The pressure dependent phonon modes of predominant wurtzite InAs nanowires has been investigated in a diamond anvil cell under hydrostatic pressure up to 58 GPa. The TO and LO at Gamma point and other optical phonon frequencies increase linearly whil
e the LO TO splitting decreases with pressure. The recorded Raman modes have been used to determine the mode Gruneisen parameters and also the value of Borns transverse effective charge. The calculated Borns transverse effective charge exhibits a linear reduction with increasing pressure implying an increase in covalency of nanowires under compression. The intensity of the Raman modes shows a strong enhancement as the energy of E1 band gap approaches the excitation energy, which has been discussed in terms of resonant Raman scattering. An indication of structural phase transformation has been observed above pressure 10.87 GPa. We propose this transformation may be from wurtzite to rock salt phase although further experimental and theoretical confirmations are needed.
We report a combined electron transmission and Raman spectroscopy study of InAs nanowires. We demonstrate that the temperature dependent behavior of optical phonon energies can be used to determine the relative wurtzite fraction in the InAs nanowires
. Furthermore, we propose that the interfacial strain between zincblende and wurtzite phases along the length of the wires manifests in the temperature-evolution of the phonon linewidths. From these studies, temperature-dependent Raman measurements emerge has a non-invasive method to study polytypism in such nanowires.
The authors report that anisotropic confining potentials in laterally-coupled semiconductor quantum dots (QDs) have large impacts in optical transitions and energies of inter-shell collective electronic excitations. The observed anisotropies are reve
aled by inelastic light scattering as a function of the in-plane direction of light polarization and can be finely controlled by modifying the geometrical shape of the QDs. These experiments show that the tuning of the QD confinement potential offers a powerful method to manipulate electronic states and far-infrared inter-shell optical transitions in quantum dots.
