Narrow Results

The growth of high-quality continuous film of graphene on less than $1\mu$m-thick Cu film is proven to be a challenging task due to the solid-state dewetting of Cu during the high-temperature chemical vapor deposition (CVD) process. In this paper, we introduce the use of nanostructured black Si (b-Si) as a template for Cu evaporation to mitigate the dewetting of Cu thin film. Using a cold-wall CVD system at a process temperature of 825${}^{\circ }$C, even Cu thickness, $t_{\mathrm{\text{Cu}}}=600$ nm on polished SiO₂/Si substrate is poor for maintaining Cu as a continuous film. If the polished SiO₂/Si is replaced with SiO₂/b-Si, the minimum $t_{\mathrm{\text{Cu}}}=400$ nm is sufficient. According to the Cu trapping mechanism, moving Cu particle is trapped in the nanostructured trenches of SiO₂/b-Si during annealing and CVD growth processes. Continuous monolayer graphene with a grain size of $\sim 1\mu$m without defect is obtained on Cu/SiO₂/b-Si substrate. The improved adhesion of Cu to the SiO₂/b-Si enables dry-transfer of graphene by mechanical peeling using a polyvinyl alcohol (PVA) film. Our solution is promising for obtaining flat graphene and a recyclable Cu/SiO₂/b-Si substrate.

Effects of the different ultrasonic powers on copper electrodeposition from non-cyanide alkaline baths by using pyrophosphate as complexing agent were investigated by different electrochemical methods. Cyclic voltammetry and current transient measurements were used to characterize the nucleation and growth mechanism. It is very obvious that the reduction potential moves to more positive one as the ultrasonic power increases. The quartz crystal microbalance (QCM) and chronoamperometric method were used to study the relationship between the mass change and the deposition time. It was found that the current efficiency of electrolyte under 0, 60, 80 and 100 W is 91.95%, 92.14%, 89.25% and 96.11%, respectively measured by QCM measurements. The surface morphology of the electrodeposited Cu films is analyzed by scanning electron microscopy (SEM). The morphology of copper films electrodeposited under the power of 60 W and 80 W presents a compact surface and the grains are fine and uniform.

A conductive Cu thin film with a thickness of 170nm, electrical resistivity of 8.9(2) $\times 10^{-3}\mathrm{\Omega }$cm and adhesion strength of 12(7) MPa was fabricated at 180^∘C in air. The spray solutions were prepared by electrolyzing Cu electrodes in an aqueous solution of ammonium formate, and then by adding ethylenediamine-N, N, N${}^{\prime }$, N${}^{\prime }$-tetraacetic acid (EDTA). The surface morphology image of resultant Cu thin film, observed by a field emission scanning electron microscope, revealed Cu grains with particle sizes of ca. $80\pm 30$nm. It was indicated that the Cu complex containing EDTA ligand in the spray solution plays important roles to (1) provide enough amount of carbon atoms as a reducing agent for phase transition of its coordinated Cu${}^{2+}$ to crystalline Cu⁰ and (2) prevent the product from oxidation under atmospheric O₂ during spray coating.