September 8, 2009

"Surface and Interface Studies by Variable Low Energy Positron Beam at Kalpakkam"

Professor Viswanathan
Vice Chancelor of Sri Chandrasekharendra Saraswathi Viswa Mahavidyalaya ( SCSVMV)


The availability of mono-energetic positron beams of tunable energy in the range of a few eV to about 20keV has added a new dimension to the experimental scenario involving depth resolved surface sensitive techniques. Variable low energy positron beam studies of near- surface defects in single layered, bi-layered and multi-layered thin film structures are discussed.The results are based on the research work carried out at IGCAR, Kalpakkam, as detailed below.

  1. Results on Ar ion induced defect structure in low dose samples of Si and amorphization in high dose samples of irradiated Si will be discussed.
  2. Positron sensitivity to Ar decorated vacancies and Ar bubbles as a function of depth in Aluminum will be presented.
  3. A study of inter diffusion and defect evolution across the interface in Al/Ge bi – layer is discussed.
  4. Results on strain relaxation and defect formation in GaAs based thin film heterostructures are presented.
  5. Studies on metal –silicon junctions like Pd/Si, Ni/Si and Co/Si are discussed, as the use of metal silicides is important in semiconductor technology.Important issues like diffusion , defect production and new phase formation in silicides are addressed and positron beam results are complemented by the concurrent use of other depth resolved surface techniques like RBS,AES and GIXRD.


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