Mangesh S. Diware

Temperature dependence of the dielectric functions and the critical points of InSb by spectroscopic ellipsometry from 31 to 675 K

We report the complex dielectric function of InSb for temperatures from 31 to 675 K and energies from 0.74 to 6.42 eV. The spectra were obtained by rotating-compensator spectroscopic ellipsometry on bulk InSb. The critical point (CP) energies were determined using numerically calculated second energy derivatives of the data. At low temperature, the CP structures are blue-shifted and significantly sharpened relative to those seen at high temperature. The temperature dependence of the E1, E1+Δ1, E0′, Δ5cu-Δ5vu (0.35, 0, 0), E0′+Δ0′, Δ5cl-Δ5vu (0.35, 0, 0), E2, E2′, E2+Δ2, E2′+Δ2, E1′, E1′+Δ1′, and E1′+Δ1′+Δ1 CPs was determined by fitting to a phenomenological expression that contains the Bose-Einstein statistical factor or to a linear equation. In particular, temperature dependences of CPs below 100 K and those of the E0′, E0′+Δ0′, E2′, E2+Δ2, E2′+Δ2, E1′+Δ1′, and E1′+Δ1′+Δ1 transitions have not previously been reported.

Parameterization of the dielectric function of InP from 1.19 to 6.57 eV for temperatures from 25 to 700 K

We present an analytic expression that accurately represents the dielectric function ɛ = ɛ1 + iɛ2 of InP from 1.19 to 6.57 eV for temperatures from 25 to 700 K. The original data were obtained on a InP substrate by spectroscopic ellipsometry. The analytic representation is based on the parametric model, which is known to accurately portray ɛ without unphysical assumptions. The ɛ data are successfully reconstructed by eight Gaussian-broadened polynomials and a pole and can be used to determine ɛ as a continuous function of energy and temperature within the limits given above. Our results should be useful in a number of contexts, including device design and in situ monitoring of deposition. A representative deposition example is discussed.

Label-free detection of hepatitis B virus using solution immersed silicon sensors

Highly sensitive solution immersed silicon (SIS) biosensors were developed for detection of hepatitis B virus (HBV) infection in the early stage. The ultrasensitivity for overlayer thickness at the nonreflecting condition for the p-polarized wave is the basis of SIS sensing technology. The change in thickness due to biomolecular interactions and change in refractive index of the surrounding buffer medium were assessed simultaneously using two separate ellipsometric parameters (Ψ and Δ), respectively, from a single sensing spot. A direct antigen-antibody affinity assay was used to detect and quantify hepatitis B surface antigen (HBsAg), which is the early stage biomarker for HBV infection. The detection limit of 10 pg/ml was achieved for HBsAg in the human blood serum, which is comparable with the results of enzyme-linked immunosorbent assay and other hybrid assays. The SIS sensors response time was less than 10 min. The SIS sensors exhibit excellent stability and high signal-to-noise ratio, and are cost-effective, which makes them a suitable candidate for point-of-care applications.

Stability of UV exposed RR-P3BT films by spectroscopic ellipsometry

Stability of regioregular poly(3-butylthiophene) (RR-P3BT) films under irradiation of ultra-violet (UV) light has been studied by spectroscopic ellipsometry at room temperature. Consistent decrease in dielectric function with UV exposure time showed the degree of degradation of polymer. This work suggests that, protective methods are mandatory to use this kind of material in optical devices.

In-situ study of molecular dynamics in a water environment by using imaging ellipsometry

We report on the dynamics of bio molecules and a high polymer in a water environment by using imaging ellipsometry (IE). The morphology of collapsed films of arachidic acid (AA) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) Langmuir monolayers in a liquid solution is investigated. The IE images clearly show that the multilayer domains and thickness of the collapsed region change sensitively depending on Langmuir compression. Also, the adsorption of bovine serum albumin is observed by using total internal reflection resonance IE (TIRIE), which has the advantage of IE and surface plasmon resonance. We believe that IE is a powerful technique for analysis and applications of bio materials.