Consideration of contribution of hot-electron injection to the resistive switching of sputter-deposited silicon oxide film

<p>This paper considers the contribution of hot electrons to the resistive switching of sputter-deposited silicon oxide films based on experiments together with semi-2D Monte Carlo simulations. Using various device stack structures, this paper examines the impact of hot-electron injection on resistive switching, where conduction-band offset and fermi-level difference are utilized. Support is found for the predictions that hot-electron injection reduces the switching voltage and this should reduce the dissipation energy of switching. It is predicted that two-layer metal stacks can significantly reduce the number of oxygen vacancies in the sputter-deposited silicon oxide film after the reset process. It is also demonstrated that, in unipolar switching, the number of E’ or E” centers of the sputter-deposited silicon oxide film is relatively large.</p>

Multimodal Plasmonic Hybrids: Efficient and Selective Photocatalysts

Important efforts are currently under way in order to implement plasmonic phenomena in the growing field of photocatalysis, striving for improved efficiency and reaction selectivity. A significant fraction of such efforts have been focused on distinguishing, understanding and enhancing specific energy transfer mechanisms from plasmonic nanostructures to their environment. Herein we report a synthetic strategy that brings together two of the main physical mechanisms driving plasmonic photocatalysis into an engineered system by rationally combining the photochemical features of energetic charge carriers and the electromagnetic field enhancement inherent to the plasmonic excitation. We do so by creating hybrid photocatalysts that integrate multiple plasmonic resonators in a single entity, controlling their joint contribution through spectral separation and differential surface functionalization. This strategy allows us to study the combination of different photosensitization mechanisms when activated simultaneously. Our results show that hot electron injection can be combined with an energy transfer process mediated by near-field interaction, leading to a significant increase of the final photocatalytic response of the material. In this manner, we overcome the limitations that hinder photocatalysis driven only by a single energy transfer mechanism, and move the field of plasmonic photocatalysis closer to energy-efficient applications. Furthermore, our multimodal hybrids offer a test system to probe the properties of the two targeted mechanisms and open the door to wavelength-selective photocatalysis and novel tandem reactions.

Understanding the Mechanism of Plasmon-Driven Water Splitting: Hot Electron Injection and Near Field Enhancement Effects

Utilizing plasmon-generated hot carriers to drive chemical reactions has currently become an active area of research in solar photocatalysis at the nanoscale. However, the mechanism underlying exact transfer and the generation dynamics of hot carriers, and the strategies used to further improve the quantum efficiency of the photocatalytic reaction still deserve a further look. In this work, we perform a nonadiabatic excited-state dynamics study to depict the correlation between the reaction rate of plasmon-driven water splitting (PDWS) and the sizes of gold particles, the incident light frequency and intensity, and the near-field's spatial distribution. Four model systems, \ce{H2O} and \ce{Au20}@\ce{H2O} separately interacting with the laser field and the near field generated by the Au nanoparticle (NP) with a few nanometers in size, have been investigated. Our simulated results clearly unveil the mechanism of PDWS and hot-electron injection in a Schottky-free junction: the electrons populated on the antibonding orbitals of \ce{H2O} are mandatory to drive the \ce{OH} bond breaking and the strong orbital hybridization between \ce{Au20} and \ce{H2O} creates the condition for direct electron injection. We further find that the linear dependence of the reaction rate and the field amplitude only holds at a relatively weak field and it breaks down when the second {\ce{OH}} bond begins to dissociate and field-induced water fragmenting at a very intensive field, and that with the guarantee of electron injection, the water splitting rate increases with the increase of NP's size. This study will be helpful for further improving the efficiency of the photochemical reactions involving the plasmon-generated hot carriers and expanding the applications of hot carriers in varieties of chemical reactions.

Recent Progress on Metal-Enhanced Photocatalysis: A Review on the Mechanism

Metal-enhanced photocatalysis has recently received increasing interest, mainly due to the ability of metal to directly or indirectly degrade pollutants. In this review, we briefly review the recent breakthroughs in metal-enhanced photocatalysis. We discussed the recent progress of surface plasmon resonance (SPR) effect and small size effect of metal nanoparticles on photocatalysis; in particular, we focus on elucidating the mechanism of energy transfer and hot electron injection/transfer effect of metal nanoparticles and clusters while as photocatalysts or as cophotocatalysts. Finally, we discuss the potential applications of metal-enhanced photocatalysis, and we also offer some perspectives for further investigations.

Facile Synthesis of 1T-MoS2 Nanoflowers Using Hydrothermal Method

Molybdenum disulfide (MoS2) is one of the promising 2D materials thanks to its outstanding physicochemical properties and therefore is predicted to play a key role in optoelectronics devices and energy applications. MoS2 exhibits three phases with distinctive crystal structure depending on its stacking order: 1T (metallic), 2H (semiconducting), and 3R (semiconducting). Among all of them, 1T-MoS2 has become the center of interest due to its e.g., high catalytic activity. However, most of the methods to obtain 1T-MoS2 are complex and costly, for example strain engineering, electron beam treatment, and plasmonic hot electron injection. As response, we here demonstrate a facile and cost-efficient hydrothermal route at 200 °C to synthesize MoS2 with high content of 1T phase. MoS2-200 °C nanoflowers has an average diameter of 2.96 µm with the S/Mo atomic ratio of 1.50 and the band gap of 1.39 eV. It has an additional diffraction peak at 2θ = 9.22o, indicating the transformation of semiconducting 2H into metallic 1T. Higher concentration of 1T phase in MoS2-200 °C is also indicated by high intensity of the E1g Raman peak.