Apparatus for In-situ Defect Analysis (AIDA) Investigations by Positron Annihilation Spectroscopy

A unique high vacuum system for defect manipulation and analysis has been developed and installed at the Helmholtz-Zentrum Dresden-Rossendorf. The setup combines several experimental techniques for that purpose, e.g., material evaporation, ion beam modifications, and temperature treatment with the positron annihilation spectroscopy, and sheet resistance measurements.

AIDA utilizes a monoenergetic positron beam which is tungsten moderated, magnetically guided and pre-accelerated in the range of 30 eV to 35 keV. The positron beam is extracted from an intense 22Na source and enables sample depth profiling by Doppler broadening spectroscopy. The coincidence Measurements are performed by two HPGe detectors with energy resolution of (780 ± 20) eV at 511 keV, whereas the standard single HPGe detector Doppler broadening with energy resolution of (1.09 ± 0.001) keV is applicable for the varied energy scans. AIDA consist of a load lock chamber mechanism for halogen preliminary heating up to 150°C and loading a sample holder through a linear transfer to the MBE chamber by a basic pressure of 10-7 mbar. The sample holder is then mounted on a sophisticated 5 axis manipulator which is available for resistometry investigations by a 4-point probe module during isochronal annealing by a resistive heater at a base pressure of about 10-8 mbar. Thus, defects can be annealed up to 1300 K or stabilized down to 50 K and meanwhile residual resistivity measurements can be performed. In order to determine influence of vacancy complexes and their distribution onto magnetic, structural, and morphological sample properties, simultaneously ion irradiation by an energy range from (0.001 – 5) keV can be realized. The Ion Source is suitable for depth profiling and enables operation with reactive and noble gases by a current density of <200 µA/cm2. A Quartz oscillator provides a useful and progressive indication of coating thickness during the deposition process. Eventual, defect role during a dynamic formation of nanostructures on the semiconductor surface, e.g. Si or Ge, can be investigated during ion irradiation.