The development of high-performance photocatalysts is essential for advancing sustainable hydrogen production. In the present work, an innovative approach to electron lifetime engineering aimed at enhancing the photocatalytic performance of 1D CdS nanowires by strategically incorporating Ni and titanium nitride (TiN) layers. It demonstrates the electron lifetime mechanism of 1D photocatalyst can be optimized through the introduction of uneven surface and heterojunction. The lifetime of electrons is influenced by the interplay between geometry and electronic structure, directly correlating with photocatalytic efficiency in an exponential decay pattern. Time-correlated single photon counting (TCSPC) measurements provide detailed insights into recombination events and non-radiative properties. Transmission electron microscopy (TEM) and ultraviolet photoemission spectroscopy (UPS) analyses reveal that the prolonged electron lifetime in CdS/Ni/TiN photocatalysts is attributed to the combination of the uneven surface and the passivation of surface energy state on CdS. The single-molecule surface catalytic sites are also observed from super-resolution fluorescence imaging. This perspective first illustrates an integrated discussion on hydrogen production, optical properties, electronic structure, and surface-active sites. The optimal heterostructured CdS achieves a 20.55-fold improvement in hydrogen production. Electron lifetime engineering offers a promising pathway in high-performance 1D photocatalysts for hydrogen production and other energy conversion applications.

The technology of semiconductor photocatalystshas become an important research area. 2D molybdenum disulfide (MoS2) is recognized as a promising catalyst for photoelectrocatalytic and photocatalytic (PC) hydrogen evolution reaction (HER). However, owing to its 2D nature of low optical cross‐section, the effective light absorption needs to be further boosted. Herein, we dramatically amplify the light‐matter interaction by hybridizing these photocatalysts with plasmonic materials that present strong electromagnetic field confinement and with nanowires that offer efficient light management. Such a system is designed in the heterostructure of silicon nanowires (SiNW)/ gold nanoparticles (AuNP)/ MoS2 nanofilms (SiNW/AuNP/MoS2), which demonstrates excellent PC HER. The absorption frequency of 2D‐MoS2, the resonance frequency of the 0D‐AuNP, and the antireflection frequency of 1D‐SiNW match with the visible range, enabling this heterostructure to effectively utilize solar energy. Additionally, an optimal MoS2 nanofilm that is a mixture of 1 T and 2 H phases was prepared with high reproducibility using facile pyrolysis. Moreover, the SiNW substrate validates high antireflection properties, achieving 95% visible light absorption. In addition, SiNW forms a p–n junction with the MoS2 to facilitate charge separation. The synergetic hybrid of 1D‐SiNW/0D‐AuNP/2D‐MoS2 nanofilms exhibits the highest hydrogen generation rate of 246 mmol g−1 h−1.

The growing global energy demand and heightened environmental consciousness have contributed to the increasing interest in green energy sources, including hydrogen production. However, the efficacy of this technology is contingent upon the efficient separation of charges, high absorption of sunlight, rapid charge transfer rate, abundant active sites and resistance to photodegradation. The utilization of photocatalytic heterostructures coupling two materials has proved to be effective in tackling the aforementioned challenges and delivering exceptional performance in the production of hydrogen. The present article provides a comprehensive overview of operational principles of photocatalysis and the combination of photocatalytic and piezo-catalytic applications with heterostructures, including the transfer behavior and mechanisms of photoexcited non-equilibrium carriers between the materials. Furthermore, the effects of recent advances and state-of-the-art designs of heterostructures on hydrogen production are discussed, offering practical approaches to form heterostructures for efficient hydrogen production.

Scalable nanoelectronics with energy‐efficient logic technology is crucial for next‐generation edge devices. Low‐dimensional semiconductors, such as transition metal dichalcogenides and single‐walled carbon nanotubes (SWCNTs), have tunable properties with reduced short‐channel effects. The unique properties of each material can be utilized owing to the heterogeneous integration of multiple semiconducting channels to form complementary metal‐oxide‐semiconductor (CMOS) logic. However, the integration remains challenging. This study reveals the realization of low static power hetero‐CMOS inverters by the integration of n‐type monolayer MoS 2 and p‐type SWCNT networks. The balanced inverter exhibits a large peak gain of ≈67 at a supply voltage of 2 V with the customized design of the wafer‐scale synthetic process and channel integration. An ultralow standby power consumption of ≈5 pW and a practical peak gain of ≈7 at a reduced supply voltage of 0.25 V are achieved. A high noise margin (>70%) validates the circuit's tolerance to external noises and the dynamic analysis of the inverting amplifier in push–pull configuration exhibits a large AC gain. This work paves the way toward the wafer‐scale integration of low‐dimensional materials for low‐power nanoelectronics.

