Aerosol jet 3D printing and high temperature characterization of nickel nanoparticle films

Three-dimensional (3D) nanoparticle printing has emerged as a versatile and environmentally friendly manufacturing technique to fabricate metallic films for microelectronic applications. In this letter, we report the synthesis of 500 nm thick nickel films by aerosol jet nanoparticle printing and assess their stability at high temperatures. In-situ impedance spectroscopy is used to measure the electrical properties of the films from 25 °C to 500 °C, at frequencies from 0.02 kHz to 300 kHz. It is observed that the real part of impedance of the films increases from room temperature to 350 °C monotonously, indicating a positive temperature coefficient of resistance (TCR). Upon further heating, however, the films exhibit an unstable electrical behavior, with TCR increasing by two orders of magnitude between 350 °C and 500 °C. Thermogravimetric analysis (TGA) of nickel nanoparticles was performed to understand the underlying reason of electrical instability beyond 350 °C, which showed that the particle oxidation starts at about 325–350 °C and leads to a mass gain of 19.35% at 500 °C, indicating significant thermal oxidation. The electrical stability of the films at high temperatures is thus controlled by their thermal oxidation, which starts at a much lower temperature (350 °C) when compared to bulk nickel (600 °C). Implications of this result on the applicability of the 3D printing method to synthesize metal films for high temperature applications are discussed.