[Paper Review] Electrical and optical properties of ITO thin films prepared by DC magnetron sputtering for low-emitting coatings

Hadi Askari, Hamidreza Fallah+2 more|arXiv (Cornell University)|Sep 18, 2014

ZnO doping and propertiesMaterials Science1 references20 citations

TL;DR

This study investigates DC magnetron sputtering of ITO thin films on glass substrates to optimize low-emissivity (low-e) coatings with high infrared reflectance and visible transparency. By tuning sputtering power and oxygen flow at 400 °C, the authors achieved 89.5% infrared reflectance (emittance <11%) and 85% visible transparency, with carrier concentration and plasma wavelength measured for optimal electrical and optical performance.

ABSTRACT

Optimized DC magnetron sputtering system for the deposition of transparent conductive oxides (TCOs), such indium tin oxide (ITO) on glass substrate has been applied in order to achieve low-emitting (low-e) transparent coatings. To obtain the concerned electrical resistance and high infrared reflection, first the effect of applied sputtering power then oxygen flow on the properties of films have been investigated. The other depositions parameters are kept constant. Film deposition at at temperature 400 degree of Celsius in oxygen flow of 3 Standard Cubic Centimeters per Minute results in transparent and infrared reflecting coatings. Under this condition the highest attained average reflectance in the infrared is (λ=3-25 micron) 89.5% (lowest emittance equals to less than 11%), whereas transparency in the visible is 85% approximately. Plasma wavelength and carrier concentration was measured.

Motivation & Objective

• To develop transparent conductive oxide (TCO) coatings with low thermal emissivity for energy-efficient windows.
• To optimize ITO thin film deposition using DC magnetron sputtering for enhanced infrared reflectance and visible transparency.
• To investigate the influence of sputtering power and oxygen flow on electrical and optical properties of ITO films.
• To achieve a balance between high infrared reflectance and high visible transmission for low-e coating applications.
• To measure plasma wavelength and carrier concentration to correlate with film performance.

Proposed method

• DC magnetron sputtering was used to deposit ITO thin films on glass substrates at a fixed temperature of 400 °C.
• Sputtering power and oxygen flow rate were systematically varied while other deposition parameters were held constant.
• Oxygen flow was optimized at 3 sccm to achieve desired film stoichiometry and electrical properties.
• Optical transmittance and reflectance were measured across the visible (400–700 nm) and infrared (3–25 μm) spectral ranges.
• Plasma wavelength and carrier concentration were experimentally measured to evaluate electrical performance.
• Film thickness and surface morphology were characterized to support optical and electrical analysis.

Experimental results

Research questions

• RQ1 How does varying sputtering power affect the electrical and optical properties of ITO thin films?
• RQ2 What is the optimal oxygen flow rate for achieving high infrared reflectance and visible transparency in ITO films?
• RQ3 Can ITO films deposited via DC magnetron sputtering achieve low emissivity (<11%) while maintaining high visible transmittance (>80%)?
• RQ4 What is the relationship between carrier concentration and plasma wavelength in sputtered ITO films?
• RQ5 How do deposition temperature and oxygen flow jointly influence film performance for low-emissivity coatings?

Key findings

• At 400 °C and 3 sccm oxygen flow, the ITO film achieved an average infrared reflectance of 89.5% across the 3–25 μm range.
• The film exhibited an emissivity of less than 11%, confirming its suitability for low-emissivity applications.
• Visible transmittance reached approximately 85% in the 400–700 nm range, indicating high optical clarity.
• Carrier concentration and plasma wavelength were measured, providing insight into the film's electrical conductivity.
• Optimal film performance was achieved at a specific combination of sputtering power and oxygen flow, with other parameters held constant.
• The study confirms that DC magnetron sputtering can produce high-performance ITO coatings for energy-efficient glazing.