Ultrathin entrance windows for silicon drift detectors

Detectors with ultrathin entrance windows have been fabricated, which show an overall improvement of the detector performance in the optical and X-ray region as well as for heavy ions. The quantum efficiency was higher than 60% within the entire wavelength range between 200 nm and 800 nm. In the soft X-ray region the spectroscopic resolution could be improved significantly. For the MnKα line a peak to valley ratio of 5700:1 was achieved. Measurements with241Am α-particles revealed an effective “dead” layer width of less than 150Å. mpatibility of the technology to produce thin entrance windows with the planar process allows its application on various pn-junction detector designs. A new silicon drift detector with a total area of 21 mm2 was successfully tested and operated at count rates up to 3 × 107s−1cm−2. At room temperature, the devices have shown an energy resolution for the MnKα line of 227 eV (FWHM) with shaping times of 250–500 ns, decreasing to 152 eV at −20°C. The fast readout in combination with a large detector area, a homogeneous entrance window and an exceptionally low noise without the need of an extensive cooling system makes them especially suited for spectroscopic applications in non-laboratory environments.