DIAMOND MEMBRANES - APPLICATIONS FOR SINGLE-ION DETECTION USING SECONDARY-ELECTRON EMISSION

The assessment of mechanisms for radiation damage in both biological a nd semiconductor systems is much enhanced by ensuring that each cell o r memory unit is hit by one and only one ion. Such ''single ion'' syst ems operate by detecting the passage of an ion and using the signal to deflect the beam upstream thus ensuring that only a single ion is inj ected to the system at a time. For biological investigations of the ef fects of single ion impact on living cells, the ion needs to be extrac ted from the vacuum of the accelerator through a thin window into the atmosphere. The requirements on such a window are: (a) that it be thin enough to allow the passage of the ion through it without excessive e nergy loss; (b) that it possess mechanical strength sufficient to surv ive the pressure differential; and (c) that upon passage of the ion th rough it, a sufficiently large signal is generated to ensure a 100% ef ficient detection of the passage of the ion. This set of demanding req uirements can be met by a thin diamond window fabricated by CVD techni que, taking advantage of the high secondary electron yield of B-doped diamond. In the present work, we report on the use of B-doped diamond membranes for this purpose. (C) 1998 Elsevier Science S.A.