Microstructural features correlated with the electrical properties and plasticity-based deposition of silver particles through the vacuum kinetic spray process

Abstract

Although the vacuum kinetic spraying (VKS) process is primarily used to fabricate thin films from ceramic materials, other materials or material combinations have also been deposited through this method. However, the detailed deposition process is not yet fully understood. In this study, the Ag particle deposition process and subsequent electrical resistivity of the patterned Ag coating fabricated on Al2O3 and Si substrates were investigated. Although Ag film was formed on both substrates, Ag coating on the Si substrate with a low roughness of 1.7 nm was easily peeled off while that on Al2O3 having a high roughness of 222.0 nm was well preserved, implying the importance of an anchoring layer for the film adhesive strength. Under gas flow rates of 10 and 18 L/min, patterned films formed on the Al2O3 substrate with the thickness of 1.37 and 2.26 μm, and accordingly, the measured electrical resistivities were 3.08 × 10−5 and 7.86 × 10−5Ω−Cm, respectively. In the coating microstructure, relatively large crystallites of 63.79 nm, high boundary/interface fractions, and interfacial nanopores were observed (unlike on typical VKSed films), which can deteriorate the electrical resistivity in addition to low pattern thickness and its shape. Furthermore, based on the findings, the deposition features of soft particles and hard substrates are discussed in terms of anchoring layer formation, initial weak bonding, deposited particle delamination, and bonding consolidation, and a plasticity-based deposition process is hypothesized.