D. E. Aspnes

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  • D. E. Aspnes
  • Journal of the Optical Society of America. A…
  • 2004
I investigate the dependence of shot-noise-limited uncertainties of the ellipsometric parameters psi, and delta for the rotating-analyzer ellipsometer (RAE) and the rotating-compensator ellipsometer (RCE) of the polarizer-sample-compensator-analyzer type. The development is general and takes into account correlations among the Fourier coefficients of the(More)
The theoretical precision attainable from a number of types of ideal null and photometric ellipsometers is investigated quantitatively. Photometric and modulated null ellipsometer systems are shown to be approximately comparable with respect to precision when operating under shot-noise limited conditions. Differences are due principally to intrinsic(More)
The observation of surface-plasmon resonances in indium tin oxide (ITO) thin films is complemented with the effects of hybrid ITO/Au conducting layers where charge densities can be tuned. Where carrier densities are similar (ITO and nanoparticle Au), the plasmonic behavior is that of a monolithic ITO thin film. Where the carrier density of one layer is much(More)
We describe the design, construction, alignment, and calibration of a photometric ellipsometer of the rotating-analyzer type. Data are obtained by digital sampling of the transmitted flux with an analog-to-digital converter, followed by Fourier transforming of the accumulated data with a dedicated minicomputer. With an operating mechanical rotation(More)
We systematically measure the dielectric function of atomically thin MoS2 films with different layer numbers and demonstrate that excitonic effects play a dominant role in the dielectric function when the films are less than 5-7 layers thick. The dielectric function shows an anomalous dependence on the layer number. It decreases with the layer number(More)
We describe simple modifications to photometric polarimeter and ellipsometer systems that greatly reduce nonlinearity, component drift, and digital noise effects. A photomultiplier feedback circuit is described and analyzed that varies the effective system linearity by means of a single control. Linearity to 5 x 10(-4) over more than three orders of(More)
A procedure is outlined in which the symmetry of the ellipsometer is used to provide the information needed for its own alignment. Alignment is based upon four null measurements taken on a transparent reflecting surface. These are related to the tilt angles of the polarizer and analyzer telescope arms, and reference angles for which the transmitted(More)
Absolute constraints, namely, the Schwarz inequality and a complementary expression derived by us, are used to obtain corresponding absolute constraints on the Fourier coefficients of the intensity transmitted through rotating-compensator polarimeters and ellipsometers. These expressions allow the investigation of artifacts that result in mixed or(More)