Lateral Barrier Research Articles

Experimental assessment of an air curtain-sealed personal protective equipment for medical care: Influence of breathing and thermal plume

This paper presents the performance assessment of a novel air-sealed visor for medical care based on experiments. This Personal Protective Equipment (PPE) provides effective aerodynamic sealing of the breathing zone, thus reducing the risk of inhaling droplets and aerosols carrying a potential viral load. The air curtain supply system was designed after computational fluid dynamics exploratory simulations to determine suitable airflow conditions. The main parameters under study are the air curtain velocities and the fraction of contaminated air in the breathing zone. The impact of different airflow rates, human breathing, thermal plume and lateral barriers to reduce the risk of leakage, was investigated. For the designed airflow rate and considering the worst-case scenario with a contaminated environment, results indicate that this PPE can reduce the contaminated air in the breathing zone by 31% and 82%, without and with lateral physical barriers, respectively. Although the human body thermal plume has a high impact on the air curtain velocity profile, it just affects the device efficiency by 2%. The breathing process increases the air curtain velocities improving the PPE efficiency by 32%. This study shows the potential of using a visor with aerodynamic sealing as an infection control barrier for healthcare workers.

Physical modelling of the interaction between a tunnel and a building in a liquefying ground and its mitigation

The fast growth of the built environment in liquefaction-prone areas requires new design challenges to be overcome. A significant soil shear strength and stiffness loss associated to soil liquefaction, possibly occurring during severe earthquakes, may induce effects on buildings and on shallow and light structures such as urban tunnels. In densely urbanised areas, interaction between underground and aboveground structures may results in a detrimental combination of such effects.The paper discusses the results of a series of centrifuge tests carried out at the Schofield Centre (Cambridge, UK) modelling the dynamic interaction between an urban tunnel and a building in sand undergoing cyclic liquefaction. Four reduced-scale models were tested at increased gravity to model a prototype 60 times larger. A rectangular aluminium frame embedded in a layer of homogeneous Hostun sand represented a section of a metro tunnel. An aluminium sway frame represented a simple building founded in the same layer, at a side of the tunnel. The experimental results show that in typical urban spacing, sand liquefaction in the foundation ground affects the reciprocal interaction between the kinematic of the tunnel and the building.Centrifuge modelling investigated whether it is possible to mitigate or prevent such interference by improving ground through the addition of hydrated laponite beneath the tunnel floor or as lateral vertical barrier between the building foundation and the tunnel. The results also show the importance of temporary structures – often used to support soil excavation during cut-and-cover tunnel construction – in reducing the effects of interaction between the tunnel and the building in the liquefying soil.

Lateral p-type GaN Schottky barrier diode with annealed Mg ohmic contact layer demonstrating ideal current–voltage characteristic

We have demonstrated the fabrication process for a lateral p-type Schottky barrier diode (SBD) with the annealed Mg ohmic contact layer on a MOVPE-grown p-GaN wafer and measured the electrical characteristic of the diode. Because of the selective-area ohmic contact, the interface between the Schottky electrode and p-type GaN is well protected from any damage introduced by dry-etching or regrowth. The ideality factor of the forward current–voltage characteristic is as low as 1.09 at room temperature and an on–off ratio above 109 is also achieved. Various metals are deposited as the Schottky electrode and the work function dependence of the Schottky barrier height is confirmed with a pinning factor of 0.58. The temperature dependence of the current–voltage characteristic indicates that the GaN p-type SBD still fits the thermionic emission mode at 600 K with an ideality factor of 1.1. The reverse current of the p-SBD is also studied with the Poole–Frenkel emission model, and the trap energy level in the p-GaN is confirmed.

