Investigation of the Nanomechanical Properties of Crystalline Anatase Titanium Dioxide Films Synthesized Using Atomic La
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https://doi.org/10.1007/s11837-020-04347-6 Ó 2020 The Minerals, Metals & Materials Society
ADVANCED COATING AND THIN FILM MATERIALS FOR ENERGY, AEROSPACE AND BIOLOGICAL APPLICATIONS
Investigation of the Nanomechanical Properties of Crystalline Anatase Titanium Dioxide Films Synthesized Using Atomic Layer Deposition Y.S. MOHAMMED,1,2 K. ZHANG,2,3 P. LIN,2,3 H. BAUMGART and A.A. ELMUSTAFA 1,2,4
,2,3
1.—Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA 23529, USA. 2.—Applied Research Center, Thomas Jefferson Lab, Newport News, VA 23606, USA. 3.—Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529, USA. 4.—e-mail: [email protected]
Crystalline titanium dioxide (TiO2) polycrystalline films of 500 nm thickness were synthesized using atomic layer deposition (ALD) on p-type Si (100) substrates. The crystal structure, phase purity, film thickness and morphology were characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The nanomechanical properties were measured using nanoindentation. Due to low temperature ALD deposition, XRD revealed a single anatase phase growth. FE-SEM images indicate columnar grain structure growth primarily in the vertical directions. The hardness was measured as 5 GPa at 24% film thickness, which is considerably softer compared to the reported benchmark values of the well-known rutile phase of 12 GPa. The elastic moduli were estimated as 138 and 145 GPa for samples A and B, respectively. Samples A and B are identical except that sample A is slightly thicker; the slight difference in thickness has no influence on the results.
INTRODUCTION Titanium dioxide (TiO2) thin films have found their way into a plethora of applications and have enjoyed renowned attention. TiO2 films are used in artificial heart valves because of their superb biocompatibility.1 They are also used in heterogeneous catalysis as a corrosion-protective coating2 and as electrode material in lithium rechargeable batteries. The photocatalytic activity of TiO2 is exhibited in both the anatase and the rutile phases. Selfcleaning windows have been created by harnessing the photocatalytic properties of TiO2 coatings on glass. Hydroxyl radicals are generated upon exposure to ultraviolet light, which breaks down organic dirt on windows and simultaneously enhances
(Received April 24, 2020; accepted August 21, 2020)
hydrophilicity. Likewise, the photocatalytic properties of TiO2 thin films are manifest in medical applications such as bactericidal coatings of wound care gauze and surgical instruments. Investigating the effect of Sn content on the structural and photoelectrochemical properties of TiO2 nanostructure, Kumar et al. concluded that 3 at.% Sn doping impeded the formation of anatase structure and helped the formation of the rutile structure.3 In their study, the hydrophilic TiO2 nanostructure was grown by the sol–gel process.3 Mansoor et al. investigated the photoelectroc
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