  Understanding the origin of planets that have formed in binary stars is
fundamental to constrain theories of binary and planet formation. The planet
occurrence rate in binaries with a separation $\lesssim 50$ AU is only $\sim$
one third that of wider binaries or single stars. This may indicate that a
close companion has a ruinous influence on planet formation, because it can
truncate the protoplanetary disc and pump up planetesimals eccentricity and
collision probability. Nevertheless, observations have revealed a few of these
systems, which challenge current planet formation theories. Dynamical
interactions can deliver planets into S-type orbits. In this paper, we consider
as a possible scenario for forming S-type planets in close binaries the single
star-binary star interactions that commonly take place in star clusters. We
find that the final fraction and orbital properties of S-type planets in close
binaries are mainly determined by the mass ratio of the stars involved in the
close encounter, and the initial binary and planet semi-major axes. Present and
upcoming missions, as TESS, PLATO and CHEOPS may shed new light on the origin
of S-type planets in close binaries.
