BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Memento EPFL//
BEGIN:VEVENT
SUMMARY:III-V nanowires studied using cathodo-luminescence
DTSTART:20120522T093000
DTSTAMP:20260510T135545Z
UID:0af5da388f864d17326a2cf49fe6dfb55c9205cbd925a6acd94a644c
CATEGORIES:Conferences - Seminars
DESCRIPTION:Anders Gustafsson\, Lund University\, Sweden\nWe investigated 
 properties of GaAs- and InP-based nanowires (NWs) on a sub-micron scale us
 ing cathodo-luminescence imaging and spectroscopy. All NWs were grown by M
 OCVD\, seeded by size-selected gold particles. The diameter of the gold pa
 rticles in this study was typically 30 - 80 nm. The composition in the cor
 e was either kept constant (e.g. GaAs or InP) or changed along the length 
 (e.g. a segment of GaInAs in a GaAs core). The emission from the core depe
 nds strongly on growth temperature\, surface preparation and crystal struc
 ture of the GaAs. Axial GaAs/GaInAs/GaAs heterostructures were used to stu
 dy diffusion effects and radial hetero-structures were studied with respec
 t to homogeneity. Uncapped GaAs NWs show a diffusion length of about 100nm
 . When capped with an AlGaAs\, it improves to about 1µm. The InP cores we
 re covered by thick InP\, followed by a thin InAs and a thick InP layer. T
 he InAs layer serves as a radial quantum well (RQW). In addition\, the cry
 stal structure of the InP core can result in a controlled super-lattice of
  segments of zinc-blende (ZB) and wurtzite (WZ)\, with typical segment len
 gths of about 200nm. The RQW shows thickness fluctuations differing by a s
 ingle InAs layer in thickness on the pure WZ. Growth on the super-lattice 
 results in larger thickness variations\, forming quantum dots on the ZB fa
 cets. The shell can improve the emission intensity\, as long as it is defe
 ct free\, which is normally the case for AlGaAs on GaAs. However when the 
 shell is strained\, like GaInP on GaAs\, dislocations can be introduced in
 to the shell. For low mismatch this can lead to local relaxation of the st
 rain\, as evidenced by local variations in the emission energy from the NW
  cores. For a higher mismatch\, the emission can be degraded locally due t
 o the introduction of dislocation\, resulting in dark bands in the images 
 of the NW cores.
LOCATION:DIA003
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR