Raman analysis of Ga+ ion imaging using focus ion beam on InAs bulk surface
Date Issued
2015
Date
2015
Author(s)
Huang, Tien-Hao
Abstract
In this thesis, the effect of focused ion beam (FIB) imaging on the crystallinity of InAs was investigated by Raman scattering. The as-grown InAs sample shown a LO-plasmon couple mode (L-) at high laser power due to low carrier concentration. We lower the laser power (2 kW/cm2) to avoid this effect. The FIB ion imaging region (beam energy at 30 keV) shown a damaged LO mode, and the spatial correlation model was applied to fit this mode. The fitting result gives a short correlation length characteristic and invariant with ion fluence. We attribute this large damage in InAs surface to the high beam current density and the low dwell time of the FIB imaging process. In addition, low ion energy will prefer to nuclear stopping which will lead to damage the sample. In the other hand, due to the low InAs thermal conductivity, the imaging process also lead to a high local temperature in the imaging region and annihilated the defects, which reduce the relation between fluence and correlation length. Lower the beam energy, the correlation length shows a relation to ion fluence because of the low local temperature which suppresses the effect of annihilated the defects. Moreover, the TO mode intensity from damaged layer increase with fluence due to the collision cascade effect increase the damaged layer thickness. At beam energy of 30 keV , the damaged layer thickness is thicker than that of beam energy of 5 keV/16 keV. However, the undamaged LO at beam energy of 30 keV shows a higher intensity. We attributed to large annihilated defects at surface region which revived the damaged crystallinity.
Subjects
InAs
focus ion beam
ion imaging
Raman
Type
thesis
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