Interface engineering in epitaxial growth of sputtered β-Ga2O3 films on Si substrates via TiN (111) buffer layer for Schottky barrier diodes

The native amorphous silicon oxide (SiO2) layer formed on the Si substrate leads to the (100) preferred orientation for β-phase gallium oxide (β-Ga2O3), which encounters various defects in β-Ga2O3, such as twin boundaries and stacking faults etc. The (111) preferred orientation of titanium nitride (TiN) hetero-buffer layer can be used in the interface between β-Ga2O3 and Si substrates to reduce the lattice mismatch between them and increase the (˗201) preferred orientation for β-Ga2O3. The lattice mismatch between TiN (111) and β-Ga2O3 (˗201) is 0.76%, which is less than the β-Ga2O3 (˗201)/Si (111) about ˗6.3%. The β-Ga2O3 and TiN films were grown using radio-frequency magnetron sputtering on Si substrates, which possess polycrystalline nature as revealed using X-ray diffraction patterns and high-resolution transmission electron micrographs. The optimal parameters are found as, process atmosphere: Ar = 10 sccm, RTA: 800 °C for β-Ga2O3/TiN (300 nm)/Si. This work highlights the effect of the TiN hetero-buffer layer, the process atmosphere, and annealing temperatures on the microstructural and surface morphology of β-Ga2O3 films. The lateral Schottky barrier diode (SBD) were fabricated using the optimized β-Ga2O3/TiN (300 nm)/Si film. The Baliga's Figure of Merit (BFOM) of the lateral SBD is 7.60 × 10−2 kW/cm2, which exhibits 4 order of BFOM higher than that of β-Ga2O3/Si SBD due to interface engineering. The β-Ga2O3/TiN (300 nm)/Si hetero-structure demonstrates a promising material to be employed in the next generation β-Ga2O3 based power devices.

Septin Defects Favour Symmetric Inheritance of the Budding Yeast Deceptive Courtship Memory.

Mnemons are prion-like elements that encode cellular memories of past cellular adaptations and do not spread to progenies during cell divisions. During the deceptive courtship in budding yeast, the Whi3 mnemon (Whi3mnem) condenses into a super-assembly to encode a mating pheromone refractory state established in the mother cell. Whi3mnem is confined to the mother cell such that their daughter cells have the ability to respond to the mating pheromone. Confinement of Whi3mnem involves its association with the endoplasmic reticulum membranes and the compartmentalization of these membranes by the lateral membrane diffusion barrier at the bud neck, the limit between the mother cell and the bud. However, during the first cell division after the establishment of the pheromone refractory state, this adaptation is more likely to be inherited by the daughter cell than in subsequent cell divisions. Here, we show that the first cell division is associated with larger daughter cells and cytokinesis defects, traits that are not observed in subsequent cell divisions. The cytoskeletal septin protein shows aberrant localisation in these divisions and the septin-dependent endoplasmic reticulum membrane diffusion barrier is weakened. Overall, these data suggest that cytokinesis defects associated with prolonged cell division can alter the confinement and inheritance pattern of a cellular memory.

1651-V All-Ion-Implanted Schottky Barrier Diode on Heteroepitaxial Diamond With 3.6 × 10⁵ On/Off Ratio

In this letter, we have reported a lateral diamond Schottky barrier diode (SBD) that was fabricated on a heteroepitaxial diamond substrate using all ion-implantation processes. The SBD exhibited a lower reverse leakage current, which resulted in an unprecedentedly high rectification ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.6\times 10^{{5}}$ </tex-math></inline-formula> when compared to ion-implanted diamond diodes. The reverse breakdown voltage was measured to be 1.65 kV- the highest measurement ever reported among ion-implanted diamond devices. In addition, the ideality factor and Schottky barrier height were determined as 4.9 and 1.4 eV, respectively, under the forward bias conditions. This study revealed the improvement of ion-implanted diamond SBD by using high-quality heteroepitaxial diamond substrates and low channel doping concentration.

