Magnetron sputtering process for homogeneous internal coating of hollow cylinders

Thin copper coatings were prepared on the internal surface of glass tubes with an inner diameter of 17.6 mm. Depending on the configuration of the applied magnetic field, the thickness of the coatings varies along the axial direction between maximal, graded, or constant in the middle of the substrates. By adjusting the magnetic field configuration and compensating asymmetries of the experimental set-up, coatings with a low deviation in thickness over more than 50% of the total substrate length were achieved. The coatings have a smooth surface and a dense structure with small grains.