We report on a study of several different electrode technologies to avoid the "dead layer" problem in ionization and phonon-based dark matter detectors. We have found the most success with an amorphous blocking layer electrode structure, and have demonstrated background electron rejection of 95% above 20 keV. 1.# INTRODUCTION The CDMS dark matter experiment uses detectors which reject background electron recoils produced photons and electrons from the less-ionizing nuclear recoils expected for WIMP dark matter by simultaneously measuring the amount of ionization and phonons in a semiconductor detector at millikelvin temperatures (Ref. 1). The ionization measurement is different from standard detectors operating at 77 K. At these low temperatures kT is much less than the 10 meV excitation energy of impurities, so no thermally generated free-charge is present and the detector can be purposefully put into a neutralized state with very few ionized impurity sites. Charge collection is th..
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