Optimal Experimental Condition of IR pMAIRS Calibrated by Using an Optically Isotropic Thin Film Exhibiting the Berreman Effect

Abstract

Infrared (IR) p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) is a useful spectroscopic tool for revealing the molecular anisotropic structure in a thin film, which is used for the molecular orientation analysis of many functionalized organic thin films. Infrared pMAIRS provides both in-plane (IP) and out-of-plane (OP) vibrational mode spectra, which are influenced by the choice of the angles of incidence, i.e., angle set. To obtain quantitatively reliable pMAIRS spectra, therefore, the optimal angle set must be revealed. In a former study, an optimization study was carried out on a silicon substrate by using the band intensity ratio of the IP and OP spectra of highly oriented molecules in a thin film, which has a problem that the optimized results cannot be used for another substrate. In the present study, a totally new idea using an optically isotropic thin film as a standard sample is proposed to comprehensively explore the optimal angle set on various substrates: the band shift due to the Berreman effect of a strongly absorbing compound is used, instead of the band intensity. This new approach makes the pMAIRS calibration for various substrates a much easier task. With the optimal angle set, the molecular orientation angle in the film calculated by the pMAIRS spectra is also found to be reliable quantitatively. This technique opens a user-friendly way to a reliable molecular orientation analysis in an ultrathin film using IR pMAIRS.

Influence of Alkoxy Chain Length on the Properties of Two‐Dimensionally Expanded Azulene‐Core‐Based Hole‐Transporting Materials for Efficient Perovskite Solar Cells

“…According to the AFM topology data, the surface of af ilm of Azu-Me on as ilicon substrate is exceptionally flat and homogeneous with ar oot-mean-square surfacer oughness( R q )o fj ust 0.16 nm (Figure 10 b). Furthermore, p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) [44][45][46] showed almost identicalI P( in-plane) and OP (out-of-plane) spectra,w hich indicatest he completely random orientation of Azu-Me (Figure 10 c). The other azulened erivatives also form highly uniform, randomly orientated, amorphous films.…”

Impact of Kinetically Restricted Structure on Thermal Conversion of Zinc Tetraphenylporphyrin Thin Films to the Triclinic and Monoclinic Phases

“…An as-grown film, in fact, is known to give almost no diffraction signals, 6,16,19,20 which results in a misleading impression that all these films are composed of the randomly oriented amorphous portions, since the XRD pattern retrieves no orientation information for minute fractions of both crystallites and amorphous aggregates. In recent years, keen attention is attracted for p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) [21][22][23] as a powerful tool for characterizing the polymorphs and molecular orientation in such a low-crystallinity film. For the pMAIRS analysis, the C-H out-of-plane deformation vibration (denoted as (C-H)) band of an aromatic ring is a highly useful band for discussing the molecular structure in an organic semiconductor thin film, since the band intensity and position are correlated with the ring orientation and the polymorphs, respectively.…”

Phthalimide‐Based Transparent Electron‐Transport Materials with Oriented‐Amorphous Structures: Preparation from Solution‐Processed Precursor Films

“…Considering the low crystallinity of the films, it is reasonable to assume that these films contain amorphous components which do not appear in the GIXD patterns. The molecular orientation of the thin films was further investigated by pMAIRS, which is a powerful technique to discuss the molecular structure including the amorphous regions . The band of C−H out‐of‐plane bending vibration (denoted as γ (C−H)) of aromatic rings is useful for discussing the molecular orientation since the transition moment of this vibration mode is perpendicular to the ring plane.…”

“…The molecular orientation of the thin films was further investigated by pMAIRS, which is a powerful technique to discuss the molecular structure including the amorphous regions. [36][37][38] The band of CÀ H out-of-plane bending vibration (denoted as γ(CÀ H)) of aromatic rings is useful for discussing the molecular orientation since the transition moment of this vibration mode is perpendicular to the ring plane. According to the surface selection rule of pMAIRS, [36][37][38] when the γ(CÀ H) band appears stronger in the in-plane (IP) spectrum than that in out-of-plane (OP) one, the rings have the edge-on orientation, whereas the face-on orientation is revealed when the OP band is stronger than the IP one.…”

“…The film morphology was examined by atomic force microscopy (AFM) analysis. The molecular orientation in thin films was investigated using two complimentary techniques; two‐dimensional grazing incidence X‐ray diffraction (2D‐GIXD), which is sensitive to the periodic structures in the film, and p‐polarized multiple‐angle incidence resolution spectrometry (pMAIRS), which returns orientation information on all the molecules in the film, including amorphous regions …”