ELASTIC RECOIL SELECTION BY PULSE-SHAPE ANALYSIS

Recoils ejected by alpha-particles are detected by low-resistivity det ectors at low bias. Pulses from scattered alpha-particles that cross t he depletion layer are rejected by pulse shape analysis. Using 500 OME GA cm detectors the maximum pulse height recorded for alpha-particles corresponds to an energy of 4 MeV. Further suppression of pulses cause d by alpha-particles awaits the construction of detectors optimized fo r operation at low bias as well as the development of faster electroni cs. Using a 13.4 MeV alpha-particle beam oxygen has been detected from layers as deep as 250 nm. Sensitivity was improved to 5 x 10(14) atom s/cm2 and a surface depth resolution of 12 nm was obtained for N in Si 2N0.86O3. The depth range and sensitivity may be further improved usin g higher bombarding energies.