AVS 45th International Symposium
    Thin Films Division Monday Sessions
       Session TF-MoM

Paper TF-MoM10
Application of High Speed Four-Parameter Stokes Vector Spectroscopy to the Characterization of Textured and Specular Transparent Conducting Oxide Thin Films

Monday, November 2, 1998, 11:20 am, Room 310

Session: Transparent Conductive Oxides
Presenter: P.I. Rovira, Pennsylvania State University
Authors: P.I. Rovira, Pennsylvania State University
R.W. Collins, Pennsylvania State University
Correspondent: Click to Email
A rotating-compensator multichannel ellipsometer has been used to measure the four unnormalized Stokes vector elements associated with the polarization state of polarized light reflected from both specular and textured transparent conducting SnO@sub 2@:F films. This technique provides not only the ellipsometry angles (@PSI@, @DELTA@), but also the reflectance R and the degree of polarization p. With a photodiode array detector, spectra in (@PSI@, @DELTA@), R, p) having 100 points from 1.5 to 3.75 eV can be collected with a minimum acquisition time of ~32 ms. In contrast to rotating-polarizer multichannel ellipsometry which tends to be inaccurate when @DELTA@ equals 0° or ±180°, or p<1, the rotating-compensator approach provides high accuracy measurements of the phase shift @DELTA@ over its full range (-180° to 180°) even when p<1. Therefore, this new configuration permits us to make accurate ellipsometric measurements for SnO@sub 2@:F films on glass substrates, which is the structure of choice for large area device applications such as photovoltaics. In addition to conventional microstructural characterization using the ellipsometry angles (@PSI@, @DELTA@), we have incorporated light scattering due to the textured surfaces into the analysis using the reflectance and degree of polarization. From the latter analysis, information on the SnO@sub 2@:F texture can be extracted. The results are consistent with direct images by scanning electron microscopy and atomic force microscopy. A comparison of the degree of polarization measured for the specular and textured SnO@sub 2@:F films suggests that deviations in p from unity for the latter are due to the detection of light multiply-scattered by the texture into the specular direction. Finally, the rotating-compensator multichannel ellipsometer developed here can be readily adapted to real time analysis of solar cells prepared on textured transparent conducting oxide films in commercial processes.