Experimental investigations of the photoelectric properties of CdGa2S4 single crystals were carried out. The study examined the temperature dependence of the photocurrent (within the 110–420 K range), as well as the spectral dependence and transient characteristics of optical quenching at T = 300 K. Optical quenching of the photocurrent was observed within a secondary light beam energy range of 0.6 - 2.49 eV. Measurements revealed energy levels at Ec - 0.21 eV, Ec - 0.42 eV, and Ec - 1.06 eV, as well as sensitizing levels at Ev + 0.89 eV. The decrease in photocurrent at temperatures above 300 K is attributed to thermal quenching. Both optical and thermal quenching of photoconductivity in CdGa2S4 crystals are ascribed to changes in the charge state and exchange dynamics of sensitizing and recombination centers.
ZnFe2-xYbxO4 with (x = 0, 0.01, 0.02, 0.03, 0.05, 0.07, and 0.09) have been successfully synthesized by the sol-gel method at 750°C. X-ray diffraction results showed a single phase and crystalline nanopowders of spinel-type structure with cubic symmetry and space group . The lattice parameters increase with Yb3+ concentrations. The BET specific area of ZnxFe2-xYbxO4 (x = 0.03) was determined to be the larger 13.59 m2/g. The crystallite size was determined by Rietveld to be in the range of 29-104 nm. FTIR spectra showed two strong absorption bands, a common characteristic of the spinel structure. Further, the shifting of the lower absorption band toward a higher frequency confirms that Yb3+ ions predominantly replaced Fe3+ ions in octahedral sites. The formation of the spinel phase in the samples was also validated by Raman scattering, with asymmetric broadening, and a systematic shift in the Raman spectra was observed as a function of Yb3+ concentration. Scanning electron microscopy SEM showed that powders consist of micrometric aggregation of smaller particles. EDS examinations verified that the chemical elements Zn, Fe, Yb, and O are present in all samples. The direct bandgap energy values are calculated by Tauc’s plot, and it indicates a semiconductor character of our compound, revealing an increase and enhancement in bandgap energy values from 1.82 to 2.4 eV with Yb3+ substitution.
A deformation (strain) model of the spectrum of the density of localized states Nss(E,X) in p-Si(B,Mn) under uniaxial pressure X is presented. It is shown that shifts of trap levels can be described by the deformation energy Ed = kappa X, a mechanical analog of kT. At a fixed temperature T = 77 K, increasing X leads to a shift and restructuring of the spectrum: thermodonor (TD) levels move toward the conduction band, whereas manganese (Mn) levels shift toward the valence band, which agrees with the opposite trends observed in rho(X) and mu(X).
The interaction behavior of 1.25 MeV Co ions with Si, ZnO, and Mg-doped ZnO (ZnO:Mg) targets has been systematically analyzed using the latest SRIM 2013 simulations. The findings show that atomic displacements, the production of vacancies and energy loss are greatly influenced by the composition and structural density of the target. The results reveal that the highest number of atomic displacements is observed in crystalline Si, followed by ZnO, whereas Mg-doped ZnO exhibits the lowest displacement level. On the other hand, ZnO exhibits moderate defect generation, as its high atomic density and bonding energy make it harder for the lattice to become disordered. Moreover, the presence of Mg in the ZnO matrix slightly reduces overall damage, indicating that the lattice is more stable and tolerant to radiation. These results indicate that Mg doping improves the structural robustness of ZnO against high-energy Co-ion bombardment, thereby making ZnO:Mg films more appropriate for radiation-resistant optoelectronic and sensing applications.
Background: HDR brachytherapy represents a cornerstone in prostate cancer management by enabling high tumor doses while sparing surrounding normal tissues. Radiobiological modelling allows quantitative assessment of tumour control and normal tissue complication probability for optimization of fractionation schedules. Objective: The purpose of this study is to comparatively appraise the radiobiological outcome of two HDR brachytherapy regimens, 13.5 Gy × 2 fractions versus 15 Gy × 1 fraction, regarding tumor control probability, normal tissue complication probability, and dose-effect metrics in patients presenting with intermediate- to high-risk prostate cancer. Materials and Methods: A retrospective analysis of 20 patients treated by Co-60 HDR brachytherapy was performed. The treatment planning was image-based, in which, target and organ-at-risk delineation was followed standard guidelines. BED, EQD2, and Deff were computed using the linear-quadratic model. TCP and NTCP modeling utilized Poisson-based and Lyman–Kutcher–Burman methods, respectively. Correlations between radiobiological parameters and TCP/NTCP were analyzed. Results: The single 15 Gy fraction regimen resulted in significantly higher BED, EQD2, Deff, and modeled TCP compared with 13.5 Gy×2 fractions (p ≤ 0.031). However, NTCP for urethra at 10% volume was higher in the 15 Gy group (8.42% ± 1.58 vs. 6.86% ± 1.24; p = 0.006). Strong positive correlations were observed between BED, EQD2, Deff and TCP (ρ = 0.984–1.000; p < 0.001). NTCP at 30% urethral volume negatively correlated with BED, EQD2, and Deff (ρ ≈ -0.52; p = 0.003). Conclusions: Higher radiobiological doses (BED, EQD2, Deff) in prostate HDR brachytherapy are strongly associated with improved tumor control, with Deff showing perfect correlation with TCP. A single 15 Gy fraction yields greater radiobiological effectiveness than 13.5 Gy × 2. Urethral toxicity shows no clear correlation at 10% volume but a strong negative correlation at 30%, indicating that higher doses may reduce toxicity at this level. Radiobiological modeling is thus valuable for optimizing HDR planning, enhancing tumor control prediction, and balancing urethral toxicity.
