Raman scattering characterization and electron phonon coupling strength for MeV implanted InP(111)

Abstract

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 nanocrystalline zones in InP lattice after implantation. A crystalline/ amorphous (c/a) phase transition is observed at the fluence of 1 × 10 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.

Microstructural and optoelectronic properties of polycrystalline InP films deposited by RF magnetron sputtering

“…Sharp Raman lines at about 304 cm À 1 and 342 cm À 1 are attributed to TO and LO phonon scatterings, respectively. The observed phonon energies are in good agreement with the phonon modes found in the literature for InP single crystals [31] and polycrystalline InP films [24]. The peaks observed at about 608 cm À 1 , 643 cm À 1 and 682 cm À 1 in films corresponds to the 2TO, LOþTO, and 2LO modes, respectively.…”

Nano Pattern Formation and Surface Modifications by Ion Irradiation

“…The softening of the modes, suggests development of tensile stress after sputtering 32 . Due to the Frohlich interactions 36 , LO is a more surface sensitive mode and thus its modfications may reflect the structural changes on the InP surface 37 . modes can be attributed to the phonon confinement effects in nanodots 37 .…”

“…Due to the Frohlich interactions 36 , LO is a more surface sensitive mode and thus its modfications may reflect the structural changes on the InP surface 37 . modes can be attributed to the phonon confinement effects in nanodots 37 . At t c , a reduction in shift to 1.8 cm -1 (LO feature at 349.7 cm -1 ) suggests a slight relaxation in stress.…”

Studies of Self-Organized Nanostructures on InP(111) Surfaces After Low Energy Ar+ Ion Irradiation

“…The shift in the LO and TO modes as well as the asymmetricity in these peaks after 30min, appear more than that seen after 40min. All this may be due to the higher phonon confinement due to smaller InP nanodots [11] at 30min.…”

“…However, none of these studies displayed any surface smoothening behavior. [11]. The Raman spectrum after 5 min sputtering shows shifts for both the LO and TO phonons towards lower wave numbers.…”