| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 104 === This study focuses on the processing and evaluation of TiNxOy thin films by DC unbalanced magnetron reactive sputtering using air as a reactive gas. The films were prepared on silicon, ITO glass, and glass substrates respectively and the films with different characteristics by varying the air ratio. Replacing nitrogen/oxygen mixed gas with air as a reactive gas allows the process to conduct at high base pressure of 1.3×10-2 Pa (low vaccum) which can greatly reduce the processing time and have more economically environmental benefits.
The main deposition parameters varied the air/Ar flow ratio with simple method in a range of 0.10-0.50. The experimental parameters of the working pressure (＝0.26 Pa), power (＝350 W), deposition time (＝20 min), substrate bias (＝-50 V) were fixed throughout the study. Comparing the color, crystal structure, microstructure, chemical composition, electrical, carrier concentration, carrier mobility, optoelectronic, mechanical, and capacitance are the properties of TiNxOy films with different air/Ar flow ratio. For comparison and evaluation, films were also deposited at a low base pressure of 1.1×10-3 Pa (high vaccum) and decrased the deposition time as well.
As the air/Ar flow ratio increased from 0.10 to 0.25, the films revealed color from golden→dark yellow→brown→silver to violet with rock-salt structured TiN→rock-salt crystalline TiNxOy and amorphous TiNxOy. The N/Ti of the films was 0.23-1.05 with 7-58% of oxygen. The resistivities of the films were in the range of 140-3.52×106 μΩ-cm from conductor to semi-conductor. They were n-type semi-conductors and major carrier of the films was electrons. The increase of air/Ar flow ratio causes the carrier concentration and carrier mobility decrease which oxygen content of the films makes the electron binding energy higher might remove valence electrons and extend the extent of oxidation can change the optoelectronic properties of the films. As air/Ar flow ratio at 0.25, the film was almost transparent and revealed semi-conductive material. The capacitance of the films decreased from 165.53 mF/cm2 to 0.4 mF/cm2 as the air/Ar flow ratio increased.
Nitrogen and oxygen content within the films and air were different because the dissociation energy of nitrogen and oxygen in the plasma were also different. The dissociation energy of nitrogen is smaller than that of oxygen, which enhances the impimgement rate of nitrogen. Furthermore, the surface energy of Ti, N and O on the films surface will also cause different content of nitrogen and oxygen within the films and air.
To evaluate the application of decorative coatings, the mechanism with different color of the films can be divided into two categories: intrinsic and extrinsic color. The films with intrinsic color are conductive, crystalline and opaque which are similar to metal. The films with different number of electrons will influence the configuration of electrons and present different of color. On the other hand, the films with extrinsic color are insulating, amorphous and transparent which are similar to oxide. The binding force of atoms in the films is strong and lead to decrease the electrons so the films will become transparent. Moreover, the films with different substrate, thickness and viewing angle might present variety color and colorful films. It might have a wide range of uses for decorative coatings.
Choicing air/Ar flow ratio at 0.15 and 0.20 to evaluate the application of transparent conductive films. It can elevate transmittance of the films by decreasing the deposition time. Although the films with the best transmittance of 56% and 67% as air/Ar flow ratio at 0.15 and 0.20 respectively at 1 min deposition time, the films are amorphous and insulating. However, resistivity and transmittance of the films decrease to 3440±30 μΩ-cm and 31% with 3 min deposition time and air/Ar flow ratio at 0.15 which have an opportunity to obtain transparent conductive films in this study.
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