Defects and Impurities at the Si/Si(100) Interface Studied with Monoenergetic Positrons

Abstract

Positrons implanted with varying energies (0-20 keV) have been used to study silicon epilayers grown by molecular-beam epitaxy on Si (100) substrates. Defects at the initial growth interface and throughout the overlayer have been observed and depth profiled. In addition, field-driven positron drift observed in some of the epilayers is shown to be consistent with estimated concentrations of (active) interfacial impurities. The study demonstrates that positrons can be used nondestructively to profile structural defects and electric fileds in thin films and at interfaces.

Characterization of the interface region during the agglomeration of silicon nanocrystals in silicon dioxide

“…22 The Si nanocrystals themselves cannot account for this decrease, either. The diffusion length of positrons in defect-free Si is usually 215-250 nm, 23 which is significantly larger than the sizes of nc-Si in our sample. Moreover, it is known that many interfaces are normally introduced between the SiO 2 matrix and nc-Si.…”

Theory of positrons in solids and on solid surfaces

“…See the caption of Fig Positrons emanating from a radioactive source have a continuous energy spectrum characteristic of a beta decay, with end-point energies of the order of MeV's. There are now techniques available (see, e.g. , Schultz and Lynn, 1988) where high-energy positrons from radioactive sources or pair production can be moderated to a monochromatic beam with controllable kinetic energies from a few eV up to the keV region. In either case, positrons rapidly lose their energy in condensed matter.…”

Amorphisation and intermetallic nanophase formation in ball-milled Al–Ti–Si studied through positron lifetime spectroscopy

“…This result is significant from the positron annihilation point of view since the grain sizes are all well below the diffusion length of positrons on thermalisation after entering the grains. The mean thermal diffusion length of positrons in Al and Si are 120 [9] and 214 nm [10] and in Ti should be similar. Hence the positrons entering grains smaller than these dimensions will invariably diffuse out to the grain surfaces or boundaries and annihilate there.…”