Se-Jung Oh

XPS, AES and SEM analysis of recent dental implants.

Today, surface chemistry modifications of titanium implants have become a development strategy for dental implants. The present study investigated the chemistry and morphology of commercially available dental implants (Nobel biocare TiUnite, Astra AB OsseoSpeed, 3i Osseotite, ITI-SLA). X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy were employed for the analysis of surface chemistry. The morphology was investigated by scanning electron microscopy. The present study demonstrated the major differences of surface properties, mainly dependent on the surface treatment used. The blasting and acid etching technique for the OsseoSpeed, Osseotite and SLA surfaces generally showed mainly TiO(2), but a varying surface morphology. In contrast, the electrochemical oxidation process for TiUnite implants not only produces microporous surface (pore size: 0.5-3.0microm), but also changes surface chemistry due to incorporation of anions of the used electrolyte. As a result, TiUnite implants contain more than 7at.% of P in oxide layer and higher amounts of hydroxides compared to the other implants in XPS analysis. F in OsseoSpeed implants was detected at 0.3% before as well as after sputter cleaning.

Comparison of HfO2 films grown by atomic layer deposition using HfCl4 and H2O or O3 as the oxidant

HfO2 gate dielectric thin-films were deposited on Si wafers using an atomic-layer deposition (ALD) technique with HfCl4 and either H2O or O3 as the precursor and oxidant, respectively. Although the ALD reactions using either H2O or O3 were successfully confirmed at a deposition temperature of 300 °C, the structural and electrical properties of the HfO2 films grown using the two oxidants were quite different. The stronger oxidation power of the O3 compared to H2O increased the oxygen concentration in the HfO2 film and the rate of interfacial SiO2 formation even at the as-deposited state. Because of the larger oxygen concentration, the decrease in the capacitance density of the film grown with O3 after rapid thermal annealing at 750 °C under N2 atmosphere was slightly larger than that of the HfO2 film grown with H2O. Apart from this weakness, all the other electrical properties, including the fixed charge density, the interface trap density, the leakage current density and the hysteresis in the capacitance–...

Thermal annealing effects on the structural and electrical properties of HfO2/Al2O3 gate dielectric stacks grown by atomic layer deposition on Si substrates

HfO2/Al2O3 gate dielectric thin film stacks were deposited on Si wafers using the atomic layer deposition technique. A 3.3-nm-thick Al2O3 interlayer was grown at 400 °C using Al(CH3)3 and O3, and 2.5–3.5-nm-thick HfO2 films were grown at either 300 or 400 °C using HfCl4 and H2O. Thermal annealing of the dielectric film stack at temperatures ranging from 400 to 1000 °C under pure N2 atmosphere resulted in variation of the equivalent oxide thicknesses. The equivalent oxide thickness of the dielectric film stack showed a minimum after annealing at 650 °C irrespective of the HfO2 film growth temperature. High temperature (>800 °C) annealing induced the formation of SiO2 and intermixing between the HfO2 and Al2O3 layers, which resulted in an increase in the equivalent oxide thickness of the film stack. The structural changes in the stacked films as a function of the annealing temperature were compared with those of HfO2 and Al2O3 single layers. The film stack showed minimal hysteresis (<15 mV) behavior in the ...

Effect of oxygen partial pressure on the Fermi level of ZnO1−x films fabricated by pulsed laser deposition

We investigated the influence of oxygen deficiency on the Fermi level (EF) of ZnO thin film prepared by pulsed laser deposition (PLD). For this purpose, we adopted in situ x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The oxygen deficiency was effectively controlled by varying the oxygen partial pressure [P(O2)] during the PLD. The EF shifted by +0.6 eV as the P(O2) decreased from 10 to 3.3 Pa. This shift indicates a significant change in the energy balance in the oxygen-deficient ZnO films. This fact suggests that the very large change in the resistivity of ZnO thin films resulting from the oxygen deficiency could be attributed to the EF shift rather than grain boundary formation in the ZnO film.

