Tin dioxide ultrafine particle thin films were deposited by the dc gas discharge activating reaction evaporation technique over four different substrates: fused quartz, monocrystalline Si, microcrystalline glass, and commercial glass. Changes in both the morphology and crystallinity of the films were studied by scanning tunneling microscopy and X-ray diffraction, respectively, as a function of different substrates and deposition conditions. The results showed that the morphology and crystallinity strongly depended on not only the nature of the substrate, but also the deposition conditions. The interesting surface “structural unit” was obtained by using a higher dc gas discharge voltage under relative low oxygen partial pressure (V d 82 611100 V and P(O 2 ) = 5.0 Pa). It suggests that a high discharge voltage was necessary to obtain the films with rich crystallinity and/or special microstructure.