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Silicon photonics with the advantages of low power consumption and low fabrication cost is a crucial technology for facilitating high-capacity optical communications and interconnects. The graphene photodetectors (GPDs) featuring broadband operation, high speed, and low integration cost can be good additions to the SiGe photodetectors, supporting high-speed photodetection in wavelength bands beyond 1.6 μm on silicon. Here we realize a silicon-integrated four-channel wavelength division multiplexing (WDM) optical receiver based on a micro-ring resonator (MRR) array and four p-n homojunction GPDs. These photo-thermoelectric (PTE) GPDs exhibit zero-bias responsivities of ∼1.1 V W−1 and set-up limited 3 dB-bandwidth >67 GHz. The GPDs show good consistence benefiting from the compact active region array (0.006 mm2) covered by a single mechanically exfoliated hBN/graphene/hBN stack. Moreover, the WDM graphene optical receiver realized 4 × 16 Gbps non-return-to-zero optical signal transmission. To the best of our knowledge, it is the first GPD-array-based optical receiver using high-quality mechanically exfoliated graphene and edge graphene-metal contacts with low resistances. Apparently, our design is also compatible with CVD-grown graphene. This work sheds light on the large-scale integration of GPDs with high consistency and uniformity, enabling the application of high-quality mechanically exfoliated graphene, and promoting the development of the graphene photonic integrated circuits.

This study aims to explore the relationship among student engagement, adversity quotient, and academic achievement in higher education institutions, and to examine the moderating role of self-efficacy. Data from 413 college students were collected using convenience sampling and analyzed using the PROCESS macro in SPSS. The results indicate that student engagement positively affects academic achievement and that the adversity quotient plays a significant mediating role between student engagement and academic achievement. Furthermore, self-efficacy was found to have a moderating effect between student engagement and the adversity quotient, potentially strengthening the positive impact of student engagement on the adversity quotient to a certain extent. The study suggests that educators should focus on enhancing student engagement and self-efficacy and design personalized educational interventions to improve students’ adversity quotient and academic achievement.

Mid-infrared (MIR) silicon photonics have attracted great interest for potential applications in on-chip spectroscopy, free-space communication, and remote imaging. Currently, the high-performance and fabrication-friendly fiber-to-chip grating couplers operating at 3–4 μm wavelength band are still desired urgently. Here, we propose an efficient method for designing a 2D subwavelength grating coupler. The few analytical fitting parameters defining the subwavelength grating periods and fill factors in two dimensions enable a high design degree of freedom and a low search space dimension, resulting in high figure-of-merit and fast convergence simultaneously. The developed 3.7 μm grating coupler showcases record-high coupling efficiency both theoretically (−2.2 dB) and experimentally (−4.4 dB) among the 3–4 μm MIR counterparts. This study provides an effective method for designing fiber-to-chip grating couplers, by which the MIR grating couplers with high performance and fabrication ease are developed, thus paving the way for developing high-performance silicon photonic integrated circuits operating in the MIR wavelength band. [ABSTRACT FROM AUTHOR]

All‐optical modulation plays a key role in next‐generation optical processing and has attracted enormous attention worldwide. With extraordinary optoelectronic characteristics and friendly integration compatibility with various nanostructures, graphene shows great potential for ultrafast and energy‐efficient all‐optical modulation. Here, high‐efficiency on‐chip all‐optical modulation is experimentally demonstrated based on ultra‐thin silicon/graphene hybrid waveguides, which are complementary‐metal‐oxide‐semiconductor‐compatible and easy to fabricate. Owing to the enhanced light‐graphene interaction enabled by the ultra‐thin silicon photonic platform, the optical nonlinear absorption in graphene is greatly enhanced and a modulation depth of >2 dB is achieved with a saturation threshold of 0.9 pJ per pulse for a 50‐µm‐long modulator. The measured modulation efficiency is as high as 0.052 dB µm−1. Furthermore, the proposed all‐optical modulator has the potential to operate at a bandwidth of hundreds of gigahertz. The present hybrid integration of graphene on ultra‐thin silicon photonic waveguides paves the way toward the applications of on‐chip ultrafast and energy‐efficient all‐optical information processing. [ABSTRACT FROM AUTHOR]

