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Suppressing sintering of supported particles is of importance for the study and application of metal-TiO2system. Theoretical study of Ostwald ripening of TiO2(110)-supported Pd particles would be helpful to extend the understanding of the sintering. In this paper, based on density functional theory (DFT), the surface energy of Pd and the total activation energy (the sum of formation energy and diffusion barrier) of TiO2-supported Pd were calculated. Since the total activation energy is mainly contributed from the formation energy, it is indicated that the ripening of Pd particles would be in the interface control limit. Subsequently, the calculated surface energy and total activation energy were used to simulate Ostwald ripening of TiO2(110)-supported Pd particles. As a result, in comparison with larger particles, smaller particles would worsen the performance of ripening-resistance according to its lower onset temperature and shorter half-life time. The differences on ripening-resistance among different size particles could be mitigated along with the increase of temperature. Moreover, it is verified that the monodispersity can improve ripening resistance especially for the smaller particles. However, the different performances of the ripening originating from difference of the relative standard deviation are more obvious at higher temperature than lower temperature. This temperature effect for the relative standard deviation is the inverse of that for the initial main particle size. It is indicated that the influence of dispersity of TiO2(110)-supported Pd particles on ripening may be more sensitive at higher temperature. In this contribution, we extend the first principle kinetics to elaborate the ripening of Pd on TiO2(110). It is expected that the information from first principle kinetics would be helpful to the study in experiments.

Motivated by improving the performance of self-powered deep-UV (DUV) photodetector (PD), for the first time, Pt plasmonic nanoparticles (NPs) were embedded in hybrid PEDOT: PSS/ $\beta $ -Ga2O3 heterojunction interface to maximize light-matter interaction. Profiting from the maximized direct enhancement of the optical field in active region by Pt plasmonic NPs resonance coupling, the increased light absorption excites abundant photogenerated carriers, which are rapidly separated by spatially coincident strong junction electric field. As a result, the resultant PD exhibits higher photocurrent and obtains an improved responsivity of 55.4 mA/W, EQE of 27 %, detectivity of $1.9\times 10^{{14}}$ Jones, and faster response speed under self-powered mode. The optimized optical field in active region caused by embedded Pt plasmons resonance coupling is the reason for the improvement of light absorption and photoresponsivity, which is verified by theoretical simulation. This work demonstrates for embedded plasmonic enhancement in DUV spectral region, providing an innovative pathway for the optimized design of high-sensitivity DUV PDs.

Mixed dimensional van der Waals heterostructure based on layered two-dimensional molybdenum disulfide (MoS2) interfaced to gallium nitride (GaN) has attracted tremendous attention due to its unique properties and application in novel electronic, optoelectronic, and quantum devices. However, developing facile synthesis methods and insights into the exciton dynamics for this system still remains a major challenge. Here, a simple and cost-effective method is demonstrated for large-scale synthesis of monolayer MoS2on differently doped GaN substrates. A mixed aqueous solution of Na2MoO4and NaOH is spin-coated on GaN and sulfurated in one step by chemical vapor deposition (CVD). High quality monolayer MoS2nanosheets with side length over 400 μm and surface coverage ratio of more than 90 % are achieved on GaN. Furthermore, the PL intensity, excitonic transition ratios and ultrafast exciton dynamics of MoS2are observed to be largely modulated by the doping type of GaN, owing to substrate-induced doping, which is proved by Raman, PL and transient absorption spectroscopy. Notably, p-GaN can attract electrons from monolayer MoS2and weaken its intrinsic n-doping, thereby facilitating higher PL intensity as well as longer exciton lifetime, while n-GaN provides strong n-doping and generates opposite effect. This work hereby presents a pathway for large-scale synthesis of MoS2/GaN heterostructures and further understanding of their charge transfer properties and exciton dynamics, which should inspire their applications for optoelectronic devices.

Low-dimensional molybdenum disulfide (MoS2) is a versatile platform for ultrathin electronic, optoelectronic, and quantum devices, owing to the unique properties emerged in the reduced dimensionality. However, it remains challenging to develop facile synthesis methods for explicit control of their morphology and dimensionality. Herein, a simple and cost-effective method is developed for fast and controllable synthesis of monolayer MoS2nano-microribbons. A mixed aqueous solution of Na2MoO4and NaOH was spin-coated on a sapphire substrate and sulfurated viaa one-step chemical vapor deposition. NaOH concentration can control the morphology and orientation distribution of MoS2, while the growth time can control the thickness of MoS2. Notably, high-quality monolayer MoS2nano-microribbons with aspect ratios over 100 and widths as narrow as 200 nm were successfully synthesized, as confirmed by optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman and photoluminescence spectroscopies. In addition, a phototransistor was fabricated based on the monolayer MoS2nano-microribbons, demonstrating an excellent current on/off ratio of 9 × 105, a high photo-to-dark current ratio of 105, and a strong responsivity of 8.6 A W−1. Therefore, this work presents an alternative pathway for the synthesis of high-aspect-ratio MoS2ribbons, which could inspire their applications for ultrathin electronic and optoelectronic devices.