Silver (Ag) has excellent properties such as low resistivity and high reflectance. However, Ag thin films on oxide substrates have the disadvantage of agglomeration by annealing due to poor adhesion to the substrates and easy migration of Ag atoms. In this paper, multilayer films with Al nanolayers at the surface and interface were prepared and annealed up to 600 °C in vacuum. It was found that agglomeration was remarkably suppressed compared to Ag single film. In addition, other metals were also investigated as surface nanolayers and the main properties required for them were clarified. Then, the Al and Ti surface nanolayers were deposited on Ag films and their optical properties and durability under high humidity were investigated. We found that Ag films deposited with 1 nm Al or Ti layer showed the same reflectance as silver single film. After the environmental test at 55 °C, 90% relative humidity for 16 h, considerable agglomeration occurred in the Ag single film, but not in the Ti/Ag and Al/Ag films. As a result, the specular reflectance of the multilayers remained high even after the test. It was also confirmed that the protective layer should be continuously deposited on the Ag film in vacuum to achieve the highest agglomeration suppression effect.

A phase field method is used to computationally study formation and morphology of multiple simultaneous conducting filaments, consistent with experimentally observed data of many oxide-based resistive switching thin films. In contrast to existing phase field methods that require an idealized pre-defined axisymmetric conducting filament model, producing only one conducting filament, our method produces multiple conducting filaments without a priori model constraints. Our computational results are consistent with observed irregular bulk current-voltage behavior associated with oxide-based thin films often attributed to existence of multiple conducting filaments, and usually understood to be a performance limiting factor.

Experimental data suggests that multiple conductive filament (CF) formation in oxide-based memristive thin films depends on the film’s geometry. We used a computational phase-field model, without a priori model constraints, and studied the effects of the variation of geometry and dimensions in a three-dimensional sample on the formation of multiple conducting filaments and how they evolve within a sample. In this paper, we show the propensity of multiple CF to form within a variation of lateral and axial dimensions as well as different depths.

Photovoltaic solar cells (SCs) based on dense arrays of III-V nanowires are believed to possess huge potentials for further improvement of their solar power conversion efficiency. A strategy to achieve this goal requires the exploitation of light wave-guiding mechanism and novel physical concepts. The former mechanism is demonstrated for GaAs- AlGaAs core-shell NWs: large enhancement (up to 200´ that of homogeneous – only core – nanowires) of the GaAs near band-edge absorption have been experimentally estimated and ascribed to a wave-guiding of incident light by the surrounding AlGaAs shell. Optimization of such absorption enhancement requires careful design and control of the AlGaAs shell thickness during nanowire self-assembly. Adoption of an intermediate-band gap semiconductor (IBGS) as the SC active material allows to combine the multiband absorption functionality of IBGS with advantages associated to nanowire-based SCs; the use of dilute nitrides III-V alloys within core-multishell NW-based SCs is a very promising solution. Advantages are briefly discussed, along with major challenges in self-assembling such nanowire by MOVPE.

Indium phosphide (InP) quantum dots (QDs) are attracting attention in the display industry due to their lack of heavy metals and unique optical properties. In order to use QDs in displays, the narrower the emission peaks of QDs, the better, and a display made with QDs having narrow emission peaks achieves higher color saturation. However, it is still challenging to fabricate InP QDs that are comparable to the optical properties of cadmium-based QDs. In recent years, most of the literature has focused on the study of narrow-peak green InP QDs, and the research on narrow-peak red InP QDs is very rare. To fabricate red-light InP QDs with narrow emission peaks, ZnInP QDs cores were first fabricated with different Zn precursors (Zn(ud), ZnBr₂, ZnCl₂) and varying ratios of Zn to In (Zn/In=0, 1, 2 and 3). The experimental results revealed that when the ratio of Zn to In is 1, the absorption wavelength of the QD core increases with larger particle sizes. Subsequently, the ZnInP QDs were enveloped with double shell materials to create core-shell-shell QDs. Among them, the prepared ZnInP/ZnSeS/ZnS core/shell/shell QDs (CSS-QDs) had an emission wavelength of 603 nm and full width at half maximum (FWHM) of 52 nm. The color gamut of WLEDs obtained by mixing red CSS-QDs with green phosphors (Silicate phosphors, EG2762) are 94 % of NTSC. This result is beneficial to the application of the InP red QDs in the high color gamut display.

