QUANTITATIVE THIN FILM & SURFACE ANALYSIS 1H - 238U
Rutherford Back-scattering Spectrometry (RBS) is a powerful tool for determining the structure and elemental composition of thin film samples: a high-energy beam of helium or hydrogen ions is directed at a sample. Ions that scatter elastically from the nuclei of atoms in the sample are detected using a silicon particle detector. The energy of the scattered ion depends on the mass and depth of the target atom, so that the composition and depth of the sample atoms can be determined. The Rutgers General Ionex tandem accelerator is capable of producing He++ ions up to 5.1 MeV via a multi-stage acceleration process.
Variations of RBS include Elastic Recoil Detection Analysis (ERDA) for quantitative determination of hydrogen and nuclear reaction analysis (NRA) for sensitive determination of light elements from Li-Ne.
RBS can also be used to obtain depth dependent information on the crystalline quality of single crystal samples. This technique, called "ion channeling," can probe the degree of damage (induced by ion bombardment or other means) in a crystal, or determine the amount of substitutional or interstitial species in a lattice.
- Measure thin Film composition/thickness/stoichiometric ratio
- Determine areal concentrations (atoms/cm2)
- Quantify film density (when thickness is known)
- Analyze hydrogen content (ERDA)
- Determine near surface crystallinity
- Signal Detected: Backscattered H or He atoms
- Elements Detected: H-U
- Detection limits: 0.001-10 at%
- Depth resolution: 100 - 200 Angstroms
- Lateral resolution/probe size: 2mm
- Non-destructive compositional analysis
A 2 MeV He++ RBS spectrum from an Al2O3 sample with Au and Ni thin films deposited on the surface. The data has been fitted using a SIMNRA simulation in order to determine the thickness of the different films and the order in which they were deposited on the surface. The He++ ions that scatter from Au retain most of their kinetic energy due to the relatively high mass of the Au nucleus while those ions that scatter from the Ni, Al, and O nuclei lose more energy and hence reach the detector with a smaller kinetic energy
Dr Hussein Hijazi
Department of Physics & Astronomy
Rutgers The State University of New Jersey
136 Frelinghuysen Rd., Piscataway, NJ 08854
Email: hh464 AT physics.rutgers.edu