This Letter is about the role of the bottom electrode in the resistive switching of SiNx-based resistive random-access memory. Titanium nitride (TiN) and platinum (Pt) are used as bottom electrodes to fabricate devices whose I–V characteristics are compared. The devices with Pt as the bottom electrode have digital resistive switching behavior with a main memory window. However, the devices with TiN as the bottom electrode provide an analog resistive switching with the gradual operation. We propose that this switching difference is due to the different work functions of the top and bottom electrodes and the nitrogen-rich layer formed at the SiNx/TiN interface. The work function of the bottom electrode is larger than the top electrode in the device with Pt electrodes, which are considered non-reactive. However, the difference in the work functions between the bottom and top electrodes is not much for the device with a TiN electrode. As the nitrogen-rich layer formed at the SiNx/TiN interface has nitrogen accommodation ability, the nitrogen ions are more likely to drift to the bottom electrode, and resistive switching changes from digital to analog for the device with TiN electrodes. [ABSTRACT FROM AUTHOR]

In this Letter, a Pt/SiNx/TiN/Ta resistive random access memory (RRAM) is proposed, which has low switching voltage, uniform resistance distribution, excellent cycle-to-cycle stability, and excellent nonvolatile performance. As an insertion layer, TiN prevents excessive absorption of nitrogen ions by a Ta electrode and avoids the formation of the unstable metal–semiconductor interface, which significantly reduces cycle-to-cycle variability of SiNx-based RRAM. Due to high conductivity, the TiN layer has a small voltage divider effect when voltage was applied, which helps to achieve low power consumption characteristics. This paper provides a direction for improving performance of nitride-based RRAM, which is useful for further development of highly reliable RRAM. [ABSTRACT FROM AUTHOR]

This article presents an analysis of the effect of the Ta‐doping position on the performance of SiNx‐based resistive random access memories by comparing the electrical properties and conduction mechanisms of the devices. The electrical test results show that when the doping position moves down in the resistive switching (RS) layer, the resistance window of the device increases during the resistive switch process. However, the consistency of the parameter distribution decreases. The conduction mechanism of all Ta‐doped devices behaves as space charge limited current. According to the analysis of the RS model of the device, Ta in the RS layer connects and disconnects with the localized conductive filaments. The adjustment ability of the doping layer on the conductive channel and the reduction of the device stability when the doping position moves up are proposed. Proper Ta doping in the middle of the RS layer of the device allows the device to obtain a large resistance window with relatively stable characteristics. [ABSTRACT FROM AUTHOR]

Silver nanoparticles are susceptible to oxidation and have accordingly received less attention than gold nanoparticles; ultrastable silver nanoparticles are now reported, which can be produced in very large quantities as a single-sized molecular product, and the origins of their enhanced stability are elucidated using a single-crystal X-ray structure and first-principles calculations. Silver nanoparticles as good as gold Noble metals in nanoparticulate form find practical application as catalysts and in optoelectronics, energy conservation and many other fields. Gold nanoparticles, stable and easy to use, have proved much more useful and so have been studied more extensively than silver nanoparticles, which tend to be susceptible to oxidation. Anil Desireddy et al. describe a simple recipe for the large-scale production of single-sized silver nanoclusters, whose electronic structure gives them exceptional chemical stability. With the availability of stable silver nanoparticles, the metal's desirable electrical and physical properties, abundance and comparatively low cost could be harnessed in a wealth of new applications. Noble-metal nanoparticles have had a substantial impact across a diverse range of fields, including catalysis.sup.1, sensing.sup.2, photochemistry.sup.3, optoelectronics.sup.4,5, energy conversion.sup.6 and medicine.sup.7. Although silver has very desirable physical properties, good relative abundance and low cost, gold nanoparticles have been widely favoured owing to their proved stability and ease of use. Unlike gold, silver is notorious for its susceptibility to oxidation (tarnishing), which has limited the development of important silver-based nanomaterials. Despite two decades of synthetic efforts, silver nanoparticles that are inert or have long-term stability remain unrealized. Here we report a simple synthetic protocol for producing ultrastable silver nanoparticles, yielding a single-sized molecular product in very large quantities with quantitative yield and without the need for size sorting. The stability, purity and yield are substantially better than those for other metal nanoparticles, including gold, owing to an effective stabilization mechanism. The particular size and stoichiometry of the product were found to be insensitive to variations in synthesis parameters. The chemical stability and structural, electronic and optical properties can be understood using first-principles electronic structure theory based on an experimental single-crystal X-ray structure. Although several structures have been determined for protected gold nanoclusters.sup.8,9,10,11,12, none has been reported so far for silver nanoparticles. The total structure of a thiolate-protected silver nanocluster reported here uncovers the unique structure of the silver thiolate protecting layer, consisting of Ag.sub.2S.sub.5 capping structures. The outstanding stability of the nanoparticle is attributed to a closed-shell 18-electron configuration with a large energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, an ultrastable 32-silver-atom excavated-dodecahedral.sup.13 core consisting of a hollow 12-silver-atom icosahedron encapsulated by a 20-silver-atom dodecahedron, and the choice of protective coordinating ligands. The straightforward synthesis of large quantities of pure molecular product promises to make this class of materials widely available for further research and technology development.sup.14,15,16,17,18., Author(s): Anil Desireddy [sup.1] , Brian E. Conn [sup.1] , Jingshu Guo [sup.1] , Bokwon Yoon [sup.2] , Robert N. Barnett [sup.2] , Bradley M. Monahan [sup.1] , Kristin Kirschbaum [...]

