Direct detection and imaging of low-energy electrons with delta-doped charge-coupled devices

We report the use of delta-doped charge-coupled devices (CCDs) for direct d etection of electrons in the 50-1500 eV energy range. We show that modifica tion of the CCD back surface by molecular beam epitaxy can greatly improve sensitivity to low-energy electrons by introducing an atomically abrupt dop ant profile to eliminate the dead layer. Using delta-doped CCDs, we have ex tended the energy threshold for detection of electrons by over an order of magnitude. We have also measured high gain in response to low-energy electr ons using delta-doped CCDs. The effect of multiple electron hole pair produ ction on the observed signals is discussed. Electrons have been directly im aged with a delta-doped CCD in the 250-750 eV range. (C) 1998 American Inst itute of Physics. [S0003-6951(98)03549-9].