Temperature dependence of the absorption spectra in CdTe-doped glasses

Abstract

We present absorption spectra as a function of temperature for CdTe quantum dots in doped glasses. We calculate the absorption spectra considering the transition energies from a spherical k • p model. We consider also the inhomogeneous broadening due to the quantum-dot size distribution and the homogeneous broadening, due mainly to electron-phonon interactions. The samples grown with a two-step heat treatment present very thin size distributions, with a standard deviation of 5.8%, which is comparable to the best CdSe samples in the literature. Also, the results show that the homogeneous width increases as the quantum-dot size decreases, indicating an enhancement of the electron-phonon interaction for small dots.

Recombination Dynamics of CdTe/CdS Core−Shell Nanocrystals

“…Since CdTe has the largest spin-orbit splitting of 0.927 eV among CdS, CdSe, and CdTe, the split-off band is expected to mix only weakly with the topmost valence band. The energies of the lowest electron-hole pair transitions have been computed for CdTe NCs using different methods based on EMA or tight-binding calculations. − In experiments, the quantized electronic levels are observed to shift monotonically with decreasing size without any crossing or anticrossing, reflecting the rather simple valence-band structure of CdTe. , We therefore use likewise a simple EMA model to estimate the theoretical exciton band edge structure of the CdTe NCs neglecting the thin CdS shell and assume complete strain relaxation. The inset of Figure shows the size dependence of the first absorption peak position at T = 295 K. On the basis of the size-dependent absorption maximum and the data from TEM, we use the size of R = 3.5 nm as a base for the discussion of effects of electron−hole exchange interaction in our CdTe NCs in the following.…”

Optical Absorption and Transmission Electron Microscopy Analysis of CdTe Quantum Dots Size Distribution

“…The inhomogeneous broadening due to the quantum dot size distribution and the homogeneous broadening due mainly to electron-phonon interactions have also been considered. The standard deviation for the size-distribution is 5,8 % according to this analysis [2].…”

Photonic Crystal Fiber Temperature Sensor Based on Quantum Dot Nanocoatings

“…These data can be approximated by an exponential signal with a correlation factor of R 2 = 0.998, rather better than the obtained absorption spectra measured in the precedent section. In some previous works [26][27][28]30], the sensors apparently showed a linear behavior due to the narrower temperature range used. The average sensitivity of this sensor is 0.00465…”

“…Surprisingly, although optical absorption spectrum is an important QD feature which can also be used for sensing temperature, as was proposed in earliers publications [30], there are few works related to temperature sensors based on QD which study the variation of optical absorption for temperature sensing [31]. In order to measure this parameter, a lowpass optical filter and a deuterium and halogen white light source (Oceanoptics DH 2000) were used in the Figure 4 setup.…”