We performed a comprehensive study on the La(1-x)Ca(x)MnO(3)/SrTiO(3):Nb junctions with different hole content and film thickness. It is found that the interfacial barrier, which determines the physical properties of the junctions, shows a strong dependence on crystallographic orientation, and it is substantially higher for the (110) than for the (100)-orientated junctions. The difference in barrier height is further found to exhibit a systematic variation with Ca content and film thickness (t). It reduces from similar to 0.09 to 0.02 eV for a x increase from 0.1 to 1 with a fixed t=200 nm, and experiences a growth by similar to 0.06 eV corresponding to the variation in t from 10 to 160 nm for a constant x=0.33. Similar phenomena have been observed in the La(0.67)Ba(0.33)MnO(3)/SrTiO(3):Nb junctions. In the scenario of different polarity mismatches at the (100) and (110) interfaces in the two series of junctions, these results can be qualitatively understood. (C) 2010 American Institute of Physics. [doi:10.1063/1.3447797]