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: Department of Physics “E.R. Caianiello”, University of Salerno, Fisciano, 84084, Italy; National Institute of Nuclear Physics (INFN), Sezione di Napoli Gruppo Collegato di Salerno, Napoli, 80126, Italy; Department of Engineering, DING, University of Sannio, Benevento, 82100, Italy; National Research Council-SuPerconducting and Other INnovative Materials and Devices Institute (CNR-SPIN), University of Salerno, Fisciano, 84084, Italy; Department of Industrial Engineering, DIIN, University of Salerno, Fisciano, 84084,Italy; RicLab, Limited Liability Company, Pasadena, CA, 91104, United States; National Research Council-National Institute of Optics, CNR-INO, Pisa, 56124, Italy; School of Engineering, University of Basilicata, Potenza, 85100, Italy; Department Electrical and Information Technology Engineering, University of Naples “Federico II”, Napoli, 80138, Italy; Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, 00184, 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.


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