Roll or web coating on polymer substrates is done by magnetron or other techniques of sputtering. The optical and electronic properties of ITO films are highly dependent on the deposition parameters and the starting composition of evaporation material used. The deposited film layer must contain a high density of charge carriers for it to conduct. These carriers are free electron and oxygen vacancies, and an excessive population produces absorption. The refractive index for a film that is transparent in the visible region remains near 1.95 and is not strongly dependent on the deposition parameters.
Index is generally of secondary concern for conducting applications.
The extinction coefficient will vary with conductance. The deposition parameters play interdependent roles in the optimization of film properties. Principal among the deposition parameters are partial pressure of oxygen, substrate temperature, rate of deposition and material composition. For sputter processes, a high energy plasma can be substituted for a high substrate temperature. Recommended preconditioning consists of slowly sweeping a low power electron beam to gradually and uniformly fuse the surfaces of the material and avoid hole drilling by the beam.