| Molybdenum is a common kind of rare metal, and it is widely used in industry, aerospace field and daily lives because of its high melting point, malleability, stable performance and resistance to corrosion. The Mo thin films is an important material of scattering layer, Ti-Mo alloy films have a good application prospects, MoN thin films are widely used in friction and wear components. As the CIS (CIGS) solar cell research and development, it is found that Mo can be used as a back electrode layer of CIS (CIGS) thin film solar cells, Even the best contact layer. In addition, the quality of Mo films have significant directly impact on the CIGS absorber layer nucleation, growth, morphology and crucial affect to the efficiency of solar cells as a back electrode. Currently, yet some studies of the back electrode is not clear.In this paper, the Mo thin films as a back contact of solar cell were deposited on soda-lime glass using DC magnetron sputtering process. The structure, morphology, and electrical properties of Mo films with the change of sputtering time, thickness of film, annealing temperature, substrate temperature have been performed by XRD, SEM, Stylus Profiler, four-probe tester et al.(1)The Mo bilayer films were deposited at high pressure firstly, then at low pressure. The results show that the buffer layer with rough surface and many defects has poor crystallization, and high resistivity, whose R-T relationship reflects the characteristics of the semiconductor. The resistivity of the thin film decreases with the top layer’s deposition time increasing, in addition, the R-T relationship of these films shows metal feature. Compared with the monolayer film, bilayer films have lower resistivity and shorter sputtering time, so it is great satisfied with the requirement of CIGS solar cell back electrode.(2) To maintain the total thickness of Mo bilayer films, it is changed the thickness ratio betwween low pressure and high pressure layer, it is studied that the structures, morphology and electrical properties of Mo thin films influence of annealing temperature. With the increase of the thickness of high pressure layer, the film crystallization becomes poor and the resistivity increased. At different annealing temperatures, when at room temperature, the crystallization of Mo bilayer films is poor, and the resistivity is high. With the increase of annealing temperature400℃, it had good crystallization and low resistance, with the temperature increased, the crystallization of the thin films were improvement, the resistivity were decreased. However, the annealing temperatures was too high will bereduced film quality, at500℃, crystallization and resistance is bad. Therefore, annealing temperature of400℃is of the best annealing temperature as Mo Back electrode.(3) The Mo thin film prepared at different substrate temperatures from room temperatures to300℃, the crystallization, resistivity changed rarely. The substrate temperatures rises to400℃, it shows good crystallization and low resistivity.500℃, owing to the high temperature from substrate temperature, the evaporation of atoms affect the characteristics of the film, and it shows that films decrease the grain size, the surface of the surface particles are made of a long strip, Corresponding, the roughness and resistivity increased.In this paper, Mo Monolayer thin film have been deposited with different deposition times. The films deposited at short time are preferentially oriented along (110) plane, and surface morphology of the films scatter triangular particles, and the electrical resistivity of films is low, The corresponding growth model of the Mo films is Thorton’s Zone Model. Accordingly, the films deposited beyond15min show (211) preferred orientation, there are rectangles particles on surface, the electrical resistivity is high. The corresponding growth model of the Mo films change from Thorton’s Zone Model to texture to crystal zone2structure. |
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