Continuous few-layer MoS2 thin films composed of the stacked MoS2 nanoflakes were fabricated with a facile thermal decomposition method. These nanoflakes possess exposed active sites which are beneficial to the pho-tocatalytic properties. Defect engineering with the aim to generate more exposed edges accompanied with abundant excited carriers by variation of Ar plasma power has been carried out. Positive results were indeed obtained. On the other hand, increasing exposed active edges/defects induced by Ar plasma was found to lead to the occurrence of oxidation in air with time. The variations of crystallinity, S/Mo ratio, and oxygen adsorption after Ar plasma treatment were investigated by high resolution transmission electron microscopy, high resolution x-ray analysis of photoemission spectroscopy as well as Raman spectroscopy. The few-layer MoS2 bombarded by Ar plasma with 30 W power provides the optimal photocatalytic enhancement in hydrogen production about 1.4 times reaching 246 mmolg -1h -1and the photocurrent density was increased by about 15 times to the pristine one. In addition, MoS2/Au system from our previous survey is also utilized this method can generate 338 mmol/g -1h -1, as high as 188% enhancement compared to pristine one. The increase in conductivity for Ar plasma treated MoS2 thin films is attributed to the formation of 2D phase of MoOx with higher electron mobility. The investigation has clarified the influence of defects on the photocatalytic performance. Nevertheless, the defects were found to be unstable when the samples were stored in the air. It is highly desired to pursue a scheme to stabilized the defects for practical applications.

In this study, we applied a piezo-potential to ZnO/ZnS/MoS2 heterostructures through ultrasonication to improve the separation of photoexcited electrons and holes and, thereby, increase their ability to mediate the production of H2. We prepared the ZnO/ZnS/MoS2 heterostructures through hydrothermal synthesis from MoS2 flakes and ZnO microrods, with the ZnS layer formed spontaneously between the ZnO and MoS2 structures. The production of H2 over these heterostructures irradiated with light varied with respect to the mixing ratio of ZnO and MoS2, with the MZ-0.5 heterostructure providing the best performance (4.45 mmol g-1 h-1). When introducing a piezopotential through ultrasonication during the photocatalytic reaction, the rate of H2 production increased dramatically to 10.42 mmol g-1 h-1-approximately 230% higher than that under light irradiation alone. The piezo-potential caused band tilting that facilitated charge transfer; accordingly, recombination was suppressed and the rate of H2 production increased. This combination of a novel multi-heterostructured photocatalyst and piezoelectricity is a cost-effective and non-toxic approach toward the production of H2 as a renewable energy source.

The events of repeating nucleation in point contact reactions between nanowires of Si and Ni or Co have been revisited here due to uphill diffusion as well as an extremely high supersaturation, over a factor of 1000, needed for the nucleation. Also what is the diameter of the point contact needs to be defined. The stepwise growth of nanoscale epitaxial silicide can occur because the repeating nucleation events are restricted in nanoscale wires.

Effects of high-k dielectric MoO3 and Ta2O5 interlayers on the lasing thresholds of ZnO/high-k material/Al nanolasers have been investigated. The results demonstrated the high-dielectric-constant materials as the interlayers over the epitaxially grown aluminum (Al) film consisting of high-quality ZnO nanowires constructing superb low threshold surface-plasmon polariton lasers. High-quality ZnO nanowires grown via the chemical vapor deposition process were used as the gain media placed over a single-crystalline Al film deposited via molecular beam epitaxy. For high metallic losses in the Al film, high k-dielectric material films (MoO3 and Ta2O5), deposited using the electron beam technique, are inserted in the midst of the Al film and ZnO nanowires to reduce the material losses and enhance the optical confinement. It has been found that the lasing threshold varies with the increasing thickness and reduces while increasing the dielectric constant. The performances are compared with those of similarly fabricated nanolasers with Al2O3 and WO3 dielectric interlayers. The critical roles of dielectric constants of the dielectric interlayers in influencing the thresholds of lasing are elucidated. Highly suppressed losses in lasing can be attributed to the dielectric layer that manifests the strong energy confinement in the sub regime. It also shows that the correlation of the lasing threshold with the dielectric constant value applies mainly to the same laser system. For different systems, other factors such as the crystallinity and defects present should be taken into consideration.

