As described herein, we investigate the effects of the plasma state on boron（B）-doped diamond（BDD）resistivity. Preparing BDD of various volume resistivities is difficult. Various studies have examined control of the BDD resistance value, necessitating systematic investigations of the relation between resistivity and B contents in plasma. Therefore, plasma during growth was measured using optical emission spectroscopy （OES）to clarify the relation between emission species and resistance values. For each condition, OES revealed peaks of B（249.7 nm）, BH （433.1 nm）, BO（436.3 nm）, H_α, H_β, CH, and C₂. Electrical resistivity measurements obtained using the four-point probe method with mini mum volume resistivity of 0.3 Ω·cm were obtained. With increasing B-containing emission species such as B, BH, and BO intensity in OES spectra, resistivity was decreased. Results suggest that B-containing emission species in OES spectra influence the resistivity of BDD.

Needs for adhesive bonding in automotive production are increasing. One difficulty with adhesive bonded parts is their deterioration over time. Therefore, using steel sheets with different attributes, we investigated the deterioration behavior of adhesive-joined parts. Results demonstrated that deterioration over time is attributable to reduced strength of interfacial adhesion between the metal surface and the adhesive, and that the degree of deterioration depended on the metal coating type. Furthermore, the deterioration behavior was affected by the difference in the bonding state, which depended on the type of metal coating and adhesive. For this study, we estimated the bonding condition between the galvanized steel sheets and the adhesive by examining the work of adhesion and surface free energy. Then we examined the adhesive bonding aging mechanism. That examination, conducted in the early stage of deterioration, revealed that the intermolecular force was cut by water penetrating the adhesion interface, and that the adhesive strength was reduced. In contrast, when the deterioration occurred over a long term, the deterioration was accelerated further by corrosion of the galvanized steel sheet. Additionally, results show that existence of the chemical bonds at the adhesive interface was more important than intermolecular forces for suppressing deterioration.