Morphology and microstructure analysis of nano-silver thin films deposited by laser-assisted maskless microdeposition

Abstract

In this paper, the morphology and microstructure of silver micro-lines fabricated by laser-assisted maskless microdeposition (LAMM) are investigated. In LAMM technology, suspensions of silver nano-particles are used for layer-by-layer deposition and laser post-sintering. One of the major issues in LAMM is the large number of parameters involved in the process, which in turn results in a challenging process optimization. To address this issue, a design of experiments (DOE) method is used. The topography of the sintered samples was investigated using scanning electron microscopy (SEM) and white light interferometry. The results of DOE show that the deposition flow rate and the deposition scanning speed can significantly affect the width of the fabricated patterns, while the deposition thickness is mostly affected by the laser power and the number of deposited layers. In the microstructural analysis, it is observed that high laser effective energies can increase the densification of the sintered layers, in which the particles are closely packed. This is also evident from the level of electrical conductivity of the sintered samples. It is shown that the conductivity of the sintered samples is increased up to 2 × 105 S m−1 by raising the laser effective energy density to 2.5 × 106 J m−3. In addition, the results of mechanical tests, performed by a nanoindentation instrument, give a hardness of 0.8 GPa and Young's modulus of 50 GPa for the samples.