Multi-mode resistive spectroscopy for precisely controlling morphology of extremely narrow gap palladium nanocluster array.

During the deposition of a metallic material on a substrate, a nanocluster-array structure with an extremely narrow gap is formed transiently at the transition between isolated clusters and the continuous film. It is known that the nanocluster array shows a unique electrical property different from that of isolated clusters and the continuous film. The electrical property of the nanocluster array changes significantly depending on its morphology, and precise control of the deposition time is indispensable to obtain a desired electrical property. However, the detection of the transition is not straightforward. To overcome this problem, we develop the multi-mode resistive spectroscopy. It evaluates the morphological change during deposition using resonant vibrations of a piezoelectric material and enables the fabrication of nanocluster arrays with a slightly different morphology. Palladium nanocluster arrays with different morphologies are fabricated using this method, and the availability of the multi-mode resistive spectroscopy is demonstrated by evaluating their electrical response to hydrogen gas.