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Novel properties offered by self assembled nanowires (NWs) based on III-V materials, make them a potential candidate for electronic and optoelectronic industry. An emerging field,“spintronic” is of marvellous importance in scientific and technological applications. Dilute magnetic semiconductors (DMS) specially the discovery of Mn doped III-As [1, 2] leads the way to fabrication of semiconductor spin devices [3]. A wide number of III-V NWs have been grown by several techniques, including, metalorganic vapor phase epitaxy [8, 9] and molecular beam epitaxy (MBE)[10]. One major problem of self assembled nanowires is the presence of defects in these NWs. Work has been reported on the analysis of defects and disorders in heterostructures, thin films and in crystals by using the phonon confinement model [11-13]. All these authors gave the qualitative analysis of defects and disorders in thin films or single crystals but to the best of our knowledge no one has estimated the defect density in a single NW. Here, we study the structural defects present along the body of NWs carried out by means of µ-Raman scattering. A detailed analysis of the defect density in GaAs and InAs NWs and surface phonons will be presented. Phonon confinement model (PCM) will be used to fit the LO phonon peaks, which also takes into account contribution for asymmetry in the line shape due to presence of surface optical (SO) phonons and structural defects. This also allows us to determine the correlation lengths in these wires, the average distance between defects and defect density in these nanowires. Influence of these defects on SO phonon will also be investigated …
Publication date: 
1 Jan 2010

Narjis Begum, Bhatti, Arshad S, Fauzia Jabeen, Silvia Rubini, Faustino Martelli

Biblio References: 
Pages: 255-272