Photoresist Research Articles

Significant negative differential resistance and current limiting effects of cyclo[14]carbon-based molecular devices with graphene electrodes

Through tip-induced dehalogenation and retro-Bergman ring-opening reaction of fully chlorinated anthanthrene (C14Cl10), the cyclo[14]carbon (C14) was prepared. Owing to its distinctive physical properties, C14 holds the potential to serve as the core unit of functional electronic devices. Herein, the density functional theory combined with the non-equilibrium Green's function technique was used to investigate the electronic transport properties of molecular devices composed of C14 molecules and graphene electrodes, systematically. We find that molecular devices composed of polyynic and cumulenic structures of C14 exhibit a significant negative differential resistance effect and effective current limiting ability at low bias voltages, respectively. Moreover, by calculating and analyzing the transmission function and projected density of states under different biases, a reasonable explanation of those effects is provided.

Tripodal Triptycenes as a Versatile Building Block for Highly Ordered Molecular Films and Self-Assembled Monolayers.

ConspectusThe design of properties and functions of molecular assemblies requires not only a proper choice of building blocks but also control over their packing arrangements. A highly versatile unit in this context is a particular type of triptycene with substituents at the 1,8,13-positions, called tripodal triptycene, which offers predictable molecular packing and multiple functionalization sites, both at the opposite 4,5,16- or 10 (bridgehead)-positions. These triptycene building blocks are capable of two-dimensional (2D) nested hexagonal packing, leading to the formation of 2D sheets, which undergo one-dimensional (1D) stacking into well-defined "2D+1D" structures. This ability makes it possible to form large-area molecular films having long-range structural integrity even on polymer substrates, which can be used to enhance the performance of organic devices. Importantly, the 2D assembly ability of tripodal triptycenes is robust and not impaired when chemically modified with functional molecular units and even with polymer chains. In addition, introducing suitable functionalities that act as anchoring groups results in reliable tripodal monomolecular assembly on application-relevant inorganic substrates, which is generally considered quite a challenging task. Self-assembled monolayers (SAMs) have been formed on Au(111), Ag(111), and indium tin oxide. On gold, these SAMs feature the nested hexagonal packing typical of 2D triptycene sheets, whereas, on silver, a distinct polymorphism with several different packing motifs occurs. Along with basic, nonsubstituted tripodal SAMs, specifically functionalized monolayers have been designed. A substitution pattern in which three nitrile tail groups build the outermost surface of a tripodal triptycene-based SAM has allowed for the study of femtosecond charge transfer dynamics across the triptycene framework, with a particular emphasis on the so-called matrix effects involving intramolecular pathways. The functionalization of the bridgehead position with a ferrocene tail group has enabled single-molecule observation of redox reactions and the creation of assemblies of unique molecular rectifiers, exhibiting highly effective rectification at a very low bias voltage. Complementary to the synthesis of these complex functional triptycenes, a strategy of on-surface click reactions has been designed. Indeed, a tripodal triptycene having an ethynyl tail group at the 10-position, capable of click reactions with azide functionalities, works well, allowing successive molecular layer deposition. The performance of tripodal triptycene-based SAMs has also been tested in the context of electron beam lithography (EBL) and nanofabrication, leading to the finding that these SAMs can serve as negative resists for EBL due to the efficient cross-linking, giving rise to triptycene-stemming carbon nanomembranes (CNM). These membranes feature the lowest lateral material densities used to date for CNM preparation, which makes them unique in this regard.

Electrochemically grafted molecular layers as on-chip energy storage molecular junctions

Molecular junctions (MJs) are well celebrated nanoelectronics devices for mimicking conventional electronic functions including rectifiers, sensors, wires, switches, transistors, negative differential resistance, and memory followed by the understanding charge transport...

Molecular-scale in-operando reconfigurable electronic hardware.

