engleski

Elastic recoil detection analysis for large recoil angles (LA-ERDA)

In this paper, elastic recoil detection (ERD) measurements at recoil angle of 60 degrees using ion-induced electron emission (IEE) for particle identification are presented. In our IEE system for particle identification, recoiled target atoms and scattered projectiles penetrate a set of thin carbon foils before their energy is analyzed in a solid state detector. Particle identification is based on the fact that the total number of electrons emitted from the foils depends on the particle nuclear charge. This method is characterized by its low minimum detectable energy, which stimulated us to study ERDA at 60 degrees. Due to collision kinematics and due to the angular dependence of the scattering cross-sections, it is expected that the sensitivity can be significantly improved. In this work, the detection efficiency of the IEE particle identification system for H recoils at energies below 1 MeV was determined. LA-ERDA measurements were performed with He-4 and C-12 projectiles using two different types of samples with a well-known amount and depth distribution of H atoms near the surface. Sample 1 consisted of a 50 mu g/cm(2) melamine layer evaporated on a flat Si substrate, sample 2 was a Si wafer with implanted H. Sensitivity and depth resolution were measured using LA-ERDA with a recoil angle of 60 degrees and ERDA with recoil angles of 30 degrees and 45 degrees. The results for different recoil geometries and projectiles are discussed and compared with theoretical predictions.

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