Tunneling Layer Research Articles

In Situ Self-Assembly of Nanoscale Particles into Macroscale Ordered Monolayers with Enhanced Memory Performance.

In situ fabrication of macroscale ordered monolayers of nanoparticles (NPs) on targeted substrates is highly desirable for precision electronic and optical devices, while it remains a great challenge. In this study, a solution is provided to address this challenge by developing a colloidal ink formulation and employing the direct-ink-writing (DIW) technique, where on-demand delivery of ink at a targeted location and directional evaporation with controllable rate are leveraged to precisely guide the deposition of polystyrene-grafted gold NPs (Au@PS NPs) into a macroscale monolayer with an ordered Au NP array embedded in a PS thin film. A 2D steady-state diffusion-controlled evaporation model, which explains the parameter dependence of the experimental results and gives semiquantitative agreement with the experimental evaporation kinetics is proposed. The ordered monolayer is used as both nanocrystal floating gates and the tunneling layer for nonvolatile memory devices. It shows significantly enhanced performance compared with a disordered NP film prepared by spin coating. This approach allows for fine control of NP self-assembly to print macroscaleordered monolayers directly onto substrates, which has great promise for application in broad fields, including microelectronic and photoelectronic devices, sensors, and functional coatings.

An In-Situ Formed Tunneling Layer Enriches the Options of Anode for Efficient and Stable Regular Perovskite Solar Cells

HighlightsIt is first disclosed that the key to the efficient regular Ag-perovskite solar cells (PSCs) is a tunneling layer (silver iodide, AgI) that is in situ formed by the natural reaction between Ag and the migrated iodide.Based on the discovery, an ultrathin and uniform tunneling layer can be deposited on the fragile perovskite/charge transport layer to enrich the options of electrodes for efficient and stable regular PSCs.

A novel passivating contact approach for enhanced performance of crystalline silicon solar cells

Passivated contacts based on ultrathin silicon oxide (SiOx) layers and phosphorus-doped nanocrystalline silicon oxide (nc-SiOx(n)) layers have been examined for their application in tunnel oxide-passivated contact (TOPCon) solar cells. Passivated contact nc-SiOx(n)/SiOx, is accomplished by implementing a thermally grown SiOx tunnel layer and a plasma-enhanced chemical vapor deposited (PECVD)-grown nc-SiOx(n) layer, which are subsequently transformed into a more crystalline phase by annealing at a higher temperature. In this research, a 3.2 × 3.2 cm solar cell was fabricated, where the base material was n-type crystalline silicon (c-Si(n)), and an aluminum oxide (Al2O3) acts as a passivation layer which helps to enhanced the passivation properties and indium tin oxide (ITO) layer was used on the front side, which could serve as an anti-reflection coating (ARC), respectively. The influence of the temperature, doping level, and thickness of nc-SiOx(n) on the surface passivation of the contacts was investigated. Superior recombination current density (Jo) values of up to 2.9 fA/cm2 were assessed for the nc-SiOx(n)/SiOx contacts. TOPCon solar cells with top boron-doped emitter, Al2O3, and ITO/rear stack of nc-SiOx(n)/SiOx passivation contacts were formed and resulted in Voc = 650 mV and FF = 78%. Furthermore, we focused on ameliorating the achievements of solar cells using a transparent passivating contact-based nc-SiOx(n), as well as the passivation process and operating principle.

Dielectric Front Passivation for Cu(In,Ga)Se2Solar Cells: Status and Prospect

Cu(In,Ga)Se2(CIGSe) solar cells are among the most efficient thin‐film solar cells on lab scale. However, this thin‐film technology has relatively large upscaling losses for commercial technology. To tackle this, paradigm shifts are proposed that allow for simpler, cost‐effective, and efficient CIGSe solar cells. Front passivation using dielectric layers is one of the options being investigated as this is widely used in Si technology. Research on front passivation for CIGSe is in an early stage and no improvements are made yet. A close comparison with silicon technology is made to understand why it seems to be more difficult for CIGSe solar cells. In general, chemical passivation is less effective, resulting in higher interface defect densities than seen for Si. Also, field‐effect passivation requires positive charges, which have not been implemented yet on the CIGSe front surface. Finally, for Si passivation, often a high‐temperature annealing step is applied, which is not possible for CIGSe. It is proposed to apply a dielectric tunneling layer with positive fixed charges in combination with an electron transport layer to move forward. A list of potential dielectric layers that could be suitable for CIGSe is provided.