It is challenging to reconfigure devices at molecular length scales. Here we report molecular junctions based on molecular switches that toggle stably and reliably between multiple operations to reconfigure electronic devices at molecular length scales. Rather than static on/off switches that always revert to the same state, our voltage-driven molecular device dynamically switches between high and low conduction states during six consecutive proton-coupled electron transfer steps. By changing the applied voltage, different states are accessed resulting in in operando reconfigurable electronic functionalities of variable resistor, diode, memory, and NDR (negative differential conductance). The switching behavior is voltage driven but also has time-dependent features making it possible to access different memory states. This multi-functional switch represents molecular scale hardware operable in solid-state devices (in the form of electrode-monolayer-electrode junctions) that are interesting for areas of research where it is important to have access to time-dependent changes such as brain-inspired (or neuromorphic) electronics.

TCAD Study of Giant Negative Differential Resistance in Nanoscale Ferroelectric Field-Effect Transistors

TCAD Study of Giant Negative Differential Resistance in Nanoscale Ferroelectric Field-Effect Transistors

Emergence of Negative Differential Resistance Through Hole Resonant Tunneling in GeSn/GeSiSn Double Barrier Structure

Emergence of Negative Differential Resistance Through Hole Resonant Tunneling in GeSn/GeSiSn Double Barrier Structure

Monolithic Integration of p-GaN HEMT with Anti-parallel Lateral Rectifier to Reduce the Negative Resistance Effect

Monolithic Integration of p-GaN HEMT with Anti-parallel Lateral Rectifier to Reduce the Negative Resistance Effect

The negative differential resistance of nitrogen implanted TiO2

The microstructure and negative differential resistance (NDR) effect of nitrogen implanted rutile TiO2 were investigated by measuring the XPS, Raman spectra and current voltage curves. It was found that the light illumination has large influence on the NDR effect. Under the illumination of 60 mW laser light, a large NDR with a small electric field (1250 V/cm) is obtained. This electric field is about three orders smaller than that reported in literature (1×106 V/cm). The electric field induced tunneling is the possible mechanism of electric transport at higher field region. The NDR is thought to be related to the light and nitrogen dopant induced reaction including the destroying of water, the scavenging of electron, and the surface oxidation transform of non-stoichiometric TiO2−x to stoichiometric insulating state. The results of this paper are not only useful in understanding the mechanism of NDR, but also useful in providing an effective method in manipulation NDR.

Ultra-fast etching of photoresist by reactive atmospheric-pressure thermal plasma jet with surface temperature measurement

Abstract Atmospheric-pressure reactive thermal plasma jet (R-TPJ) with Ar and O2 gas mixture was applied to etching of photoresist (PR) on silicon wafer. An optical interference contactless thermometry (OICT) and optical emission spectroscopy were carried out to clarify the relationship between the etching rate, amount of atomic oxygen radicals, and PR surface temperature. The results show that O2 flow rate and surface temperature are obviously related to the etching rate of PR. The R-TPJ irradiation with input current at 60 A reaches surface temperature of 720 K within 7 ms and achieved etching rate of 84 μm/s.

Interface engineering of van der Waals heterostructures towards energy-efficient quantum devices operating at high temperatures

Abstract Quantum devices, which rely on quantum mechanical effects for their operation, may offer advantages, such as reduced dimensions, increased speed, and energy efficiency, compared to conventional devices. However, quantum phenomena are typically observed only at cryogenic temperatures, which limits their practical applications. Two-dimensional materials and their van der Waals (vdW) heterostructures provide a promising platform for high-temperature quantum devices owing to their strong Coulomb interactions and/or spin-orbit coupling. In this review, we summarise recent research on emergent quantum phenomena in vdW heterostructures based on interlayer tunnelling and the coupling of charged particles and spins, including negative differential resistance, Josephson tunnelling, exciton condensation, and topological superconductivity. These are the underlying mechanisms of energy-efficient devices, including tunnel field-effect transistors, topological/superconducting transistors, and quantum computers. The natural homojunction within vdW layered materials offers clean interfaces and perfectly aligned structures for enhanced interlayer coupling. Twisted bilayers with small angles may also give rise to novel quantum effects. In addition, we highlight several proposed structures for achieving high-temperature Majorana zero modes, which are critical elements of topological quantum computing. This review is helpful for researchers working on interface engineering of vdW heterostructures towards energy-efficient quantum devices operating above the liquid nitrogen temperature.

