Intrinsic Transport Properties Research Articles

Solution-processed, ultrasensitive, high current density vertical phototransistor using porous carbon nanotube electrode

Multi-wall carbon nanotube (MWCNT) thin film has been identified as the ideal electrode material due to their inherent electronic and optoelectronic properties. We have successfully fabricated a vertical field-effect phototransistor (vFEpT) using MWCNT as a porous source electrode. The optimized MWCNT electrodes showed an electrical conductivity of 3.92 × 103 S/m and a sheet resistance of about 490 Ω/□, with a layer thickness of about 520 nm. The as-fabricated transistor has p-type conductivity because of the unintentional doping of the PbS layer and the intrinsic hole transport property of the MWCNT network. Additionally, the device shows excellent photoelectric performance at 30 mWcm−2 of illumination, with a high current density of 2.3 × 10−3 Acm−2. With a high conductivity network for carrier transfer and separation, the special characteristics of MWCNT nanoporous thin film enable improved photoelectric properties, such as a high photoresponsivity of 3.16 AW−1 and a specific detectivity of 2.33 × 1012 Jones when illuminated at 808 nm light irradiance with an intensity of 0.6 µW/cm2. Furthermore, the device demonstrated a steady dynamic response to an optical signal, with rising and falling times of 31.8 ms and 32.9 ms, respectively. This work presents a new method for creating high-performance vertical phototransistors with MWCNT as the source electrode.

Dimeric Carbazole Core Based Dopant‐Free Hole Transport Material for n‐i‐p Planar Perovskite Solar Cell

AbstractA profitable approach for improving the stability of n‐i‐p planar perovskite solar cell (PSC) is developing dopant‐free hole transport materials (HTMs) with desirable intrinsic charge transport properties. In this work, by adopting a metal‐free catalytic intramolecular C─C coupling reaction, a carbazole dimer‐based fused‐ring is synthesized, and further developed a small molecular dopant‐free HTM abbreviated as NCz‐DM with appropriate energy level, excellent hole transport and film formation properties. Applied in n‐i‐p planar PSC, an impressive power conversion efficiency (PCE) of 24.0% is achieved, together with enhanced humidity, thermal and light stability, which is among the high level of ever‐reported results for PSCs utilizing small molecular dopant‐free HTM.

Polymorph‐Dependent Multi‐Level Supramolecular Self‐Assembly and Local Charge Transport of a Conjugated Polymer in Solution and Solid States

AbstractThe polymorphic behavior of conjugated polymers enables tunable optoelectronic properties, but their transport mechanism remains elusive due to the inherent complexity and uncontrollability of polymorphic self‐assembly behaviors and electronic processes at various length scales, alongside the ambiguous relationship between solution and solid states. Herein, precise control of multi‐level supramolecular self‐assembly of a polymorphic conjugated polymer, N‐PDPP4T‐HD with two distinct semi‐crystalline aggregated phases (β1 and β2) via solvent engineering is demonstrated. β1 forms 1D worm‐like nanostructures in solution, whereas β2 generates 2D nanoscale lamellar configuration, confirmed by experimental observation and molecular dynamic simulation. Such solution‐state features are inherited in the solid state (1D nanofibers for β1 and 2D granular‐like structures for β2). X‐ray characterizations reveal larger crystalline domains on the nanometer scale, reduced π‐stacking distance on the Ångstrom scale, and diminished paracrystallinity disorder for solid‐state β2. Going beyond conventional DC transistor characterizations, contact‐free ultrafast terahertz spectroscopy to unveil AC short‐range, intrinsic transport properties is employed. Longer charge carrier scattering time and thus intrinsic mobility of β2 result in threefold higher short‐range photoconductivity than β1. This work establishes the “solution structure – solid structure – local transport” relation in polymorphic conjugated polymers and provides new opportunities for high‐performance plastic electronic devices.

Rational Construction of Two-Dimensional Conjugated Metal-Organic Frameworks (2D c-MOFs) for Electronics and Beyond.