Design and Optimization of Self‐Isolation GaN HEMT with Lateral‐Polarity‐Structure

Herein, polarization‐induced self‐isolation free from process damages in AlGaN/GaN high‐electron‐mobility transistor (HEMT) by the incorporation of lateral‐polarity structure (LPS) is demonstrated. The incorporation of LPS into the AlGaN/GaN heterojunction shows that 2D electron gas (2DEG) is formed in the III‐polar heterojunction but depleted in the N‐polar counterpart. A large lateral barrier height of 3.5 eV between the III‐polar and N‐polar domain boundary is revealed and buffer leakage is proved to be responsible for the weakened isolation characteristics. To suppress the buffer leakage, the influence of the AlGaN buffer on the leakage current is comprehensively investigated. Compared to pure GaN film and AlGaN/GaN heterojunction, two‐terminal isolation leakage current in AlGaN/GaN/Al0.2Ga0.8N heterojunction is greatly reduced by about nine orders of magnitude to as low as 10−11 A as experimentally confirmed. The incorporation of LPS into AlGaN/GaN heterojunction provides a novel planar isolation technique with excellent device performance by eliminating the isolation leakage path.

Mechanistic understanding of the interfacial properties of metal-PtSe2 contacts.

With the advantages of a moderate band gap, high carrier mobility and good environmental stability, two-dimensional (2D) semiconductors show promising applications in next-generation electronics. However, the accustomed metal-2D semiconductor contact may lead to a strong Fermi level pinning (FLP) effect, which severely limits the practical performance of 2D electronics. Herein, the interfacial properties of the contacts between a promising 2D semiconductor, PtSe2, and a sequence of metal electrodes are systematically investigated. The strong interfacial interactions formed in all metal-PtSe2 contacts lead to chemical bonds and a significant interfacial dipole, resulting in a vertical Schottky barrier for Ag, Au, Pd and Pt-based systems and a lateral Schottky barrier for Al, Cu, Sc and Ti-based systems, with a strong FLP effect. Remarkably, the tunneling probability for most metal-PtSe2 is significantly high and the tunneling-specific resistivity is two orders of magnitude lower than that of the state-of-the-art contacts, demonstrating the high efficiency for electron injection from metals to PtSe2. Moreover, the introduction of h-BN as a buffer layer leads to a weakened FLP effect (S = 0.50) and the transformation into p-type Schottky contact for Pt-PtSe2 contacts. These results reveal the underlying mechanism of the interfacial properties of metal-PtSe2 contacts, which is useful for designing advanced 2D semiconductor-based electronics.

Comparison of contact metals evaporated onto monolayer molybdenum disulfide

Understanding and improving the contact resistance of two-dimensional materials for the fabrication of next-generation devices is of vital importance to be able to fully utilize the new physics available in these materials. In this work, eight different contact metals (Ag, Au, Cr, Cu, In, Mo, Ni, and Ti) have been investigated using the same sample of monolayer MoS2. Through the fabrication and testing of multiple, identically sized field-effect transistor devices per contact metal, we compensate for large variability in electrical properties of as-grown chemical vapor deposition MoS2 and deduce the relative performance of each metal. The general trend of lower work function metals having lower contact resistance holds with In, Ag, and Ti performing the best of the metals tested. Our results are compatible with recent research suggesting that the contact resistance in undoped, monolayer MoS2 is dominated by a lateral junction resistance, and we provide context for how this manifests in device-to-device variation. Multiple orders of magnitude differences in contact resistance are observed between metals and can be explained by this lateral barrier operating in the thermionic-field emission regime.