Low-damage plasma oxidation treatment for AlN/GaN high-electron-mobility transistors (HEMTs) was developed in this letter, with which high-performance enhancement-mode (E-mode) AlON/AlN/GaN HEMTs were demonstrated. After removal of in situ SiN cap layer within gate area, remote plasma oxidation (RPO) treatment of 4.9nm AlN barrier layer at 300 °C leads to formation of AlON insulator layer and effective depletion of 2-D electron gas channel, without etch-induced damage or serious interfacial issues compared with the commonly used gate- recess metal-insulator-semiconductor HEMTs. Thanks to the low-damage RPO treatment, the achieved E-mode HEMTs with threshold voltage of 0.4 V exhibit quite a small loss of output current (7.8%) compared with the depletion-mode devices. In addition, the AlON gate insulator layer results in a remarkable increase in breakdown voltage of devices from 20 V to 74 V, which benefits the high-voltage operation of AlN/GaN technology. Further investigation shows that the oxidation process of AlN barrier tends to be saturated with treatment time increasing, providing a promising solution to the high-performance E-mode operation of scaled GaN-based HEMTs in RF applications. [ABSTRACT FROM AUTHOR]

This Letter investigates the effect of non-inert electrode thickness on the performance of complementary resistive switching (CRS). Five devices with different Ta electrode thicknesses (0, 2, 5, 10, and 20-nm) are fabricated. For devices with 2, 5, and 10-nm electrode thicknesses, CRS behavior can be obtained through an evolution process, while devices with 0 and 20-nm Ta electrode thicknesses always maintain stable bipolar resistive switching behavior. By analyzing the evolution process and current conduction mechanisms, the influence of non-inert electrode thickness on the performance of CRS is studied, and different oxidation degrees of a non-inert electrode are used to explain the different resistive switching performance in these devices. Aside from that, the model is verified by applying an asymmetric voltage sweeping method. This paper further clarifies the physical mechanism of CRS behavior in non-inert electrode resistive random access memory and provides a way to optimize the performance of CRS behavior. [ABSTRACT FROM AUTHOR]

Bacteriophage [lambda] gene Q protein and the related proteins of other lambdoid phages are transcription antiterminators that interact both with DNA in the late gene promoter segment and with RNA polymerase subunits. Using hybrids between Q of [lambda] and the related Q of phage 80, we characterized elements of both Q and DNA that contribute to the DNA binding function. In particular, we found a C-terminal segment of the protein that is responsible for binding specificity and an ~15 residue segment on a predicted alpha helix within this segment at which alanine substitutions decrease DNA binding. We identified a six-nucleotide segment located between the -35 and -10 promoter elements that confers binding specificity and is the site of point mutants that impair binding, and we isolated suppressors in [lambda] Q that restore binding function by increasing the overall binding affinity. We also identified putative zinc finger structures in both proteins.

The introduction of PbS QD (quantum dot) films has been proved, dramatically, to optimize the resistive switching (RS) performance in oxide resistive random access memory. In order to optimize parameters to a greater extent, the necessity of in-depth understanding of the resistance switching mechanism is self-evident. In this paper, PbS QD layers were inserted into a Ta/AlOxNy/Pt structure device in different positions in order to investigate the influence of the device structure in the PbS QD film inserted device. The Ta/PbS QDs/AlOxNy/Pt device with a Ta anion reservoir and a PbS QD film anion reservoir in the same direction exhibits excellent optimization of parameters, which is ideal for low-power devices. A model is constructed to elaborate the resistive switching process. Moreover, modulation of PbS QD film thickness on RS has been studied. A device with middle thickness of the PbS QD films combines low voltage, low current, and excellent stability, which is believed to be a favorable structure for the PbS QD inserted device. [ABSTRACT FROM AUTHOR]

This paper reported the Pt/AlOxNy/Ta structure with oxygen scavenging metal Ta as a top electrode in order to achieve excellent data storage and the artificial synaptic function. As a series resistance layer and a thermal enhanced layer, the TaOx interface layer between the resistance switching (RS) layer and the top electrode (TE) can greatly affect the RS characteristics. These effects can be attributed to properties of the interface layer such as thermal and electrical conductivities, suggesting that properties of the interface layer should be carefully and systematically considered if excellent RS characteristics are desirable. Based on the electrical testing and current conduction mechanism analyses, the major factors affecting the bipolar gradual RS behavior can be concluded as the property of the interface layer between the RS layer and TE, the Joule heating caused by current, and the distribution of the electric field on the interface layer. [ABSTRACT FROM AUTHOR]

