Stress in polycrystalline GaN films prepared by r.f sputtering M. Pal Chowdhury, R. K. Roy, S. R. Bhattacharyya and A. K. Pal Eur. Phys. J. B, 48 1 (2005) 47-53 Published online: 09 December 2005 DOI: 10.1140/epjb/e2005-00379-8