Micro- and nanostructures in vapor-phase-grown AlN on face-to-face annealed sputtered AlN (FFA Sp-AlN) templates formed on nanopatterned sapphire substrates (NPSS) were comprehensively analyzed using transmission electron microscopy. The comparison between metal-organic vapor-phase epitaxy-grown AlN/FFA Sp-AlN/hole-type NPSS (Sample MOH) and hydride vapor-phase epitaxy-grown AlN/FFA Sp-AlN/cone-type NPSS (Sample HVC) showed apparent differences in the morphology of dislocation propagation, presence of voids, shape of polarity inversion boundaries, and crystal structure on the slope region of NPSS. Notably, cross-sectional and plan-view observations revealed that the quality of FFA Sp-AlN significantly affects the threading dislocation density in the vapor-phase-grown layer. At the slope region of the AlN/NPSS interface, -AlON was observed in the MOH sample, while highly misaligned AlN grains were observed in the HVC sample. These characteristic crystal structures affect the occurrence of dislocations via different mechanisms in each sample. This study provides practical information for strategically controlling the micro- and nanostructures formed in AlN/NPSS structures for high-performance AlGaN-based deep-ultraviolet emitters.

To ensure stability for low-cost electronics used in direct contact with ionic solutions (such as electronic biosensors), electrodes are frequently passivated to protect against current leakage, which leads to corrosion. The epoxy-based polymer SU-8 yields favorable properties for passivation against ionic solutions. However, it is nearly universally patterned via cleanroom techniques, which increases device cost and fabrication complexity. Printing electronic components has been shown to be a viable approach for decreasing fabrication cost. Previous reports on SU-8 printing focus on the resultant printed structure, with little emphasis on its subsequent use as a passivation layer. Here, we demonstrate the printing of SU-8 with an aerosol jet printer using ultrasonic aerosolization. We show that SU-8 can be printed without reformulation, and that printed SU-8 is a viable passivation layer over conductive silver lines, when tested in ionic solutions. Extending the printed SU-8 film beyond the underlying conductive electrodes by 100 μm produced a six order of magnitude decrease in leakage current and resulted high stability over 20 voltage sweeps. Finally, we optimized post-printing cure time to 15 minutes at 160°C, which further minimized leakage current. While the development of low-cost, electronic biosensing devices has increasingly moved towards printing methods, the lack of a printed passivation strategy has hindered this transition. The advancements made in this study towards an aerosol jet printable SU-8 passivation layer provide useful progress towards a fully printed, stable electronic biosensing device.

The electron energy band alignment of the monolayer MoSe/oxide/Si system is characterized by internal photoemission spectroscopy, where the oxide is AlO or SiO. Raman and photoluminescence spectroscopic measurements confirm the high quality of monolayer MoSe exfoliated with gold film as medium. At the oxide flat-band condition, the band offset from the monolayer MoSe valence band maximum to the AlO and SiO conduction band minimum are measured to be (4.10 ± 0.05) eV and (4.80 ± 0.05) eV, respectively. By referencing the recently reported band gap value of 2.18 eV for monolayer MoSe, we obtain the electron affinity of monolayer MoSe to be (3.8 ± 0.1) eV on AlO/Si and (3.5 ± 0.1) eV on SiO/Si. It is believed that the results from this study will help accelerate the design of electronic and optoelectronic devices that employ this class of two-dimensional materials.

Rigorous electrostatic modeling of the specimen-electrode environment is required to better understand the fundamental processes of atom probe tomography (APT) and guide the analysis of APT data. We have developed a simulation tool that self-consistently solves the nonlinear electrostatic Poisson equation along with the mobile charge carrier concentrations and provides a detailed picture of the electrostatic environment of APT specimen tips. We consider cases of metals, semiconductors, and dielectrics. Traditionally in APT, and regardless of specimen composition, the apex electric field has been approximated by the relation , which was originally derived for sharp, metallic conductors; we refer to this equation as the "k-factor approximation". Here, is tip-electrode bias, is the radius of curvature of the tip apex, and is a dimensionless fitting parameter with . As expected, our Poisson solver agrees well with the k-factor approximation for metal tips; it also agrees remarkably well for semiconductor tips-regardless of the semiconductor doping level. We ascribe this finding to the fact that even if a semiconductor tip is fully depleted of majority carriers under the typical conditions used in APT, an inversion layer will appear at the apex surface. The inversion forms a thin, conducting layer that screens the interior of the tip -thus mimicking metallic behavior at the apex surface. By contrast, we find that the k-factor approximation applied to a purely dielectric tip results in values far greater than the typical range for metallic tips. We put our numerical results into further context with a brief discussion of our own, separate, experimental work and the results of other publications.

