Solid-state VUV lamp created in Japan

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 – the range of vacuum-UV light. The new lamp is 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.

Vacuum UV (VUV) 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.

The potential of the VUV lamp to be powerful tool for the surface treatment and optical cleaning was demonstrated S. ONO/Nagoya Institute of Technology (NITech)

The new lamp avoids issues associated with existing commercial vacuum UV lamps, which are bulky and expensive, use a lot of power, run hot and have short lifetimes, and contain toxic gasses that can pollute the environment and harm people.

In a report published in APL-Materials*, the Japanese team describes how this solid-state phosphor promises to make future, low-power vacuum UV lamps that will be more flexible in design as well as being smaller, longer lasting and relatively heat-free – all traits that are typical advantages of solid state lighting in general.

"Our lamp is a promising light source in terms of lifetime, size, heat conduction and stability," said Shingo Ono, an associate professor at the Nagoya Institute of Technology in Japan, who led the research. "[It] has the potential to be an excellent alternate light source to low-pressure mercury lamps, excimer lamps and deuterium lamps."

In addition to Professor Ono and his colleagues at Nagoya Institute of Technology, the team was comprised of researchers from Universiti Teknologi Malaysia; the Tokuyama Corporation in Tokyo; Tohoku University in Sendai, Japan; and the Kyushu Institute of Technology in Kitakyushu, Japan.

One of the hurdles they faced was to safely fabricate the phosphor using a compound containing fluoride, which is itself a toxic, corrosive and potentially dangerous chemical to handle. One way would have been to use an inflow of gaseous fluoride to coat the surface of the KMgF3 thin film, but instead the team discovered a safer route to fabricating it with pulsed laser deposition -- a way of layering thin films of chemicals onto surfaces through irradiation with a focused laser beam.