HIGH DEPTH RESOLUTION ERDA OF H AND D BY MEANS OF AN ELECTROSTATIC SPECTROMETER

In the standard elastic recoil detection analysis of H and D the energ y resolution and - as a consequence - also the depth resolution are li mited by essentially three effects: the kinematic errors due to the fi nite size of the beam spot on the target and of the solid angle of the detector, the finite energy resolution of the commonly used silicon s urface-barrier detectors, and the energy straggling of the recoil ions in the shielding foil in front of the detector. By the use of an elec trostatic spectrometer the first two effects can be reduced considerab ly, while the third effect is eliminated completely. The present paper describes an experimental setup employing such a spectrometer. With t his setup an energy resolution of DELTAE = 3.3 keV has been obtained i n case of the analysis of H and of DELTAE = 4.5 keV in case of D in ne ar surface layers. It corresponds to depth resolutions of 1.8 nm (H) a nd 1.5 nm (D) in Cu for a primary beam of 4.3 MeV Ne at an incidence a ngle of 19' and with the detector positioned at a recoil angle of 38-d egrees. With grazing incidence (5-degrees) and a slightly improved set up a depth resolution in the monolayer range should be obtainable. The paper discusses the different effects contributing to the energy reso lution and gives various examples for applications which include the a nalysis of D2O on an oxidized silicon surface and of H and D on a clea n copper surface. In a final section the performance of the present se tup is compared with that of the well known N-15 resonance technique c ommonly used for the analysis of hydrogen.