scholarly journals Molecular Orientation Analysis of a C8-BTBT Thin Film Grown under an External Temperature Gradient

2018 ◽  
Vol 16 (0) ◽  
pp. 79-83 ◽  
Author(s):  
Hidetaka Watanuki ◽  
Kei Mitsuhara ◽  
Masaru Takizawa
Keyword(s):  
Thin Film ◽  
Temperature Gradient ◽  
Molecular Orientation ◽  
External Temperature ◽  
Orientation Analysis

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

2016 ◽  
Vol 71 (5) ◽  
pp. 901-910 ◽  
Author(s):  
Nobutaka Shioya ◽  
Shingo Norimoto ◽  
Naoki Izumi ◽  
Miyako Hada ◽  
Takafumi Shimoaka ◽  
...  
Keyword(s):  
Thin Film ◽  
Molecular Orientation ◽  
Orientation Angle ◽  
Band Intensity ◽  
Band Shift ◽  
Optimal Angle ◽  
Orientation Analysis ◽  
Oriented Molecules ◽  
Out Of Plane ◽  
Spectroscopic Tool

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.

scholarly journals Vapor flux and recrystallization during dry snow metamorphism under a steady temperature gradient as observed by time-lapse micro-tomography

2012 ◽  
Vol 6 (5) ◽  
pp. 1141-1155 ◽  
Author(s):  
B. R. Pinzer ◽  
M. Schneebeli ◽  
T. U. Kaempfer
Keyword(s):  
Temperature Gradient ◽  
Physical Properties ◽  
Time Lapse ◽  
Phase Changes ◽  
External Temperature ◽  
Vapor Flux ◽  
Snow Metamorphism ◽  
Diffusion Enhancement ◽  
Micro Tomography ◽  
Snow Microstructure

Abstract. Dry snow metamorphism under an external temperature gradient is the most common type of recrystallization of snow on the ground. The changes in snow microstructure modify the physical properties of snow, and therefore an understanding of this process is essential for many disciplines, from modeling the effects of snow on climate to assessing avalanche risk. We directly imaged the microstructural changes in snow during temperature gradient metamorphism (TGM) under a constant gradient of 50 K m−1, using in situ time-lapse X-ray micro-tomography. This novel and non-destructive technique directly reveals the amount of ice that sublimates and is deposited during metamorphism, in addition to the exact locations of these phase changes. We calculated the average time that an ice volume stayed in place before it sublimated and found a characteristic residence time of 2–3 days. This means that most of the ice changes its phase from solid to vapor and back many times in a seasonal snowpack where similar temperature conditions can be found. Consistent with such a short timescale, we observed a mass turnover of up to 60% of the total ice mass per day. The concept of hand-to-hand transport for the water vapor flux describes the observed changes very well. However, we did not find evidence for a macroscopic vapor diffusion enhancement. The picture of {temperature gradient metamorphism} produced by directly observing the changing microstructure sheds light on the micro-physical processes and could help to improve models that predict the physical properties of snow.

Molecular orientation and thermal stability of thin-film organic semiconductors

2021 ◽  
Vol 88 ◽  
pp. 106014
Author(s):  
Han-Nan Yang ◽  
Shou-Jie He ◽  
Tao Zhang ◽  
Jia-Xiu Man ◽  
Yongbiao Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Thermal Stability ◽  
Organic Semiconductors ◽  
Molecular Orientation ◽  
Thermal Stability Of
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