Structural properties of indium tin oxide thin films by glancing angle deposition method

Area of Science:

• Materials Science
• Thin Film Technology
• Optical Engineering

Background:

• Indium tin oxide (ITO) is a crucial transparent conductive material.
• Controlling the structural and optical properties of ITO films is essential for device performance.
• Glancing angle deposition (GAD) offers a method to tailor thin film microstructures.

Purpose of the Study:

• To investigate the impact of deposition angle and rate on the structural and optical properties of ITO films.
• To understand the relationship between film microstructure and optical characteristics.
• To optimize ITO film properties for potential applications.

Main Methods:

• Indium tin oxide (ITO) films were deposited on sapphire substrates using electron beam evaporation.
• Glancing angle deposition (GAD) was employed with varying deposition angles (0°, 30°, 45°, 60°) and deposition rates (2, 3, 4 Å/s).
• Ellipsometry was used to analyze film properties, including void fraction and refractive index.

Main Results:

• Increasing the deposition angle led to a higher void fraction and a decrease in refractive index (from 2.18 to 1.38 at 500 nm).
• The refractive index, particularly in the 550 nm-800 nm range, was also dependent on the deposition rate.
• Transmittance of a 235-nm-thick ITO film grown at 60° showed 20-80% coverage, increasing with deposition angle in the visible spectrum.

Conclusions:

• Deposition angle is a critical parameter for controlling the microstructure and optical properties of GAD-deposited ITO films.
• Higher deposition angles result in more porous structures with lower refractive indices.
• The findings provide insights for tailoring ITO films for specific optical and electronic applications through controlled GAD.