ConspectusTwo-dimensional conjugated metal-organic frameworks (2D c-MOFs) have emerged as a novel class of multifunctional materials, attracting increasing attention due to their highly customizable chemistry yielding programmable and unprecedented structures and properties. In particular, over the past decade, the synergistic relationship between the conductivity and porosity of 2D c-MOFs has paved the way toward their widespread applications. Despite their promising potential, the majority of 2D c-MOFs have yet to achieve atomically precise crystal structures, hindering the full understanding and control over their electronic structure and intrinsic charge transport characteristics. When modulating the charge transport properties of two-dimensional layered framework materials, decoupling the charge transport processes within and in between layers is of paramount importance, yet it represents a significant challenge. Unfortunately, 2D c-MOFs systems developed so far have failed to address such a major research target, which can be achieved solely by manipulating charge transport properties in 2D c-MOFs. 2D c-MOFs offer a significant advantage over organic radical molecules and covalent organic frameworks: polymerization through oxidative coordination is a viable route to form "spin-concentrated assemblies". However, the role of these spin centers in charge transport processes is still poorly understood, and the intrinsic dynamics and properties of these spins have seldom been investigated. Consequently, overcoming these challenges is essential to unlock the full potential of 2D c-MOFs in electronics and other related fields, as a new type of quantum materials.In this Account, we summarize and discuss our group's efforts to achieve full control at the atomic level over the structure of 2D c-MOFs and their applications in electronics and spintronics, thereby providing distinct evidence on 2D c-MOFs as a promising platform for exploring novel quantum phenomena. First, we unravel the key role played by the rational design of the ligands to decrease the boundary defects, achieve atomically precise large single crystals, and investigate the intrinsic charge transport properties of 2D c-MOFs. The advantages and disadvantages of the current structural elucidation strategies will be discussed. Second, the fundamental challenge in 2D c-MOF charge transport studies is to decouple the in-plane and interlayer charge transport pathways and achieve precise tuning of the charge transport properties in 2D c-MOFs. To address this challenge, we propose a design concept for the second-generation conjugated ligands, termed "programmable conjugated ligands", to replace the current first-generation ligands which lack modifiability as they mainly consist of sp2 hybridization atoms. Our efforts also extend to controlling the spin dynamics properties of 2D c-MOFs as "spin concentrated assemblies" using a bottom-up strategy.We hope this Account provides enlightening fundamental insights and practical strategies to overcome the major challenges of 2D c-MOFs for electronics and spintronics. Through the rational design of structural modulation within the 2D plane and interlayer interactions, we are committed to making significant steps forward for boosting the functional complexity of this blooming family of materials, thereby opening clear perspectives toward their practical application in electronics with the ultimate goal of inspiring further development of 2D c-MOFs and unleashing their full potential as an emerging quantum material.

Intrinsic spin transport properties observed in contamination-free graphene-based spin valve

Graphene-based spintronics has attracted great interest while the spin transport and relaxation in clean graphene at low temperatures are still unrevealed. Here, we present an all-dry van der Waals transfer technique to fabricate contamination-free single-layer graphene based lateral spin valve devices. We have obtained a non-local resistance as large as 125 Ω and a spin lifetime of up to 2.47 ns at room temperature simultaneously. Strikingly, an unexpected temperature dependence of spin transport has been observed, where the spin lifetime τ and the spin diffusion length λ decrease with decreasing temperatures below 150 K (τmin = 2 ns, λmin = 10.7 μm at 1.5 K and τmax = 4.63 ns, λmax = 14.5 μm at 150 K). By measuring the oblique Hanle spin precession, we find that the spin-lifetime anisotropy of our device is more pronounced out-of-plane at 75 K. This suggests that the spin relaxation in clean graphene is more effected by the out-of-plane spin orbit field or gauge fields at low temperatures. Our results provide new insight into the fundamental spin transport of graphene, paving a way for their practical applications in spintronics.

