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The technique of point-defect engineering (PDE), with excess vacancies produced near the surface region by MeV Si ion implantation, has been applied to form ultrashallow junctions with sub-keV B implants. PDE can reduce boride-enhanced diffusion that dominates the enhanced diffusion of ultralow energy B implants. PDE can further sharpen the dopant profile and enhance boron activation. For 1×1015/cm2, 0.5 keV B implant, B solid solubility has been enhanced over a wide temperature range of 750–1000 °C, with an enhancement factor of 2.5 at 900 °C. These features have enabled a shallower and sharper box-like boron junction achievable by PDE in combination with ultralow energy 0.5 keV B implantation. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The secondary ion mass spectrometry (SIMS) response function to a B “δ surface layer” has been investigated. Using electron-gun evaporation combined with liquid nitrogen cooling of target, we are able to deposit an ultrathin B layer without detectable island formation. The B spatial distribution obtained from SIMS is exponentially decaying with a decay length approximately a linear function of the incident energy of the oxygen during the SIMS analysis. Deconvolution with the response function has been applied to reconstruct the spatial distribution of ultra-low-energy B implants. A correction to depth and yield scales due to transient sputtering near the Si surface region was also applied. Transient erosion shifts the profile shallower, but beam mixing shifts it deeper. These mutually compensating effects make the adjusted distribution almost the same as original data. The one significant difference is a buried B peak observed near the surface region. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Stability of p[sup +]/n junctions remains a critical issue for device performance. We report that the technique of point-defect engineering (PDE) can substantially increase the stability of ultrashallow junctions formed by molecular-beam epitaxy. It is shown that an as-grown 15 nm, 2×10[sup 20]/cm[sup 3] B-doped Si layer becomes unstable during 10 min thermal anneal above 650 °C. The thermal stability can be increased by performing a 5×10[sup 15]/cm[sup 2] 1 MeV Si ion implantation. The B profile with the MeV Si implant does not show significant diffusion during annealing up to 750 °C, and the final junction depth after an 800 °C/10 min anneal is about half that of an annealed unimplanted sample. Although with Mev implantation the as-implanted B profile becomes slightly deeper due to recoil implantation, and some of the B has been electrically deactivated by the MeV implantation, PDE is advantageous for postgrowth thermal processes above 700 °C. The mechanism causing the instability is discussed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We propose an electrically tunable temporal imaging system (TIS) based on four-wave mixing in a dispersion engineered graphene-based waveguide, which could realize a magnification factor of 1000× for a signal consisting of two 100-fs-wide pulses separated by 500 fs and a large working bandwidth of about 700 nm. The TIS was analyzed by solving the couple-mode equations in detail. It was demonstrated that the working wavelength range could be tuned via a small disturbed bias voltage applied to the graphene layer without changing the geometric structure of the waveguide. These results provide attractive insights for potential applications in integrated optics and optical communications. [ABSTRACT FROM AUTHOR]

Rates of microbial processes are fundamental to understanding the significance of microbial impacts on environmental chemical cycling. However, it is often difficult to quantify rates or to link processes to specific taxa or individual cells, especially in environments where there are few cultured representatives with known physiology. Here, we describe the use of the redox-enzyme-sensitive molecular probe RedoxSensor™ Green to measure rates of anaerobic electron transfer physiology (i.e., sulfate reduction and methanogenesis) in individual cells and link those measurements to genomic sequencing of the same single cells. We used this method to investigate microbial activity in hot, anoxic, low-biomass (~10³ cells mL-1) groundwater of the Death Valley Regional Flow System, California. Combining this method with electron donor amendment experiments and metatranscriptomics confirmed that the abundant spore formers including Candidatus Desulforudis audaxviator were actively reducing sulfate in this environment, most likely with acetate and hydrogen as electron donors. Using this approach, we measured environmental sulfate reduction rates at 0.14 to 26.9 fmol cell-1 h-1. Scaled to volume, this equates to a bulk environmental rate of ~103 pmol sulfate L-1 d-1, similar to potential rates determined with radiotracer methods. Despite methane in the system, there was no evidence for active microbial methanogenesis at the time of sampling. Overall, this method is a powerful tool for estimating species-resolved, single-cell rates of anaerobic metabolism in low-biomass environments while simultaneously linking genomes to phenomes at the single-cell level. We reveal active elemental cycling conducted by several species, with a large portion attributable to Ca. Desulforudis audaxviator. [ABSTRACT FROM AUTHOR]

After a major nuclear accident occurs in a nuclear facility, it is of great significance to quickly enter the accident area to obtain the radiation distribution of the site of nuclear leakage and radioactive contamination. In order to overcome the traditional nuclear emergency monitoring methods, which are prone to radiation damage to personnel, poor mobility and low efficiency, this paper designs and implements a UAV radiation monitoring system, which can quickly enter the sky over radioactive contaminated areas for radiation monitoring. The UAV radiation monitoring system mainly includes wide-range G-M counter tube, cerium bromide scintillator detector, data acquisition system and data transmission system. The above devices can be built on the UAV to measure the real-time radiation dose rate and energy spectrum at 0-100 m low altitude.