Analysis of electrical properties in lateral Schottky barrier diode based on n-GaN and AlGaN/GaN heterostructure

In this paper, the lateral Schottky barrier diodes (SBDs) with small capacitance and low turn-on voltage (Von) were fabricated on n-GaN and AlGaN/GaN heterostructure. The capacitances of lateral n-GaN SBD and lateral AlGaN/GaN SBD are 1.35 pF/mm and 0.70 pF/mm, respectively. Compared with the planar SBDs, the capacitances of lateral SBDs are reduced by about two orders of magnitude without sacrificing the performance of on-resistance (Ron) and reverse leakage current. For the planar and lateral n-GaN SBDs, the value of the Von is similar. However, compared with the planar AlGaN/GaN SBD, the Von of lateral AlGaN/GaN SBD is reduced from 1.64 V to 0.87 V owing to the anode metal directly contacting the two-dimensional electron gas. According to temperature-dependent I-V results, the barrier inhomogeneity of the lateral SBD is more intensive than the planar SBD, which is attributed to etching damage. The withstand voltage of SBD is a very important parameter for power electronic applications. Compared with the breakdown voltage of 73 V in the lateral n-GaN SBD, the lateral AlGaN/GaN SBDs exhibit a breakdown voltage of 2322 V. In addition, we found that Schottky contact introduces anode resistance (RA) by analysing the Ron distribution of lateral SBDs. The experimental results also show that the RA of lateral n-GaN SBD and lateral AlGaN/GaN SBD are 10.5 Ω mm and 9.2 Ω mm respectively, which are much larger than the ohmic contact resistance due to worsening anode contact by metal-induced gap states.

Effect of gamma irradiation on GaN lateral Schottky barrier diodes

The effect of gamma irradiation on GaN lateral Schottky barrier diodes (SBDs) has been investigated. Six gamma irradiation conditions were carried out, namely 100/500 k rad, 1 M rad, 100/500 k rad and 100°C, and 1 M rad and 100°C. All the irradiated devices have a similar parameter variation tendency. There is no change for turn-on voltage. The on-state resistance is reduced from 5.32~5.53 Ω to 5.10~5.26 Ω, while the reverse leakage at -100 V is increased from 3.53~4.99 μA to 4.13~5.79 μA. The interface information extracted is improved slightly, demonstrating the anode/GaN interface is improved, and the passivation/AlGaN interface may be degraded. The slight variation of irradiated performance demonstrates that the GaN lateral SBDs are hardly affected by gamma irradiation.

MATHEMATICAL LATERAL THINKING OBSTACLES IN SOLVING GEOMETRIC PROBLEMS BASED ON BRAIN DOMINANCE

Creative thinking was characterized by the emergence of new ideas which was an important skill for students. Lateral thinking was one way to grow new ideas. Generally, related research was carried out to see the thinking process and its level only with the results of the majority of low levels (especially in geometry problems), so further research was needed to find out what were the obstacles. This study aims to find mathematical lateral thinking barriers based on brain dominance. This research was a qualitative research with a case study approach. The instruments were a brain dominance test, creativity questions, and geometry questions for lateral thinking. Triangulation of data collection techniques was carried out To ensure data validity. Obtained two main subjects LCS and RCS. Analysis of subjects' answers, interview and observations transcripts were carried out by coding the inhibiting factors then analyzed by Toulmin's arguments analysis. We findings that left-brain dominant student experience ontogenic barriers in finding something new caused bounded by concepts and right-brain dominant student experience epistemological barriers in finding different ways cause bounded by context. Further research was needed with students who have high mathematical abilities and creativity to find out how to overcome lateral thinking obstacles.

P-type ohmic contacts of MBenes with MoS2 for nanodevices and logic circuits

Based on first-principles calculations and quantum transport simulations, we systematically investigate the possibility of using two-dimensional transition metal borides (MBenes) as electrodes for two-dimensional monolayer MoS2 via interfacial interactions, band bending, vertical Schottky barrier, tunneling probability, and lateral Schottky barrier. The weak interaction between the functionalized MBenes and MoS2 results in MoS2 retaining its original intrinsic properties while significantly reducing the Fermi level pinning effect; this, is perfectly consistent with the revised Schottky–Mott model after considering charge redistribution. Combined with band calculations and device local projection density of states, MoS2/TiBO, MoS2/TiBF, and MoS2/MoBO, either with the vertical hole Schottky barrier or the lateral hole Schottky barrier, are negative, forming p-type ohmic contacts. Our work provides theoretical guidance for constructing high-performance nanodevices and MoS2-based logic circuits for large-scale integrated circuits. We demonstrate the outstanding potential of MBenes as electrodes for nanodevices.

