Study Of SnS₂,Cu₂SnS₃ Thin Films And Devices Prepared By RF Magnetron Sputtering

SnS₂ and Cu₂SnS₃ are novel semiconductor optoelectronic materials. In recent years,SnS₂ and Cu₂SnS₃ thin films have become research hotspots,due to their potential use in the areas of photovoltaic devices, photoelectric detectors and so on, as well as their low cost, lack of toxicity, earth-abundant constituent elements and excellent electrical and optical properties.In this thesis, the preparation and characterization of SnS₂ and Cu₂SnS₃ thin films by RF magnetron sputtering,and the characteristics of heterojunction devices based on SnS₂ thin films and Cu₂SnS₃ thin films were studied.A series of thin film samples have been deposited on glass substrates under various sputtering power and argon pressure by RF magnetron sputtering technique with an SnS₂ target.The effects of preparation conditions on the properties of the films were investigated.The crystal and phase structure of the thin films were studied by X-ray diffraction and laser Raman spectroscopy. The chemical composition, optical properties of the SnS₂ thin films were characterized by energy disperse X-ray spectroscopy,ultraviolet-visible-near infrared spectrophotometry ?UV-Vis-NIR?. The atomic ratio,optical constants and bandgap of the SnS₂ thin films were calculated and analyzed. The results show that the optimal condition for SnS₂ thin films is the sputtering power of 60W and the argon pressure of 0.5Pa,and the film is aligned along ?001? preferred orientation with the high transmittance and refractive index in the visible region,a small extinction coefficient and a direct bandgap of 2.81eV.Cu₂SnS₃ thin films were deposited on glass substrates by RF magnetron sputtering technique and then were rapidly annealed.The crystalline structure,phase composition,chemical composition, surface morphology and optical propertiesof Cu₂SnS₃ thin films grown using SnS₂ and Cu₂S mixture targets(the molar ratio of SnS₂ and Cu₂S of?1:1,1:1.5 or 1:2? and under different sputtering power ?40W and 80W? were investigatedby X-ray diffraction?XRD?, Raman spectroscopy?Raman?, energy dispersive X-ray spectroscopy?EDS?, atomic force microscopy?AFM? and ultraviolet-visible-near infrared spectrophotometry ?UV-Vis-NIR?.The results show that the optimal molar ratio of SnS₂ and Cu₂S for mixture target is 1:1.5, and all the prepared thin films using this target are crystallized. The higher sputtering power is beneficial for the improvement of crystalline quality, degree of preferential orientation and stoichiometry of thin films, for the decrease of roughness of thin films and for the enlargement of average crystallite sizes of thin films. The optical constants?refractive index, extinction coefficient and absorption coefficient?, dielectric constants and optical conductivity of thin films are calculated.Under the condition of sputtering power of 80W, the film sample possesses high crystalline quality and degree of preferential orientation,the least strain,the molar ratio Cu:Sn:S of 1.89:1:2.77,lower average surface roughness?0.742nm?,anaverage crystallite diameterof 332nm, the absorption coefficient of 104cm-1 and the direct band-gap of 1.32eV .The n-SnS₂/p-Si heterojuction devices were fabricated which exhibit good rectifying behaviors and weak photovoltaic properties. The photocurrent under the reverse bias voltage is increased by increasing illumination intensity.The photoconducting mechanism of the devices are controlled by the presence of exponential distribution of trap centers in the forbidden band of SnS₂. The p-Cu₂SnS₃/n-Si heterojuction devices were fabricated. The device exhibits good rectifying behaviors and photocurrent response properties.