Model-based electrolyte design for near-neutral aqueous zinc batteries with manganese-oxide cathodes

Most modern zinc-ion batteries (ZIBs) with MnO2 cathodes utilize near-neutral aqueous electrolytes based on a zinc sulfate (ZnSO4) salt. They achieve good cycling stabilities with high intrinsic safety, employ environmentally friendly materials, and deliver competitive volumetric energy densities. However, the limited solubility of zinc-sulfate species influences the performance and cycling mechanism of these cells. We examine the speciation and solubility limits of ZnSO4, zinc chloride (ZnCl2), and zinc triflate (Zn(CF3SO3)2) in aqueous solutions and simulate their intrinsic transport properties. We use our earlier developed and validated full-cell model to investigate the effects of several electrolytes on the two-phase cycling behavior. Previously, we reported that the origin of the second phase is based on an interaction mechanism between cathodic dissolution and a precipitation reaction at the cathode. We investigate this interplay between electrolyte stability and cathodic dissolution based on electrolyte choice. Our theory-based approach allows us to identify performance indicators of aqueous electrolytes and draws a consistent pathway to optimize electrolyte design for manganese-based ZIBs.

High-Performance Hard X-Ray Imaging Detector Using Facet-Dependent Bismuth Vanadate.

Bismuth vanadate (BiVO4) exhibits large absorption efficiency for hard X-rays, which endows it with a robust capacity to attenuate X-ray radiation across a broad energy range. The anisotropic properties of BiVO4 allow for the manipulation of their physical and chemical characteristics through crystallographic orientation and exposed facets. In this study, the issue of heavy recombination caused by sluggish electron transport in BiVO4 is successfully addressed by enhancing the abundance of the (040) crystal face ratio using a Co2+ crystal face exposure agent. The facet-dependent modifications exhibit excellent and balanced intrinsic charge transport properties, and finely optimize both the sensitivity and detection limit of BiVO4 X-ray detectors. As a result, ultra-stable BiVO4 metal oxide X-ray detectors demonstrate a high sensitivity of 3164 µC Gyair -1 cm-2 and a low detection limit of 20.76 nGyair s-1 under 110 kVp hard X-rays, establishing a new benchmark for X-ray detectors based on polycrystalline Bi-halides and metal oxides. These findings highlight the significance of crystal orientation in optimizing materials for X-ray detection, setting a new sensitivity record for X-ray detectors based on polycrystalline Bi-halides and metal oxides, which paves the way for the development of advanced, low-dose, and highly stable imaging systems specifically for hard X-rays.

DFT study of the intrinsic electronic, optical, NBO, transport, and thermodynamic properties of 12,12-dimethyl-7-phenyl-7,12-dihydrobenzo[a]acridine-3-carbonitrile (BACN)

In this study, we investigate the structural, vibrational, electronic, optical, transport, and thermodynamic properties of pure BACN using density functional theory (DFT). The B3LYP, B3PW91, CAM-B3LYP and ωB97XD functionals associated with the basis sets 6-31G(d,p) and 6-311G(d,p) were used. With regard to the electronic and transport properties, analysis of the HOMO and LUMO frontier orbitals, the gap values obtained and the reorganisation energies show that BACN is a good donor-acceptor semiconductor and has a good hole transport capacity. The study of non-linear optical properties shows that BACN is a good candidate for applications in nonlinear optics (NLO) because of its first-order hyperpolarisability, which is higher than that of urea. The time density functional theory (TD-DFT) approach was used for the photophysical analysis of BACN. It was found that BACN exhibits a maximum absorption in the near-UV range, peaking at 222.42 nm, and strong emission in the near-UV range with a maximum wavelength value of 229.75 nm through TD-CAM-B3LYP/6-311G(d,p). The Stokes shift values obtained indicate that the molecule is chemically stable. The full width at half-maximum (FWHM) and radiative lifetime values for this molecule are 19.924 nm and 16.071 ns, respectively. These results show that BACN is a fluorescent material that can be used as an emitter material for designing and improving the colour purity of organic light-emitting diodes (OLEDs).

Thermal Transport in Pentagonal CX2 (X = N, P, As, and Sb).

