Speaker
Description
Rutherford Backscattering (RBS) technique is one of the most useful techniques to measure the hetero-structure film thickness and the composition of the sample. In this technique, sample is irradiated with light ions (usually 2-3 MeV α-particles or protons) and the elastically backscattered projectiles at large angles are detected. The mass of the target atoms could be identified from the energy of the backscattered projectile. We have employed the RBS technique to measure of the thickness and composition of Ge/Si quantum dot (islands) hetero-junction as-deposited sample and for a series of annealed samples. The simulated result of the as-deposited sample has been used to extract the equivalent Ge layer thickness, which is found to be 14 monolayers (ML) thick. A successive decrease of the intensity of Ge peak for different duration of annealing indicates the consumption of metastably thick Ge wetting layer during prolong annealing. The metastable Ge wetting layer greater than 3ML beneath alloyed islands is feeding them during annealing to increase the island volume. The broadening of Ge peak RBS spectra is due to the decrease of Ge mole fraction in the resultant Si1-xGex alloys, with the increase of annealing time. Rutherford back scattering spectroscopy (RBS) was carried out with 2 MeV He+ incident normally on the samples, with the detector fixed at a scattering angle 165°. All measured data were simulated and analyzed using SIMNRA version 6 developed by Max-Planck-Institute for Plasma physics, Garching, Germany.
