Low temperature, pressure-assisted sintering of nanoparticulate silver films

Andre D. Albert ^a, Michael F. Becker ^b, John W. Keto ^c, Desiderio Kovar ^d
^a Materials Science and Engineering Program, Center for Nano and Molecular Science and Technology and Texas Materials Institute,
The University of Texas at Austin, Austin, TX 78712, USA
^b Department of Electrical and Computer Engineering, Center for Nano and Molecular Science and Technology, Texas Materials Institute,
The University of Texas at Austin, Austin, TX 78712, USA
^c Department of Physics, Center for Nano and Molecular Science and Technology, Texas Materials Institute,
The University of Texas at Austin, Austin, TX 78712, USA
^d Department of Mechanical Engineering, Center for Nano and Molecular Science and Technology, Texas Materials Institute,
The University of Texas at Austin, Austin, TX 78712, USA

Received 17 August 2007; received in revised form 14 December 2007; accepted 16 December 2007

Abstract
The laser ablation of microparticle aerosol (LAMA) process was used to direct-write nanostructured, patterned films of silver with
thicknesses in the range 20–200 µm at room temperature. A critical difference between the LAMA process and conventional processes
for depositing patterned, thick films is that the LAMA process does not require surfactants that can interfere with post-deposition sin-
tering. Thus, LAMA-produced films allow the intrinsic sintering of nanoparticulate films to be studied directly. Post-deposition sintering
was conducted over a range of temperatures (100–175 °C) and compression loads (25–600 N) and the strength and electrical resistivity of
the sintered samples were measured. The samples were characterized using optical microscopy, profilometry, SEM, and XRD and the
density of the deposits were determined from the grain size, resistivity and known relationships between these parameters and density.
LAMA-produced films were found to sinter to produce high strength, high conductivity films at temperatures 50–100 °C lower than con-
ventional processes that use organic additives. Mechanisms for the low-temperature sintering of the nanostructured films are discussed
and compared with established theory for pressure-assisted sintering.