Two-dimensional (2D) materials with a pentagonal structure have many unique physical properties and great potential for applications in electrical, thermal, and optical fields. In this paper, the intrinsic thermal transport properties of 2D pentagonal CX2 (X = N, P, As, and Sb) are comparatively investigated. The results show that penta-CN2 has a high thermal conductivity (302.7 W/mK), while penta-CP2, penta-CAs2, and penta-CSb2 have relatively low thermal conductivities of 60.0, 36.9, and 11.8 W/mK, respectively. The main reason for the high thermal conductivity of penta-CN2 is that the small atomic mass of the N atom is comparable to that of the C atom, resulting in a preferable pentagonal structure with stronger bonds and thus a higher phonon group velocity. The reduction in the thermal conductivity of the other three materials is mainly due to the gradually increased atomic mass from P to Sb, which reduces the phonon group velocity. In addition, the large atomic mass difference does not result in a huge enhancement of the anharmonicity or weakening of the phonon relaxation time. The present work is expected to deepen the understanding of the thermal transport of main group V 2D pentagonal carbons and pave the way for their future applications, also, providing ideas for finding potential thermal management materials.

Intrinsic Water Transport in Moisture-Capturing Hydrogels.

Moisture-capturing hydrogels have emerged as attractive sorbent materials capable of converting ambient humidity into liquid water. Recent works have demonstrated exceptional water capture capabilities of hydrogels while simultaneously exploring different strategies to accelerate water capture and release. However, on the material level, an understanding of the intrinsic transport properties of moisture-capturing hydrogels is currently missing, which hinders their rational design. In this work, we combine absorption and desorption experiments of macroscopic hydrogel samples in pure vapor with models of water diffusion in the hydrogels to demonstrate the first measurements of the intrinsic water diffusion coefficient in hydrogel-salt composites. Based on these insights, we pattern hydrogels with micropores to significantly decrease the required absorption and desorption times by 19% and 72%, respectively, while reducing the total water capacity of the hydrogel by only 4%. Thereby, we provide an effective strategy toward hydrogel material optimization, with a particular significance in pure-vapor environments.

Comprehensive Study on Carbon-Coated Silver for Improved Tribo-Electrical and Wetting Performance

The rise in electrification has considerably increased the demand for high-efficiency and durable electrical contact materials. Carbon nanoparticles (CNP) are a promising coating material due to their intrinsic transport properties (thus minimizing the impact on conductivity), their proven solid lubricity (potentially improving tribological performance), and their hydrophobic wetting behavior (potentially providing atmospheric protection). In this study, carbon nanotube and nanohorn coatings are produced via electrophoretic deposition on silver-plated surfaces, followed by tribo-electrical and wetting characterization. The proposed coatings do not negatively affect the conductivity of the substrate, showing resistance values on par with the uncoated reference. Tribo-electrical characterization revealed that the coatings reduce adhesive wear during fretting tests while maintaining stable and constant electrical contact resistance. Furthermore, CNP-coated surfaces show a hydrophobic wetting behavior toward water, with graphite and carbon nanotube (CNT) coatings approaching super-hydrophobicity. Prolonged exposure to water droplets during sessile drop tests caused a reduction in contact angle (CA) measurement; however, CNT coatings’ CA reduction after five minutes was only approximately 5°. Accordingly, CNP (specifically CNT) coatings show auspicious results for their application as wear and atmospheric protective barriers in electrical contacts.

Layered carbon nitride films deposited under an oxygen-containing atmosphere and their electronic properties

Layered carbon nitride (g-C3N4) is a novel semiconducting and functional material for optoelectronic applications. The physical and chemical properties of g-C3N4 films differ depending on the preparation atmosphere. Herein, we deposited g-C3N4 films under a mixed oxygen (O2)-nitrogen (N2) gas atmosphere and studied their effects on the carrier transport properties. Although no significant change in the film orientation was observed, the deposition rate decreased as the O2 gas ratio in the mixed N2/O2 atmosphere increased. Despite their thinness, the luminescence intensity of g-C3N4 films deposited under an O2-containing atmosphere increased by 3.5–5.0 times compared to that deposited under an N2 atmosphere. With respect to voltage application, carrier transport owing to the thermionic emission and/or direct tunneling initially followed ohmic conduction, followed by insufficient trap-filled conduction. As the applied voltage increased further, fully trap-filled conduction was confirmed owing to Fowler–Nordheim tunneling. Moreover, the conductivity type could be changed to p-type and n-type using N2 gas and mixed N2/O2 gas atmospheres, respectively, during film deposition. In addition to the intrinsic transport properties, the intentionally formed Schottky barrier also affected the carrier transport; therefore, the diode-like rectifying behavior of the current density was achieved.

