Infrared spectroscopic ellipsometry study of vinylidene fluoride (70%)-trifluoroethylene (30%) copolymer Langmuir-Blodgett films

We report the studies of the molecular conformation and chain orientations through characterization of the vibrational modes in crystalline Langmuir–Blodgett films of the polyvinylidene fluoride/trifluoroethylene copolymer. The infrared spectra obtained by polarized reflectometry and ellipsometry showed that the ferroelectric phase has predominantly all-trans conformation and the paraelectric phase has predominantly alternating trans-gauche conformation, as in solvent-formed films of the same copolymer. The results showed that the polymer chains are predominantly parallel to the film plane with a random in-plane orientation and most of the ferroelectric phase vibrational mode behaviors are consistent with the published mode assignments. The ferroelectric phase optical dispersion curves in the infrared range were extracted from the data analysis based on a uniaxial model

Conduction-band electron effective mass in Zn\u3csub\u3e0.87\u3c/sub\u3eMn\u3csub\u3e0.13\u3c/sub\u3eSe measured by terahertz and far-infrared magnetooptic ellipsometry

We determine the electron effective mass parameter m*=0.086±0.004 m0 of thin-film n-type low-chlorine-doped Zn0.87Mn0.13Se with free-charge-carrier concentration N=4.5x1017 cm-3 and optical mobility ) =300±20 cm2 / (V s) using magneto-optic generalized ellipsometry in the terahertz and far-infrared spectral domain for wave numbers from ω =30–650 cm-1. The room-temperature measurements were carried out with magnetic fields up to 3 T. We employ synchrotron and black-body radiation sources for the terahertz and far-infrared spectral regions, respectively. Comparison with previous experimental results from samples with considerably higher free electron density and theoretical calculations suggest that our value is sufficiently unaffected by band nonparabolicity and provides a good approximation of the Γ -point conduction band mass in Zn0.87Mn0.13Se. We further provide optical phonon mode parameters and the high-frequency dielectric constant

Anisotropic contrast optical microscope

An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm2 object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves sensitivity to a total mass required for detection by 4 orders of magnitude. We detail the design and operation principles of the anisotropic contrast optical microscope, and we present further applications to the detection of nanoparticles, to novel approaches for imaging chromatography and to new contrast modalities for observations on living cells