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The MgZnO/SiO2/ZnO metal–semiconductor–metal (MSM) dual-band UVA and UVB photodetectors (PDs) with different MgZnO thicknesses were fabricated by RF sputter. From the dark current, it was found that the PD with 200 nm thick MgZnO had a lower leakage current, which implies less defect density and better crystal quality. Therefore, the FWHM of the X-ray diffraction and grain size of the scanning electron microscope image for PDs with a thicker MgZnO thickness were narrower and larger than those of the others. From the photoluminescence (PL) at room temperature, the main defect types of the MgZnO/SiO2/ZnO thin film included Ov, Oi, and Zni. Then, a variable and voltage-controlled tunable wavelength of UV PD from UVB to UVA can be well accomplished by using a SiO2 blocking layer inserted between the MgZnO and ZnO thin film. Therefore, at a lower and higher bias voltage, the PD with a 200 nm thick MgZnO can detect the UVB and UVA range, respectively. [ABSTRACT FROM AUTHOR]

The effects of drain-source distance and applied voltage on low-frequency noise behavior of AIGaN/GaN metal-oxide- semiconductor heterostructure field-effect-transistors incorporated with a photochemical vapor deposited (photo-CVD) SiO2 gate oxide layer were investigated. According to our studies, the normalized noise power density is inversely proportional to L′ (=Ld-s - Lgate) when devices are biased in the linear region. However, the drain-source distance alone exerts little influence on low-frequency noise in the saturation and cutoff regions. Furthermore, the l/fr noise characteristics and the F value were affected by the interface state distribution in the energy bandgap as the gate bias was varied. The normalized noise power density determined is independent of the drain-source voltage in the linear region, but it exhibits an enhancement in the saturation region in response to an increase in the drain-source voltage. However, the noise power density then becomes constant when devices are biased in the cutoff region. [ABSTRACT FROM AUTHOR]

Objective. The arrangement of chromosomes in the cell nucleus has implications for cell radiosensitivity. The development of new tools to utilize Hi-C chromosome conformation data in nanoscale radiation track structure simulations allows for in silico investigation of this phenomenon. We have developed a framework employing Hi-C-based cell nucleus models in Monte Carlo radiation simulations, in conjunction with mechanistic models of DNA repair, to predict not only the initial radiation-induced DNA damage, but also the repair outcomes resulting from this damage, allowing us to investigate the role chromosome conformation plays in the biological outcome of radiation exposure. Approach. In this study, we used this framework to generate cell nucleus models based on Hi-C data from fibroblast and lymphoblastoid cells and explore the effects of cell type-specific chromosome structure on radiation response. The models were used to simulate external beam irradiation including DNA damage and subsequent DNA repair. The kinetics of the simulated DNA repair were compared with previous results. Main results. We found that the fibroblast models resulted in a higher rate of inter-chromosome misrepair than the lymphoblastoid model, despite having similar amounts of initial DNA damage and total misrepairs for each irradiation scenario. Significance. This framework represents a step forward in radiobiological modeling and simulation allowing for more realistic investigation of radiosensitivity in different types of cells., (Creative Commons Attribution license.)

A new nanodosimetry-based linear-quadratic (LQ) model of cell survival for mixed-LET radiations has been developed. The new model employs three physical quantities and three biological quantities. The three physical quantities are related to energy depositions at two nanometre scales, 5 nm and 25 nm. The three biological quantities are related to the lesion production and interaction probabilities and the lesion repair rate. The coefficients alpha and beta of the LQ formula (alpha D + beta D(2)) are explicitly expressed in terms of the three physical quantities and the three biological quantities. The new model is shown to be consistent with the previously published cell survival curves of V-79 cells. The advantage of this new model is that it can be conveniently adopted to estimate the iso-effect for radiotherapies that involve ionizing radiation of mixed LET. An example is given to estimate the cell survival fractions for a high-dose-rate mixed neutron and gamma-ray field from a (252)Cf source.