Study On The Surface Structure Control And Property Of SiC/SiN_x Thin Films

The energy crisis and more serious environmental pollution have greatly pro moted therapid development of photovoltaic industry; it’s very important for the solar cells to speedup the popularization and application by reducing the cost and improving the photoelectricconversion efficiency. The high efficient thin film solar cells should be keeping a lowreflectivity and light trapping effectively in the solar spectrum range. The light trappingstructure is one of the effective ways to improve the solar cells light absorption and reducethe materials thickness which results in cost down, also can make more incident lighttransmit in no selective among full-wave band. This paper discusses the influence ofmagnetic field on the growth of thin films, to realize the light trapping structureoptimization under control, using magnetic field to affect the particle movement instead ofthe traditional chemical etching method.SiC/SiN_xthin films were deposited on the single crystal silicon, quartz glass andstainless steel substrate by R.F. magnetron sputtering, and the surface morphology,microstructure, the properties were characterized respectively by atomic (AFM), X-raydiffraction, steps meter, ultraviolet-visible spectrophotometer and scratch tester. Theinfluence of the common sputtering parameters on the growth, surface morphology and theproperties were studied systematically. On the base of the optimization of sputteringprocess parameters, the ideal result was obtained after the control of the additionalmagnetic field over the growth of SiC/SiN_xthin films to induce light trapping, which canprovide a good reference for us to reduce the cost and improve the films transmission rate.In addition, the relationship between the applied magnetic field and the microstructure,surface morphology and transmittance of the samples was discussed. The results s how that:(1) In a certain range, with the increase of the sputtering power, the thin films’ growthrate and the surface roughness gradually increase; the residual stress and the density of thefilms were improved; simultaneously, the films composite and membrane-adhesion gotbetter; similarly, the films refractive index became higher when the sputtering powerincreased, for example, the refractive index ranges between1.7and2.3, when thesputtering power got70W to160W. (2) The deposition rate increases with increasing sputtering pressure then decreaseswhen it came up to the maximum peak1.0Pa. At the same time, the surface roughnessdecreases, and tends to planarization. Relatively low sputtering pressure is helpful toimprove the kinetic energy and mobility of the particle on the thin films surface, which isbeneficial to the particle’s aggregation and the island formation.(3) The films prepared are still present amorphous structure or microcrystallinewhether the applied magnetic field was introduced or not, however, the surfacemorphology markedly got changed, especially in the strong magnetic field.(4) The transmission rate is not so high in the visible and near infrared band range(400~900nm), a maximum of only80%even with basal negative bias, that it is necessaryto increase. The applied magnetic field especial strong magnetic field can effectivelyimprove the optical transmittance of the samples, when the magnetic field in the center is1.50T, the optical transmittance of the SiC/SiN_xin the visible and near infrared wavelengthsection reached90%, close to the blank control group of quartz glass base, thus has goodoptical characteristics. This may due to the applied magnetic field reduces the nucleationactivation energy barriers of the films, promotes the films’ nucleation and growing up, alsoit can change the arrangement of atoms and molecules, matching and migration behavior,so the silicon nitride/silicon carbide films appeared more ideal light trapping.