(Invited) Microwave Dielectric Relaxation Spectroscopy: A Technique to Inform Ion Transport in Hydrated Polymer Membranes

Providing sustainable supplies of purified water and energy is a critical global challenge for the future, and polymer membranes will play a key role in addressing these clear and pressing global needs for water and energy. Polymer membrane-based processes dominate the desalination market because they are more energy efficient than thermal desalination processes, and polymer membranes are crucial components in several rapidly developing power generation and energy storage applications that rely on membranes to control, selectively, rates of ion transport. Much remains unknown about the influence of polymer structure on basic intrinsic transport properties, and these relationships are important for designing next generation polymer membrane materials.Key to controlling ion transport in membranes for water purification and energy applications is engineering interactions between ions and the solvated polymer matrix. Microwave dielectric relaxation spectroscopy is a tool that enables study of hydrated polymer membranes because water molecule dipoles can be probed in the microwave frequency region. This technique can provide unique insight into hydrated polymer dielectric permittivity (or dielectric constant) properties, which are critical in emerging thermodynamic modeling of ion transport in hydrated polymers. This presentation discusses the use of microwave dielectric relaxation spectroscopy to uncover structure property relationships in hydrated polymers and, more broadly, presents an overview of research aimed at further understanding fundamental structure/property relationships that govern small molecule transport in polymeric materials considered for desalination and electric potential field-driven membrane applications that can help address global needs for clean water and energy.

Modulations for Quantum Electronic Material Transports by Vacuum Annealing Methods

Gapless linear band structure quantum electronic materials play important roles in quantum computing developments due to their novel superb electronic transport properties and two-dimensional (2D) gateable device possibility. However, the sensitive surface of quantum electronic materials easily reacted with ambient air molecules so as to change their intrinsic transport properties. We review a series of our works to show the importance of surface reactions in quantum electronic materials, such as graphene. By using different electronic transport facilities and in situ vacuum annealing methods, we are able to gently clean the absorbed air molecules on graphene so as to change the carrier densities and the electronic transport properties, which is a great improvement for 2D-quantum material-based quantum chips and computing devices.

A simple and efficient process for the synthesis of 2D carbon nitrides and related materials

We describe here a new process for the synthesis of very high quality 2D Covalent Organic Frameworks (COFs), such a C2N and CN carbon nitrides. This process relies on the use of a metallic surface as both a reagent and a support for the coupling of small halogenated building blocks. The conditions of the assembly reaction are chosen so as to leave the inorganic salts by-products on the surface, to further confine the assembly reaction on the surface and increase the quality of the 2D layers. We found that under these conditions, the process directly returns few layers material. The structure/quality of these materials is demonstrated by extensive cross-characterizations at different scales, combining optical microscopy, Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). The availability of such very large, high-quality layers of these materials opens interesting perspectives, for example in photochemistry and electronics (intrinsic transport properties, high gap substrate for graphene, etc...).

