https://iopscience.iop.org/article/10.1088/1361-6463/aa67bf/pdf

The electronic band structure of Ge1−x Sn x in the full composition range: indirect, direct, and inverted gaps regimes, band offsets, and the Burstein–Moss effect

Arsenene nanoribbons for sensing NH3 and PH3 gas molecules – A first-principles perspective

Micro/nano structures have unique optical, electrical, magnetic, and thermal properties. Studies on the preparation of micro/nano structures are of considerable research value and broad development prospects. Several micro/nano structure preparation techniques have already been developed, such as photolithography, electron beam lithography, focused ion beam techniques, nanoimprint techniques. However, the available geometries directly implemented by those means are limited to the 2D mode. Laser machining, a new technology for micro/nano structural preparation, has received great attention in recent years for its wide application to almost all types of materials through a scalable, one-step method, and its unique 3D processing capabilities, high manufacturing resolution and high designability. In addition, micro/nano structures prepared by laser machining have a wide range of applications in photonics, Surface plasma resonance, optoelectronics, biochemical sensing, micro/nanofluidics, photofluidics, biomedical, and associated fields. In this paper, updated achievements of laser-assisted fabrication of micro/nano structures are reviewed and summarized. It focuses on the researchers' findings, and analyzes materials, morphology, possible applications and laser machining of micro/nano structures in detail. Seven kinds of materials are generalized, including metal, organics or polymers, semiconductors, glass, oxides, carbon materials, and piezoelectric materials. In the end, further prospects to the future of laser machining are proposed.

The Fabrication of Micro/Nano Structures by Laser Machining.

Two-dimensional WS2-based nanosheets modified by Pt quantum dots for enhanced room-temperature NH3 sensing properties

Graphene is one of the astounding recent advancements in current science and one of the most encouraging materials for application in cutting-edge electronic gadgets. Graphene and its derivatives like graphene oxide and reduced graphene oxide have emerged as significant nanomaterials in the area of sensors. Furthermore, doping of graphene and its derivatives with heteroatoms (B, N, P, S, I, Br, Cl and F) alters their electronic and chemical properties which are best suited for the construction of economical sensors of practical utility. This review recapitulates the developments in graphene materials as emerging electrochemical, ultrasensitive explosive, gas, glucose and biological sensors for various molecules with greater sensitivity, selectivity and a low limit of detection. Apart from the most important turn of events, the properties and incipient utilization of the ever evolving family of heteroatom-doped graphene are also discussed. This review article encompasses a wide range of heteroatom-doped graphene materials as sensors for the detection of NH3, NO2, H2O2, heavy metal ions, dopamine, bleomycinsulphate, acetaminophen, caffeic acid, chloramphenicol and trinitrotoluene. In addition, heteroatom-doped graphene materials were also explored for sensitivity and selectivity with respect to interfering analytes present in the system. Finally, the review article concludes with future perspectives for the advancement of heteroatom-doped graphene materials.

/pdf/heteroatom-doped-graphene-as-sensing-materials-a-mini-review-1r6c0gym3l.pdf

Heteroatom-doped graphene as sensing materials: a mini review

A supersaturation of nitrogen atoms is found in the surface layer of microstructured silicon after femtosecond (fs) laser irradiation in NF3. The average nitrogen concentration in the uppermost 50 nm is about 0.5 ± 0.2 at. %, several orders of magnitude higher than the solid solubility of nitrogen atoms in silicon. The nitrogen-hyperdoped silicon shows high crystallinity in the doped layer, which is due to the repairing effect of nitrogen on defects in silicon lattices. Nitrogen atoms and vacancies can be combined into thermal stable complexes after fs laser irradiation, which makes the nitrogen-hyperdoped silicon exhibit good thermal stability of optical properties.

A nitrogen-hyperdoped silicon material formed by femtosecond laser irradiation

Electricity-based response to NH3 of graphene oxide (GO) is demonstrated at ppm level at room temperature. The GO film prepared on planar silicon substrate shows weak response when exposed to 50 ppm NH3, response time less than 30 s and recovery time about 100 s. More interestingly, the GO film coated on laser-textured silicon substrate shows significant enhancement for sensor response, and meanwhile response/recovery time is mainly preserved. Furthermore, a good response of textured GO film is detected in a dynamic range of 5–100 ppm NH3. The surface morphology and chemical bonds of the textured GO film are studied by scanning electron microscope (SEM), Fourier Transform Infrared (FT-IR) Spectrometer and X-ray Photoelectron Spectrometer (XPS), respectively. The NH3 response is attributed to the polar oxygen configurations of GO and the enhanced response is due to the richer oxygen configurations that stem from cobwebby microstructure of GO.

