Preparation And Characterization Of Bi_xSb_2-xSe₃ Thin Films Deposited By Silar Method

Bi₂Se₃ and Sb₂Se₃ compounds have so many merits that they are applied in the fields of photoelectric device, thermionic condenser and light information memorizer. If we can adopt a new process to combining Bi₂Se₃ and Sb₂Se₃ into Bi_xSb_2-xSe₃, it may possess some new material properties. Successive ionic layer adsorption and reaction (SILAR) method is a new films deposited technology which belongs to liquid growing films and holds some merits of chemistry bath deposited (CBD) method and atomy layer extension (ALE) method. This method appeared advantaged in preparing multi-compound films.A kind of simple films thickness device is invented through lots of experimentations by SILAR. We prepared many samples of Bi_xSb_2-xSe₃ thin films in different conditions and process parameters using this device. Some of samples were tested and characterized by electronic probe, XRD, XPS, SEM, AFM, ultraviolet -visible light spectrophotometer. After discussed and analyzed, some conclusions were drawn:(1) The samples of Bi_xSb_2-xSe₃ thin films, which were well-proportioned, compact andhad tight adhesion, had been grown on the glass substrate at room temperature by SILAR method. Elementary optimizing process parameters were gained, namely, Bi(NO₃)₃(pH equal to 6～6. 5) and C₄H₄KO₇Sb(pH equal to 7.5～8) acted as unitary cationic precursor, Na₂SeSO₃ (pH equal to 8～8. 5), reactant of Na₂SO₃ and Se powder acted as anionic precursor. The substrate was respectively immersed in cationic precursor solution and anionic precursor solution for 50s and 40s. The time of in flowing distilled water was 30s.(2) TEA effectively controlled reaction velocity, which stood guarantee for growingfiner quality films. SILAR cycles could expediently control the thickness of simples. The thickness attained 1.5～2.0μm after cycles were finished 100～150.(3) Testing results showed The sheet Resistance of Bi_xSb_2-xSe₃ thin films was about10⁵Ω./ with n-type conductivity. XRD showed the films appeared sharp reflection and crystal property greatly ameliorated at 230°C for 4 hours. The average grains size increased to 70～80nm from 50～60nm without annealing. Besides, the bandgap reduced after annealing. AFM and SEM testing showed: Bi_xSb_2-xSe₃ thin films were homogeneous , compact and well covered to the substrate surface.(4) The bandgap Bi_1.09Sb_0.91Se₃ and Bi_1.28Sb_0.72Se₃ were respectively about 1.73eV and1.58eV, which showed bandgap reduced as Bi content increased. So continuous various bandgap could gain through adjusting Bi content in Bi_xSb_2-xSe₃, which had theory values and applied merits to research new material and investigate new devices.