Effects of plasma nitridation of Al2O3 interlayer on thermal stability, fixed charge density, and interfacial trap states of HfO2 gate dielectric films grown by atomic layer deposition

HfO2/Al2O3 gate dielectric thin-film stacks were deposited on Si wafers using an atomic-layer-deposition technique. A 2.3-nm-thick Al2O3 interlayer was grown at 450 °C using Al(CH3)3 and O3, and (4–5)-nm-thick HfO2 films were grown at 400 °C using HfCl4 and H2O as precursors. Because the Al2O3 interlayer was not an effective Si-diffusion barrier layer on its own, the Al2O3 interlayer was plasma treated under an NH3 atmosphere at 790 °C for 40 s. The plasma treatment increased the Al2O3 interlayer thickness by approximately 1 nm and decreased the overall capacitance density of the film stack. However, the thermal stability of the capacitance density was greatly improved as a result of the treatment resulting in a similar capacitance density after postannealing at 800 °C in a N2 atmosphere to that observed in nontreated samples after similar annealing conditions. The signs and amount of the fixed charges of the Al2O3/Si and HfO2/Al2O3 interfaces greatly depend on the nitridation of the Al2O3 layer. Furtherm...

Spectroscopic evidence for limited carrier hopping interaction in amorphous ZnO thin film

The electronic structure of amorphous ZnO film (a-ZnO) was examined by O K- and Zn L3-edge x-ray absorption spectroscopy and valence band photoemission spectroscopy. Comparative studies of a-ZnO and a wurtzite ZnO (w-ZnO) revealed a decrease in Zn 4s-O 2p hybridization strength and the localization of Zn 4s band as a consequence of local structural disorder, indicating limited electron hopping interactions in a-ZnO. The 0.1 eV higher Fermi-level of a-ZnO compared to w-ZnO suggests that the electrical properties of a-ZnO are different from those in w-ZnO due to structural disorder, even in the absence of impurities or grain boundaries.

The effect of calcium ion concentration on the bone response to oxidized titanium implants

AIM To investigate the effect of calcium concentration on the bone tissue response to Ca-incorporated titanium implants. MATERIALS AND METHODS Two titanium surfaces containing 4.2% and 6.6% calcium were prepared using the micro-arc oxidation process. The implants were inserted in the tibia of nine New Zealand White rabbits. After 6 weeks of healing, the bone response to the implants was quantitatively compared by biomechanical and histomorphometrical measurements. RESULTS Ca 4.2% and Ca 6.6% containing implants revealed no distinctive differences in their qualitative surface chemistry; chemical bonding state of Ca in titanium oxide was mainly calcium titanates. No significant differences were observed between two implants in peak removal torque and shear strength comparisons (P>0.05). Histomorphometrical analyses presented no significant differences in bone-metal contact, bone area and newly formed bone measurements between two implants (P>0.05). CONCLUSIONS From biomechanical and histomorphometrical measurements, the two calcium concentrations in this study did not differ significantly with respect to their influence on the bone tissue response. This similar bone response in rabbit tibiae may be explained by the similarity of the qualitative Ca chemistry in titanium surfaces.

Charge and magnetic states of rutile TiO2 doped with Cr ions

We observe that the electronic and magnetic properties of Cr-doped rutile TiO2 single crystals are highly dependent on growth conditions. The ferromagnetic component of magnetic susceptibility is observed to be enhanced for samples grown under oxygen-rich conditions. To understand the charge state of Cr dopants and their role in response to an external magnetic field, we carry out density functional theory calculations for Cr-doped rutile TiO2. Using the results of formation energy calculations in the presence of oxygen vacancies and Cr atom substitution at the Ti sites, we demonstrate that the Cr3+ state is a source of Curie-Weiss-type magnetic response, whereas the Cr4+ defect states contribute to the ferromagnetic component. We also provide the electronic structures of various defect configurations and attempt to explain the optical and electronic properties of the Cr-doped system.