| Transparent conductive films have introduced a great interest in the applications of Solar-cell, flat display, gas sensors, thermal conductive glass and so on. Aluminum doped zinc oxide (AZO) films is one of the most important transparent conductive films due to its high transmittance in the visible area (>80%), excellent conductivity(<10-3 ?·cm), wide resources, low costs and none toxic. However, the conductivity is still restricted by the large misfit between Si substrates and AZO film. It is necessary to analyze the interfacial misfit and carry out optimization design.In this work, a series of parameter process optimization were firstly conducted on the deposition of aluminum doped zinc oxide films using magnetron sputtering method. The influence of deposition temperature, sputtering power, and working pressure on the film properties and microstructure was detailed discussed. It was found out that when the sputtering power was adjusted for 100 W, Ar flow for 10 sccm, working pressure for 0.4 Pa, deposition temperature for 250?, the AZO film has a relatively low resistivity 3.75×10-3 ?·cm (150 nm). Moreover, samples with different deposition time were prepared to modify the different stages of film deposition. It was found out that when the deposition time was 5 min, film deposition was on the later stage of island growth, and when the deposition time was 20 min, film deposition was on the initial stage of coalescence.Using these parameters, AZO films with 30 and 150 nm were prepared on the substrates of (100)si, (110)Si, and (111)Si. The resitivity was ordered to be (100)Si> (110)Si> (111)Si.At the later stage of island growth, the thickness was about 30 nm, the AZO grains on the three substrates are in round shape and the mean grain size were measured to be 5.6,6.5 and 5.0 nm. At the initial stage of coalescence, the film thickness was about 150 nm, grains on the (100)si and (110)si elongated along [2110]ZnO, the grain size along each direction was measured to be 16.7/7.5 and 18.9/10.1 nm. Grains on the (111)si showed us a hexagonal shape, the grain size was measured to be 19.3 nm. At the latter stage of island growth, the grain size was dominated by the interfacial misfit and the surface energy, at this stage, the grain size can be predicated by the secondary O-Lattice model. At the initial stage of coalescence, the grain size was dominated by the elastic strain energy and the dislocation energy. At this stage, the grain size can be predicted by the combination of energy calculation and the secondary O-Lattice model.Based on the interfacial misfit analysis, Ag parallelism rule was used to calculate the potential irrational Si surface which can be used on the coherent growth of AZO film. On the basis of (100)Si surface, three kinds of irrational Si surface were achieved I1:(1,0.070,0)Si,I2 (1,0.037,0)Si, and I3:(1,0.098,0)Si; on the basis of (110)Si, three kinds of irrational Si surface were achieved I4(1,0.141)Si, I5:(1,1,0.073)Si, and I6:(1,1,0.132)Si; on the basis of (111)Si surface, no irrational Si surface was achieved. These Si surfaces have a series of periodical terraces with secondary dislocations which can decrease the interfacial misfit efficiently.Lastly, six kinds of Si substrates were prepared, and the film deposition was conducted. It was found out that, in the case of (100)Si series, the sheet resistance (5 min and 20 min) was efficiently decreased and the mean in-plane grain size on the three irrational Si substrates increased more or less in comparison with the grains on the substrate of (100)Si.The sheet resistance of with sample at the later stage of island growth has a decrease about 47% and the sample at the initial stage of coalescence has a decrease about 67% compared with the film on the substrate of (100)Si. Moreover, the grain spin phenomenon on the substrate of (100)Si disappeared on the three irrational Si substrates and the mean in-plane grain size increased more or less and agreed well with the sheet resistance. In the case of (110)Si series, only samples at the initial stage of island growth on the three irrational substrates have optimizing effect on the sheet resistance. The sheet resistance of I5 with sample at the later stage of island growth has a decrease about 39%. With the increase of the deposition time to 20 min, the optimizing effect disappeared. The mean in-plane grain size agreed well with the sheet resistance. Moreover, the grain spin phenomenon on the substrate of (110)Si disappeared on the three irrational Si substrates due to the optimization of the misfit along [2110]ZnO. A futher morphology investigation showed that, AZO grains on I4?I5?I6 have no obvious increase compared with grains on (110)Si substrates. |
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