Compositional analysis based upon electron holography and a chemically sensitive reflection
Bristol :Iop publishing ltd
CONFERENCE SERIES- INSTITUTE OF PHYSICS
Royal-Microscopical-Society Conference on Microscopy of Semiconducting, Materials, MAR 25-29, 2001, UNIV OXFORD, OXFORD, ENGLAND
, p. 33-36
We present a method for compositional analysis of low-dimensional semiconductor heterostructures. The suggested procedure is based upon electron holography and the exploitation of the chemically sensitive (002)-reflection that is available in sphalerite type material. We apply an off-axis imaging condition where the strongly excited (002)-beam is centred on the optic axis. From the centred sideband of the hologram we use the phase of the (000)-beam and the modulus of the amplitude of the chemically sensitive (002)-reflection to evaluate the local composition and the local specimen thickness in an iterative and self-consistent way. The application of the procedure is demonstrated using an AlAs/GaAs(001) superlattice with a nominal period of 5 nm and a layer thickness of 2.5 nm. The concentration profile was fitted with a segregation model from which we obtain a superlattice period of (4.86 +/- 0.03) nm, a total amount of AlAs of (2.5 +/- 0.2) nm per AlAs layer and a segregation efficiency of R=0.51 +/- 0.02.