High Power Figure‐of‐Merit, 10.6‐kV AlGaN/GaN Lateral Schottky Barrier Diode with Single Channel and Sub‐100‐µm Anode‐to‐Cathode Spacing (Small 37/2022)

Schottky Barrier Diodes GaN is a promising candidate for next-generation power electronic devices, but its potential is far from being realized. In article number 2107301, Peng Chen, Rong Zhang, Youdou Zheng, and co-workers demonstrate a high power figure-of-merit, 10.6-kV AlGaN/GaN lateral Schottky barrier diode with single channel, and sub-100-μm anode-to-cathode spacing without any other additional structures, which gives a clear and positive answer that GaN can be used in ultra-high voltage applications.

High Power Figure-of-Merit, 10.6-kV AlGaN/GaN Lateral Schottky Barrier Diode with Single Channel and Sub-100-µm Anode-to-Cathode Spacing.

GaN-based lateral Schottky barrier diodes (SBDs) have attracted great attention for high-power applications due to its combined high electron mobility and large critical breakdown field. However, the breakdown voltage (BV) of the SBDs are far from exploiting the material advantages of GaN at present, limiting the desire to use GaN for ultra-high voltage (UHV) applications. Then, a golden question is whether the excellent properties of GaN-based materials can be practically used in the UHV field? Here, UHV AlGaN/GaN SBDs are demonstrated on sapphire with a BV of 10.6kV, a specific on-resistance (RON,SP ) of 25.8mΩcm2 , yielding a power figure-of-merit (P-FOM=BV2 /RON,SP ) of 4.35GWcm-2 . These devices are designed with single channel and 85-µm anode-to-cathode spacing, without other additional electric field management, demonstrating its great potential for the UHV application in power electronics.

The role of non-homogeneous barrier on the electrical performance of 15R–SiC Schottky diodes grown by in-situ RF sputtering

In the present work, we have demonstrated the impact of barrier inhomogeneities on the electrical characteristics of silicon carbide (SiC) based Schottky barrier diodes (SBDs). Ohmic and Schottky contacts were deposited on RF sputtered 15R–SiC film under optimized growth conditions. Forward biased current-voltage (I–V) measurement in the temperature range of 300–420 K was employed to extract the diode parameters (barrier height, ideality factor, and Richardson constant), considering the thermionic emission (TE) as dominant charge transport mechanism. The obtained value of barrier height φB and ideality factor n exhibited anomalies as compared to theoretically predicted values. It was attributed to the co-existence of multiple charge transport mechanism owing to defect induced lateral barrier inhomogeneities at the metal-semiconductor interface. Further, Gaussian distribution of φB, as established by Warner and Guttler was incorporated along with TE model to analyze the temperature dependent I–V data to understand the non-ideality in diode parameters. Eventually, the obtained diode parameters as per the modified charge transport mechanism were found to be in close alignment with the predicted values.

Investigation on Capacitance Collapse Induced by Secondary Capture of Acceptor Traps in AlGaN/GaN Lateral Schottky Barrier Diode.

In this study, a dedicated dynamic measurement system was used to investigate the transient capacitance and recovery process of AlGaN/GaN lateral Schottky barrier diodes (SBDs). With the consideration of acceptor traps in the C-doped buffer, the C-V characteristics and transient capacitance were measured and analyzed, and the results were simulated and explained by Silvaco TCAD (technology computer aided design). The ionization of acceptor traps and the change of electric potential were monitored in transient simulation to investigate the origin of the capacitance collapse in the SBD. The results suggest the significant impact of traps in the GaN buffer layer on the capacitance collapse of the device, and the secondary capture effect on the variation of acceptor ionization. Based on the study of transient capacitance of SBD, this work could be extended to the Miller capacitance in high electron mobility transistor (HEMT) devices. Moreover, the report on the stability of capacitance is essential for GaN devices, and could be further extended to other aspects of device research.