Anionic Photoacid Generator Bound Polymer Photoresists With Improved Performance for Advanced Lithography Patterning

ABSTRACTChemically amplified resist (CAR) has gained considerable attention in the realm of extreme ultraviolet lithography (EUVL) due to their exceptional photosensitivity, high resolution, and commercialization. This work presents the development of an anionic photoacid generator (PAG) bound polymer (PGM) photoresist composed of three rationally selected monomeric units: 2‐Phenyl‐2‐propyl methacrylate (PPMA), γ‐butyrolactone‐3‐yl methacrylate (GBLMA), and triphenyl sulfonium salt 1,1,2‐trifluorobutanesulfonate methacrylate (MTFBS‐TPS). Electron beam lithography (EBL) studies demonstrate that the PGM photoresist functions as a positive tone photoresist with commendable sensitivity (27.9 μC/cm2) and contrast (6.53). When compared under similar conditions, with equal amounts of PAG and identical processing, the PGM photoresist exhibited superior pattern fidelity, ease of handling, and higher line resolution (25 nm) relative to the triphenyl sulfonium triflate (TPS‐OTF) blend polymer (PG‐T) photoresist. This enhancement is probably caused by anionic PAG directly attaching to the polymer backbone, which mitigates acid diffusion during the post‐exposure baking (PEB) process. Moreover, the PGM photoresist obtained a pattern of 37.5 nm at 50 mJ/cm2 in the EUVL test. The positive tone resists were successfully applied for the fabrication of nanoscale patterns.

Resistive switching behavior of quasi-2D CsPbBr3 memristors: Impact of ambient atmosphere on logic storage and computing integration with anti-crosstalk and reconfiguration features

Passive units integrating storage and computing with anti-crosstalk and multi-logic reconstruction are crucial for high computing power and high-density non-volatile storage. In this study, we report an anti-crosstalk and reconfigurable logic memory based on a single passive quasi-two-dimensional (2D) CsPbBr3 device. The effect of the ambient atmosphere (air and N2 environments) on the resistive behavior of the memristors is explored. In air, these devices exhibit negative differential resistance (NDR) effects and antipolar resistive switching behavior, while in N2, they display irreversible switching from low-resistance state to high-resistance state. Various active electrodes (Ag, Cu, Au, and C) were employed to investigate this phenomenon. It is proposed that in air, O ions interact with surface defects under high alternating voltage, retaining a significant quantity of Br− ions within the quasi-2D CsPbBr3, resulting in capacitive-like behavior. Conversely, in N2, surface defects capture Br− ions, leading to the absence of a hysteresis loop in the I-V characteristic. Under N2 operation, write-once-read-many (WORM) capability is achieved. Surprisingly, operating under air enables integrated non-volatile storage and computing, facilitating 12 reconfigurable logic operations in a passive 1R structure and suppressing sneak current in crosstalk setups. This study emphasizes the pivotal role of air in the resistive switching mechanism and provides novel insights for developing next-generation memories tailored for high-density integrated circuits and storage-computing integration.

Inflection of Resistive Switching Behavior in Atomically Precise Silver Cluster-Assembled Materials.

