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Detection and measurement for UV Sticker Labels |
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| Release time:2013-10-07 Source:admin Reads: | |
| Vacuum UV sticker label or VUV (wavelengths shorter than 200 nm) is blocked by air but can propagate through a vacuum. These wavelengths are strongly absorbed by molecular oxygen in the air. Pure nitrogen (with less than about 10 ppm oxygen) is transparent to wavelengths in the range of about 150 – 200 nm. This has practical significance, since semiconductor manufacturing processes have been using wavelengths shorter than 200 nm. By working in oxygen-free gas, the equipment does not have to be built to withstand vacuum. Some other scientific instruments that operate in this spectral region, such as circular dichroism spectrometers, are also commonly nitrogen-purged. Technology for VUV sticker label instrumentation was largely driven by solar astronomy physics for many decades, but more recently some photolithography applications for semiconductors have been developed in this range. While optics can be used to remove unwanted visible light that contaminates the VUV, in general, detectors can be limited by their response to non-VUV radiation, and the development of "solar-blind" devices has been an important area of research. Wide-gap solid-state devices or vacuum devices with high-cutoff photocathodes can be attractive compared to silicon diodes. Recently, a diamond-based device flew on the solar observation satellite LYRA (see also Marchywka Effect). Extreme UV (EUV) sticker label is characterized by a transition in the physics of interaction with matter: wavelengths longer than about 30 nm interact mainly with the chemical valence electrons of matter, whereas shorter wavelengths interact mainly with inner-shell electrons and nuclei. The long end of the EUV/XUV spectrum is set by a prominent He+ spectral line at 30.4 nm. XUV is strongly absorbed by most known materials, but it is possible to synthesize multilayer optics that reflect up to about 50% of XUV radiation at normal incidence. This technology, which was pioneered by the NIXT and MSSTA sounding rockets in the 1990s, has been used to make telescopes for solar imaging (current examples are SOHO/EIT and TRACE), and equipment for nanolithography (printing of very small-scale traces and devices on microchips). |
