Ocean Optics ElliCalc - Manual (Page 56)

Ocean Optics Germany GmbH Thin Film Metrology
55
11.3 Interference
The arrangement in the picture below shows the case of an oblique incidence.
The measurement of ellipsometry of thin films is a good example of an interference problem:
The incoming wave splits up in a reflected and a transmitted wave at each external or internal surface. The
amplitudes of these partial waves depend on:
1.angle of incidence (if this angle is >0, then polarization plays
an important role)
2.refraction index and absorption index of all layers
Now the superposition of ALL waves (with different phase relations, amplitudes) has to be done. If the
layers are thin and flat you have to add amplitudes and not intensities (see your physics text book). So
you may end up with „destructive and constructive interference“: a positive amplitude and a negative
amplitude may add up to zero. This is why your measured intensities usually have maxima and minima.
reflected intensity
70°
layer
substrate
transmitted (and
absorbed) intensity
70°