Takashi Masuda

Spectral parameters and Hamaker constants of silicon hydride compounds and organic solvents

Cyclopentasilane (CPS) and polydihydrosilane, which consist of hydrogen and silicon only, are unique materials that can be used to produce intrinsic silicon film in a liquid process, such as spin coating or an ink-jet method. Wettability and solubility of general organic solvents including the above can be estimated by Hamaker constants, which are calculated according to the Lifshitz theory. In order to calculate a Hamaker constant by the simple spectral method (SSM), it is necessary to obtain absorption frequency and function of oscillator strength in the ultraviolet region. In this report, these physical quantities were obtained by means of an optical method. As a result of examination of the relation between molecular structures and ultraviolet absorption frequencies, which were obtained from various liquid materials, it was concluded that ultraviolet absorption frequencies became smaller as electrons were delocalized. In particular, the absorption frequencies were found to be very small for CPS and polydihydrosilane due to sigma-conjugate of their electrons. The Hamaker constants of CPS and polydihydrosilane were successfully calculated based on the obtained absorption frequency and function of oscillator strength.

Effect of annealing and hydrogen radical treatment on the structure of solution-processed hydrogenated amorphous silicon films

We investigate the structure distribution of solution-processed (Sol. P) hydrogenated amorphous silicon (a-Si:H) films along the thickness direction and the effect of hydrogen-radical treatment (H-treatment) by Raman spectroscopy. Sol. P a-Si:H films have a stress distribution along the thickness direction, and the degree of such distribution depends on annealing temperature and duration. H-treatment affects the stress and short-range order (SRO) of a-Si:H films. The results suggest a formation mechanism for Sol. P a-Si:H films through network reconstruction and H-treatment.

Measurement of Surface Free Energy of Transmission Electron Microscopy Substrate and Its Surface Modification for Use in Self-Assembly Experiment

In this research, we analyzed and modified the surface of a transmission electron microscopy (TEM) substrate for the observation of a self-assembled pattern. First, we estimated that the surface free energy of the TEM substrate is 41.1±5.6 mJ/m2 by measuring the dynamic contact angle of inkjet droplets. Second, the surface free energy distribution of a TEM substrate was measured. It was found that the TEM substrate has a homogeneous surface free energy value. Third, we modified the surface of a TEM substrate using self-assembled monolayers (SAMs) and analyzed the surface of the TEM substrate-modified SAMs by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). It was confirmed that SAMs can assemble on the graphite surface. As a result, we obtained a method to control the total surface free energy of a TEM substrate from 12 to 50 mJ/m2 using SAMs.