First order Raman spectra of Si nanocrystals exhibit large shift and width, strongly exceeding the theoretical calculated values. The disagreement between theory and experiment is dramatically increasing for the smallest nanocrystal sizes. Here, we present a novel theoretical approach showing one-, two-, or three-dimensional quantum effects, due to the limited size of the corresponding coordinate of the quantum structure. The method can be applied to nanosized layers, quantum wires and/or quantum dots. The agreement of the present theory with experimental data is dramatically improved.
The change in the local order of amorphous sputter deposited GeTe thin films irradiated with Ge + ion and its influence on the subsequent thermal induced crystallization has been investigated by means of micro-Raman spectroscopy and in situ time-resolved reflectivity. A reduction in the Ge-rich tetrahedral species and an enhancement of the crystallization kinetics occurred in the irradiated amorphous samples. The rearrangement of the amorphous network is suggested to be related to thermal spikes effects rather than to the defects produced by the ions in the collision cascade.
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