  Bulk Scandium trifluoride ($\mathrm{ScF_3}$) is known for a pronounced
negative thermal expansion (NTE) over a wide range of temperature, from
$10~\mathrm{K}~\text{to}~ 1100~\mathrm{K}$. The structure of $\mathrm{ScF_3}$
can be described as an $\mathrm{ABX_3}$ perovskite with an empty A-site and a
space group of Pm-3m. Growing thin films of $\mathrm{ScF_3}$ allows for tuning
the lattice constant, the thermal expansion, and the construction of devices
based upon differential thermal expansion. We have investigated the growth of
$\mathrm{ScF_3}$ films on oxide and fluoride substrates using pulsed laser
deposition (PLD) This letter describes the successful growth recipe for
producing high quality epitaxial $\mathrm{ScF_3}$ thin films on positive
thermal expansion (PTE) lithium fluoride ($\mathrm{LiF}$) substrates, at
substrate temperature, $350^{\circ}\mathrm{C}$ with a laser repetition rate of
$1~\mathrm{Hz}$, with an energy per pulse of $600~\mathrm{mJ}$, under a vacuum
of $1.5\times 10^{-6}~ \mathrm{torr}$, for a growth time of $6$ hours. However,
even for films with excellent epitaxy and sharp peaks along the principal axes,
diffraction peaks from certain crystallographic directions are extremely broad,
with the example of ($104$) reflections, in this work. We attribute this
broadening to disorder in the $\mathrm{F_6}$ octahedral rotations that occur as
an attempt to accommodate the large temperature-induced lattice mismatch that
results in cooling from the growth temperature for this system of a NTE film
mated to a PTE substrate.
