LAUSR

Energy dispersive x-ray analysis (XEDS) has increased its sensitivity with the introduction of windowless multi detector systems in transmission electron microscopy. Today routinely atomic resolution compositional maps and maps with big field of view (512x512 pixel) can be acquired within minutes of acquisition time[1]. Here the increased sensitivity due to the higher collection angles (~12srad), the use of SDD detectors with low deadtime and the windowless design are the main reason for this achievement[2]. Nevertheless windowless design creates a problem in detection at elevated temperatures since the sensors see the light of the heater element of the holder, which flood the sensor with signal and makes work at above 400 C impossible [3]. Even the use of MEMS based holders[4] with reduced heated area does not prevent this problem in XEDS analysis at high temperatures. The traditional way of preventing this effect is to introduce a metal window in front of the sensor to block the light of the heater to reach the sensor. But this approach reduces the sensitivity of the system significantly as you can see in the graph in figure 1, which compares windowless with windowed SDD detector in sensitivity. This strong decline in sensitivity is already caused by a thin polymer window, which still allows part of the light of the heater to reach the sensor and the effect using a metal window (Be,Al) due to its higher mass thickness is even more dramatic and not optimum for heating experiments using XEDS.