Modulating Electron Conducting Properties at Lithium Anode Interfaces for Durable Lithium-Sulfur Batteries.

The lithium (Li) ion and electron diffusion behaviors across the actual solid electrolyte interphase (SEI) play a critical role in regulating the Li nucleation and growth and improving the performance of lithium-sulfur (Li-S) batteries. To date, a number of researchers have pursued an SEI with high Li-ion conductivity while ignoring the Li dendrite growth caused by electron tunneling in the SEI. Herein, an artificial anti-electron tunneling layer with enriched lithium fluoride (LiF) and sodium fluoride (NaF) nanocrystals is constructed using a facile solution-soaking method. As evidenced theoretically and experimentally, the LiF/NaF artificial SEI exhibits an outstanding electron-blocking capability that can reduce electron tunneling, resulting in dendrite-free and dense Li deposition beneath the SEI, even with an ultrahigh areal capacity. In addition, the artificial anti-electron tunneling layer exhibits improved ionic conductivity and mechanical strength, compared to those of routine SEI. The symmetric cells with protected Li electrodes achieve a stable cycling of 1500 h. The LiF/NaF artificial SEI endows the Li-S full cells with long-term cyclability under conditions of high sulfur loading, lean electrolyte, and limited Li excess. This study provides a perspective on the design of the SEI for highly safe and practical Li-S batteries.

21.16%-efficiency p-type TOPCon solar cell with ALD-Al2O3/MoOx/Ag as a hole-selective passivating contact

High-performance hole-selective passivating contact is of significance in obtaining the high efficiency of a full-area carriers-selective contact-based solar cell. In this work, we prepared a hole-selective passivating contact of Al2O3/MoOx/Ag and applied it to the rear of the p-type tunneling oxide passivated contact (TOPCon) solar cell. It is found that the ultrathin atomic-layer-deposited (ALD) Al2O3 as a tunneling layer played an essential role in improving the hole selectivity of Al2O3/MoOx/Ag structures, and the optimal thickness of the tunneling layer Al2O3 is ∼ 0.56 nm. An ultra-low resistivity of 1.84 mΩ‧cm2 was obtained on the Al2O3 (0.56 nm)/MoOx (7 nm)/Ag (120 nm) structure. Benefiting from the high-performance hole selectivity, the highest efficiency of 21.16% was successfully achieved on the p-type TOPCon solar cell, which to our knowledge is the highest efficiency of the MoOx-based p-type TOPCon solar cells. This work demonstrates that the hole-selective passivating contact of Al2O3/MoOx/Ag possesses great potential in the full-area carriers-selective contacts based solar cell.

Fowler-Nordheim tunneling mechanism for performance improvement in graphene 2D/GaN 3D heterojunction ultraviolet photodetector

The Fowler-Nordheim tunneling (FNT) is an important tunneling mechanism and an efficient route to improve the photoresponse of a photodetector. Herein, we report the quantum mechanical FNT mechanism based on graphene 2D/GaN 3D ultra-shallow van der Waals heterojunctions ultraviolet (UV) photodetector via atomic layer deposition Al2O3 tunneling layer, and the conversion between direct tunneling (DT) and FNT has also been systematically studied. At reverse bias (<−0.253 V) with the high build-in field, the high-speed photogenerated carriers overcome the thin insulator layer through the FNT, occurring impact ionization during the process resulting in a multiplication of the photocurrent. Consequently, the photodetector demonstrates pronounced photoresponse performances working under a weak light of 5 μW/cm2 at −2 V, including remarkable responsivity (122.57 A/W), ultrahigh specific detectivity (5.63 × 1014 Jones), and high sensitivity (1.29 × 107%), which indicated that the device has excellent weak light detection ability. This work presents a novel route to fabricate high-performance optoelectronic devices by using the FNT tunneling mechanism.

