The electrochemical deposition of copper ͑Cu͒ thin film on polycrystalline ruthenium ͑Ru͒ electrode surface was investigated in a sulfuric acid plating bath. Scanning electron microscopic characterization indicated that a continuous thin Cu film ͑150 Å and above͒ could be conformally coated on Ru with good control of thickness. The nucleation and growth of Cu on Ru was studied using the potentiostatic current-transient method. The results support a predominantly progressive nucleation of Cu on the Ru surface. In addition, X-ray diffraction patterns indicated ͑i͒ a principally ͑111͒ texture of the electrochemically grown Cu on Ru and ͑ii͒ the absence of any new phase or compound formation between the two metals, even after annealing up to 800°C. Scotch tape peel tests showed that Cu films adhered strongly to Ru, both before and after the annealing treatments. The lack of metallurgical interaction and strong adhesion between Cu and Ru at elevated temperatures underscore the potential application of Ru as a new Cu diffusion barrier.
Interfacial stability of electroplated copper on a 5nm ruthenium film supported by silicon, Cu∕(5nmRu)∕Si, was investigated using Rutherford backscattering and high-resolution analytical electron microscopy. Transmission electron microscopy (TEM) imaging shows that a 5nm Ru film is amorphous in contrast to the columnar microstructures of thicker films (20nm). Direct Cu plating on a 5nm Ru film yielded a homogeneous Cu film with over 90% plating efficiency. It is demonstrated that 5nm Ru can function as a directly plateable Cu diffusion barrier up to at least 300°C vacuum anneal. TEM reveals an interlayer between Ru∕Si, which expands at the expense of Ru upon annealing. Electron energy loss spectroscopy analyses show no oxygen (O) across the Cu∕(5nmRu)∕Si interfaces, thereby indicating that the interlayer is ruthenium silicide (RuxSiy). This silicidation is mainly attributed to the failure of the ultrathin Ru barrier at the higher annealing temperature.
The structure and electrochemical properties of arrayed nitrogen-containing carbon nanotube
(CN
x
NT)−platinum nanoparticle (Pt NP) composites directly grown on Si substrates have been
investigated. The CN
x
nanotube arrays were grown by microwave-plasma-enhanced chemical vapor
deposition first and then acted as the template and support for Pt dispersion in the following sputtering
process. Under the same sputtering conditions, it was found that well-separated Pt NPs would form with
an average diameter of 2 nm on the arrayed NTs while a continuous Pt thin film was observed on the
bare Si substrate. X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and electron microscopy
were employed to study bonding and structure changes with increasing deposition time. Implications of
the C1s and N1s bonding changes in XPS and their possible relation to the NT−Pt composite structures
with self-limited size distribution are discussed. Cyclic voltammograms show well-behaved curves in
methanol oxidation, suggesting an efficient electronic conduction mechanism from the substrate via CN
x
NTs to reach individual Pt NPs is in operation. Such an integrated nanocomposite approach possesses a
high potential for micro direct methanol fuel cell applications.
The pulsed plasma polymerization of tetramethyltin monomer was studied as a function of the radio frequency (rf) duty cycle employed, all other plasma variables being held constant. Progressive increases in the relative tin content of the plasma deposited films were observed with systematic decreases in the rf duty cycles employed during film formation. The variations in tin content of these films were documented by XPS, FT-IR, TEM, AFM, and electrochemical analyses. A particularly interesting aspect of this work is the microstructure of the films which reveals spherical tin particles of essentially uniform diameters (20-30 nm) independent of the duty cycle during deposition. The increasing metal content in these films with decreasing duty cycle corresponds to increased aggregation of these nanosized particles into progressively larger sized clusters. The results obtained are supportive of the use of the variable duty cycle pulsed plasma deposition technique as a new route to improved nanoscale film chemistry control in the synthesis of organometallic composite films.
A simple, direct route to preparation of surface immobilized hydrogel films is described. Specifically, low pressure RF pulsed plasma polymerization of 1-amino-2-propanol and 2-(ethylamino)ethanol monomers produced thin hydrogel films deposited on substrates located in the plasma reactor. The successful syntheses were carried out under plasma conditions which not only yield the hydrogel but are also sufficiently energetic to produce films strongly grafted to the substrates. The polymer films obtained exhibit the thermoresponsive property of hydrogels, as shown by film color change with temperature. Additional evidence for the phase transition properties of these films was obtained using water contact angle and capillary rise measurements. The plasma polymerization approach provides an unusually simple route to synthesis of hydrogels in which the films are pin-hole free and are of easily controlled thickness. An important added advantage, particularly for applications involving biomaterials, is the conformal property of the plasma generated polymer films. The results obtained suggest that this approach should be applicable to a variety of other monomers and, based on differences observed with the present two monomers, suggest synthesis of films which exhibit a range of phase transition temperatures.
The kinetics and morphologies of Cu deposition on HF‐treated silicon surfaces were investigated by atomic force microscopy (AFM), inductively coupled plasma mass spectroscopy (ICP/MS), and graphite furnace atomic absorption spectroscopy (GFAAS). The early stage (<60 s) of Cu deposition, as characterized by AFM, was found to be dominated by the nucleation of nanometer‐sized Cu nuclei on HF‐treated silicon surfaces. After 60 s of Cu deposition, the total grain number of Cu deposits was leveled to a constant plateau. However, a significant grain size increase of deposition Cu nuclei was noticed. We employed an AFM volume‐integration technique in conjunction with the ICP/MS and GFAAS measurements to demonstrate that the Cu deposition rate was limited by the diffusion of
Cu2+
ions across the stationary solution layer toward the silicon surface.
salt of 2-crystal data and summary of data collection and refinement, fractional coordinates and thermal parameters, anisotropic thermal parameters, interatomic distances, and interatomic angles (5 pages). Ordering information is given on any current masthead page.(22) There is some evidence that MM2 may tend to overestimate the amount of pyramidalization in 1, n -3.4
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