Although mechanical exfoliation allows the preparation of flakes of two-dimensional (2D) layered materials from their bulk counterparts in a cost-efficient and versatile manner, it has been difficult to correlate the surface morphology of the exfoliated flakes with their fundamental electrical characteristics. In this study, we used mechanical exfoliation to prepare 2D layered titanium trisulfide (TiS3) nanoribbons having thicknesses varying from a few to tens of nanometers. Interestingly, the bulk electrical conductivity of the exfoliated TiS3 nanoribbons was correlated to their surface roughness, rather than their thickness. Furthermore, at temperatures from 80 K to 280 K, the distinctive behavior of the electrical conductivity in the exfoliated nanoribbons was also significantly dependent on the surface roughness. Measurements of intrinsic field-effect electron mobilities unveiled that the dominant mobility scattering mechanism transitioned from phonon scattering to coulombic and/or surface roughness scattering upon increasing the surface roughness, thereby resulting in distinctive temperature-dependent electrical conductivity behavior. Accordingly, simple measurements of surface morphologies can provide information regarding the fundamental electrical properties of 2D exfoliated layered flakes, potentially leading to greater use of layered materials in semiconductor applications.

Two-dimensional-on-three-dimensional (2D/3D) halide perovskite heterostructures have been extensively utilized in optoelectronic devices. However, the labile nature of halide perovskites makes it difficult to form such heterostructures with well-defined compositions, orientations, and interfaces, which inhibits understanding of the carrier transfer properties across these heterostructures. Here, we report solution growth of both horizontally and vertically aligned 2D perovskite (PEA)2PbBr4 (PEA = phenylethylammonium) microplates onto 3D CsPbBr3 single crystal thin films, with well-defined heterojunctions. Time-resolved photoluminescence (TRPL) transients of the heterostructures exhibit the monomolecular and bimolecular dynamics expected from exciton annihilation, dissociation, and recombination, as well as evidence for carrier transfer in these heterostructures. Two kinetic models based on Type-I and Type-II band alignments at the interface of horizontal 2D/3D heterostructures are applied to reveal a shift in balance between carrier transfer and recombination: Type-I band alignment better describes the behaviors of heterostructures with thin 2D perovskite microplates but Type-II band alignment better describes those with thick 2D microplates (>150 nm). TRPL of vertically aligned 2D microplates is dominated by directly excited PL and is independent of the height above the 3D film. Electrical measurements reveal current rectification behaviors in both heterostructures with vertical heterostructures showing better electrical transport. As the first systematic study on comparing models of 2D/3D perovskite heterostructures with controlled orientations and compositions, this work provides insights on the charge transfer mechanisms in these perovskite heterostructures and guidelines for designing better optoelectronic devices.

Although efficient H-2 evolution through water splitting under irradiation with light would solve severe global environmental and energy issues, finding efficient and eco-friendly photocatalysts from earth-abundant elements remains challenging. In this paper, we report WS2-MoS2 in-plane few-layer heterostructures that function as efficient photocatalysts. Because of the built-in potential at the epitaxially-grown WS2-MoS2 interface, the electron-hole carriers underwent rapid separation upon irradiation with light, such that the H-2 generation yield rate reached as high as 9.83 mmol g(-1) h(-1). This improved photocatalytic H-2 evolution from purely twodimensional in-plane heterostructures has the potential to deliver outstanding catalysts for solar energy conversion as well as the production of chemical fuels.

