Rheology printing of an ultra-fine conductive Ru–La–O line

Abstract

We previously developed a method for producing highly conductive RuO2 films using a solution-based process. In this paper, we describe the further development of this material to produce fine patterns for use in nano-sized devices through a newly developed direct imprinting process, named nano-Rheology Printing (n-RP). This process involves the fine patterning of the precursor gel by an imprinting process to generate fine solid patterns while avoiding potential pattern breakage during sintering. The pattern breaking is typically caused by the crystallization nature of an oxide material, which may become more prominent when the size is reduced to less than 100nm. To solve this problem, we investigated the properties of the Ru–La system and observed that a small addition of La to Ru greatly improved the viscoelastic property of the gel without any noticeable reduction of conductivity. The Ru–La system also exhibited an amorphous state over a wide composition range, and thus the fine gel patterns produced by the imprinting process were resistant to breakage during sintering. These unique properties of the Ru–La system were thought to result from the molecular crystalline nature of the La gel. Based on the results, the n-RP method could successfully fabricate a fine line of the Ru0.75-La0.25O oxide with a width of 30nm and with good conductivity.