Ni-doped TiO nanoparticles have been synthesized by a modified sol-gel method. The crystal phase composition, particle size, and magnetic and optical properties of the samples were comprehensively examined using x-ray diffraction analysis, transmission electron microscopy, Brunauer-Emmett-Teller surface area analysis, Raman spectroscopy, magnetization measurements, and ultraviolet-visible (UV-Vis) absorption techniques. The results showed that the prepared Ni-doped TiO samples sintered at 400°C crystallized completely in anatase phase with average particle size in the range from 8 nm to 10 nm and presented broad visible absorption. The bactericidal efficiency of TiO was effectively enhanced by Ni doping, with an optimum Ni doping concentration of 6% ( = 0.06), at which 95% of were killed after just 90 min of irradiation. Density functional theory (DFT) calculations revealed good agreement with the experimental data. Moreover, the Ni dopant induced magnetic properties in TiO, facilitating its retrieval using a magnetic field after use, which is an important feature for photocatalytic applications.

An Al/-Si/poly[2-methoxy-5-(2-ethylhexoxy)--phenylenevinylene] (MEH-PPV)/Ag organic heterojunction has been prepared using homemade ultrasonic spray pyrolysis (USP) equipment for deposition of the organic thin film and physical vapor deposition (PVD) for the metallic contacts. The organic layer produced on glass was analyzed by optical and morphological methods. The bandgap of the organic thin film was found to be ~ 2.03 eV with a thickness of around 140 nm, using ultraviolet-visible (UV-Vis) and scanning electron microscopy (SEM) characterization, respectively. The amorphous nature of the MEH-PPV polymer was confirmed by its x-ray diffraction pattern. To determine the electrical parameters, the heterojunction based on MEH-PPV was characterized by current-voltage (-) and capacitance-voltage (-) measurements in the dark at room temperature. The ideality factor and barrier height of the organic heterojunction were found to be 3.6 eV and 0.56 eV to 0.59 eV, respectively, with an average series resistance of 94.39 Ω, based on the - characteristics. The barrier height was also calculated based on the capacitance-voltage measurements, yielding slightly different results due to the applied frequencies of 10 kHz ( ) and 1 MHz , respectively.

The ion-sensitive field-effect transistor (ISFET) is a popular technology utilized for pH sensing applications. In this work, we have presented the fabrication, characterization, and electrochemical modeling of an aluminum oxide (AlO)-gate ISFET-based pH sensor. The sensor is fabricated using well-established metal-oxide-semiconductor (MOS) unit processes with five steps of photolithography, and the sensing film is patterned using the lift-off process. The AlO sensing film is deposited over the gate area using pulsed-DC magnetron-assisted reactive sputtering technique in order to improve the sensor performance. The material characterization of sensing film has been done using x-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray photoelectron spectroscopy techniques. The sensor has been packaged using thick-film technology and encapsulated by a dam-and-fill approach. The packaged device has been tested in various pH buffer solutions, and a sensitivity of nearly 42.1 mV/pH has been achieved. A simulation program with integrated circuit emphasis (SPICE) macromodel of the AlO-gate ISFET is empirically derived from the experimental results, and the extracted electrochemical parameters have been reported. The drift and hysteresis characteristics of the AlO-gate ISFET were also studied, and the obtained drift rates for different pH buffer solutions of 4, 7, and 10 are 0.136 A/min, 0.124 A/min, and 0.108 A/min, respectively. A hysteresis of nearly 5.806 A has been obtained. The developed sensor has high sensitivity along with low drift and hysteresis.

