Abstract
The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible ...nanogenerators. Within this group, SnS is a potential choice for such nanogenerators due to its favourable semiconducting properties. To date, access to large-area and highly crystalline monolayer SnS has been challenging due to the presence of strong inter-layer interactions by the lone-pair electrons of S. Here we report single crystal across-the-plane and large-area monolayer SnS synthesis using a liquid metal-based technique. The characterisations confirm the formation of atomically thin SnS with a remarkable carrier mobility of ~35 cm
2
V
−1
s
−1
and piezoelectric coefficient of ~26 pm V
−1
. Piezoelectric nanogenerators fabricated using the SnS monolayers demonstrate a peak output voltage of ~150 mV at 0.7% strain. The stable and flexible monolayer SnS can be implemented into a variety of systems for efficient energy harvesting.
Abstract
A major health concern of the 21
st
century is the rise of multi-drug resistant pathogenic microbial species. Recent technological advancements have led to considerable opportunities for ...low-dimensional materials (LDMs) as potential next-generation antimicrobials. LDMs have demonstrated antimicrobial behaviour towards a variety of pathogenic bacterial and fungal cells, due to their unique physicochemical properties. This review provides a critical assessment of current LDMs that have exhibited antimicrobial behaviour and their mechanism of action. Future design considerations and constraints in deploying LDMs for antimicrobial applications are discussed. It is envisioned that this review will guide future design parameters for LDM-based antimicrobial applications.
Limited levels of UV exposure can be beneficial to the human body. However, the UV radiation present in the atmosphere can be damaging if levels of exposure exceed safe limits which depend on the ...individual the skin color. Hence, UV photochromic materials that respond to UV light by changing their color are powerful tools to sense radiation safety limits. Photochromic materials comprise either organic materials, inorganic transition metal oxides, or a hybrid combination of both. The photochromic behavior largely relies on charge transfer mechanisms and electronic band structures. These factors can be influenced by the structure and morphology, fabrication, composition, hybridization, and preparation of the photochromic materials, among others. Significant challenges are involved in realizing rapid photochromic change, which is repeatable, reversible with low fatigue, and behaving according to the desired application requirements. These challenges also relate to finding the right synergy between the photochromic materials used, the environment it is being used for, and the objectives that need to be achieved. In this review, the principles and applications of photochromic processes for transition metal oxides and hybrid materials, photocatalytic applications, and the outlook in the context of commercialized sensors in this field are presented.
Herein, the fundamentals of UV photochromism for transition metal oxides and organic materials are presented. The recent applications of UV photochromic materials consisting of oxides or composite of oxides and organic materials, known as hybrids, are comprehensively discussed. The review concludes with a summary of applications, challenges, and future pathways for this field.
Scattering-free transport in vacuum tubes has always been superior to solid-state transistors. It is the advanced fabrication with mass production capability at low cost which drove solid-state ...nanoelectronics. Here, we combine the best of vacuum tubes with advanced nanofabrication technology. We present nanoscale, metal-based, field emission air channel transistors. Comparative analysis of tungsten-, gold-, and platinum-based devices is presented. Devices are fabricated with electron beam lithography, achieving channel lengths less than 35 nm. With this small channel length, vacuum-like carrier transport is possible in air under room temperature and pressure. Source and drain electrodes have planar, symmetric, and sharp geometry. Because of this, devices operate in bidirection with voltages <2 V and current values in few tens of nanoamperes range. The experimental data shows that influential operation mechanism is Fowler–Nordheim tunnelling in tungsten and gold devices, while Schottky emission in platinum device. The presented work enables a technology where metal-based switchable nanoelectronics can be created on any dielectric surface with low energy requirements.
In the quest to discover the properties of planar semiconductors, two‐dimensional molybdenum trioxide and dichalcogenides have recently attracted a large amount of interest. This family, which ...includes molybdenum trioxide (MoO3), disulphide (MoS2), diselenide (MoSe2) and ditelluride (MoTe2), possesses many unique properties that make its compounds appealing for a wide range of applications. These properties can be thickness dependent and may be manipulated via a large number of physical and chemical processes. In this Feature Article, a comprehensive review is delivered of the fundamental properties, synthesis techniques and applications of layered and planar MoO3, MoS2, MoSe2, and MoTe2 along with their future prospects.
In the quest for alternative two‐dimensional semiconductors, layered molybdenum trioxide and dichalcogenides are gaining significant scientific interest. This Feature Article delivers a comprehensive review of the fundamental properties, synthesis techniques, and applications of layered MoO3, MoS2, MoSe2, and MoTe2 as well as exploring their future prospects in the field of two‐dimensional semiconductors.
