  Structural modifications in InP(111) due to 1.5 MeV implantation of Sb have
been characterized using first order and second order Raman spectroscopy. With
both Longitudinal Optical (LO) and Transverse Optical (TO) modes allowed for
InP(111), we have investigated the evolution of both these modes as a function
of fluence. Intensity, linewidth and shifts of the phonons, for both first
order and second order Raman modes, display the increase in damage in the
lattice with increasing fluence. The results suggest that the presence of a
charge layer in the vicinity of the surface may be effecting the first order
Raman data. A LO phonon-plasmon coupled mode, due to the charge layer, has also
been observed that becomes sharper and more intense with increasing fluence.
Results also show the presence of tensile stress along with the coexistence of
crystalline InP regions and amorphous zones in the lattice. Consequently phonon
confinement is observed. Phonon Confinement model (PCM) has been applied here
to estimate the coherence length and the size of nano-crystalline zones in InP
lattice after implantation. A crystalline/ amorphous (c/a) phase transition is
observed at the fluence of $1\times10^{14} ions/cm^{2}$. The electron-phonon
coupling strength has been measured by utilizing the second order Raman modes.
This coupling strength is seen to decrease as the nano-crystalline zones, in
the implanted lattice, become smaller.
