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Recent progress on scanning probe microscopy technology is remarkable. In recent years, we have developed new technique called non-contact scanning nonlinear microscopy (NC-SNDM), as a probe microscopy technique with atomic resolution following STM and AFM. NC-SNDM can observe not only real space topography but also microscopic dipole moment distribution of atomic cluster on top of the single crystal substrate such as Si(111)7x7 surface.[1] This microscopy technique has a high sensitivity to variation of capacitance of surface atom cluster by new CE™ developed tip height control system using high order dielectric signal. Meanwhile, in recent decades, nanotechnology called the next generation technique attracts our interest. As one category of nanotechnology, fabrications of unique organic devices have been recently studied. However, such a device performance strongly depends on arrangement and dielectric characteristic of organic molecule in the boundary. Fortunately, almost organic molecules may have electric dipole moment with large nonlinear dielectric component due to an anisotropic structure. Accordingly, we paid attention to the organic molecular on ordered surfaces in order to investigate potentiality of NC-SNDM technique. In this study, we report dielectric characteristics and local electric dipole moment distribution of fullerene and endohedral metallofullerene molecules on Si(111)7x7 surface by NC-SNDM under ultra high vacuum condition. Fullerene molecules were fabricated on Si(111)7x7 surfaces by thermal deposition under 10-10 Torr. Our NC-SNDM data showed that the adsorption state and some internal structures of C60 on Si(111)7x7 surface were observed by NC-SNDM feedback system. Thus, NC-SNDM can resolve real space topography with an atomic resolution for organic materials. In addition, the signals originated from nonlinear dielectric properties of C60 molecule on the Si(111)7x7 surface were also observed. However, ordered state of electric dipole moment was not observed due to the isotropic structure of C60 molecule. Thus, those results indicate that NC-SNDM may be also powerful technique for organic materials on various substrates.
[1]R. Hirose, K. Ohara. and Y. Cho, Nanotechnology 18, 084014 -1-5 (2007).
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