Laser applications in advanced micro/nanoscale technology have traditionally been constrained by the diffraction limit, restricting lasers from achieving nanoscale dimensions. This study introduces an innovative method utilizing a semiconductor-insulator-metal (SIM) structure to fabricate substrate-free surface plasmon polariton (SPP) lasers. This novel design not only substantially reduces the device footprint but also decreases the laser threshold, thereby improving the electromagnetic field confinement. By eliminating the need for a substrate, our approach potentially enhances the integration of micro/nanoscale technologies. This advancement represents a significant step forward in the development of compact and efficient optoelectronic devices, offering new opportunities for innovation across various scientific and engineering fields.

We present a novel photodetector that involves the metasurface-induced scattering of a vertically oriented photon beam into a circularly oriented directional and guided light propagation, resulting in enhanced detection efficiency in an ultra-thin photoabsorption layer. The higher absorption efficiency is enabled by an enhanced photon density of states while substantially reducing the optical group velocity of light and extending the photon material interaction time compared to traditional semiconductor photodetectors without an integrated metasurface. Such detectors with a very thin absorption layer can enable high-efficiency and high-speed photodetectors needed in ultrafast computer networks, data communication, imaging and quantum systems.

Graphene growth from chemical vapor deposition (CVD) commonly employs methane (CH₄) as carbon precursor but requires temperatures in excess of 900°C. Aromatic hydrocarbons, especially toluene (C₇H₈), may lower the growth temperatures well below 600°C, while preserving graphene quality; however, molecular decomposition reactions and early nucleation steps of CVD graphene using toluene are not known in details. We investigate the decomposition steps of toluene adsorbed onto Cu(111) and c(4x2)-reconstructed Si(100) surfaces through DFT calculations. The geometry and energy of toluene and most likely decomposition by-products were analyzed for various adsorbate structural configurations. Early decomposition reactions were studied through investigation of minimum energy pathways and transition states. Low activation energies were found for H removal from the methyl group of toluene physisorbed on Cu(111) (1.20 eV) or chemisorbed on Si(100) (1.39 eV), leading to the formation of benzyl radicals; further dehydrogenation reactions of the latter lead to C₇H₆, C₇H₅ and C₇H₄ fragments, their formation being energetically feasible on Cu (energy barriers in the 0.87-1.62 eV range) but not on Si. These radicals may act as active species in the formation of sp²-bonded carbon nuclei during CVD growth of graphene. Anthracene (C₁₄H₁₀) formation from two closeby C₇H₅ radicals has been studied through meta-dynamics and umbrella sampling methods applied to molecular dynamics simulations. Preliminary results indicate that zig-zag anthracene could easily form onto Cu(111), the energy barriers being below 1.1 eV. A prohibitive energy was instead obtained for (100)Si, hindering anthracene formation on this substrate under practical CVD conditions.

