Study Of Silicon Thin Films Deposited By Magnetron Sputtering

The solar cells is a new industry in China,which developing very fast in resent years.The higher performance price ratio of a-Si:H and c-Si:H thin film solar cells in silicon based solar cells was verified through the development of this field.The silicon thin films have been prepared by magnetron sputtering method in order to get scientific datum needed in the process to deposit high quality device-level films by optimizing the processing conditions.The magnetron sputtering is a simple,fast film deposition method,which can deposit doped silicon thin films without the usage of toxic or flammable gases,instead,use the polycrystalline as target to deposit films by Ar⁺ sputtering.The band gaps and properties were controlled by adjusting H₂ partial pressure and processing conditions.Compared to other film-deposition techniques, magnetron sputtering is a promising silicon thin film solar cells fabricating method for its high deposition rate and thus induced captivating economic efficiency.In the eyes of the author,this method is hopeful to reduce the cost of solar cells dramatically.The silicon thin films were deposited on float glass using sputtering and the properties and structure influenced by process parameters were studied.The conclusions of the thesis can be listed as follows:1,With the increasing of H₂ partial pressure,the optical bad gap(Eg) of Si:H films increased,the refractive index(n),absorption coefficient(α) and extinction coefficient(k) decreased.The intermediate range order of the silicon film decreases with increasing hydrogen dilution ratio.As the H₂ dilution ratio increasing,the deposition rate,increased at the beginning and then dropped,was over 10nm/min in condition of low sputtering power and high hydrogen dilution ratio.2,The improved substrate temperature lead to increased n,α,k as well as intermediate range order.Eg also be influenced by substrate temperature,and decreased gradually,then changed to be steady with the temperature increasing.3,Increasing of the sputtering current,with the exception of the sample deposited at the sputtering current of 0.14A,the band gap of the film is correspondingly decreased while the refractive index and the absorption coefficient increased.The intermediate range order of the silicon film is comparatively high when deposited at low sputtering power.The deposition rate almost monotonically increases with the sputtering current increasing and can reach 30nm/min at comparatively high sputtering power.4,With the increasing of wavelength,the reflective index,absorption coefficient and extinction coefficient(k) decreased.The Raman spectures reveal that there was no crystal grown in the deposition process.By changing the processing conditions,the absorption coefficient varied from 10⁴cm^-1 to 10⁵cm^-1,and the extinction coefficient changed arouned 0.3.5,The intermediate range order of films tested after Long-term placement, decreased dramatically from Raman spectrure.The IR spectrure reveals that there were Sill,SiH₂ or(SiH₂)_n groups and Si-O bonds existing in films and the state of these groups keep steadly with the increase of H₂ prossure.We also conclude from XPS that the deposited films are composed of N,C,O,Na,Si elements and the Na⁺ ion can not diffuse to the surface of the films which has the thickness of over 40nm even deposited at high temperature.