Abstract
Vanadium has 11 oxide phases, with the binary VO
2
presenting stimuli-dependent phase transitions that manifest as switchable electronic and optical features. An elevated temperature induces ...an insulator–to–metal transition (IMT) as the crystal reorients from a monoclinic state (insulator) to a tetragonal arrangement (metallic). This transition is accompanied by a simultaneous change in optical properties making VO
2
a versatile optoelectronic material. However, its deployment in scalable devices suffers because of the requirement of specialised substrates to retain the functionality of the material. Sensitivity to oxygen concentration and larger-scale VO
2
synthesis have also been standing issues in VO
2
fabrication. Here, we address these major challenges in harnessing the functionality in VO
2
by demonstrating an approach that enables crystalline, switchable VO
2
on any substrate. Glass, silicon, and quartz are used as model platforms to show the effectiveness of the process. Temperature-dependent electrical and optical characterisation is used demonstrating three to four orders of magnitude in resistive switching, >60% chromic discrimination at infrared wavelengths, and terahertz property extraction. This capability will significantly broaden the horizon of applications that have been envisioned but remained unrealised due to the lack of ability to realise VO
2
on any substrate, thereby exploiting its untapped potential.
Spectrally-selective monitoring of ultraviolet radiations (UVR) is of paramount importance across diverse fields, including effective monitoring of excessive solar exposure. Current UV sensors cannot ...differentiate between UVA, B, and C, each of which has a remarkably different impact on human health. Here we show spectrally selective colorimetric monitoring of UVR by developing a photoelectrochromic ink that consists of a multi-redox polyoxometalate and an e
donor. We combine this ink with simple components such as filter paper and transparency sheets to fabricate low-cost sensors that provide naked-eye monitoring of UVR, even at low doses typically encountered during solar exposure. Importantly, the diverse UV tolerance of different skin colors demands personalized sensors. In this spirit, we demonstrate the customized design of robust real-time solar UV dosimeters to meet the specific need of different skin phototypes. These spectrally-selective UV sensors offer remarkable potential in managing the impact of UVR in our day-to-day life.
Transition metal oxides (TMOs) are a fascinating class of materials due to their wide ranging electronic, chemical and mechanical properties. Additionally, they are gaining increasing attention for ...their thermoelectric (TE) properties due to their high temperature stability, tunable electronic and phonon transport properties and well established synthesis techniques. In this article, we review TE TMOs at cryogenic, ambient and high temperatures. An overview of strategies used for morphological, compositing and stoichiometric tuning of their key TE parameters is presented. This article also provides an outlook on the current and future prospects of implementing TMOs for a wide range of TE applications.
We demonstrate that the energy bandgap of layered, high‐dielectric α‐MoO3 can be reduced to values viable for the fabrication of 2D electronic devices. This is achieved through embedding Coulomb ...charges within the high dielectric media, advantageously limiting charge scattering. As a result, devices with α‐MoO3 of ∼11 nm thickness and carrier mobilities larger than 1100 cm2 V−1 s−1 are obtained.
Memristive devices are the precursors to high density nanoscale memories and the building blocks for neuromorphic computing. In this work, a unique room temperature synthesized perovskite oxide ...(amorphous SrTiO3: a‐STO) thin film platform with engineered oxygen deficiencies is shown to realize high performance and scalable metal‐oxide‐metal (MIM) memristive arrays demonstrating excellent uniformity of the key resistive switching parameters. a‐STO memristors exhibit nonvolatile bipolar resistive switching with significantly high (103–104) switching ratios, good endurance (>106I–V sweep cycles), and retention with less than 1% change in resistance over repeated 105 s long READ cycles. Nano‐contact studies utilizing in situ electrical nanoindentation technique reveal nanoionics driven switching processes that rely on isolatedly controllable nano‐switches uniformly distributed over the device area. Furthermore, in situ electrical nanoindentation studies on ultrathin a‐STO/metal stacks highlight the impact of mechanical stress on the modulation of non‐linear ionic transport mechanisms in perovskite oxides while confirming the ultimate scalability of these devices. These results highlight the promise of amorphous perovskite memristors for high performance CMOS/CMOL compatible memristive systems.
High performance CMOS/CMOL compatible memristive arrays based on amorphous SrTiO3 thin films with engineered oxygen deficiencies are presented. Isolated nano‐switches are found to be responsible for the excellent switching performance of a‐STO memory cells. Nanoscale electromechanical investigations highlight the assistive role of mechanical stress in nanoionics based conduction and resistive switching in a‐STO devices and confirm their ultimate scalability.
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