At present, the physical mechanism of complementary resistive switching (CRS) devices remains controversial. In this Letter, stable CRS can be achieved in Pt/AlOxNy/Ta resistive random access memory (RRAM). A dynamic evolution from bipolar resistive switching to CRS can be evidently observed in non-inert electrodes RRAM. The causes of CRS behavior are analyzed in detail, and these phenomena are attributed to the different oxidation degrees of the top electrode and propose that the transition state can be used as a signal for the emergence of CRS behavior. Moreover, the model is partially supported by measured switching behavior of the Pt/AlOxNy/TaOx device. This research contributes to the understanding of the CRS behavior physical mechanism in non-inert electrodes RRAM devices. [ABSTRACT FROM AUTHOR]

Archie's parameters are substantial to be investigated in the evaluation of water saturation. Many researchers adhered to the opinion that Archie's equation can still be applied to water saturation calculation in shale if the accuracy of relative parameters could be improved. External conditions, such as temperature, confining pressure, water salinity, wettability, and displacement, may influence the determination of Archie's parameters. The aim of the study is to investigate the effect of salinity on Archie's parameters and their correlation with mineral composition and pore structure. The mineral contents and petrophysical properties were firstly acquired through X-ray diffraction (XRD) and basic measurements. Rock-electric experiments under different salinity were conducted on deep shale samples taken from Longmaxi (LMX) Formation in Luzhou (LZ). The results indicate that Archie's parameters of " a ," " b ," " m ," and " n " under actual brine salinity are assigned to 1.47, 1, 1.26, and 1.6, respectively. Our cementation factor is lower than that in other studies including (shaly) sandstones, carbonates, and shales, probably due to the extremely low porosity in study area. Salinity has a positive effect on cementation factor (m) and saturation exponent (n), suggesting the traditional assignment to Archie's parameters is inappropriate. It was concluded that the complicated pore structure and high porosity mainly associated with clay mineral may trigger the increased cementation factor. Further mathematical derivations confirmed that the rock resistivity is inextricable from pore system and establish a physical model. The paper provides a solid evidence base for further understanding and evaluation of water saturation in unconventional shale reservoirs, more significantly, innovatively unveils the research into Archie formula in deep shale reservoirs of southern Sichuan basin. [ABSTRACT FROM AUTHOR]

In this work, the mechanism of reliability of high resistance state (HRS) in AlOxNy-based resistive random access memory (RRAM) has been studied. The Ta/AlOxNy/Pt devices with high quality of the Schottky contact in the Ta/AlOxNy interface show excellent HRS reliability and low power consumption characteristics. We propose that the resistive switching (RS) process is caused by the migration of oxygen ions in the AlOxNy-based RRAM device, and the quality of the metal–semiconductor Schottky contact directly determines HRS reliability in AlOxNy-based RRAM. [ABSTRACT FROM AUTHOR]

This Letter studies the effect of crystallinity on the performance of AlN-based resistive random access memory using rapid thermal annealing. We compared I–V characters of devices fabricated at different annealing temperatures. By increasing the crystallinity of an AlN film, switching voltages and the memory window increase. Meanwhile, the reliability of the device improves. It is found that the electron conduction mechanism fits in with the space-charge-limited conduction model. Based on the above phenomena, we purpose that the crystallization leads to a decrease in vacancies within the AlN film, while it enhances local effects of grain boundaries on the electron transport. Both of these conclusions can result in an increase in switching voltages and the memory window. This paper can provide a platform for further studies on improving the performance of AlN-based devices. [ABSTRACT FROM AUTHOR]

This Letter studies the effect of the nitrogen capture ability of quantum dots on resistive switching characteristics of AlN-based resistive random access memory. We prepared a single layer AlN device and four types of AlN/PbS quantum dot stacked structure devices with different concentrations. Compared with the single layer AlN device, the AlN/PbS quantum dot stacked structure devices exhibit excellent resistive switching characteristics, such as forming-free, low power consumption, and excellent stability. We propose that the resistive switching process is determined by the migration of nitrogen ions and the lead sulfide (PbS) quantum dot layer as a natural nitrogen ion reservoir, which can improve the resistive switching characteristics. Moreover, the size of the natural nitrogen ion reservoir can be modulated by changing the concentration of quantum dots. [ABSTRACT FROM AUTHOR]