Measurement of UV from a Microplasma by a Microfabricated Amorphous Selenium Detector

We spectrally demonstrate for the first time that an amorphous selenium metal-semiconductor-metal detector can be used for the measurement of ultraviolet photons (200-400 nm) generated from a portable battery-operated microplasma that is used as a light source. An advantage of this low-cost detector is that the device structure allows photons to strike the light-sensitive layer directly rather than through electrodes or blocking layers. Another advantage is that despite operation at high electric fields of up to 43 V/mu m, the dark current of the detector at room temperature is 3 pA/mm(2). Therefore, detector cooling is not required, and this facilitates portability for measurements on-site (i.e., in the field and away from a laboratory). Spectral response was monitored using a scanning monochromator, and it was compared with that obtained by a portable spectrometer fitted with a linear charge-coupled device detector. To demonstrate detector responsivity, emission signals with an appreciable signal-to-noise ratio were obtained by introducing nanogram amounts of the sample into the microplasma.