Qualitative and quantitative studies of the oxidation of polycrystalline copper (Cu) thin films upon exposure
to ambient air conditions for long periods (on the order of several months) are reported in this work. Thin
films of Cu, prepared by thermal evaporation, were analyzed by means of X-ray photoelectron spectroscopy
(XPS) to gain an understanding on the growth mechanism of the surface oxide layer. Analysis of high-resolution Cu LMM, Cu2p3/2, and O1s spectra was used to follow the time dependence of individual oxide
overlayer thicknesses as well as the overall oxide composite thickness. Transmission electron microscopy
(TEM) and spectroscopic ellipsometry (SE) were used to confirm the results obtained from XPS measurements.
Three main stages of copper oxide growth were observed: (a) the formation of a Cu2O layer, most likely due
to Cu metal ionic transport toward the oxide−oxygen interface, (b) the formation of a Cu(OH)2 metastable
overlayer, due to the interactions of Cu ions with hydroxyl groups present at the surface, and (c) the
transformation of the Cu(OH)2 metastable phase to a more stable CuO layer. These three stages were found
to occur simultaneously and to be mutually dependent on each other. The findings of this study may provide
guidance in choosing the optimal conditions to fabricate and store copper-based ultra-large-scale integrated
(ULSI) circuits.
Titanium (Ti) osseointegration is critical for the success of dental and orthopaedic implants. Previous studies have shown that surface roughness at the micro- and submicro-scales promotes osseointegration by enhancing osteoblast differentiation and local factor production. Only relatively recently have the effects of nanoscale roughness on cell response been considered. The aim of the present study was to develop a simple and scalable surface modification treatment that introduces nanoscale features to the surfaces of Ti substrates without greatly affecting other surface features, and to determine the effects of such superimposed nano-features on the differentiation and local factor production of osteoblasts. A simple oxidation treatment was developed for generating controlled nanoscale topographies on Ti surfaces, while retaining the starting micro-/submicro-scale roughness. Such nano-modified surfaces also possessed similar elemental compositions, and exhibited similar contact angles, as the original surfaces, but possessed a different surface crystal structure. MG63 cells were seeded on machined (PT), nano-modified PT (NMPT), sandblasted/acid-etched (SLA), and nano-modified SLA (NMSLA) Ti disks. The results suggested that the introduction of such nanoscale structures in combination with micro-/submicro-scale roughness improves osteoblast differentiation and local factor production, which, in turn, indicates the potential for improved implant osseointegration in vivo.
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