The most attractive aspect of perovskite nanocrystals (NCs) for optoelectronic applications is their widely tunable emission wavelength, but it has been quite challenging to tune it without sacrificing the photoluminescence quantum yield (PLQY). In this work, we report a facile ligand-optimized ion-exchange (LOIE) method to convert room-temperature spray-synthesized, perovskite parent NCs that emit a saturated green color to NCs capable of emitting colors across the entire visible spectrum. These NCs exhibited exceptionally stable and high PLQYs, particularly for the pure blue (96%) and red (93%) primary colors that are indispensable for display applications. Surprisingly, the blue- and red-emissive NCs obtained using the LOIE method preserved the cubic shape and cubic phase structure that they inherited from their parent NCs, while exhibiting high crystallinity and high color-purity. Together with the parent green-emissive NCs, the obtained blue- and red-emissive NCs provided a very wide color gamut, corresponding to a Digital Cinema Initiatives-P3 of 140% or an International Telecommunication Union Recommendation BT.2020 of 102%. With the superior optical merits of these LOIE-manipulated NCs, a corresponding color conversion luminescence device provided a high external quantum efficiency (10.5%) and extremely high brightness (970 000 cd/m(2)). This study provides a valid route toward highly stable, extremely emissive, and panchromatic perovskite NCs with potential use in a variety of future optoelectronic applications.

A large conductivity difference exists between the {0001} and {101̄0} faces of a GaN wafer. Current-rectifying I – V curves were obtained with electrodes contacting both faces simultaneously.

Although colloidal lead halide perovskite quantum dots (PQDs) exhibit desirable emitter characteristics with high quantum yields and narrow bandwidths, instability has limited their applications in devices. In this paper, we describe spray-synthesized CsPbI3 PQD quantum emitters displaying strong photon antibunching and high brightness at room temperature and stable performance under continuous excitation with a high-intensity laser for more than 24 h. Our PQDs provided high single-photon emission rates, exceeding 9 × 106 count/s, after excluding multiexciton emissions and strong photon antibunching, as confirmed by low values of the second-order correlation function g(2)(0) (reaching 0.021 and 0.061 for the best and average PQD performance, respectively). With such high brightness and stability, we applied our PQDs as quantum random number generators, which demonstrably passed all of the National Institute of Standards and Technology's randomness tests. Intriguingly, all of the PQDs exhibited self-healing behavior and restored their PL intensities to greater than half of their initial values after excitation at extremely high intensity. Half of the PQDs even recovered almost all of their initial PL intensity. The robust properties of these spray-synthesized PQDs resulted from high crystallinity and good ligand encapsulation. Our results suggest that spray-synthesized PQDs have great potential for use in future quantum technologies (e.g., quantum communication, quantum cryptography, and quantum computing).

A novel CdS/TiN core-shell structure has been synthesized to produce the hydrogen gas in the photocatalytic water splitting (PWS) with sacrificial agents under simulated solar light (AM 1.5G). The single-crystalline and high-aspect-ratio CdS nanowires (NWs) are coated with different thicknesses of TiN layer. In particular, the CdS NWs with a thickness of 15-nm TiN showed the best performance in hydrogen production that can improve the hydrogen production rate by about 362% compared to the CdS NWs. In the meantime, it can avoid the detrimental issues regarding the use of CdS alone such as low stability and release of toxic component. This significant improvement of the TiN outer layer is a synergetic effect of three main factors, including the improvement of light absorption and electron concentration caused by surface plasmon resonance (SPR) enhancement effect, the reduction of the possibility of photo-induced carrier recombination, and the outstanding chemical stability during photocatalytic water splitting. In addition, the effects of protective TiN layer on the electric fields generated by light irradiance on the system have been calculated and simulated with the finite-difference time-domain (FDTD) method. The results are consistent with the proposed mechanism for best performance with plasmonic enhancement. The work represents a significant advance in the production of hydrogen via photocatalytic water splitting.

Electrical conductivity measurements show that the {100} faces of a perfect SrTiO3 cube are insulating, but the {110} faces of a SrTiO3 truncated rhombic dodecahedron are considerably more conductive. Interestingly, compared to electrodes touching the proximal {110} faces, adjacent {110} face contacts give notably higher current. Unexpectedly, while the {110} faces of a truncated rhombic dodecahedron remain much more conductive than its {100} faces, the adjacent conductive {110} facets may cause the poorly conductive {100} facets to become more conductive through slight current leakage to the adjacent conductive faces. Consistent with previous insulating behavior observed for a {110}-bound Cu2O rhombic dodecahedron, the {110} faces of a Cu2O rhombicuboctahedral microcrystal remain insulating. Thus, the influence of adjacent conductive facet may be avoided using sharper electrodes. Still, the adjacent facet effect may always be present even with the use of sharp electrodes. Current-rectifying asymmetric I-V curves were recorded with electrodes contacting the {100} and {110} faces of a SrTiO3 truncated rhombic dodecahedron. The electrical facet effects can be understood with different degrees of band bending at these crystal surfaces and thus different barrier heights to charge carrier transport across these surfaces. Finally, high-resolution transmission electron microscopy (HR-TEM) images over the surfaces of SrTiO3 truncated rhombic dodecahedra and cubes were taken, showing notable shifts in atomic positions within the few layers of surface lattice planes relative to the atomic positions of the interior lattice, suggesting that the lattice deviations within the thin surface layer as predicted by density functional theory (DFT) calculations may be visually observable.

