Probing the effects of thermal treatment on the electronic structure and mechanical properties of Ti-doped ITO thin films

• Published in: Journal of alloys and compounds 2017-10, Vol.721, p.333-346
• Main Authors: Taha, Hatem, Henry, David J., Yin, Chun-Yang, Amri, Amun, Zhao, Xiaoli, Bahri, Syaiful, Le Minh, Cam, Ha, Nguyen Ngoc, Rahman, M. Mahbubur, Jiang, Zhong-Tao
• Format: Article
• Language: English
• Subjects: Annealing; Chemical bonds; Chemical compounds; Chemical synthesis; Electron spin; Electronic structure; Heat treatment; Indium tin oxides; ITO; Mechanical properties; Modulus of elasticity; Nanoindentation; Oxidation; Protective coatings; Raman spectroscopy; Sol-gel; Sol-gel processes; Spin coating; Temperature; Thermal treatment; Thin films; Tin; Titanium doped indium tin oxide; Titanium nitride; Transparent conductive oxide; Wear resistance; X ray photoelectron spectroscopy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.06.007

Titanium-doped indium tin oxide thin films were synthesized via a sol-gel spin coating process. Surface chemical bonding states and mechanical properties have been investigated as a function of titanium content (2 and 4 at%) and annealing temperature ranging from 400 to 600 °C with increments of 100 °C. Raman analysis was performed to study the phonon vibrations for the prepared samples and the results revealed the existence of ITO vibrational modes. The elemental compositions, bonding states and binding energies of the film materials were investigated using X-ray photoelectron spectroscopy (XPS) technique. The XPS results indicated that the ratio of the metallic elements (In, Sn, Ti) to the oxygen on the surface of the thin film coatings decreased due to the increase of the oxide layer on the surface of the thin films. Also, by increasing the annealing temperature up to 600 °C, the Ti 2p and Cl 2p signals were no longer detected for both 2 and 4 at% Ti contents, respectively, due to the thicker surface oxidation layer. Mechanical properties of the synthesized films were also evaluated using a nanoindentation process. Variations in the hardness (H) and the elastic modulus (E) were observed with different Ti at% and annealing temperatures. The hardness is within the range of 6.3–6.6 GPa and 6.7–6.8 GPa for 2 and 4 at% Ti content samples, respectively, while the elastic modulus is within the ranges of 137–143 and 139–143 GPa for 2 at% and 4 at% Ti contents samples, respectively. A combination of the highest H and E were achieved in the sample of 4% Ti content annealed at 600 °C. Furthermore, the H/E ratio ranges from 4.5 × 10−2 to 5.0 × 10−2 which reflects a reasonable level of wear resistance. •Ti-doped ITO thin films synthesized via spin coating technique.•Ti contents (2 and 4) at% and post annealing (400–600°) C were used.•Surface chemical bonding states were determined via XPS.•Hardness is in the range 6.3–6.8 GPa.•Young's Modulus is in the range 137–143 GPa.