tailieunhanh - Nanotechnology and Nanoelectronics - Materials, Devices, Measurement Techniques Part 5

Tham khảo tài liệu 'nanotechnology and nanoelectronics - materials, devices, measurement techniques part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 70 4 Nanolayers Fig. Geometric and material definitions in the ellipsometer experiment Fig. Ellipsometer 71 split up into a parallel and a perpendicular fraction. The two fractions have a phase difference A 0. After reflection the new phase difference A of the two fractions transforms a linear oscillation into an elliptical oscillation of the form x2 y2 2x y cos A A2 B2 AB sin2 A . A and B are the amplitudes of the two oscillation directions in the previous coordinate system Fig. . It should be noted that the phase angle A between the components of the ellipse applies to the selected coordinate system only. By rotating the coordinate system the phase changes. In particular A n 2 holds if the large semiaxis and the new x axis coincide. Such a coordinate transformation takes place if the elliptically polarized beam is exposed to a quarter wave retarder. Its two polarization directions are put in the directions of the ellipse axis so that the fast beam corresponds to the lagging component of the ellipse angle of rotation of the quarter wave retarder from the x-direction . Since the two beams Characterization of Nanolayers 71 Fig. Oscillation ellipse after reflection catch up with each other again a linearly polarized beam develops which can be brought to extinction with an analyzer. The direction of the linearly polarized beam to the reference plane is . ri rather ri n 2 is measured with the analyzer is known as the direction of rotation of the quarter wave retarder. The criterion of the correct determination of ri and is the extinction of the beam behind the analyzer. Thus the axes ratio of the ellipse is given as tan J tan -5 . The knowledge of this angle enables us to determine the ratio of the oscillation components B A tan y in the reference plane system cos 2 cos 2J cos 25 . For the phase difference A in the reference plane system we find x . tan 2 J tan A z z . tan 25 What has been achieved so far Originally a .