A study of electrical conductance of hydrogenated amorphous silicon(a-Si:H) films deposited on optical waveguides in a soda-lime glass (SLG) substrate is carried out, from the viewpoint of electrical instability ofa-Si:H caused by the penetration of Na ions from the glass into the film. The optical waveguides were prepared byK+–Na+orAg+–Na+ion exchange using thermal or field-assisted methods. The effective thickness of optical waveguides was of several micrometers. The obtained results show that in the case ofa-Si:H film deposited on silver waveguide there is a dependence of electrical conductance on measurement duration, if strongly weakened as compared with film deposited on the original SLG substrate. Thea-Si:H films deposited on potassium waveguide and on Na-extracted surface are as stable, as the referent samples with Corning 7059 (Na-free) glass substrate. ©1997 American Institute of Physics.