Study of the Electronic Structures of Organic Solids by Inverse Photoemission Spectroscopy

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Inverse photoemission spectroscopy is a powerful technique for examining the electronic structures of solids by measuring the emission of high energy photons caused by impinging electrons into the solid sample. In this research project, we have constructed an inverse photoemission spectrometer for studying the structure of the vacant electron-ic states in organic solids, about which only little information have been studied previously. We designed the spectrometer consulting with the groups of Tokyo University. Who have already constructed their own spectrometer. Special care was paid for designing an instrument suitable for studying both organic and inorganic solids. By the beginning of the academic year of 1991. We completed the construction of the vacuum chambers, parts for the electron gun, light detection system, and the electronics system. Also we have developed the software for handling the collected data. These parts were assembled together, followed by the vacuum test, activat … More ion and adjustment of the electron gun, and other adjustments. After these things were finished satisfactory, the inverse photoemission spectra of evaporated gold films were measured for examining the performance of the instrument, giving spectra in good agreement with those reported in the literature. With establishing the successful construction of the spectrometer, we proceeded in measuring the inverse photoemission spectra of the semiconductors Te, SnTe, and PbTe, for which no previous reports are available. The obtained spectra give information about the electronic structures of the vacant states of these materials. Then we have measured the inverse photoemission spectra of representative organic solids : benzene and Cuphthalocyanine, which gave information about the electronic structures of these materials such as the energy of the lowest vacant orbitals. Although there still exist several experimental problems. The present study opened a way for more detailed understanding of the electronic structures of organic solids. Less