Bottom-up design of electronic materials based on nanometer-sized building blocks requires precise control over their self-assembly process. Atomically precise metal nanoclusters (NCs) are the well-characterized building blocks for crafting tunable nanomaterials. Here, a solution-processed assembly of a newly synthesized molecular silver nanocluster (0 D Ag12-NC) into a 1D nanocluster chain (1 D Ag12-CAM) is mediated by 4,4'-bipyridine linker Both 0 D Ag12-NC and 1 D Ag12-CAM consist of Ag12 core that adopts the cuboctahedron geometry protected by organic ligands. The resistive switching devices are fabricated in a sandwich-like structure of ITO (Indium tin oxide)/X/Ag (where X is either 0 D Ag12-NC or 1 D Ag12-CAM). The device based on 1 D Ag12-CAM exhibited excellent resistive switching behaviour, enduring up to 1000 cycles and boasting a fivefold higher Ion/Ioff ratio compared to the device based on the molecular 0 D Ag12-NC nanocluster. Furthermore, the device based on 1 D Ag12-CAM demonstrated negative differential resistance (NDR) phenomena, achieving a peak-to-valley ratio of 2.34 with a switching efficiency of 23 Ns. This work highlights the importance of interconnecting molecular nanoclusters into 1D nanocluster chains for fine-tuning resistive memory properties in futuristic electronic appliances.

Current Mechanisms in Zinc Diffusion-Doped Silicon Samples at T = 300 K

This work is devoted to the study of current flow in diffusion-doped zinc silicon samples in the dark and when illuminated with light with an intensity in the range from 0.6 to 140 lx and at a temperature of 300 K. At T = 300 K and in the dark, the type of the I–V characteristic contained all areas characteristic of semiconductors with deep energy levels. It was found that when illuminated with light, the type of I–V characteristics of the studied Si samples depended on the value of the applied voltage, the electrical resistivity of the samples, the light intensity, and their number reached up to 6. In this case, linear, sublinear, and superlinear sections were observed, as well as the switching point (sharp current jump) and areas with negative differential conductivities (NDC). The existence of these characteristic areas of the applied voltage and their character depended on the intensity of the light. The experimental data obtained were interpreted in the formation of low dimensional objects with the participation of multiply charged zinc nanoclusters in the bulk of silicon. They changed the energy band structure of single-crystal silicon, which affected generation-recombination processes in Si, leading to the types of I–V characteristics observed in the experiment.

Dynamical Mechanism of Memristor and its Phase Transition

Abstract A device is defined as the memristor if it exhibits a pinched hysteresis loop in the current-voltage plane, and the loop area shrinks with the increasing of driven frequency until it gets a single-valued curve. However, it is still limited to explain the underlying mechanism for these fingerprints. In this letter, we propose the differential form of the memristor function, and we disclose the dynamical mechanism of the memristor according to the differential form. The symmetry of the curve is only determined by the driven signal, and the shrinking loop area results from the shrinking area enclosed by driven signal and the time coordinate axis. Significantly, we find the condition for the phase transition of a memristor, and the resistance switches between the positive resistance, local zero resistance, and local negative resistance. This phase transition is confirmed in HP memristor. These results advance the understanding of the dynamics mechanism and phase transition of memristor.

Analysis of the Parity-Time Symmetry Model in the Receiver-Based Wireless Power Transfer

Parity-time (PT) symmetry has made encouraging progress in wireless power transmission (WPT), exhibiting significant advantages in terms of system robustness and transmission efficiency. However, there are still challenges that need to be addressed, particularly when classical schemes operate at a fixed frequency in the weak coupling region, where even minor changes in coupling strength can result in excessive current surges. This paper introduced a novel PT-symmetric WPT system featuring negative resistance constructed on the receiver side. We first established a theoretical framework for the classical two-coil PT-symmetric magnetically coupled resonant WPT system and subsequently extended it to incorporate the PT-symmetric WPT system with negative resistance on the receiver. This topological coil configuration facilitated stable power delivery over a broader range, with the capability of self-tuning frequency without requiring additional frequency modulation. This adaptability enabled the system to cater to diverse scenarios and opens up a novel avenue for practical applications of PT symmetry in WPT. Finally, we designed a 10 W prototype to demonstrate the effectiveness of our topology, and the experimental results aligned with our theoretical calculations, validating the feasibility and potential of our PT-symmetric WPT system.

