Investigation of atmospheric pressure filamentary discharges and its application for film deposition on inner surface of tubes, cavities and flat surfaces

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A new plasma source for thin film deposition inside long thin tubes as well as on at surfaces at atmospheric pressure conditions has been developed in the first phase of the FOR 1123. The developing plasma may be separated in a leader-type plasma between the driven and the grounded electrode and a bullet-like outside the electrodes. Leader discharges in argon with small methane admixture are ignited inside the tube to be coated. Amorphous carbon films with good quality are deposited inside the tube within the leader region. Under the grounded area, the leader is transformed to a bullet-discharge. The leader plasma has been characterized by quantitative OES using a recently published method. On this basis, a plasma chemical model has been developed. In the next phase of the project we will: 1) compare our OES method with TALIF and absorption spectroscopy, 2) investigate the transformation of leader to bullet discharge time and space resolved, 3) analyze the bullet discharge and 4) evaluate the ignition of stepped leader discharge, the branching of leader discharge. Further on, under more technological aspects we will investigate 1) the homogenous deposition of long tubes using movable grounded electrodes, 2) of several tubes simultaneously and 3) of at surfaces with and without cavities.