Electron diffraction investigations carried out on flash evaporated mercury zinc sulphide films with mercury concentration ( atomic percentage, x ) in the range 0.16 ≤ x ≤ 0.84 grown on freshly cleaved single crystal KCl substrates maintained at temperatures (Ts) between 65°C and 225°C indicate the films grow as single phase ternary alloy films with b.c.c. structure. Presence of a single phase alloy of the type HgxZn1−xS in the films is corroborated by a single absorption edge observed in the optical absorption measurements. The lattice parameter varies between 5.26Å and 4.52 Å as ‘x’ is varied between 0.16 and 0.84. The lattice parameter is observed to decrease slightly with increase of Ts for all compositions. The average grain size is observed to increase between 0.020 microns and 0.058 microns with increase of Ts in all films. Results of room temperature d.c. resistivity measurements show the resistivity to decrease with increase in mercury concentration ‘x’ in the films at a given Ts; ( for ‘fs=225°C, ρ(x=0.16) = 100.6 Ω-cm and ρ(x=0.84) = 10−0.4 Ω-cm ). The resistivity of films with a particular mercury concentration is, however, observed to increase with increase in the substrate temperature; ( for x=0.84 film, typical resistivity values are, ρ(Ts = 65 C) =10−2 Ω-cm and ρ(Ts = 225 C) = 10−0.4 Ω-cm). The observed resistive behavior of the films hints towards predominant grain boundary conduction in the films.