Emergence and Evolution of Crystallization in TiO2 Thin Films: A Structural and Morphological Study

Year: 2021

Authors: Durante O., Di Giorgio C., Granata V., Neilson J., Fittipaldi R., Vecchione A., Carapella G., Chiadini F., De Salvo R., Dinelli F.,; Fiumara V., Pierro V., Pinto I.M., Principe M., Bobba F.

Autors Affiliation: Univ Salerno, Dept Phys ER Caianiello, I-84084 Fisciano, Italy; Natl Inst Nucl Phys INFN, Sez Napoli Grp Collegato Salerno, I-80126 Naples, Italy; Univ Sannio, Dept Engn, DING, I-82100 Benevento, Italy; Univ Salerno, Natl Res Council, SuPerconducting & Other INnovat Mat & Devices Ins, I-84084 Fisciano, Italy; Univ Salerno, Dept Ind Engn, DIIN, I-84084 Fisciano, Italy; Ltd Liabil Co, RicLab, Pasadena, CA 91104 USA; CNR, CNR INO, Natl Inst Opt, I-56124 Pisa, Italy; Univ Basilicata, Sch Engn, I-85100 Potenza, Italy; Univ Naples Federico II, Dept Elect & Informat Technol Engn, I-80138 Naples, Italy; Museo Stor Fis & Ctr Studi & Ric Enrico Fermi, I-00184 Rome, Italy.

Abstract: Among all transition metal oxides, titanium dioxide (TiO2) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO2 thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250-1000 degrees C, and the TiO2 thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO2 thickness and annealing temperature, both ultimately affecting the degree of crystallinity.

Journal/Review: NANOMATERIALS

Volume: 11 (6)      Pages from: 1409-1  to: 1409-18

More Information: This research was funded by INFN (Italian National Institute for Nuclear Physics), and EGO (European Gravitational Observatory), under the projects Virgo and ET_ITALIA.
KeyWords: thin films; TiO2 anatase; crystallization; surface imaging; phonon lifetime
DOI: 10.3390/nano11061409

Citations: 28
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