Synthesis of Cu or Cu2O-polyimide nanocomposites using Cu powders and their optical properties.

Nanocomposites consisting of Cu or Cu2O nanoparticles in various polyimide (PI) films were successfully prepared using polyamic acid (PAA) and Cu powders. Cu powders were dissolved into PAA solutions, and the solutions were spin-coated onto the substrates. Cu or Cu2O nanoparticles were formed in PI film by curing in a reducing or inert atmosphere, respectively. The Cu nanoparticles were transformed to Cu2O nanoparticles by post-heat treatment in an oxidizing atmosphere after curing in a reducing atmosphere. Transmission electron microscopy showed that uniform, round Cu2O nanoparticles 6.0 nm in diameter were dispersed in the PI film by post-heat treatment. The addition of Cu2O nanoparticles in the 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-4,4'-oxydianiline (6FDA-ODA) PI film enhanced the refractive index of the 6FDA-ODA PI film from 1.60 to 1.72 at 633 nm, and the transparency of the nanocomposite film was about 70-90% in the visible region and remained around 90% beyond 550 nm.

Fabrication of copper nanoparticles in a thick polyimide film cured by rapid thermal annealing.

We investigated the imidization of a polyimide (PI) and the formation of Cu nanoparticles in a PI film by curinga precursor of PI (polyamic acid (PAA) dissolved in n-methyl-2-pyrrolidinone) in a reducing atmosphere in the rapid thermal annealing (RTA) system. A Cu film was deposited onto the SiO2/Si substrate, and the PAA was spin-coated onto the Cu film. After the PAA reacted with the Cu film, soft-baking was performed to evaporate the solvent. Finally, the PAA was imidized to PI at 450 degrees C by curing in a reducing atmosphere with the RTA. Fourier transform infrared spectroscopy showed that the PAA was successfully imidized by the RTA. X-ray diffraction patterns revealed that Cu nanoparticles formed by RTA curing at 450 degrees C for 5 minutes in a reducing atmosphere, and transmission electron microscopy showed that Cu nanoparticles about 6.5 nm in size were uniformly dispersed in the PI film. Curing by RTA is an attractive method because it takes only a few minutes.

Formation of Cu or Cu2O nanoparticles embedded in a polyimide film for nanofloating gate memory.

Cu and Cu2O nanoparticles were fabricated in polyimide by curing the stacked polyamic acid/Cu/polyamic acid on Si wafer and post heat treatment. Nanoparticle distribution in polyimide (a monolayer of vertically aligned nanoparticles or the randomly dispersed nanoparticles) can be controlled by changing the reactivity of Cu with PAA and curing atmosphere. About 6-7 nm sized Cu or Cu2O nanoparticles were observed in the polyimide film. The capacitance-voltage curves were measured with Al/particles in polyimide/p-Si(100) specimens at 300 K, and the capacitance hystereses were observed at different sweep voltage ranges, which indicates that Cu2O or Cu nanoparticles can be utilized in next generation flash memories.