Effect of Nanoscale Surface Roughness and Electron-Phonon Interaction on Vibrational Modes of Cadmium Telluride Using Resonant Raman Spectroscopy.

This study investigates the combined effects of nanoscale surface roughness and electron-phonon interaction on the vibrational modes of cadmium telluride (CdTe) using resonant Raman spectroscopy. Raman spectra simulations aided in identifying the active phonon modes and their dependence on roughness. Our results reveal that increasing surface roughness leads to an asymmetric line shape in the first-order longitudinal optical (1LO) phonon mode, attributed to an increase in the electron-phonon interaction. This asymmetry broadens the entire Raman spectrum. Conversely, the overtone (second-order longitudinal optical [2LO]) mode exhibits a symmetrical line shape that intensifies with roughness. Additionally, we identify and discuss the contributions of surface optical phonon mode and multiphonon modes to the Raman spectra, highlighting their dependence on roughness. This work offers a deeper understanding of how surface roughness and electron-phonon scattering influence the line shape of CdTe resonant Raman spectra, providing valuable insights into its vibrational properties.

Radiation shielding and dosimetric parameters of mexican artisanal bricks.

In this work, were determined some radiation shielding and dosimetric parameters of three types of bricks for photons energy from 1 keV to 100 GeV photons using the Phy-X/PSD software, and for comparison also has been calculated the same parameters for NBS concrete. The parameters calculated are the linear attenuation coefficients (LAC), effective atomic numbers (Zeff), half value layers (HVL), the energy absorption buildup factors (EABF) and the exposure buildup factors (EBF), as well as the coefficients to use the geometric progression (G-P) fitting method. Obtained results show that the three types of bricks can be used safely for the design of medical facilities housing mammography units (less than 30 keV).

Characteristics, as a shield against ionizing photons, of concrete blocks used in the construction industry.

INEGI reports that 81% of new constructions are built with durable materials, such as concrete blocks, including rooms where ionizing radiation is used, such as clinics and hospitals. The volume ratios used in the manufacture of concrete blocks have a 1: 5: 2 ratio of: portland cement, sand and crushed gravel. The percentage mass content of each atom in the sample is obtained with the energy-dispersed X-ray fluorescence, these results are used to calculate the characteristics such as shielding of the concrete blocks, which have been partially reported, in this work several characteristics are presented for photons from 1 keV to 100 GeV, such as linear attenuation coefficients, the hemireductive layer, the effective, atomic and electronic sections, the effective atomic number (Zef). The exposure of accumulation and energy absorption factors (EBF, EABF) of 0.5-40 mfp are reported, using the Photon Shielding and Dosimetry (PSD) software. These characteristics are compared to those of NBS concrete. The concrete blocks have an attenuation capacity for energies used in radiological equipment such as mammography, 20-35 keV; dental, 50-90 keV and for conventional radiography equipment, 70-150 keV, so the block and lightened concrete block must be considered in the calculations of primary and secondary shielding walls.

CdTe surface roughness by Raman spectroscopy using the 830 nm wavelength.

A Raman spectroscopic study was performed to detect the surface roughness of a cadmium telluride (CdTe) wafer sample, using the 514.5, 632.8 and 830.0 nm excitations wavelengths. To verify the relation between the roughness and the structure of Raman spectra, in certain zones of the sample, we measured their roughness with an atomic force microscopy. It was found that, using the 830 nm wavelength there is a direct correspondence between the spectrum structure and the surface roughness. For the others wavelengths it was found, however, that there is not a clearly correspondence between them. Our results suggest that, using the excitation wavelength of 830 nm the Raman spectroscopy can be used as an on-line roughness monitor on the CdTe growth.