Growth And Properties Of Ultrasmooth Al-Doped Silver Films On Glass Substrates

Silver has become an important material in modern industry because of its good conductivity and low loss in visible and infrared wavelength.Thus it plays an important role in many optoelectronic devices.But because of the poor wettability with some substrate materials such as silicon and silica,the roughness of the silver films grown on these substrates is very high,and the thermal stability is bad.These disadvantages limit its application in nanophotonic and optoelectronic devices.Therefore,in order to overcome the limitation of silver materials on photoelectric devices,how to improve the quality of silver films has been a hot spot for many years.In this paper,we successfully grow Al-doped silver films with smooth surface and good thermal stability by vacuum evaporation and proper doping.In this paper,we study the influences of the thickness and doping concentration and compare the results with pure silver films.The main conclusions are as follows:the surface roughness of Al-doped silver film is much lower than that of the pure silver film.In the range of 5%-25%doping concentration,the roughness of the Al-doped silver film decreases with the increase of the doping concentration.Moreover,in the range of 5nm-100nm thickness,the surface roughness of Al-doped silver films changes slightly with the increase of thickness.The thermal stability of Al-doped silver films is also better than that of the pure silver film.The surface morphology of the Al-doped silver film does not change obviously after 30 minutes of heat treatment.However,the Al-doped silver film is easier to oxidize in air,resulting in many small particles on the surface.One more layer of aluminum on the surface can effectively improve this problem.After analyzing the reasons for the different surface roughness and thermal stability of the Al-doped silver films and pure silver films,We think that the addition of aluminum increases the nucleation density at the beginning of the growth of the film,and induce the layer-by-layer growth mode during the growth process.Thus the growth patterns of Al-doped silver film is different from that of pure silver,leading to their different roughness.In addition,we calculate the optical constants of Al-doped Ag films by effective medium theory,and compare them with the experimental results.We find that with the increase of aluminum doping concentration,the absorption of Al-doped Ag films in visible band is enhanced.