High detectivity graphene/si heterostructure photodetector with a single hydrogenated graphene atomic interlayer for passivation and carrier tunneling

Hydrogenated graphene is easy to prepare and chemically stable. Besides, hydrogenation of graphene can open the band gap, which is vital for electronic and optoelectronic applications. Graphene/Si photodetector (PD) has been widely studied in imaging, telecommunications, and other fields. The direct contact between graphene and Si can form a Schottky junction. However, it suffers from poor interface state, where the carrier recombination at the interface causes serious leakage current, which in turn leads to a decrease in the detectivity. Hence, in this study, hydrogenated graphene is used as an interfacial layer, which passivates the interface of graphene/Si (Gr/Si) heterostructure. Besides, the single atomic layer thickness of hydrogenated graphene is also crucial for the tunneling transport of charge carriers and its suitable energy band position reduces the recombination of carrier. The fabricated graphene/hydrogenated-graphene/Si (Gr/H–Gr/Si) heterostructure PD showed an extremely low dark current about 10−7 A. As a result, it had low noise current and exhibited a high specific detectivity of ∼2.3 × 1011 Jones at 0 V bias with 532 nm laser illumination. Moreover, the responsivity of the fabricated PD was found to be 0.245 A W−1 at 532 nm illumination with 10 μW power. These promising results show a great potential of hydrogenated graphene to be used as an interface passivation and carrier tunneling layer for the fabrication of high-performance Gr/Si heterostructure PDs.

Numerical Simulation Research on Optimization of Large Deformation Control Parameters in Layered Slate Tunnel

In order to explore the deformation characteristics of layered slate tunnels under different dip angles of rock formations, a numerical simulation research method for optimization of large deformation control parameters of layered slate tunnels is proposed. The plane deviation, plane deformation, and DP parameters of the structure are obtained through the calculation mode. When studying the effect of overlapping rock masses on the stability of thick tunnels, the incidence angle of the rock structure is assumed to be zero. The estimated thicknesses of the dolomite limestone surrounding the tunnel are 0.3 m, 0.4 m, 0.5 m, 0.6 m, 0.7 m, 0.8 m, and 0.9 m, respectively. Select the vertical displacement to be analyzed as the result of the calculation. In order to study the influence of the structural slope on the tunnel stability, the thickness of the rock layer was 0.6 m, and the structural slopes of 5°, 15°, 30°, 45°, 60°, 75°, and 85° were used for simulation calculations. During on-site construction, focus on monitoring the tunnel section deformation before the secondary lining construction. Every 10-20 m, when the surrounding rock changes, the observation section of the enclosure convergence and vault settlement is arranged, and the peripheral displacement rate and the vault settlement rate are calculated according to the observed deformation. The results show that the vertical displacement of the top of the tunnel is generally in a “V” shape, that is, the maximum settlement in the tunnel; when the layer thickness is 0.3 m, the maximum vertical displacement of the rock layer is 7.2 mm, and the total settlement in the lining support tunnel is 8.23 mm. When the layer thickness is 0.9 m, the vertical displacement of the rock layer is 5.14 mm, and the total settlement in the lining support tunnel is 5.22 mm2; when the layer thickness was changed from 0.9 m to 0.3 m, the maximum vertical displacement of the rock layer increased by 140%, and the settlement at the vault increased by 158%. At this time, the focus of tunnel support is on both sides of the lining structure and the vault with large vertical settlement. The phenomenon that the section of YK51+032 first decreases and then increases due to the sudden appearance of mud in the surrounding YK51+040, resulting in increased short-term deformation. Only the ZK49+356 section at the entrance of the left line has a large deformation due to the thin overlying stratum, and other sections are relatively consistent, indicating the reliability of the calculation results.