Single-crystalline ZnGa2O4 epilayers with different diethylzinc (DEZn) flow rates were successfully grown on sapphire substrates. By decreasing the DEZn flow rate and keeping the deposition time constant, the operational mode of the transistors changed from depletion mode (D-mode) to enhancement mode (E-mode). The relevant electrical properties and physical characteristics are well presented and verified. An E-mode (DEZn = 10 sccm) nchannel thin-film transistor was fabricated for deep-ultraviolet (DUV) phototransistor application. In the phototransistor, the photocurrent gain values increased substantially in the DUV region, the peak value of which measures 1.54 X 10(2) at 240 nm. The superior performance of DUV phototransistors is correlated to the improvement in the quality of materials.

Epitaxial YSi2−X, TbSi2−X and ErSi2−X have been grown on (111)Si by solid phase epitaxy in ultrahigh vacuum deposited rare earth (RE) metal thin films on silicon. The evolution of vacancy ordering and defect structure in epitaxial RE silicide thin films on (111)Si have been studied by both conventional and high resolution transmission electron microscopy. Additional superlattice spots located at 1/3< % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqGH8a % apcaaIYaWaa0aaaeaacaaIXaGaaGymaaaacaaIWaGaeyOpa4daaa!3CB4! $$ < 2\overline {11} 0 >$$ 2110> in the diffraction pattern of RESi2−X are attributed to the formation of ordered vacancy in the Si sublattice planes. The splitting of extra diffraction spots is correlated to the formation of an out—of—step structure. Streamings of the split diffraction spots in the diffraction pattern are attributed to the presence of an out—of—step structure with a range of M values. For YSi2−X and ErSi2−X, the M was found to settle down to a constant value after high temperature and/or long time annealing. For TbSi2−X, M is equal to 5 throughout the annealing. Planar defects in RESi2−X films were analyzed to be stacking faults on { % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqGH8a % apcaaIXaGaaGimaiqaigdagaqeaiaaicdacqGH+aGpaaa!3CB9! $$ < 10\bar 10 >$$ 1010} planes with 1/6< % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqGH8a % apceaIXaGbaebacaaIYaGabGymayaaraGaaG4maiabg6da+aaa!3CD6! $$ < \bar 12\bar 13 >$$ 1213> displacement vectors. The size and density of stacking faults were found to increase and decrease, respectively, with annealing temperature and/or annealing time.

Plasmonics have been well investigated on photodetectors, particularly in IR and visible regimes. However, for a wide range of ultraviolet (UV) applications, plasmonics remain unavailable mainly because of the constrained optical properties of applicable plasmonic materials in the UV regime. Therefore, an epitaxial single-crystalline aluminum (Al) film, an abundant metal with high plasma frequency and low intrinsic loss is fabricated, on a wide bandgap semiconductive gallium nitride (GaN) to form a UV photodetector. By deliberately designing a periodic nanohole array in this Al film, localized surface plasmon resonance and extraordinary transmission are enabled; hence, the maximum responsivity (670 A W-1) and highest detectivity (1.48 × 1015 cm Hz1/2 W-1) is obtained at the resonance wavelength of 355 nm. In addition, owing to coupling among nanoholes, the bandwidth expands substantially, encompassing the entire UV range. Finally, a Schottky contact is formed between the single-crystalline Al nanohole array and the GaN substrate, resulting in a fast temporal response with a rise time of 51 ms and a fall time of 197 ms. To the best knowledge, the presented detectivity is the highest compared with those of other reported GaN photodetectors.