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We have measured the thickness of the oxide layer of Si wafers as a function of annealing temperature following treatment with either a modified Shiraki method (hydrophilic) or HF etching (hydrophobic). The results show that in both cases there exists a well-defined oxide layer, approximately 20 Å thick, which forms within at least 20 min of the processing. The density of this layer is initially 35% of the usual silicon oxides. The density of this layer gradually increases, approaching that of the pure oxides as the substrates are annealed from room temperature to 180 °C. These results were interpreted in terms of a complexed layer of water. These results are consistent with dynamic secondary ion mass spectrometry, which shows that the amount of oxygen at the Si interface decreases with increasing temperature. The activation energies, obtained 31.6 and 19.3 kJ/mol for the hydrophilic and hydrophobic surfaces, are consistent with the evaporation energy of water. The effect of the adsorbed water was also evident on the diffusion coefficient of PS from the Si interface. The diffusion coefficient (D*) was expressed as D* = D WLF(T) exp(−ΔE s/kT) where D WLF is the usual WLF temperature dependence diffusion coefficient, and the additional activation energy measured was ΔE s ∼ 6.7 kJ/mol per contact. The energy corresponds to the interaction energy between styrene monomers and mostly the adsorbed water layer.

Surface microstructure and chemical composition of the implant are very important for its osseointegration in vivo. In this paper, a hierarchical micropattern covered with calcium phosphate (Ca/P phase) was obtained on titanium (Ti) implant surface by femtosecond lasers (FSL) irradiation in hydroxyapatite suspension. The hierachical micropattern as well as Ca/P phase increased osteoblastic cell adhesion. Higher expression of osteogenic markers (osteocalcin, osteopontin, and runt related transcription factor-2) on the surface treated by FSL of 2.55 J/cm(2) indicated the favorable effect of laser treatment on cell differentiation. In vivo studies were carried out to evaluate the effect of laser treatment and Ca/P deposition on the osseointegration. It showed that the binding capacity between bone and FSL-treated Ti implants was obviously stronger than that between bone and polished or sand blasting and acid etching (SLA) Ti implants. Bone trabecula surrounded the FSL-treated implants without fibrous tissue after 8-week implantation. Also, higher bone mineral density was seen surrounding the FSL-treated implants. Our in vitro and in vivo studies demonstrated that the FSL induced micropattern and Ca/P phase had positive effects on the acceleration of early osseointegration of Ti implants with bone tissue.