Measurement of the response characteristics around K absorption edges of dead-layer materials of a charge-coupled device

We measure various spectral response characteristics around the oxygen, silicon, and nitrogen K absorption edges of a front-illuminated Charge-Coupled Device (CCD) X-ray detector used in the X-ray Imaging Spectrometer (XIS) developed for the ASTRO-E mission. We have evaluated X-ray Adsorption Fine Structure (XAFS) around oxygen K edge in detail. A strong absorption peak of 45% is confirmed just above the oxygen K edge and an oscillatory structure follows whose amplitude decreases from 20% at the edge to less than 1% at 0.9 keV. We also show XAFS and discuss on a change of the response function around the silicon K edge. The discontinuity of the signal-pulse-height at the silicon K edge is less than 2.9 eV. We determine the thickness of silicon, silicon dioxide, and silicon nitride in the dead-layer using the depth of the absorption edge. (C) 2001 Elsevier Science B.V. All rights reserved.