AsianScientist (Apr. 30, 2014) – A team of researchers in Japan has developed a solid-state lamp that emits high-energy ultraviolet (UV) light at the shortest wavelengths ever recorded for such a device, from 140 to 220 nanometers. This is within the range of vacuum UV light, so named because while light of that energy can propagate in a vacuum, it is quickly absorbed by oxygen in the air.
Vacuum UV light is extremely useful for industrial applications from sterilizing medical devices to cleaning semiconductor substrates because when it strikes oxygen-containing molecules on a surface, it generates highly reactive oxygen radicals, which can completely destroy any microbes contaminating that surface.
Existing commercial vacuum UV lamps are bulky and expensive. They also use a lot of power, generate excessive heat, have short lifespans and contain toxic gasses. The new lamp avoids those issues because it was fabricated with a solid-state phosphor made from a thin film of KMgF3, which is easy to make, avoids the use of toxic gasses and does not require expensive rare earth elements.
Published in the journal APL-Materials, the Japanese team led by Shingo Ono of the Nagoya Institute of Technology describes how this solid-state phosphor could be used in future low-power vacuum UV lamps that will be smaller and more flexible in design, longer lasting and relatively heat-free, traits that are typical advantages of solid state lighting in general.
One of the hurdles they faced was working with fluoride, which is toxic and corrosive. One solution would have been to use an inflow of gaseous fluoride to coat the surface of the KMgF3 thin film. Instead, the team discovered a safer route of fabricating by using pulsed laser deposition, a way of layering thin films of chemicals onto surfaces through irradiation with a focused laser beam.
“Our lamp is a promising light source in terms of lifetime, size, heat conduction and stability,” said Ono. “[It] has the potential to be an excellent alternate light source to low-pressure mercury lamps, excimer lamps and deuterium lamps.”
The article can be found at: Yanagihara et al. (2014) Vacuum ultraviolet field emission lamp utilizing KMgF3 thin film phosphor.
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Source: AIP Publishing.
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