A Negative-Based TiO2 Electrode for Aqueous Proton Batteries

Complementary solutions to Li-ion batteries must be studied for the growing need for energy demand. Accordingly, we have been interested in developing negative electrode materials of TiO2 capable of reversibly intercalating proton ions for aqueous batteries. One of these batteries’ main challenges comes from the low potential window available. Aqueous batteries cannot provide sufficient energy density with a thermodynamic working potential of only 1.23V. To do so, we have optimized the intrinsic transport properties of proton-ions can lead to the reduction of side reactions such as Hydrogen Evolution Reaction (HER).Solvothermal route synthesis made at different temperatures (from 90°C to 150°C) gives access to different TiO2 structures. At 90°C, a lamellar type lepidocrocite is obtained, including sheets of “TiO2” and water in the inter-lamellar spaces. This inter-lamellar space allows proton conduction by the Grotthus mechanism [1]. But, lepidocrocite type TiO2has been shown to be a non-conductive ionic conductor. To make it conductive, different cations can be inserted into the inter-lamellar space during the solvothermal synthesis, thus allowing the reorganization of water molecules, then facilitating the intercalation, conduction, and diffusion of protons [2]. Several levels of Zn2+ were tested: from 10 to 50 mol% relative to Ti4 +. At 150°C, we have been able to stabilize a complete condensed anatase (one polymorph of TiO2) phase while a defect anatase phase has been synthesized at a temperature between 90°C and 150°C. Interestingly, the quantity of defect can be tuned by the temperature and the hydrolysis ratio, h=nH2O/nTi=3.33 [3]. These defects are mainly cationic vacancies, thanks to X-Ray Pair Distribution Function (PDF) analysis.The electrochemical properties of these materials (shaped with carbon black as conductive support and Nafion as a binder) were studied in half-cell aqueous electrolyte buffered at pH 5 (CH3COOH/CH3COOK, pKa = 4.76, (1M)). Experimental capacities of more than 100 mAh/g, 80% of coulombic efficiency over 100 cycles have been obtained and potentials down to -1.4V (V vs Ag/AgCl, KCl saturated) have been achieved.For defective anatase (synthesized at 110°C), the CV curves exhibit two distinct peaks that can be linked to the co-existence of two sites for proton intercalation. The proton can be intercalated either inside a vacancy or within the lattice. This behavior allows a promising working potential of -1.6V with a gravimetric capacity of 250 mAh.g-1 with a 90% of efficiency over 50 cycles. Finally, the relationship between structure and electrochemical properties will be discussed in this presentation with the objective of designing an efficient MnO2/TiO2 aqueous battery.REFERENCE:[1] Wu, X.; Hong, J. J.; Shin, W.; Ma, L.; Liu, T.; Bi, X.; Yuan, Y.; Qi, Y.; Surta, T. W.; Huang, W.; Neuefeind, J.; Wu, T.; Greaney, P. A.; Lu, J.; Ji, X. Nat. Energy 2019, 4 (2), 123–130 [2] Chimie, E. D.; Analytique, C.; Centre, D. P.; Kang, P. S. Sorbonne Université Design de Matériaux Lamellaires Par Chimie Douce Pour Batteries à Proton et Ion Multivalent. 2020.[3] Kang, S; Singh. A; Badot, J-c; Reeves, K; Durand-Vidal, Serge, Legein, C; Body, Monique, Dubrunfaut, O; Borkiewez, O; Tremblay, B; Laberty-Robert, C; Dambournet, D Chemistry of Materials 2020 32 (21), 9458-9469 Figure 1

Modification of polyacrylonitrile TFC-FO membrane by biowaste-derived hydrophilic N-doped carbon quantum dots for enhanced water desalination performance

Effective membranes are critical for enhancing the productivity of the forward osmosis (FO) desalination process. In this work, a straightforward approach is presented for constructing a hydrophilic and high-flux thin film composite FO (TFC-FO) membrane onto a polyacrylonitrile (PAN) sublayer. To this purpose, biowaste-derived nitrogen-doped carbon quantum dots (BWD-NCQDs) were incorporated into the polymeric structure of the TFC selective layer, which improved surface hydrophilicity and caused the creation of more water channels, resulting in better intrinsic transport properties. In both FO and pressure retarded osmosis (PRO) membrane orientations, TFC-FO membranes containing 0.01–0.1 wt% of BWD-NCQDs showed better water permeation and NaCl rejection than the pristine TFC membrane. In the presence of 0.05 wt% of BWD-NCQDs, water flux increased by 54.7 % and reached 24.6 Lm−2 h−1, and reverse solute flux decreased by 43.3 % to 3.81 g−2 h−1 compared to the pristine membrane. The optimum membrane also showed better fouling and water desalination behavior. Therefore, modification of the membranes by hydrophilic BWD-NCQDs represents superior performance in the FO processes. This study demonstrates the potential of using hydrophilic NCQDs derived from biowaste materials to incorporate into TFC membranes and improve their FO proficiency in water desalination.

