Fröhlich vibrational modes in porous ZnSe studied by Raman scattering and Fourier transform infrared reflectance

Abstract

Arrays of parallel pores with a diameter of around 60 nm have been introduced by anodic etching in ZnSe single crystals with a free electron concentration of 4 × 1017 cm−3. Porosity-induced Fröhlich vibrational modes were studied by Raman scattering and Fourier transform infrared spectroscopy. The experimental data are compared with the results of theoretical simulation based on the effective medium theory. Traces of Se phase were evidenced at the surface of the porous matrix after anodization, the Raman active modes of this phase being incident in the region of the occurrence of Fröhlich vibrational modes inherent to porous ZnSe. To identify reliably the Fröhlich modes, Raman spectra of porous ZnSe layers were explored under different resonance conditions with several excitation wavelengths and various excitation power densities.

Temperature-Dependent Raman Scattering of ZnSe Nanowires

“…However, a qualitative relationship can be obtained from the phonon spectrum . We can tentatively assign the two peaks at 137.5 and 189.0 cm −1 to 2TA(L) [28] and 2TA 1 (K) [19], respectively, on the basis of the qualitative relationship.…”

“…However, since there are no defects observed in ZnSe nanowireshere, thus we tend to assign this mode to the multi-phonon peak: TA(X,K) + LA(X) [19]. The attribution of the peaks at 137.5 and 189.0 cm −1 still remain controversial and indistinct [19] [25] [27] [28] as mentioned in the introduction section.…”

“…The attribution of the peaks at 137.5 and 189.0 cm −1 still remain controversial and indistinct [19] [25] [27] [28] as mentioned in the introduction section. Actually, simply assigning these peaks to a certain mode are not rigorous with this resolution, because all these modes energy are very close and they cannot be distinguished from each other in the phonon spectrum [35].…”

“…Recently, one-dimensional nanomaterials have been extensively studied due to its novel and superior properties and potential applications as building blocks in nano-scale electronics [4] [5] [6] [7]. Consequently, different forms of one-dimensional ZnSe nanostructures [6] [8]- [19] have been synthesized in pursuing improved physical properties. Good knowledge of the vibration properties of this material is essential to understand transport properties and phonon interaction with the free carriers, both of which have great impact on optoelectronic device performance [10].…”

“…Thus, temperature dependence of phonon modes may provide useful information on the electronic states of energy transfer and electron-phonon coupling [13] [24]. Moreover, some Raman investigations on one-dimensional ZnSe nanomaterials remain controversial or indistinct [19] [25] [26] [27] [28]. Furthermore, the phonons are related to the properties such as thermal expansion, entropy, specific heat, thermal conductivity, electrical conductivity, optical and dielectric properties, diffusion mechanism, phase change phenomena [29] [30] [31] [32].…”