/pdf/room-temperature-nh-3-sensing-of-graphene-oxide-film-and-its-rtrv1pjyz2.pdf

Room-temperature NH 3 sensing of graphene oxide film and its enhanced response on the laser-textured silicon.

The microstructured and hyperdoped silicon as a superior photoelectric and photovoltaic material is first studied as a gas-sensing material. The material is prepared by femtosecond-laser irradiation on selenium-coated silicon and then fabricated as a conductive gas sensor, targeting ammonia. At room temperature, the sensitivity, response time, repeatability, distinguishability, selectivity, and natural aging effect of the sensor have been systematically studied. Results show that such black silicon has good potential for application as an ammonia-sensing material. On the basis of its unique optoelectronic properties, an additional optical drive is proposed for the formation of an optical and electric dual-driven sensor, which is achieved by asymmetric light illumination between the two electrode regions. In a certain range of applied voltage, the sensitivity is enhanced dramatically and even tends to be infinite. For the aged device with degraded sensitivity, a two-order increment is obtained for 500 ppm ...

"Infinite Sensitivity" of Black Silicon Ammonia Sensor Achieved by Optical and Electric Dual Drives.

Arrays of high-quality crystalline conical spikes were formed on silicon surface in the presence of NF3 with femtosecond laser irradiation. The surface of the structures is smooth, and Raman scattering spectroscopy shows that few silicon polymorphs such as a-Si, Si-XII, and Si-III were observed in the conical structures. In the mid-infrared wavelength range of 3–16 µm, the structured surface exhibits a high absorptance up to 0.8. Additionally, the absorptance of the sample remains almost unchanged after the annealing process. These properties of the structured silicon will make it a promising material for mid-infrared applications in optoelectronic fields.

https://iopscience.iop.org/article/10.7567/APEX.6.081301/pdf

Strong Mid-Infrared Absorption and High Crystallinity of Microstructured Silicon Formed by Femtosecond Laser Irradiation in NF3 Atmosphere

Airborne hyperspectral images are used for crop identification with a high classification accuracy because of their high spectral resolution, spatial resolution, and signal-to-noise ratio (SNR). However, the tradeoffs between the three core parameters of a hyperspectral imager (SNR, spatial resolution, and spectral resolution) should be considered for designing an efficient imaging system. Only a few reported studies on the analysis of the impact of SNR on identification accuracy are available. Further, the tradeoffs and mutual interactions among these parameters are rarely considered. In this empirical study, our aim was to understand the relationship among the core parameters and their effects on crop identification accuracy by analyzing the tradeoffs and mutual interactions among these parameters. We analyzed the hyperspectral images of a typical plain agricultural area in Xiongan, China, acquired by the newly developed sensor airborne multimodular imaging spectrometer (AMMIS). The fundamental images were transformed to form datasets with different ranges of spectral resolution, spatial resolution, and SNR using data reconstruction methods. We adopted the classification and regression tree (CART), random forest (RF), and k-nearest neighbor (kNN) classifiers, and observed the overall accuracy (OA) across the degraded hyperspectral datasets. The experimental results indicated that the OA decreased with a decreasing SNR. As the spectral resolution became coarser, the OA first increased, plateaued, and then decreased. However, the OA increased with decreasing spatial resolution. This study was performed with the goal of bridging the knowledge gap between the back-end hyperspectral sensor designing and its front-end applications.

Haibin Sun

Papers

A nitrogen-hyperdoped silicon material formed by femtosecond laser irradiation

Room-temperature NH 3 sensing of graphene oxide film and its enhanced response on the laser-textured silicon.

"Infinite Sensitivity" of Black Silicon Ammonia Sensor Achieved by Optical and Electric Dual Drives.

Strong Mid-Infrared Absorption and High Crystallinity of Microstructured Silicon Formed by Femtosecond Laser Irradiation in NF3 Atmosphere

Tradeoffs in the Spatial and Spectral Resolution of Airborne Hyperspectral Imaging Systems: A Crop Identification Case Study