Support on Deformation Failure of Layered Soft Rock Tunnel Under Asymmetric Stress

Support on Deformation Failure of Layered Soft Rock Tunnel Under Asymmetric Stress

Bi-exponential decay model of electron in Al2O3/Au NCs/Al2O3 structure

As state-of-the-art electronic chips were miniaturized to its limit, many small dimension issues, such as crosstalk noise, parasite capacitance, and tunneling of charges, emerged. Studying such issues shall be of interest to the research and industry field. Here, we studied the electrical behavior of electrons injected in an array of nanostructures embedded on Al2O3 dielectrics. Our multi-stack device comprised Au nanoclusters, tunneling and blocking Al2O3 oxide layers, and a Si substrate. The electrons were injected by applying a bias at the top of the atomic force microscopy tip in contact while grounding the Si substrate. Its retention and diffusion behaviors were observed by measuring the contact potential difference (CPD). The measured CPD data with time were well fitted to the bi-exponential function, which had two time constants τ1 and τ2. It indicated that at least two dominant tunneling mechanisms existed, so it was confirmed with I–V measurement using a simple tunneling device (Pt/Al2O3/Si structure). This work may provide a tool for analysis of charge transportation in a miniaturized nanostructure.

Low-Cost Compact Integrated Rectenna for Implantable Medical Receivers

This work describes a novel fully integrated rectenna circuit using tunnelling-based devices for implanted medical devices. An ASPAT (Asymmetric Spacer Layer Tunnel Diode) was used as the active rectifier due to its high non-linearity and temperature insensitivity features. A miniaturized geometry rectenna ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 5$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) with improved matching characteristics was demonstrated, by integrating a Cockcroft-Walton rectifier with an L-shaped planar folded antenna structure operating at ISM frequency bands. The circuit performance was experimentally explored at various separation distance between transmitter and receiver units. For a 5cm transmission set-up, the rectenna with a single-stage rectifier delivered 0.8V output at 20dBm transmit power. An extended doubler configuration exhibited enhanced performance when multiple stages are used, is predicted to reach 0.24mW output power at 23dBm transmit power and yielding ~1.6V output voltage with an efficiency of 0.12%. These findings can assist in compensating for the degraded antenna gain attributed to the extremely small effective-radiating area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.04\lambda $ </tex-math></inline-formula> . Furthermore, the ability of controlling the antenna input impedance helps in circumventing the requirement for a matching circuitry thereby offering further reduction in chip size.

Experimental Study on Shield Tunneling Control in Full Section Water-Rich Sand Layer of Collapsible Loess

Taking China’s first application of domestic shield tunneling in a water-rich sand layer for crossing a high-speed railway as research background, the influence of changes in the shield tunneling parameters on ground settlement is analyzed based on field tests, and a construction control method suitable for shield tunneling under a risk source in a water-rich sand layer is proposed. The test results show that the use of 10% sodium bentonite as the soil modifier for soil pressure balance shield tunneling into the water-rich sand layer has advantages, while adding 50% loess into the bentonite slurry in the gravel sand layer can greatly improve the impermeability of the soil; the settlement of soil can be effectively reduced by using the special segment with grouting holes for deep grouting and applying the adaptive transformation of the shield cutter. Based on the statistical analysis results, a reasonable range for the cutter head torque, cutter head speed, chamber pressure, bentonite injection volume, and advanced speed in the water-rich sand layer can provide a construction control basis for similar projects and provide data support for the compilation of relevant specifications.

