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Séminaire nanostructures et systèmes quantiques

Micro-Raman study of GaAs nanowires

Peng WANG

Semiconductor nanowires have been successfully grown by Au-catalyzed MBE method during the past few years, providing a new kind of 1D semiconductor with a few μm length and diameters ranging from 10 nm to 100 nm. Wurtzite and zinc blende crystalline structures exist in the semiconductor nanowires. The wurtzite is not stable in the bulk form of semiconductor and has some differences in phonon modes compared with zinc blende structure. The Micro-Raman system is a useful tool to observe the vibrations in the nanomaterials.

We concentrated on GaAs nanowires with wurtzite and zinc blende structure and developed a Micro-Raman system to make it suitable for a systematic Raman spectroscopy study of single GaAs nanowires. By now we have carried out some Raman spectroscopy measurements on single GaAs nanowires with different position and power. We have shown that the GaAs nanowires transform into crystalline As when moving the laser point across it and the transformation happens when the power is higher than 0.4mw (The wavelength of exciting laser is 514.5 nm). Then we studied the phonon modes resonance of GaAs nanowires with red laser. We focused the red laser on the Au-catalyzed Si-doped GaAs nanowires in the air and found that even in much higher energy(30mw) there was no appearance of As. We also observed a significant increase of the intensity around 790nm attributed to the electron resonance. No evidence of a modification of the phonon spectrum by doping is found in this sample.