Robust MG control considering uncertain constant power load

The destabilization of Microgrids (MGs) is attributed to the negative incremental resistance of constant power loads (CPLs). Furthermore, the inadequately damped modes of the droop control, typically employed for distributed generation (DG) power sharing, contribute to disturbances in MG dynamic performance. This paper introduces a novel control strategy aimed at mitigating instability issues associated with both CPL and droop controllers in MGs. The proposed approach utilizes an optimized H∞ control scheme, incorporating the Whale Optimization Algorithm (WOA), to enhance stability on both the CPL and distributed generation (DG) sides of the MG. The proposed controller is modeled and validated through comprehensive simulations in MATLAB, demonstrating its effectiveness under various uncertainty scenarios and disturbance conditions. These simulations demonstrate the controller's capability to effectively mitigate disturbances, optimize DG power sharing, and regulate the DC voltage of the CPL, thereby enhancing overall microgrid stability and performance. Additionally, a comparison between the proposed robust H∞ and conventional droop control schemes highlights the superiority of the proposed approach, with results confirming improved MG dynamic performance. The proposed controller exhibits a notable enhancement in Minimum Voltage Deviation (MVD), showing a substantial improvement of 96.19%. Additionally, both the Critical Response Time (CRT) and Settling Response Time (SRT) witness significant improvements of 95.33% and 97.69%, respectively, when subjected to system disturbances. Finally, the implemented MG is validated on a Real-Time Digital Simulator (RTDS), affirming the practicality of the proposed compensation technique.

Doped-δ-doped transferred electron device for sustained terahertz signal generation

Abstract The performance of a novel transferred electron device structure aimed at sustaining high-frequency signals in the terahertz (THz) range is investigated. The device uses a highly doped δ-layer to split the n-doped device into two distinct regions, forming a doped-δ-doped configuration. The first region generates high-speed electrons toward the δ-layer, while the second region utilizes negative differential resistance to modulate electron speeds and sustain oscillations. An ensemble self-consistent Monte Carlo model is employed to analyze electron dynamics and THz signal generation in this structure under a constant bias. The design demonstrates superior performance, achieving a fundamental operating frequency of 427 GHz in a 600 nm length InP device, nearly a 50% increase over conventional notch-doped design, while maintaining the current harmonic amplitude. This design achieves higher frequencies without reducing device length and increasing doping density, effectively addressing the trade-off of the Kroemer criterion. The study of the effects of varying doping densities and region lengths on device performance, highlighting the importance of optimizing these parameters to sustain current oscillations and efficiently generate THz signals. This design offers a promising solution for a compact and efficient THz source.

Topological surface states of semimetal TaSb2

Topological surface states, protected by the global symmetry of the materials, are the keys to understanding various novel electrical, magnetic, and optical properties. TaSb2 is a newly discovered topological material with unique transport phenomena, including negative magnetoresistance and resistivity plateau, whose microscopic understanding is yet to be reached. In this study, we investigate the electronic band structure of TaSb2 using angle-resolved photoemission spectroscopy and density functional theory. Our analyses reveal distinct bulk and surface states in TaSb2, providing direct evidence of its topological nature. Notably, surface states predominate the electronic contribution near the Fermi level, while bulk bands are mostly located at higher binding energies. Our study underlines the importance of systematic investigations into the electronic structures of topological materials, offering insights into their fundamental properties and potential applications in future technologies.Graphical

Positive and negative sequence impedance measurement method based on inductance switching for converters

Abstract Nowadays, the impedance-based method is a common method to study the small-signal stability of converters. Impedance measurement is the key to using this method. Common impedance measurement methods usually inject disturbances on the primary side and calculate the converter’s impedance by measuring the response excited by the disturbance. The high price and troublesome operation are the drawbacks of this method. In this paper, an impedance measurement method of the grid-tied converters by switching the grid-side inductance is proposed. By changing the grid-side inductance and injecting the same disturbance into the control system before and after the alteration, the positive and negative sequence impedance of the converters can be measured. This paper explains the measurement principle and elaborates the measurement steps. In the end, the effectiveness of the method is verified by simulations.