Optical Properties of Tellurium in the Fundamental Absorption Region

Optical properties of chalcogen-loaded zeolite (ZSM-5)

“…For the most common forms of crystalline S, Se, and Te, the optical gaps are reported to be ~4 [21], ~1.9 eV [30], and ~0.33 eV [31]. We then see some correspondences between these gaps and the present absorption edges for z-S (~3 eV) and z-Se (~2.2 eV), while a discrepancy (~0.33 and 3 eV) for Te is remarkable.…”

Thermomodulation of Optical Parameters in Tellurium

“…I n view of the fact that a t our temperature's the band-gap transitions show a blue shift, the distinct peaks 6 : 6' ; 7' ; 9' ; 10 ; 10' ; and 11' probably originate from transitions remote from H. The peaks 10; 10' (0.73 eV) are observed a t 300 K for both polarisations, while a t 100 K only the peak for E 1 ct, is observed. A similar broad but weaker structure a t =0.7 eV is found by [2] in the reflection spectrum of tellurium for E 1 c3 a t 10 K. Further interpretation of spectra without complementarj knowledge of band structure seems not possible.…”

“…3 is seen that in both cases the band-gap energy E , is smaller by a factor 1.5 to 1.8 than the experimental well-known value. I n order to adapt the theoretical value for E , to the experimental one, in C the potential V , between the atomic spheres was chosen more negative than in the first cases The temperature dependence of' the band gap determined from absorption measurements in the optical band-edge region are in tellurium determined by two opposite processes [2], a blue shift with decreasing temperature from 300 t o 100 K, a red shift in the low-temperature region down to 10 K. I n our experiments the samples with 1.8 x 1018 em-3 show a blue shift of the band-gap energy with linear expansion coefficients B = { -3.5 x 10-5eV/degfor E l c 3 .…”

Full Reconstruction of a Crystal Unit Cell Structure during Coherent Femtosecond Motion

“…One possible contribution to this damping time is the depth inhomogeneity of the probed region of the sample: as the distance from the surface increases, the excited carrier density decreases and causes the mode frequency to shift toward its equilibrium value of 3.6 THz. The longer damping time in the x-ray data may be because the 39 nm probe depth of the x ray is slightly shorter than the 58 nm absorption depth of the optical probe [24]. To quantitatively estimate this effect and to separate it from other decay mechanisms (e.g., anharmonic decay) would require very accurate measurements at many different x-ray incidence angles [25].…”