  A technique using layered wavelength shifting, scintillating and
non-scintillating films is presented to achieve discrimination of surface
$\alpha$ events from low-energy nuclear recoils in liquid argon detectors. A
discrimination power greater than $10^{8}$, similar to the discrimination
possible for electronic recoils in argon, can be achieved by adding a 50 micron
layer of scintillator with a suitably slow decay time, approximately 300 ns or
greater, to a wavelength-shifter coated surface. The technique would allow
suppression of surface $\alpha$ events in a very large next-generation argon
dark matter experiment (with hundreds of square meters of surface area) without
the requirement for position reconstruction, thus allowing utilization of more
of the instrumented mass in the dark matter search. The technique could also be
used to suppress surface backgrounds in compact argon detectors of low-energy
nuclear recoils, for example in measurements of coherent neutrino-nucleus
scattering or for sensitive measurements of neutron fluxes.