Numerical Investigation of Slurry Fracturing during Shield Tunneling under a Reservoir

The Jinan Jiluo Road Crossing the Yellow River Tunnel North Extension Project will intersect the Queshan reservoir, which currently supplies 60% of the domestic water in Jinan City. During the excavation process of the large-diameter slurry type shield used in this project, it may lead to slurry fracturing of the stratum in front of the excavation face and slurry blow-out from the surface if the slurry support pressure is too high. The leakage of shield slurry will pollute the reservoir water, and the safety of domestic water in Jinan will be threatened. Shield slurry blow-out may also lead to water inrush accidents. It is difficult to prevent slurry blow-out during shallow shield tunnel construction due to an insufficient understanding of the shield slurry fracturing mechanism. The initiation and extension of shield slurry fracturing are very complex and difficult to observe in the stratum. Currently, there is no effective method to study the slurry fracturing mechanism of shield tunneling. This paper presents a numerical simulation method of shield tunneling slurry fracturing based on the extended finite element method (XFEM). The risk of slurry blow-out in shield tunnel crossing reservoir engineering is analyzed. The advantages of the XFEM for simulating crack propagation are fully exploited. Considering the coexistence of tensile and shear failures in soft soils, embedding the combined tensile and shear failure criterion is realized in the XFEM by the secondary development of the ABAQUS extended finite element. Compared with the slurry fracturing test of blind-hole clay samples, the rationality of the simulation method for slurry fracturing in cohesive soil is verified. Through the establishment of the slurry fracturing extension model, the slurry fracturing process of shield tunneling in cohesive soil layer is simulated. The variation law of slurry pressure in the process of fracture extension is studied, and the influence of shield slurry support pressure, overburden thickness, formation shear strength, and slurry viscosity on fracture extension pressure and extension path is analyzed. Based on this numerical simulation method, the risk of slurry blow-out is analyzed in the shield tunneling intersecting the Queshan Reservoir of the Jinan Jiluo Road Crossing the Yellow River Tunnel North Extension Project.

Effect of thin tunnel layers MnO3 and V2O5 on the enhancement of single-layer organic solar cell efficiency

Layer thickness optimization has proven to be effective in the case of increasing Performance Conversion Efficiencies (PCE) of organic solar cells. In this research, optimization of the solar cell is performed and found an efficiency of 9.74%. After that, a solar cell with the insertion of some oxide layers is proposed. Two of them are the thick insulating oxide layers which have helped the efficiency to reach up to 15.23%. Under 1sun and at 1.5AM, the energy spectrum received from the sun has been calculated as 2.43eV for a 510nm light wavelength (has been considered as the peak among the visible light wavelengths), which is much more than the energy band gap of the active material. This incident is supposed to be one of the causes of the high electron tunnelling between the donor and acceptor of the LUMO (Lowest Unoccupied Molecular Orbital). Apart from its inorganic counterpart, as low charge carrier is the main concern for the organic solar cell, this can help a little by ensuring a high charge carrier and pushing the organic solar cell a step further with respect to its competitor, the inorganic solar cell.

Deep Insight into the Noise Behavior of SiGe Source Based Epitaxial Layer Tunnel Field Effect Transistor

Deep Insight into the Noise Behavior of SiGe Source Based Epitaxial Layer Tunnel Field Effect Transistor

Customizing a Coordinative Crab Molecule BCP‐3N with Multifunctionality for High‐Performance Inverted Perovskite Solar Cells

Defects at the perovskite grain boundaries and the interfaces between perovskite and charge transport layers in perovskite solar cells (PSCs) are a curse of nonradiative recombination losses and device degradation channels. Herein, the custom design and synthesis of a multifunctional small molecule (N 2,N 9‐bis(3‐(dimethylamino)propyl)‐4,7‐diphenyl‐1,10‐phenanthroline‐2,9‐dicarboxamide (BCP‐3N) featured by the π‐conjugated phenanthroline and an array of lone‐pair electron donor atoms from the carbonyl and amine groups are reported. The BCP‐3N is used as a Lewis base to multidentate passivate the undercoordinated Pb2+ ions forming an ultrathin tunnel layer, in synergy with ethanol as a green antisolvent to simultaneously orient the growth of perovskite, resulting in a significantly reduced defect density in perovskite films. With BCP‐3N, a significant increase in open‐circuit voltage (V oc = 1.12 V) is achieved of inverted (p–i–n structure) PSCs, along with a record power conversion efficiency of ≈21% among alcohol antisolvent processed cells. Also, attested are a much higher illumination and humidity stability of the BCP‐3N‐based device. Combined experimental and theoretical studies have uncovered the multifunctional roles of BCP‐3N in stabilizing high‐quality Cs–FA–MA triple‐cation mixed perovskites under light, bias, and humidity stresses, enlightening the molecular design for PSCs.

