Growth of copper and gold nanoparticles on a polyimide surface

Abstract

Polyimide samples (30 mm×30 mm×50 μ m ) were immersed in copper or gold solution and irradiated with 6 MeV electrons over the fluence range 1014–1015 e/cm2. The diffusion of copper or gold in the polyimide were confirmed by the Rutherford backscattering (RBS) technique and the depth of diffusion estimated from the corresponding RBS spectrum, was found to be ∼2.2 μm for the copper and ∼0.41 μm for the gold, at an electron fluence of 2×1015 e/cm2. The diffusion-mediated growth of the copper or gold nanoparticles was confirmed from the plasmon resonance peak that appeared at ∼630 nm for the copper diffused and ∼560 nm for the gold-diffused polyimide, irradiated at an electron fluence of 5×1014 e/cm2. The shift in the plasmon resonance peak to lower wavelength, the broadening in the X-ray diffraction peak and to some extent the scanning electron microscopy images revealed that the average size of the particles decreased from 35 to 15 nm for copper and from 60 to 45 nm for gold, as the electron fluence was increased from 1014 to 1015 e/cm2.