Dong Joo Choi

Synthesis of dual nanoparticles embedded in polyimide and their optical properties

AbstractWe investigated the formation of Cu or ZnO nanoparticles and mixture of Cu and ZnO nanoparticles dispersed in polyimide (PI) films using Cu(NO3)2 and Zn(NO3)2 salts. Each metal salt or the mixture of Cu(NO3)2 and Zn(NO3)2 salts was blended with N-methyl-2-pyrrolidinone and polyamic acid (PAA), and the solutions were spin-coated onto the substrates. Metal and metal oxide nanoparticles formed in PI films during the imidization of PAA to PI in a reducing atmosphere. X-ray diffraction analysis showed that a single phase of Cu or ZnO nanoparticles, or mixture of Cu and ZnO nanoparticles formed in PI films depending on the metal salt types, and transmission electron microscopy revealed that Cu and ZnO nanoparticles were dispersed in the PI matrix. The absorption spectra showed a surface plasmon resonance peak (SPR) of Cu nanoparticles around 600 — 620 nm or an absorption shoulder of ZnO nanoparticles around 360 — 370 nm. The SPR peak was blue-shifted in nanocomposites containing dual nanoparticles in comparison with nanocomposites containing single Cu or ZnO nanoparticles.

Formation of Cu or CU 2 O nanoparticles embedded in a polyimide film for nanofloating gate memory

A Cu nanoparticles/polyimide (PI) or CU2O nanoparticles/PI hybrid materials were fabricated by curing at 350°C for 2 hours in H2 or N2 atmosphere respectively, which resulted from the decomposition of the complex formed between a Cu film and the PI precursor, polyamic acid (PAA). Two kinds of PI films, thermosetting PI and thermoplastic PI were used. The Al was deposited on the top PI as the top electrode and In as the bottom electrode was soldered on the back side of the samples. The memory effect of Al/PI/Cu (or CU2O) nanoparticles/PI/ju-type Si (100) structure will be also discussed with the results of the capacitance-voltage (C-V) measured at room temperature.

A peel adhesion study of electroless Cu layers on polymer substrates

ABSTRACT The peel adhesion between two different electroless-plated Cu layers and polymer substrates was studied. Cu was electroless-plated onto polymer substrates using two different commercial solutions with different compositions. The adhesion strength between the electroless Cu layers and polymer substrates was measured with the 90° peel test. The adhesion was influenced by the coverage, grain size, and the thickness of the electroless Cu layer. Poor coverage of the electroless Cu layer increased the density of the pores at the interface between the Cu layer and the substrates, thereby degrading the adhesion strength because of a decrease in the contact area. In addition, the electroless Cu layers with larger nodules and larger grains were softer and had higher peel adhesion since the soft and ductile Cu layer promoted a greater amount of plastic deformation during the peel test. This led to enhanced peel adhesion. Finally, as the thickness of the electroless Cu layer increased, the peel adhesion decreased. The thicker Cu layers are not easily bent. Poor bending of the Cu layer induced less plastic deformation, causing a decrease in the peel adhesion. In conclusion, soft and thin electroless Cu layers with greater coverage are preferred in order to obtain good adhesion.

Fabrication of copper nanoparticles in 6FDA-ODA polyimide film

We investigate the formation of Cu nanoparticles in a polyimide (PI) film. The Cu nanoparticles were uniformly dispersed in the PI film by curing a precursor of PI, polyamic acid (PAA) containing Cu ions. The PAA was imidized to PI at 350°C for 2 hours in forming gas (5% H2+95% N2), accompanying the nanoparticle precipitation. X-ray diffracton patterns revealed that Cu nanoparticles formed by curing in a reducing atmosphere, and transmission electron microscopy showed that about 5 nm sized Cu nanoparticles were dispersed in the PI film.