Abstract: An installation having a housing, a substrate support (20) received in the housing, diffuser (42) for diffusing an inert gas towards the substrate support, and at least one head (30) defining an inner volume (V) opened opposite to the top, the head being provided with at least two electrodes (8, 8?, 8?) for creating an electric discharge and with an injector (7, 7?, 7?) for injecting a gaseous mixture towards the substrate. The injector has at least one injection tube (7, 7?, 7?) placed between two adjacent electrodes or between one electrode and a peripheral wall, the tube being provided with injection holes facing the substrate support, for injecting the gaseous mixture on the substrate, whereas diffuser is provided inside the head, the injection tube being placed between the substrate support and the diffuser so that, in use, the gaseous mixture is urged against the substrate by the inert gas.