Quantitative Analysis of Uniaxial Molecular Orientation in Langmuir-Blodgett Films by Infrared Reflection Spectroscopy

Abstract

In analyzing optical properties of multilayered LB films with the uniaxial anisotropy around the surface normal, a new method for calculating infrared reflection-absorbances was developed, by extending Drude's anisotropic calculation theory for two-phase system to Hansen's optical theory for thin isotropic multilayers. With this method, infrared external reflection spectra of a 9-monolayer LB film of cadmium stearate prepared on a gallium arsenide substrate were analyzed to obtain molecular orientations. The result was in fair agreement with that obtained by X-ray diffractometry. Reflection-absorbance spectra of the same LB film on a silver-evaporated slide glass at various temperatures were also analyzed by the same method and the orientation angle of each molecular group was quantitatively obtained, clarifying the process of disordering with the increase of temperature. Further, the dependence of the degree of disordering on the monolayer location in LB films were discussed in light of the isotope substitution experiment.

Analysis of the Surface Coverage of a Self-Assembled Monolayer of Octadecyl Silane on a Si(100) Surface by Infrared External-Reflection Spectroscopy

“…IR ER measurements 8,9,12 were performed on a Thermo Fischer Scientific (Madison, WI) Magna550 FT-IR spectrometer equipped with a Harrick (Pleasantville, NY) VR1-NIC Variable Angle Reflection Accessory mounted with a Harrick PWG-U1R Wire-Grid Polarizer for obtaining the p-polarization. The modulation frequency of FT-IR was 60 kHz, and the IR ray was detected by a liquid-N2 cooled MCT detector.…”

A Study on the Plasma-Treated Surfaces of MgO(100) and Quartz Substrates by Infrared Multiple-Angle Incidence Resolution Spectrometry

“…This tilt angle suggested that the structure of the contaminant was in a completely disordered state [28]. Figure 5 shows the IP mode spectra of the quartz substrate after each treatment.…”

Experimental Optimization of p-Polarized MAIR Spectrometry Performed on a Fourier Transform Infrared Spectrometer

“…Since the band locations of the νs(CH2) and νa(CH2) modes are 2850 and 2917 cm -1 , respectively, which indicate that the hydrocarbon chain has the trans-zigzag conformation, 12 Eq. (2) must hold.…”

“…When a molecule of metallic stearate is involved in an ordered monolayer, the νa(CH3) mode is known to split into the inskeleton and out-of-skeleton modes. 12,26 In this situation, the two modes would give different components on the IP and OP spectra, which depend on the molecular tilt angle. Therefore, there is always a band shift between the band locations of the νa(CH3) mode in the two spectra.…”

“…1,2 In this case, the external-reflection (ER) technique [9][10][11][12][13][14][15][16][17] is useful in place of the transmission one, since reflection occurs no matter what wavenumber range is opaque for the transmittance. On glass, however, the reflectivity is very low, 2 especially for p-polarization, due to the low refractive index (ca.…”