Electrochromic materials
Summary:
J.A. Woollam Company, Inc. (Lincoln, NE), is developing an electrochromic material that can vary the amount of light and heat it transmits, depending on the amount of voltage that’s applied. BMDO was interested in developing these materials for thermal control of space satellites in orbit, although it could someday be used to make “smart windows” that can control the amount of light that passes through them. This research has also led to a spinoff product, a spectroscopic ellipsometer used in materials characterization. Sales of Woollam's ellipsometers and associated services came to $10 million for 1999.
Technology Description:
J.A. Woollam Company, Inc. (Lincoln, NE), is developing electrochromic material that can vary the amount of light and heat that it transmits, depending on the amount of voltage that is applied to the material. Woollam has demonstrated an electrochromic thin-film structure, operating in the mid-infrared (1 to 30 microns) range, that has a potential for switching up to 70% of the emissivity.
Small scale tests of the material’s emissivity have been completed and results published. A material made with thin layers of tungsten oxide and nickel oxide has been successfully operated, covering the spectral range from 300 nanometers to 30 microns. Reversible switching capabilities have been demonstrated repeatedly with these materials as well.
MDA Origins:
Woollam completed BMDO SBIR Phase I and II work in developing an electrochromic material for spacecraft thermal control.
Spinoff Applications:
Materials with variable light and heat transmissivity would be an important tool in regulating thermal control of a space satellite in orbit. Orbiting satellites undergo extreme changes in environmental conditions, so there is a strong need for a simple thermal control surface that can be operated with low electric power. Such a material would allow spacecraft to radiate heat (from onboard electronics) at levels that can be controlled from the ground.
Although Woollam's BMDO work focused on ways to regulate emissivity in the infrared range, the results can be applied to visible light as well. A major application for this technology would be “smart” windows that could regulate incoming light by changing degrees of transparency. The more opaque a window becomes, the less light it lets through. A window with electrochromic properties could also limit the amount of infrared heat entering as well, which allows for thermal control possibilities.
In addition to thermal control, this research might also be used in the creation of thermal infrared optical switches, in which the electrochromic material can control specific wavelengths of light. These switches could be used in laser defense weapons systems as well as in infrared optoelectronics.
Commercialization:
Although the research is still in the early stages, the company plans to transfer the deposition technology that creates this material to a commercial optical coatings company, once mature.
In the course of developing the materials, J.A. Woollam also developed extensive optical and thermal measurements experience and capability. This work has led to a line of spectroscopic ellipsometers that can offer far more information than standard spectroscopy testing instruments. An ellipsometer tests the chemical properties of materials by bouncing polarized light off the material's surface and analyzing the results. This instrument allows chemical labs, thin-film producers, and microchip manufacturing plants to improve quality testing and increase volume production through the nondestructive testing of materials. A new model has been introduced that operates in the infrared range. Other models offer unique features such as the ability to test epilayer thicknesses, doping densities in semiconductors, and chemical bonding information on a nanometer scale.
The company manufactures and sells five different models with the following features:
•VASE®: Automated with a spectral range available of 190-1700 nm
•IR-VASETM: An infrared spectral coverage from 2 to 33 microns
•M-2000TM: Rotating compensator technology and variety of spectral ranges available
•M-44/88TM: Optimized for speed for in-situ and ex-situ applications
•VUV-VASETM: Measuring a huge spectral range from 146nm to 1700nm. This is the only ellipsometer commercially available that can cover this range.
Sales of ellipsometers and associated services came to $8 million for 1998 and $10 million in 1999. These instruments are used in the semiconductors field, where instruments can be used in epitaxial wafer growth and dielectric materials development. They are also used in chemical analysis labs, where ellipsometry serves an alternative to the far more expensive Fourier transform infrared (FTIR) spectroscopy for use on opaque substrates and nanometer-scale films.
Company Profile:
The company was founded in 1987 by Dr. John A. Woollam. Starting as a spin-off from the University of Nebraska, the J.A.Woollam Company, Inc. specializes in spectroscopic ellipsometry hardware, software, and services. The company is located in Lincoln, Nebraska and employs 35 people.
Contact Information:
Dr. John Woollam
J.A. Woollam Company, Inc.
645 M Street Suite 102
Lincoln NE 68508
Tel:402-477-7501
Fax:402-477-8214
email: jwoollam@jawoollam.com
web: http://www.jawoollam.com
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