Two-dimensional materials, including transition metal dichalcogenides (TMDs), have attracted attention for potential use in electronic, photonic, and optoelectronic applications. Molybdenum disulfide (MoS₂) is a widely studied TMD that offers potential for improving speed and efficiency in scaled electronic devices. However, advancing MoS₂ and other 2D materials into high volume device manufacturing requires scalable deposition and etching processes that are compatible with manufacturing constraints. Atomic layer deposition (ALD) and atomic layer etching (ALE) are scalable deposition processes that deposit and etch films at relatively low temperatures. Together, atomic layer deposition and atomic layer etching constitute complementary facets of atomic layer processing. Here, we report progress in combining thermal ALD and thermal ALE of MoS₂ followed by annealing to produce crystalline few-layer films. Combining the two processes offers greater control over film uniformity and thickness. Using ALD at 200 °C with MoF₆and H2S followed by ALE at 200 °C with MoF₆ and H₂O and post-deposition annealing in H₂S, we achieved few-layer MoS₂ films as assessed by the separation of the characteristic Raman modes of MoS₂. Using analysis of the Raman spectra for indirect assessment of defect concentrations allowed correlation of the annealing conditions to the quality of the MoS₂ films for accelerated process development. These combined thermal processes and the promising results represent progress towards the integration of MoS₂ films into device manufacturing.

Transition metal dichalcogenides (TMDs), such as MoS₂, have attracted considerable interest in the field of nanoelectronics due to their unique properties. These layered materials possess a hexagonal structure similar to graphene and exhibit semiconducting behavior, making them ideal candidates for channel materials in field-effect transistors (FETs). However, integrating these channel materials into devices requires the fabrication of a high-quality interface between the TMD and a deposited dielectric layer. The sulfur-terminated MoS₂ surface is hydrophobic, and typical films deposited via atomic layer deposition (ALD) often exhibit a high concentration of pinhole-type defects. To improve the compatibility of MoS₂ with ALD processes, we investigated the effect of seeding the surface with HAuCl₄ salts. These chloride-terminated complexes are expected to react with H₂O, resulting in a hydroxyl-terminated surface that is conducive to a well-behaved ALD process. Following surface treatment, ALD titania and alumina films were deposited using tetrakis (dimethylamino) titanium and trimethylaluminum as the metal-organic precursors, with H₂O serving as the oxidizer. Raman spectroscopy confirmed that the surface treatment did not compromise the structural integrity of MoS₂. X-ray photoelectron spectroscopy measurements verified the presence of gold and aluminum on the surface and the successful removal of chlorine during the process. Atomic force microscopy revealed that the HAuCl₄ treatment influenced the titania film nucleation and morphology; however, 6 nm titania films deposited at 100°C and 200°C still exhibited some pinholes.

Silicon photonics is a promising platform for integrating various optical components on a single chip. However, one of the major challenges is to develop efficient and compact light sources due to the poor light emission efficiency of silicon. Semiconducting transition metal dichalcogenide (TMD) shows great potential to address this issue by efficient band engineering with stacking of different TMD monolayers. In this work, we observe the bright-light emission from TMD heterobilayers (MoS2/WSe2), where interlayer excitons dominate the optical properties of materials even at room temperature. Through integrating the heterobilayers with silicon topological cavities, we observe a dominant single emission mode around 1230 nm that is outcoupled to an on-chip waveguide. Our work demonstrates a new architecture for realizing silicon photonic chip-scale integrated light sources at room temperature.

Silver based mirrors (Ag-mirrors) boast high reflectivity in the visible spectral range and low emissivity in the thermal infrared, but tend to suffer from low durability; requiring regular recoating. Conventional coatings extend the operational life of Ag-mirrors, but significantly reduce the mirror’s efficacy in the blue-UV spectral range. The solution our study proposes is a protective coating of diamond-like carbon (DLC); known for its hydrophobicity and abrasion resistance. DLC coating were produced at room temperature using filtered cathodic arc (FCA) deposition, which results in a high sp3 to sp2 bond ratio. Raman spectroscopy characterization reveals that the sp3 to sp2 ratio can be controlled by tuning the applied substrate bias. Optical characterization in turn shows only minor impairment to the Ag-mirror’s overall spectral response in the UV to NIR spectral range with a more substantial decrease in performance around the surface plasmon polariton region. FCA-deposited DLC shows promise as an alternative protective coating providing an increase in durability over conventional coatings without significantly impairing the UV response.