Field-effect transistor biosensors (Bio-FET) have attracted great interest in recent years owing to their distinctive properties like high sensitivity, good selectivity, and easy integration into portable and wearable electronic devices. Bio-FET performance mainly relies on the constituent components such as the bio-recognition layer and the transducer, which ensures device stability, sensitivity, and lifetime. Nanomaterial-based Bio-FETs are excellent candidates for biosensing applications. This review discusses the basic concepts, function, and working principles of Bio-FETs, and focuses on the progress of recent research in Bio-FETs in the sensing of neurotransmitters, glucose, nucleic acids, proteins, viruses, and cancer biomarkers using nanomaterials. Finally, challenges in the development of Bio-FETs, as well as an outlook on the prospects of nano Bio-FET-based sensing in various fields, are discussed.

Electronic products are becoming an essential part of our daily life. There is a huge demand to produce small and portable but powerful electronic products. Carbon nanotubes (CNTs) have excellent electrical, mechanical and thermal properties which can be exploited to build next-generation electronics. This paper reviews different types and properties of CNTs and also presents the CNT-based electronics along with their advantage over the conventionally used products. CNT usage in electronics, such as biosensing, energy and data storage devices, is discussed. CNT-based field emission devices, which showed outstanding results are also discussed. The current challenges of CNT-based electronics and the future of CNT in electronics applications are mentioned.

To realize the resource utilization of waste mask fibers (MF), a layer of ZnS nanoparticles was grown on MF by a one-step hydrothermal method, and a MF/ZnS sensor was successfully prepared. This is the first time that resource utilization of MF has been combined with the development of a high-performance gas sensor. The MF/ZnS sensor showed high sensitivity and recoverability to target vapors at room temperature. Compared with ZnS powder loaded on a ceramic substrate, the MF/ZnS composite responses to four analytes have been improved by 8.4~35.2 times. In addition, the time for the MF/ZnS sensor to complete one response-recovery cycle for all four analytes was less than 30 s. This should be attributed to the high gas permeability of the MF substrate, which made the ZnS particles loaded on the MF more fully exposed to contact with the target vapors. This work not only provides a simple and low-cost method to optimize the sensing performance of gas sensors but also provides a new way for the resource utilization of MF.

We report herein the synthesis of ZnFeO (ZF) nanoparticles via a simple and eco-friendly green route using lemon juice as a reducing agent and fuel. The effect of different calcination temperatures on the particle size and bandgap of grown ZF nanoparticles was investigated. The structural, morphological and optical properties of the synthesized nanoparticles were evaluated using synchrotron x-ray diffraction (S-XRD), field emission scanning electron microscopy (FE-SEM) and UV-visible diffuse reflectance spectroscopy (UV-Vis-DRS), respectively. S-XRD confirmed a spinel F-d3m phase in all four samples calcined at 350°C, 550°C, 750°C and 1000°C. The crystallite size calculated from the Debye-Scherrer equation showed an increase from 14 nm to 20 nm with the increase in calcination temperature. Williamson-Hall (W-H) analysis revealed an increase in the particle size from 16 nm to 21 nm and a decrease in the lattice microstrain from 0.913 × 10 to 0.154 × 10 with the increase in calcination temperature. The optical bandgap of the ZF nanoparticles obtained from UV-Vis-DRS decreased from 2.265 eV to 2.225 eV with the increase in calcination temperature. The ZF nanoparticles with tunable particle size, lattice microstrain and optical bandgap have potential application in ferrofluid, electromagnetic shielding, photocatalysis, hyperthermia, dye degradation and other areas.

