Elastic Recoil Detection analysis for large scattering angles (LA-ERDA)

Elastic Recoil Detection Analysis (ERDA) is one of the most useful modern ion-beam analysis techniques developed for depth profiling of light elements in surface layers and thin films. ERDA has become the technique of choice for many light element profiling applications because of simplicity, possibility of simultaneous multi- element profiling, good sensitivity and depth resolution. Recently a new system was developed at the University of Linz for ERD analysis. The system uses ion-induced electron emission (IEE) for particle identification. Compared to standard ERDA systems, this one gives better depth resolution due to the large reduction of the energy-loss straggling. The main goal of this project is to investigate for the first time ERDA for large scattering angles (>45) (Large Angle Elastic Recoil Detection Analysis, LAERDA) using the IEE system for particle identification. It is expected that LAERDA will have a larger detection probability than usual ERDA. A high detection probability can reduce the target damage by the projectile beam, when sensitive samples are analysed, and will give a smaller detection limit. The optimal conditions (ERDA parameters) for a new experimental set-up should be studied first theoretically by computer simulations and optimisation of ERDA parameters concerning sensitivity and radiation damage will be done. The results will be compared with already existing studies for other detector systems. In the existing ERDA experimental set up the scattering angle between the incoming beam and scattered ions can be selected to be 45, 30.The system should be modified so that larger scattering angles up to 75 can be selected. All parameters which have an influence on detection probability, energy resolution and profiling depth will be studied experimentally for some targets and results of this study will be compared with theoretical results obtained from the computer simulations. The H-He scattering cross sections, which deviate from Rutherford. cross sections, will be measured for selected angles. Finally, hydrogen will be analysed in some samples and minimum detection limits will be determined.