AVS 49th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeP

Paper TF-WeP19
Growth Morphology of Sputter Deposited Vitreous Titanium Dioxide Films

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Poster Session
Presenter: J.D. DeLoach, Texas Instruments
Authors: J.D. DeLoach, Texas Instruments
R.S. Sorbello, University of Wisconsin-Milwaukee
G. Scarel, Laboratorio MDM-INFM, Italy
C.R. Aita, University of Wisconsin-Milwaukee
Correspondent: Click to Email
Room temperature growth of a ceramic film usually occurs by coalescence of three-dimensional nuclei. This initial morphology leads to column formation. The boundaries between columns can be open and can have a different physiochemistry than the column interior. In this study, we use high resolution transmission electron microscopy and electron diffraction to study the growth structure of TiO@sub 2@ films. The films were sputter deposited at room temperature on <111> Si substrates from which the nascent SiO@sub 2@ layer had not been removed. The film thickness ranged from 250 to 700 nm. The films' atomic structure was vitreous, that is, had no long range order. Most of the films’ volume was amorphous with short-range order characteristic of anatase Ti-O nearest neighbor coordination. The remaining volume consisted of both anatase and rutile nanocrystallites. The most striking morphological feature observed by HREM was a network structure encompassing both amorphous and nanocrystalline regions in all films. Isolated regions within this network were on the order of tens of nanometers, increasing in size with increasing film thickness. Suboxide rings on electron diffraction patterns indicate that the network may be conducting. We suggest that this network has a profound effect on the properties of as-grown TiO@sub 2@ films, in particular on their ultraviolet and infrared optical absorption behavior. A recent@footnote 1@ infrared absorption-reflection study showed that the model dielectric function which best fit the experimental data was obtained by averaging the dielectric functions of weakly interacting TiO@sub 2@ regions of different orientations. This result was surprising because of the large polarizability of TiO@sub 2@. Further analysis in the present study using a Maxwell-Garnett approach shows that this dielectric function is consistent with TiO@sub 2@ units embedded in a conducting network. @FootnoteText@ @footnote 1@G.S. Scarel et al. J. Appl. Phys. 91 1118 (2002).