The mortality of people worldwide caused by COVID-19 has enhanced the research interest to design and develop power-efficient, low-cost, and sensitive biosensors to detect a wide range of biomolecules or foreign particles that can cause severe negative impact on humans. A novel Bio-RFET biosensor with hetero-material (HM) for source/channel and drain regions and hetero-dielectric (HD) is proposed, which acts as an -MOSFET or a -MOSFET and -TFET or -TFET. This HM-HD-RFET biosensor senses the biomolecules by the label-free dielectric modulation (DM) technique. When the biomolecules are present in the nanocavity, the biosensor can detect the biomolecules without labeling costs. It also changes the dielectric polarization within the nanocavities, and causes a drain current variation in the presence of an electric field. In this research article, (SiO + TiO) and an AlGaAs/Ge-based HD-HM-RFET have been analyzed for their use in biosensing. We found that the proposed device exhibits higher sensitivity as compared to a SiO + HfO-HM-RFET and a Si-based SiO + TiO-RFET for varying dielectric constants () from = 20-80 and charge densities in the range - 5 × 10 to 1 × 10 C/cm. Further, it can be noticed that -SiO + TiO-HM-TFET possesses the highest I-V sensitivity of 5.09 × 10, I/I ratio of 1.23 × 10, lowest SS of 20.3 mV/dec, and V of 1.48 V.

Nanomaterial-based room temperature gas sensors are used as a screening tool for diagnosing various diseases through breath analysis. The stable planar structure of boron carbide (BC) is utilized as a base material for adsorption of human breath exhaled VOCs, namely formaldehyde, methanol, acetone, toluene along, with interfering gases of carbon dioxide and water. The adsorption energy, charge density, density of states, energy band gap variation, recovery time, sensitivity, and work function of adsorbed molecules on pristine BC are analyzed by density functional theory. The computed adsorption energies of VOC are in the range of - 0.176 to - 0.238 eV, and a larger interaction distance validate the physisorption behavior of these VOCs biomarkers on pristine boron carbide monolayer. Minute changes are determined from the electronic band structure of all adsorbed systems conserving the semiconducting nature of the BC monolayer. The band gap variation upon adsorption of VOCs and interfering gases is examined between 0.05 and 0.52%. The 13.63 × 10 s recovery time of methanol is slower among VOCs, and 0.556 × 10 s of carbon dioxide (CO) is faster for desorption. The results reveal that boron carbide can be utilized as a biosensor at room temperature for the analysis of exhaled VOCs from human breath.

Two-dimensional materials are trending nowadays because of their atomic thickness, layer-dependent properties, and their fascinating application in the semiconducting industry. In this work, we have synthesized MoSe and WSe nanosheets (NSs) via a liquid-phase exfoliation method and investigated these NSs as channel materials in field-effect transistors (FET). The x-ray diffraction (XRD) pattern revealed that the synthesized NSs have a 2H phase with 0.65 nm -spacing which belongs to the (002) Miller plane. Transmission electron microscopy (TEM) studies revealed that MoSe and WSe have a nanosheet-like structure, and the average lateral dimensions of these NSs are ~ 25 nm and ~ 63 nm, respectively. From Raman spectra, we found that the intensity of the A vibrational mode decreases with the reduction in the number of layers. UV-visible spectroscopy revealed that the bandgap values of MoSe and WSe NSs are 1.55 eV and 1.50 eV, respectively, calculated using the Tauc equation. The output and transfer characteristics of the FET devices reveals that the fabricated FETs have good ohmic contact with the channel material and an ON/OFF current ratio of about 10 for both devices. This approach for the fabrication of FET devices can be achieved even without sophisticated fabrication facilities, and they can be applied as gas sensors and phototransistors, among other applications.

With the trend of technology development and carbon reduction, reducing the process temperature to prevent greenhouse effects is of great urgency. The back-end process of semiconductors is increasingly important because of the limitation of Moore's Law. High-temperature bonding is serious for semiconductor packages, which induces high cost and device damage. One of the critical ways to reduce the process temperature is to adopt low-temperature solders. In this study, we utilize the low-temperature solder Sn58Bi to achieve energy savings and device protection. The interfacial reactions between Sn58Bi and Cu after reflow and aging reactions were investigated. The solubility of Bi in Sn influences the Bi segregation at the interface. Partial Bi segregation, microvoids, and uneven CuSn were observed at the interface after aging. There is no doubt that the aforementioned structures are unfavorable for solder joint strength.