority of applications.  If your samples are ultra thin, the angle you choose to measure at should be close to the Brewster angle of the substrate in order to obtain the greatest sensitivity.  In general, however, an angle of incidence of 70° (close to the Brewster angle of Silicon) is sufficient for most other applications, regardless of the Brewster angle of the substrate.    

2.    When do I need multiple angles of incidence?

  • Generally, taking measurements at one angle of incidence is sufficient for most applications.  If the sample is complex (multilayered, graded, non-uniform, or very thick), however, it is advised to take data at 2 or 3 different angles of incidence so as to maximize the amount of data in order to reduce parameter correlations and to help determine unknowns such as thicknesses, optical properties, grading, non-uniformity, etc.

3.    Can ellipsometry measure samples placed in liquid or solid/liquid interfaces?

  • Yes, ellipsometry can be used to measure both samples placed in liquid or a solid/liquid interface.  We offer several liquid measurement accessories which help with this type of measurement.  For more information, please visit our Accessories page.

4.    How can I deal with back reflections?

  • Back reflections can be treated either mechanically before the measurement, or mathematically after the measurement.  To mechanically remove or block back reflections, you can try steps such as roughening the back side of the sample, using a mask to block the back side reflected beam, or switching to a smaller beam size so as to better separate the front and back reflected beams, hence only collecting the front reflected beam.  If you are not able to mechanically remove or block the back reflections, they may be included in the measurement, but they then need to be taken into account when modeling the sample after measurement.  The HORIBA DeltaPsi 2 software allows for the easy incorporation of back reflections for simple modeling.  For more information on the DeltaPsi 2 software, please visit our Software page.

5.    Can I measure transmission/reflection with an ellipsometer?

  • Yes, if you have a manual or automatic goniometer which is able to reach 90°, you can use the ellipsometer to measure both transmission at normal incidence, as well as reflectance at an oblique angle.  If you have a fixed angle system, you will be able to perform reflectance measurements at that angle, but would be required to use the transmission accessory for obtaining transmission measurements.  If you are interested in measuring reflectance at near normal incidence, we also offer a Reflectometry Module accessory which will allow you to do so.  For more information on the transmission and reflectometry accessories, please visit our Accessories page.

6.    Can I perform reflectometry without buying the reflectometer accessory (RM)?

  • Yes, you may collect reflectance data at an angle (usually between 45 and 75 degrees), but not at near normal incidence.  With the Reflectometry Module, however, you will be able to measure near-normal incidence reflectance For more information, please visit our Accessories page.

7.    Can I perform mapping on a sample?

  • Yes.  In order to perform mapping, you will need an automatic XY translation stage.  The DeltaPsi 2 software can provide both 2-D and 3-D maps of the resulting thicknesses and optical properties.  For more information on the Delta Psi 2 software, please visit our Software page.

8.    What accessories are available for the ellipsometer and what are they useful for?

  • We offer many accessories which allow for various types of measurements.  Some examples include, a temperature controlled stage which allows for the study of changes in optical properties with temperature, a theta or rotation stage which allows for the easy measurement of anisotropic samples, a sealed cell which allows measurements to be taken under a non-air ambient, an electrochemical cell which allows for the study of electrochemical processes, a liquid cell for measurements in liquid or liquid/solid interfaces, a reflectometry module for measuring near-normal reflectance, a transmission accessory which allows for the measurement of transmission on a fixed angle system, an XY stage which allows for mapping of samples, and a cryostat for measuring samples at low temperatures.  For more information or to view these accessories, please visit the Accessories page.  You can also view several Application Notes which utilize some of these different accessories.
Ellipsometry for Organic Webinar