  A method for combinatorial sputter deposition of thin films on microparticles
is presented. The method is developed for a laboratory-scale magnetron sputter
system and uses a piezoelectric actuator to agitate the microparticles through
oscillation. Custom-made components enable to agitate up to nine separate
batches of particles simultaneously. Due to the agitation, the whole surface of
the particles can be exposed to the sputter flux and thus can be completely
covered with a thin film. By sputtering a CrMnFeCoNi high entropy alloy target,
separate batches of polystyrene microspheres (500 um monodisperse diameter), Fe
alloy particles (300 um mean size) and NaCl salt particles (350 um mean size)
were simultaneously coated with a homogeneous thin film. In contrast, a
CrMnFeCoNi thin film that was deposited on agglomerating Al particles (5 um
mean size) only partially covers the surface of the particles. By co-sputtering
a CrMn, an FeCo and a Ni target, nine separate batches of Al particles (25 um
mean size) were coated with a CrMnFeCoNi thin film with a composition gradient.
These depositions demonstrate the ability to coat different types of particles
with uniform films (from elemental to multinary compositions) and to deposit
films with composition gradients on uniform particles.