Electrode Engineering in MoS2 MOSFET: Different Semiconductor/Metal Interfaces

AbstractThe formation of Ohmic contact between metal electrode and 2D semiconductor channel is considered a key factor for performance improvement of 2D metal–oxide–semiconductor field‐effect transistors (MOSFET). However, the Schottky barrier at the metal electrode/2D semiconductor interfaces cannot be lowered effectively due to the pinning effect of Fermi levels, which makes it hard to obtain lower Ohmic contact resistance. Until now, although physical transfer metal electrode or inserted tunneling layer has been reported to get rid of the Fermi‐level pinning effect, these different designs of electrode engineering are not systematically compared. To serve better Ohmic contact, three different designs of electrode engineering are employed in 2D MoS2 MOSFET: evaporating Ag electrode on MoS2, transferring MoS2 to Ag electrode, and inserting ultrathin AlOx tunneling layer. Our experimental results demonstrate that the transferring MoS2 to Ag electrode in 2D MoS2 MOSFET can obtain the lowest contact resistance and Schottky barrier of 0.45 Ωcm and 12.8 meV, respectively. On this basis, photodiodes with obvious rectifying behavior are fabricated using schemes of electrode engineering, due to their different Schottky barrier high. The detailed contrastive analysis in our three different designs of electrode engineering can provide valuable guidance to optimize the performance of 2D semiconductor MOSFET.

Non-volatile flash memory based on Van der Waals gate stack using bandgap tunability of hexagonal boron nitride

Electronic devices based on two-dimensional (2D) materials have extended their applications to non-volatile flash memory devices. The gate stack is a key structure in flash memory devices, and the conventional silicon-oxide-nitride-oxide-silicon (SONOS) structure has been widely applied. In this study, we propose a van der Waals (vdW) gate stack based on graphene, molybdenum disulfide (MoS2), and hexagonal boron nitride (hBN) for next-generation flash memory devices. Owing to the bandgap tunability of hBN by functionalization, hBN is capable of forming a tunneling layer, charge trap layer, and blocking layer with different bandgaps, resulting in a suitable energy band offset for program/erase operations and charge storage. This study on the vdW gate stack of MoS2/tunneling hBN/charge trap hBN/blocking hBN/graphene was carried out through technology computer-aided design (TCAD) simulation. The trapped charge density and threshold voltage (Vth) shift were investigated for different bandgaps of the hBN layers. Moreover, the pulse width and cycle were varied to reveal the charge-trapping behavior for further applications.

Ultrafast flash memory with large self-rectifying ratio based on atomically thin MoS2-channel transistor

Abstract Flash memory with high operation speed and stable retention performance is in great demand to meet the requirements of big data. In addition, the realisation of ultrafast flash memory with novel functions offers a means of combining heterogeneous components into a homogeneous device without considering impedance matching. This report proposes a 20 ns programme flash memory with 108 self-rectifying ratios based on a 0.65 nm-thick MoS2-channel transistor. A high-quality van der Waals heterojunction with a sharp interface is formed between the Cr/Au metal floating layer and h-BN tunnelling layer. In addition, the large rectification ratio and low ideality factor (n = 1.13) facilitate the application of the MoS2-channel flash memory as a bit-line select transistor. Finally, owing to the ultralow MoS2/h-BN heterojunction capacitance (50 fF), the memory device exhibits superior performance as a high-frequency (up to 1 MHz) sine signal rectifier. These results pave the way toward the potential utilisation of multifunctional memory devices in ultrafast two-dimensional NAND-flash applications.