Experimental and molecular dynamics study of the growth of crystalline TiO2

Abstract

Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputteringThin films of crystalline TiO 2 are of high interest due to their photoactivity and photoinduced hydrophilicity. Previously, preparation of TiO 2 has been described in terms of extrinsic process parameters, such as total pressure, oxygen partial pressure, or substrate bias potential. We study the growth of TiO 2 phases, rutile and anatase, by atom-by-atom molecular dynamics simulations. We focus on the effect of intrinsic process parameters including particle energy, growth temperature, and growth template. While experiments indicate that the deposition of rutile requires higher temperatures and/or energies compared to anatase, we show that the growth of previously nucleated rutile can take place in a wider range of temperatures and energies compared to anatase. In parallel, we show relationships between crystal growth and the lateral size of a crystal. The results facilitate defining new synthesis pathways for TiO 2 , and constitute phenomena which may be relevant for other ceramics. V C 2012 American Institute of Physics. [http://dx.

Atomic-scale aspects of oriented attachment

“…Briefly, in a study of nine promising force fields by Collins and Smith (1996), this potential was shown to be the best at reproducing the lattice energy, polymorphic structures, elastic and dielectric constants, and relative surface energies of TiO 2 . Further, this potential has been useful in a wide variety of applications (Eithiraj and Geethalakshmi, 2013;Houska et al, 2012;Salameh et al, 2012;Oliver et al, 1997;Bandura and Kubicki, 2003;Hamad et al, 2005;English et al, 2006;Dubrovinskaia et al, 2001). The Matsui-Akaogi force field has also been shown to perform similar to a more complex and computationally demanding variable charge model (Swamy and Gale, 2000;Swamy et al, 2001;Thomas et al, 2004).…”

Force field for realistic molecular dynamics simulations of ZrO 2 growth

“…temperature and ion bombardment) by changing just one parameter at a time. Thus, these simulations were successfully used to describe the growth of C [5], Si [6], SiC [7], SiNH [8], SiO 2 [1], MgAlO [2], TiO 2 [3] or Al 2 O 3 [4] (Ref. [4] also includes a more detailed overview).…”

“…Ref. [3] (TiO 2 ) or 4 (Al 2 O 3 ) for recent examples. On the other hand, for some equally important materials -e.g.…”

“…[4] shows that this choice may lead to even worse results. The latter choice, specifically the Buckingham interaction potential where r is the interatomic distance and q 1,2 are the charges), has been successfully used for atom-by-atom growth simulations [2][3][4]13,14] and may be therefore considered as a state of the art technique for modeling the growth of ionic metal oxides.…”

“…The latter technique (which this work deals with) has orders of magnitude lower computational costs and therefore it is crucial for simulations dealing with much larger systems and/or longer time evolutions. More specifically, one of the most important and increasingly popular strengths of classical molecular dynamics (MD) simulations is that they allow one to reproduce the atom-by-atom growth of thin film materials (most often prepared by plasma-assisted physical or chemical vapor deposition) and to obtain a lot of related information not accessible experimentally [1][2][3][4][5][6][7][8]. The first reason is that contrary to experiments, MD simulations allow one to disentangle crystal nucleation and crystal growth (by using crystalline ''substrate").…”