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Indium Tin Oxide in Chemistry

When it comes to the abbreviation “ITO”, it can be International Trade Organization, Involuntary Treatment Order, or Information Technology Outsourcing. But in chemistry, this abbreviation refers directly to a chemical material—Indium Tin Oxide.

What is Indium Tin Oxide in Chemistry?

Indium tin oxide (ITO) is a black-gray ceramic material mixed with indium oxide and tin oxide powder in a certain ratio. ITO has excellent electrical conductivity and transparency and can cut off electron radiation, ultraviolet rays, and far-infrared rays harmful to the human body. Therefore, ITO films are usually sprayed on glass, plastic and electronic display screens, used as a transparent conductive film, while reducing the harmful electronic radiation, ultraviolet and infrared. ITO sputtering target is an essential material for producing ITO films.

Now you may find there are many derivatives of indium tin oxide in chemistry, such as ITO sputtering target, ITO film, ITO glass, etc. Read on and you will figure them out.

indium tin oxide derivatives
Indium Tin Oxide Derivatives

Properties of Indium Tin Oxide

Property Value Reference
Mass density 6.8 g/cm3 J Vac Sci Tech A 19:5(2043-7); 2001
Young’s modulus (sputtered, 10wt% SnO2) 116 GPa Thin Solid Films 278:1-2(12-17); 1995
Poisson ratio (sputtered, 10wt% SnO2) 0.35 Thin Solid Films 278:1-2(12-17); 1995
Tensile or fracture strength
failure strain (105 nm film)
failure strain (16.8 nm film)
0.022
0.003
MRS Symp Proc 666 (F3.24.1 – 12); 2001
Residual stress on silicon
(sputtered, 10wt% SnO2)
-2.1 ~ -2.3 GPa Thin Solid Films 278:1-2(12-17); 1995
Index of refraction
(increases with anneal)
~1.7 @633 nm
1.8 – 2.0
Appl Surf Sci 179:1-4(181-90); 2001
J Vac Sci Tech A 19:5(2514-21); 2001
Electrical conductivity
(“standard” sputtered)
(epi, 5.7wt% SnO2)
~104 S/cm
1.3 x 104 S/cm
Thin Solid Films 411:1(1-5); 2002
Vacuum 66:3-4(419-25); 2002
Piezoresistivity: gage factor (sputtered)
(laser deposited)
0.2 ~ -14.7
2.04 ~ -77.71
J Appl Phys 91:9(6194-6); 2002
Thin Solid Films 288 (279-286); 1996
Wet etching method oxalic acid
HCl/HNO3
Langmuir 18:1(194-7); 2002
J Electron Mat 25:12(1806-17); 1996
Plasma etching method CH4/H2/Ar J Vac Sci Tech A 16:4(2177-86); 1998
Adhesion to silicon dioxide good – in pulloff tests of 1000 Å ITO and 1300-30,000 Å SiO2, failures occurred in substrate rather than ITO/oxide. Appl Surf Sci 115:1(96-102); 1997
Biocompatibility no observed inhibition of cell growth; small amount of protein adsorption Proc IEEE/EMBS Conf on Microtechnologies in Medicine & Biology (261-4);2002

Indium Tin Oxide Sputtering Target

Indium tin oxide sputtering target (ITO sputter target) is a mixture of indium trioxide (In2O3) and tin dioxide (SnO2), and is an important raw material for the preparation of ITO films. The theoretical density of the ITO target is 7115 g/cm3, while the high-quality ITO target should have a relative density of ≥99%. Such ITO targets have lower electrical resistivity, higher thermal conductivity, and higher mechanical strength. The high-density target can be sputtered on a glass substrate at a lower temperature to obtain a conductive film having lower resistivity and higher light transmittance, and even can be sputtered on the organic material.

ITO Target
Indium Tin Oxide Sputtering Target

There are four main ways to mold ITO sputtering targets, including spraying, cold isostatic pressing, hot isostatic pressing and wet forming. You can refer to Everything You Need to Know About ITO Sputtering Target for more information.

Indium Tin Oxide Film

Indium tin oxide film (ITO film) is an ITO semiconductor transparent conductive film prepared by vacuum evaporation or sputtering deposition. The film has high conductivity, high visible light transmittance, high mechanical hardness, and good chemical stability.

In recent years, ITO film has become more and more advantageous in the film manufacturing industry and has become one of the best performing transparent conductive oxides (TOCs). It is also the most commonly used thin-film material for transparent electrodes of liquid crystal displays (LCDs), plasma displays (PDPs), electroluminescent displays (EL/OLEDs), touch panels (TouchPanel), solar cells, and other electronic meters.

ITO Film
Indium Tin Oxide Film

The transmittance and resistance of the ITO film are controlled by the ratio of In2O3 and SnO2, respectively. Increasing the ratio of indium oxide can increase the transmittance of ITO, usually SnO2: In2O3=1:9. Since the thickness of tin oxide exceeds a certain degree, the transparency is usually not good enough – although the conductivity is good.

Indium Tin Oxide Glass

Indium tin oxide conductive glass (ITO glass) is made by processing a layer of ITO film by sputtering, evaporation, etc. on the basis of soda-lime-based or silicon-boron-based glass. Most electronic displays are ITO glasses.

ITO Glass
Indium Tin Oxide Glass

The ITO conductive glass applied to the LEDs also needs to be coated with a silicon dioxide barrier layer before the ITO layer is plated to prevent sodium ions on the substrate glass from diffusing into the liquid crystal in the cell. The ITO glass substrates for LEDs are generally ultra-float glass, and all the coated surfaces are glass float tin surfaces. Therefore, the final LEDs will follow the direction of the float, and irregular ripples will occur regularly.

Conclusion

In conclusion, the relationship between these three derivatives is: the ITO target is used to make ITO film, and the glass applied with ITO film is called ITO glass.

Thanks for reading this passage and hope that you now have a basic understanding of indium tin oxide in chemistryStanford Advanced Materials (SAM) is a leading sputtering target manufacturer based in Lake Forest, California. If you feel interested in the ITO sputtering target, you can go to our product page for more information, or directly send us an inquiry. You can also contact us via target@samaterials.com. Free samples are available.

About the author

Julissa Green graduated from the University of Texas studying applied chemistry. She started her journalism life as a chemistry specialist in Stanford Advanced Materials (SAM) since 2016 and she has been fascinated by this fast growing industry ever since. If you have any particular topics of interest, or you have any questions, you can reach her at julissa@samaterials.com.

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