AN OPTIMIZED SET-UP FOR TOTAL-REFLECTION PARTICLE-INDUCED X-RAY-EMISSION

MeV proton beams at small angles of incidence (0-35 mrad) are used to analyse trace elements on hat surfaces such as Si wafers or quartz sub strates. In these experiments, the particle induced X-ray emission (PI XE) signal is used in a new optimized set-up. This set-up is construct ed in such a way that the X-ray detector can reach very large solid an gles, larger than 1 sr. Use of these large detector solid angles, comb ined with the reduction of bremsstrahlung background, affords limits o f detection (LOD) of the order of 10(10) at cm(-2) using total reflect ion particle induced X-ray emission (TPIXE). The LODs from earlier TPI XE measurements in a non-optimized set-up are used to estimate LODs in the new TPIXE set-up. Si wafers with low surface concentrations of V, Ni, Cu and Ag are used as standards to calibrate the LODs found with this set-up. The metal concentrations are determined by total reflecti on X-ray fluorescence (TXRF). The TPIXE measurements are compared with TXRF measurements on the same wafers. (C) 1997 Elsevier Science B.V.