CuInSe 2 thin films have been obtained by sequential evaporation of stacked Cu and In layers, and subsequent chalcopyrite formation using elemental Se within a close-spaced graphite container placed into a newly developed vacuum environment with flowing nitrogen. Semiconductor CuInSe 2 formation has been achieved by heating the metallic precursors at temperatures as high as 400 o C during the selenization process. At an intermediate stage, at 250 o C annealing temperature, various binary selenides have been detected as reaction predecessors for CuInSe 2 formation. The final structure and morphology of the CuInSe 2 thin films have been found dependent on these predecessor binaries, the presence and amount of which can be controlled by the nitrogen flux determining the reactor pressure. This pressure changes the relative kinetics of selenization of the metallic precursors due to the modification of the availability of reactive Se species. High reactor pressure inhibits the formation of Se-rich binary compounds, and thus the adhesion problems associated with the Se-excess losses induced by the formation of CuInSe 2 can be overcome.