2020同步年報

034 ACTIVITY REPORT 2020 incident angle of the X-ray beam, γ is the tilt angle of the molecular π-plane; A is an arbitrary proportional parameter. The set-up is illustrated in Fig. 2(b) . Figure 3 depicts the dependency of the C 1s-π* absorbance on the angle of incidence of the X-rays. The fitting outcome for tilt angle γ in the π-plane is 44 o , which corresponds to a distorted face-on orientation. Thermal annealing at 260 o C further flattens γ to 42 o . In contrast, γ from the pure N2200 sample is 52 o , which indicates an edge-on configuration; it turns 5 o more upright upon the same thermal annealing. Even though the annealing treatment further rectifies the orien- Fig. 3 : Angularly dependent C 1s-π* absorbance of N2200 and FNDIT2/ N2200 SSM. TA stands for “thermal annealing”. [Reproduced from Ref. 1] tations, the fact that it does not disturb the film integrity also demonstrates the thermostability. As a complement to NEXAFS spectra, grazing-incidence wide-angle X-ray scat- tering (GIWAXS) measurements showed that the π-plane of the FNDITN2/N2200 SSM has a ratio 1:2 of edge-on to face-on. This result is derived from the crystalline part of the specimen, as only the crystallites contribute to the diffrac- tion signal. “The interface is the device,” pointed out by Herbert Kroemer, the 2000 Nobel laureate in physics. For decades, interface engineering has been a major task for the development of science and technology. The work presented here demon- strates a synthetic route for a π-conjugated polymer mono- layer with a characteristic π-plane orientation. The com- bination of NEXAFS and GIWAXS spectra also effectively determines such an orientation. It carves a path for forging functional organic/metal or organic/organic interfaces to build layered composite structures used in organic electron- ic devices. (Reported by Dr. Bo-Hong Liu) This report features the work of Yaw-Wen Yang, Chain-Shu Hsu, Keisuke Tajima and their collaborators published in J. Mater. Chem. A 8 , 6268 (2020). TLS 24A1 BM – (WR-SGM) XPS, UPS, XAS, APXPS • XPS • Soft Materials, Chemistry, Conjugated Polymers Reference 1. W. C. Wang, S. Y. Chen, Y. W. Yang, C. S. Hsu, K. Tajima, J. Mater. Chem. A 8 , 6268 (2020).