Room‐Temperature Processed Lateral Trench‐Metal–Insulator–Semiconductor Schottky Barrier Diodes with Amorphous Gallium Oxide (a‐Ga2O3) Thin Films on Single‐Crystal Silicon &lt;100&gt;

This article proposes a novel design approach for the fabrication of lateral Schottky barrier diodes (SBD) using a wide bandgap oxide semiconductor on silicon. Structural and electrical properties of the fabricated device are reported and compared with published data. The metal–insulator–semiconductor (MIS) Schottky barrier is realized between the room‐temperature sputtered Al/a‐Ga2O3 on single‐crystal &lt;100&gt; boron‐doped silicon substrate (p‐type). The device fabrication process is implemented entirely at room temperature. The proposed trench diode yields an ideality factor of 1.65 and a rectification ratio of ≈1 × 106 at ±5.0 V. The extracted specific ON resistance is 78 mΩ cm2, and the breakdown voltage is not observed for 180 V for a 200‐nm‐thin layer of a‐Ga2O3. Due to such low‐temperature process, simple fabrication steps, and notably high Baliga's figure‐of‐merit (BFOM), the proposed diode is, therefore, promising for power electronics applications.

Metal-nitride dual-anode AlGaN/GaN heterostructure Schottky barrier diodes with tunable turn-on voltage and reverse leakage current

AlGaN/GaN heterostructure lateral Schottky barrier diodes (SBDs) with TiN and NiN dual anode (DA) on sapphire substrates are investigated in this letter. The NiN anode with its high work-function leads to low leakage current and high breakdown voltage, while TiN anode with its low work-function determines the low turn-on voltage of the DA SBDs. Tunable turn-on voltage and leakage current are obtained in the DA SBDs by varying the radius of the TiN anode. As the radius of the TiN anode decreases from 80 to 8 μm, the turn-on voltage increases from 0.64 to 0.94 V, while the reverse leakage current decreases from 1 × 10−2 to 1 × 10−4 mA mm−1 at a reverse bias of −10 V and cathode–anode distance of 20 μm. The differential specific on-resistance at 100 mA mm−1 is 4.5 mΩ cm2 and barely changes with various radius of the TiN anode. A high breakdown voltage of 1.49 kV is achieved in the AlGaN/GaN DA SBDs with the radius of 80 μm of the TiN anode, obtaining a power Baliga’s figure of merit of 0.48 GW cm−2 at the cathode–anode distance of 20 μm. Besides, dynamic on-resistance increases less than 15% under pulse voltage bias at −60 V which may account on the good interface between metal nitrides and AlGaN, which is beneficial to the high frequency and high power application.

Current transport mechanism of AlGaN-channel Schottky barrier diode with extremely low leakage current and high blocking voltage of 2.55 kV

This Letter presents work on lateral AlGaN-channel Schottky barrier diodes (SBDs) with impressive reverse blocking characteristics and low onset voltage (VON). A low reverse current (IR) of 28 nA/mm and low VON of 0.60 V are obtained by utilizing an AlGaN back barrier layer with high Al composition and low work function metal as the anode. The fabricated AlGaN-channel SBD with an anode–cathode distance (LAC) of 30 μm achieves a high blocking voltage of 2.55 kV and a power figure-of-merit of 363 MW/cm2. Meanwhile, the current transport mechanism of AlGaN-channel SBDs goes through thermionic emission, thermionic field emission, and trap-assisted tunneling as the reverse bias is gradually increased. The thermal activation energy (EA) is calculated to be 141.3 meV at high reverse bias. IR at 475 K is only 3 μA/mm, which shows an adequate barrier height for rectifying at high temperature even with low VON. The AlGaN-channel SBDs show great promise for next-generation power electronics with balanced forward and reverse characteristics.