With the advancement of artificial intelligence and deep neural networks, the ease of image generation and editing has increased significantly.Consequently, the occurrence of malicious tampering and forgery using image generation tools is on the rise, posing a significant threat to multimedia security and social stability.Therefore, it is crucial to research detection methods for forged faces.Face tampering and forgery can occur through various means and tools, leaving different levels of forgery traces during the tampering process.These traces can be partly reflected in the image noise.From the perspective of image noise, the noise components reflecting tampering traces of forged faces were extracted through a noise removal module.Furthermore, noise attention was generated to guide the backbone network in the detection of forged faces.The training of the noise removal module was supervised using SRM filters.In order to strengthen the guidance of the noise removal module, the noise obtained by the noise removal module was added back to the real face image, forming a pair of supervised training samples in a self-supervised manner.The experimental results illustrate that the noise features obtained by the noise removal module have a good degree of discrimination.Experiments were also conducted on several public datasets, and the proposed method achieves an accuracy of 98.32% on the Celeb-DF dataset, 92.61% on the DFDC dataset, and more than 94% on the FaceForensics++ dataset, thus proving the effectiveness of the proposed method.

One approach to fabricate shallow junctions made of B-doped Si is to deposit B on Si, followed by knocking the B into the Si substrate with Si ions. Conventional belief is that the higher the implantation energy, the deeper the recoil profile. While this is true for low-energy incident ions, we show here that the situation is reversed for incident Si ions of higher energy due to the fact that recoil probability at a given angle is a strong function of the energy of the primary projectile. Our experiments show that 500 keV high-energy recoil implantation produces a shallower B profile than lower-energy implantation such as 10 and 50 keV. The secondary ion mass spectrometry analysis shows that the distribution of recoiled B atoms scattered by the energetic Si ions agrees with that calculated on the basis of interatomic potential suggested by W. D. Wilson, L. G. Haagmark, and J. P. Biersack [Phys. Rev. B 15, 2458 (1977)]. Sub-100 nm p[sup +]/n junctions have been realized with a 500 keV Si ion beam. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Performance of the material depends directly on the electronic and energy band structure, to improve the photoactivity of TiO2 and decrease carrier recombination centers induced by monodoping, the TiO2 thin film has been modified with V and N codopants by ion implantation for tailing and controlling the electronic structure and energy band structure. Compared to monodopant, codopants of V and N exhibit a synergistic effect in the photoactivity enhancement of TiO2. X-ray photoelectron spectroscopy (XPS) studies demonstrate that the implanted V and N ions are introduced into the lattice of TiO2 through V and N substituting Ti and O, respectively. The electronic structure of V/N codoped TiO2 was calculated by First-principles calculations based on density-functional theory, the results show the band edges of TiO2 can be tailored by V and N codopants. UV-vis spectra consistently show the absorption edge of V/N codoped TiO2 film is widen to visible light region. More importantly, the photoactivity of TiO2 film has been significantly improved after V/N codoping. The enhanced photocatalytic performance is believed to be due to the V and N codopants induced synergistic effect that not only enhances the absorption of visible light but also promotes the separation of photogenerated electrons and holes in TiO2. Besides, there exists an optimum for V/N ions implantation fluence. The capability of improving TiO2 photoactivity by V/N codoping could open up new opportunities in the development of highly efficient photocatalysts and photoelectrodes for solar energy and environmental applications. [ABSTRACT FROM AUTHOR]

Isobutyramide (IBA) has attracted considerable attention due to its expansive prospects for practical applications in the synthesis of drugs, dyes and other organic compounds. Herein we perform the high-pressure studies of IBA crystal by Raman spectral measurements at room temperature from ambient pressure to 30 GPa by using diamond anvil cells (DACs) to gain comprehensive insights into its structure and stability. Raman vibrational modes of IBA crystal at ambient pressure are resolved based on the experimental results and the first-principles theoretical calculations. High-pressure Raman scattering results show the Raman bands splitting, emergence/disappearance of the Raman bands and discontinuous wavenumber shifts at 1, 2 and 10 GPa, which indicate that IBA crystal undergoes three structural phase transitions at corresponding pressure. In addition, softening of the C = O and N-H stretching vibrational modes of IBA with increasing pressure can be interpreted by the reorganization of the hydrogen bond network of IBA molecules due to phase transition., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)