Accessories For the Ellipsometer

 

Light Sources


There are three light sources available for this instrument:

A 2 mW Helium-Neon Laser. This provides radiation at 632.8nm and should be used when the highest sensitivity is required, as this is the quietest of the 3 light sources. The size of the illumination spot is controlled by the lens system that is used the unfocused beam is around 2mm in diameter at the sample.
A 35W Quartz Halogen Lamp that allows spectroscopic measurements between 400nm and 800nm to be completed is available. The upper wavelength is limited by the Photomultiplier. The peak intensity is at around 700nm. The size of the illumination spot is controlled by the filament and lens system used but is generally around 3mm in diameter.
A 75W Hamamatsu Super Quiet Xenon Lamp is also available. This allows the wavelength range to be extended down to 200nm. The upper wavelength is again limited by the Photomultiplier to about 800nm. The intensity is almost constant above 400nm and only falls to about half that value at 300nm. The size of the illumination spot is controlled by the lens system used but is generally around 1mm in diameter.

Monochromator

With both of white light sources described above the CVI CM110 Compact 1/8 Meter Monochromator f/# 3.3 is required to make spectroscopic measurements, it provides an absolute wavelength accuracy of +/-0.2nm. Several slit sets can be used to find the optimum compromise between spectral resolution (best=0.2nm) and throughput. Above 600nm a high wavelength pass filter must be used to remove the contributions of second order diffraction from the measurement. The glass filter and holder are shown below, during a measurement the filter can be placed into its holder as the monochromator steps the wavelength.


Liquid Cell

This cylindrical cell is designed so that the top surface of the sample is mounted on a diameter and hence both the incident and reflected beams pass through the annealed glass at normal incidence, independent of the angle of incidence at the sample. This design removes the need for a data correction to be applied as the s and p components in both the incident and reflected beams are attenuated by the same amount. The cell is designed to take samples up to 6cm x 3cm x 5mm. Six ports are available for the liquid to be introduced and electrical connections to be made if electrochemical processes are to be studied. If temperature dependant measurements are to be made, water can be circulated though pipes in the liquid using a temperature controlled water bath. Combined ellipsometry and electrochemistry is also available with this fluid cell and the SAFs potentiostat.