Coexistence of Magnon-Induced and Rashba-Induced Unidirectional Magnetoresistance in Antiferromagnets.

Unidirectional magnetoresistance (UMR) has been intensively studied in ferromagnetic systems, which is mainly induced by spin-dependent and spin-flip electron scattering. Yet, UMR in antiferromagnetic (AFM) systems has not been fully understood to date. In this work, we reported UMR in a YFeO3/Pt heterostructure where YFeO3 is a typical AFM insulator. Magnetic-field dependence and temperature dependence of transport measurements indicate that magnon dynamics and interfacial Rashba splitting are two individual origins for AFM UMR, which is consistent with the UMR theory in ferromagnetic systems. We further established a comprehensive theoretical model that incorporates micromagnetic simulation, density functional theory calculation, and the tight-binding model, which explain the observed AFM UMR phenomenon well. Our work sheds light on the intrinsic transport property of the AFM system and may facilitate the development of AFM spintronic devices.

Probing the structural, mechanical, phonon, thermal, and transport properties of magnetic halide perovskites XTiBr3 (X = Rb, Cs) through ab-initio results

Herein, we have first reported the intrinsic properties, including structural, mechanical, electronic, magnetic, thermal, and transport properties of XTiBr3 (X = Rb, Cs) halide perovskites within the simulation scheme of density functional theory as integrated into Wien2k. First and foremost, the structural stability in terms of their ground state energies has been keenly evaluated from their corresponding structural optimizations, which advocate that XTiBr3 (X = Rb, Cs) has a stable ferromagnetic rather than the competing non-magnetic phase. Later on, the electronic properties have been computed within the mix of two applied potential schemes like Generalized Gradient Approximation (GGA) along with Trans-Bhala modified Becke Johnson (TB-mBJ), which thoroughly addresses the half-metallic behaviour with spin-up as metallic and in contrast to opposite spin-down channel signatures the semiconducting behaviour. Furthermore, the spin-splitting seen from their corresponding spin-polarised band structures offers a net magnetism of 2 µB which lends their opportunities to unlock the application branch of spintronics. In addition, these alloys have been characterised to show their mechanical stability describing the ductile feature. Moreover, phonon dispersions decisively certify the dynamical stability within the density functional perturbation theory (DFPT) context. Finally, the transport and thermal properties predicted within their specified packages have also been forwarded in this report.

Outstanding intrinsic carrier mobility and transport properties of environmentally stable MX (M=Ga, In; X= S, Se, Te) atomic nanowires

Structural stability, electronic, and transport properties of metal monochalcogenides MX (M = Ga, In; X = S, Se, Te) atomic nanowires have been systematically investigated. To address the effects of the environment on the stability of the nanowires in experimental settings the nanowires are exposed to environmental oxygen. Based on the first-principle calculations, we confirm the energetic, dynamic, and environmental stability of chalcogenides nanowires exhibiting semiconducting nature and bandgaps in the visible region. The electron carrier mobility for InSe, GaTe, and InS nanowires is predicted to be 32,778 cm2 V−1 s−1, 3541 cm2 V−1 s−1, and 1173 cm2 V−1 s−1, respectively, which is higher than the corresponding 2D monolayer and MoS2. The modulations in geometrical parameters are captured using simulated STM analysis. Negative differential conductance predicted for GaTe and InSe nanowires can be used as a marker to characterize them using Current-Voltage profiling. The surface storage charge value of nanowires shows bias dependence indicating the flexible use of nanowires for cathode and anode material application in supercapacitors. Moreover, the outstanding values of mobilities in these nanowires may serve as an excellent electron transport channel in nanowires-based transistors. Therefore, our present study provides significant pointers for applying MX nanowires in fast-switching electronic devices and supercapacitors.