Multi timescale infrared quantum cascade laser ellipsometry

We recently introduced a versatile infrared laser ellipsometer for sub decisecond spectroscopy and 0.03 mm2 spot sized hyperspectral imaging. Here we report on the next device generation for thin film sensitive simultaneous single shot amplitude and phase measurements. The multitimescale ellipsometer achieves 10 amp; 956;s time resolution and long term stability over hours at high spectral resolution 0.2 cm amp; 8722;1 . We investigate the temporal stages from minutes to milliseconds of fatty acid thin film formation upon solvent evaporation from acetone diluted microliter droplets. Optical thickness variations, structure modifications, and molecular interactions are probed during the liquid to solid phase transition. Multi timescale ellipsometry could greatly impact fields like in situ biosensing, microfluidics, and polymer analytics, but also operando applications in membrane research, catalysis, and studies of interface processes and surface reaction

Fast IR laser mapping ellipsometry for the study of functional organic thin films

Fast infrared mapping with sub millimeter lateral resolution as well as time resolved infrared studies of kinetic processes of functional organic thin films require a new generation of infrared ellipsometers. We present a novel laboratory based infrared IR laser mapping ellipsometer, in which a laser is coupled to a variableangle rotating analyzer ellipsometer. Compared to conventional Fourier transform infrared FT IR ellipsometers, the IR laser ellipsometer provides ten to hundredfold shorter measurement times down to 80 ms per measured spot, as well as about tenfold increased lateral resolution of 120 amp; 956;m, thus enabling mapping of small sample areas with thin film sensitivity. The ellipsometer, equipped with a HeNe laser emitting at about 2949 cm amp; 8722;1, was applied for the optical characterization of inhomogeneous poly 3 hexylthiophene [P3HT] and poly N isopropylacrylamide [PNIPAAm] organic thin films used for opto electronics and bioapplications. With the constant development of tunable IR laser sources, laser based infrared ellipsometry is a promising technique for fast in depth mapping characterization of thin films and blend

Optofluidic analysis of monolayers with infrared microscopy

This contribution reviews analytical possibilities of IR spectroscopic in situ studies of nl liquid volumes using an optofluidic cell with a plasmonic enhancement surface in a microscopic reflection geometry. Four application fields are presented 1 in situ IR microscopic analyses of the growth of self assembling monolayers, 2 chemical modification of a molecular interface, 3 functionalization of a graphene interface, and 4 streptavidin sensing by a biotinylated interface. Sub monolayer sensitivity enables the detailed monitoring and characterization of molecular adsorption isotherms, covalent binding to a molecular interface, and operando molecular recognition of proteins. For the latter the vibrational amide I and amide II fingerprint gives information on the protein secondary structure and possible structural changes as a response to the binding process. Complementary Raman vibrational spectroscopic studies could be performed with the same or related optofluidic cel

Mid infrared nanospectroscopy of Berreman mode and epsilon near zero local field confinement in thin films

Thin films with vanishing real part of the dielectric function Re[ amp; 949;] 0 in the mid infrared MIR region are promising photonic materials for manipulating and enhancing IR light matter interactions at the nanoscale. We present a nanospectroscopic characterization of two fundamental polaritonic phenomena near Re[ amp; 949;] 0 by atomic force microscope infrared spectroscopy AFM IR the Berreman mode BE in 100 nm SiO2 and Si3N4 films on Si, and epsilon near zero ENZ local field confinement in a 2 nm native SiO2 layer on Si. AFM IR is an emerging photothermal technique that provides direct information on nanoscale IR absorption, allowing unambiguous identification of BE and ENZ effects supported by simulations. We demonstrate far field applicability of polaritonic AFM IR studies by characterizing a nanoscale plasmonic ENZ grating on Si with 2 nm native SiO2 using polarization dependent IR microscop

Structure and chemical analysis in thin films by in situ IR ellipsometry

In 2007, infrared spectroscopic ellipsometry IRSE was introduced as a highly sensitive technique for in situ investigations of chemical and structural changes in thin polymer films. In this initial publication, the response of a mixed polyelectrolyte brush film in liquid environments was studied upon external pH stimuli. In the following decade, a variety of solid liquid interfaces such as various types of thin polymer and oligomer thin films including possible electrochemical preparations were investigated. Typically, these studies were motivated by respective applications of the films in optoelectronic devices, sensors or biofunctional interfaces. In 2017, in situ IRSE was brought to a new level by showing the capability for sensitive and quantitative intra and intermolecular interaction studies of thin thermoresponsive polymer films. Recently, new applications became available by the involvement of laser sources as well as by specifically designed microfluidic cells. These two issues are described in other chapters of this Encyclopedia. In the chapter Hyperspectral and time resolved IR laser polarimetry , new possibilities of laser based IR polarimetry regarding highly time resolved studies of non cyclic irreversible processes and hyperspectral imaging are discussed. Examples are the sub second spectral monitoring of a solid to liquid phase transition of a myristic acid film and hyperspectral ellipsometric imaging of a microfluidic chip. In the chapter Optofluidic analysis of monolayers with infrared microscopy , several opportunities for kinetic, chemical and structural in situ analyses of sub monolayers with IR spectroscopy in a microfluidic ml cell are reviewed. In the present chapter we focus on IRSE as a powerful method for the analysis of thin films from 5 to 12 nm at the silicon liquid interface. The methodical possibilities are of high interest in various fields of research and applications, such as bioanalytics, catalysis and material scienc

Polarization dependent and ellipsometric infrared microscopy for analysis of anisotropic thin films

Dielectric functions and anisotropic thin film properties such as electronic conductivity or molecular orientations are of high technological importance for engineering efficient optical, electronic and sensing devices. This work demonstrates for the first time how full scale polarization dependent Fourier transform infrared FTIR microscopy may be used for quantitative determination of polarized reflection coefficients of thin film samples with thicknesses down to a few nm. Out of plane and in plane optical properties of thin silicon oxide, indium tin oxide ITO and polyimide films are measured and characterized quantitatively with respect to anisotropy and thickness. Sample homogeneity is accessed using FTIR microscopic mapping. By performing measurements at multiple polarizer azimuths, we demonstrate the technique of ellipsometric microscopy. Exemplarily, ellipsometric measurements of a polyimide film are presented and discussed. We describe how introducing a retarder into the optical path would enable sensitive phase measurements via generalized infrared ellipsometric microscop

IR microfluidics for in situ sensing of molecular interfaces

Recent developments in infrared IR microfluidics for sensitive monitoring of molecular adsorption at solid liquid interfaces are briefly reviewed. A microfluidic platform is presented that uses a metallic island film for surface enhanced IR absorption SEIRA coupled to IR spectroscopies for bio sensing and vibrational investigations of molecular monolayers and their adsorption kinetics. Exemplarily, IR spectral monitoring of the monolayer formation of 4 mercaptobenzonitrile 4 MBN in liquid environment is discussed as a Langmuir isotherm. Adsorption isotherms of specific molecular vibrations are analyzed from the time dependent evolution of band amplitudes and peak areas during adsorption. Given the detection limit of 0.03 nmol cm2, the isotherms of 4 MBN, gluthathione GSH monolayer formation, and the sensing of 4 nitrobenzylmercaptan 4 NBM by the MP graphene surface are compared. Potential applications are bio and bio medical sensing as well as the study of processes, e. g., enzymatic reactions, chemical or catalytic reactions, receptor ligand interactions, and structural changes of molecules due to environmental stimul