Raman, infrared, photoluminescence and theoretical studies of the II-VI-VI ternary CdSeTe

Phonon spectroscopy of CdSe1–xTex nanocrystals grown in a borosilicate glass

“…2(a) and (b), respectively. Points represent the experimental data [15,16,[23][24][25], solid and dashed curves -calculations performed using the random-element isodisplacement model [23,24]. It is seen that, similarly to CdS 1-x Se x , in this case the CdSelike and CdTe-like LO phonon frequencies reveal a clear compositional dependence and, hence, can be applied to determine the ternary alloy composition.…”

“…In an attempt to compare our Raman data with earlier studies of phonon spectra of nanoscale [15,16] and bulk [23][24][25] CdSe 1-x Te x crystals by Raman [15,16,25] or infrared [23,24] spectroscopy, we plotted the phonon frequencies as well as the difference of the CdSe-like and CdTe-like LO phonon frequencies in Figs. 2(a) and (b), respectively.…”

“…In both reported cases the spectra for just one CdSe 1-x Te x composition were presented. Since the phonon spectra of CdSe [17][18][19][20] and CdTe [20][21][22] nanocrystals have been investigated quite extensively, it seemed interesting to study this ternary system in more detail, in particular, in order to evaluate the possibility of the application of phonon spectroscopy for non-destructive compositional assessment and to compare the obtained phonon spectra of the nanocrystals with those for CdSe 1-x Te x bulk crystals reported earlier [23][24][25].…”

STRUCTURAL AND OPTICAL PROPERTIES IN NEAR INFRARED OF CdTeSe COLOIDAL QUANTUM DOTS FOR POTENTIAL APPLICATION IN SOLAR CELLS

“…When the temperature is increased to 280 o C, most of the Te ions would have reacted, and Se ions would keep linked with Cd ions creating many Cd-Se bonds, shrinking the crystal lattice structure in the same tendency with zb-CdSe and shifting diffraction lines towards angles 2θ higher -as observed on the XRD patterns of sample created at 280 o C. Figure 2 is the Raman spectra of CdTeSe QD samples fabricated at different temperatures recorded with the micro Raman XploRa Plus using 532 nm laser as an excitation source. On the Raman spectra, two main vibrational lines appearing at 159 cm -1 and 188 cm -1 are characteristic for phonon vibrations of CdTe-like LO and CdSe-like LO modes as observed in [12,13]. When the fabricating temperature is as low as 180 o C, the intensity of the CdTe-like LO phonon is much higher compared to that of the CdSe-like LO phonon, proving that there are more formations of Cd-Te bonds than of Cd-Se in the alloy.…”

“…When the Te amount increases from 0.5 and higher, the CdSe LO phonon position is shifted towards lower frequencies, 188 cm -1 in this case, and this peak is assigned as the zb CdSe-like LO phonon mode. This can be explain as when the Te amount is low (high Se amount in the CdTeSe alloyed molecule), in the alloy can exist wurtzite (w) hexagonal structure phase; and when the Te amount is high (low Se amount), the CdTeSe alloy change to a cubic zb phase [12,13]. To protect CdTeSe QDs from surface defects, we wrapped a layer of ZnSe or ZnTe around them, with the thickness of about 2 monolayers (2 ML) of the shell material.…”