An electroplating-based plasmonic platform for giant emission enhancement in monolayer semiconductors

Two dimensional semiconductors have attracted considerable attention owing to their exceptional electronic and optical characteristics. However, their practical application has been hindered by the limited light absorption resulting from their atomically thin thickness and low quantum yield. A highly effective approach to manipulate optical properties and address these limitations is integrating subwavelength plasmonic nanostructures with these monolayers. In this study, we employed electron beam lithography and electroplating technique to fabricate a gold nanodisc (AuND) array capable of enhancing the photoluminescence (PL) of monolayer MoS$_2$ giantly. Monolayer MoS$_2$ placed on the top of the AuND array yields up to 150-fold PL enhancement compared to that on a gold film. We explain our experimental findings based on electromagnetic simulations

Spin order dependent skyrmion stabilization in MnFeCoGe hexagonal magnets

Topological magnetic skyrmions in centrosymmetric systems exhibit a higher degrees of freedom in their helicity, hence possess a great potential in the advanced spintronics including skyrmion based quantum computation. However, the centrosymmetric magnets also display non-topological trivial bubbles along with the topological skyrmions. Hence it is utmost priority to investigate the impact of different magnetic ground states and their underlying interactions on the stabilization of magnetic skyrmions in cetrosymmetric magnets. Here, we present a combined theoretical and experimental study on the role of non-collinear magnetic ground state on the skyrmion stabilization in a series of exchange frustrated non-collinear ferromagnetic system MnFe1-xCoxGe. With the help of neutron diffraction (ND) and Lorentz transmission electron microscopy (LTEM) studies, we show that hexagonal skyrmions lattice emerges as a stable field driven state only when the underlying magnetic ground state is collinear with easy-axis anisotropy. In contrast, non-topological type-II bubbles are found to be stable state in the case of non-collinear magnetic ordering with partial in-plane anisotropy. Furthermore, we also find that the skyrmions transform to the non-topological bubbles when the system undergoes a spin reorientation transition from the easy-axis to easy-cone ferromagnetic phase. Our results categorically establish the significant role of in-plane magnetic moment/anisotropy that hinders the stability of skyrmion both in the case of collinear and non-collinear magnets. Thus, the present study offers a wide range of opportunities to manipulate the stability of dipolar skyrmions by changing the intrinsic characteristics of the materials.Comment: 18 pages, 4 figure

ATHENA detector proposal - a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider

ATHENA has been designed as a general purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider. Careful technology choices provide fine tracking and momentum resolution, high performance electromagnetic and hadronic calorimetry, hadron identification over a wide kinematic range, and near-complete hermeticity.This article describes the detector design and its expected performance in the most relevant physics channels. It includes an evaluation of detector technology choices, the technical challenges to realizing the detector and the R&D required to meet those challenges

ATHENA detector proposal — a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider

ATHENA has been designed as a general purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider. Careful technology choices provide fine tracking and momentum resolution, high performance electromagnetic and hadronic calorimetry, hadron identification over a wide kinematic range, and near-complete hermeticity. This article describes the detector design and its expected performance in the most relevant physics channels. It includes an evaluation of detector technology choices, the technical challenges to realizing the detector and the R&D required to meet those challenges

Transfer of Vertically Aligned Silicon Nanowires Array Fabricated Using Metal-assisted Chemical Etching

Bulk silicon (Si) possesses an indirect bandgap and low surface area to volume Si ratio. Silicon nanowires (SiNWs), a derived material of Si, overcomes the drawbacks of Si and promises improvement in energy conversion (e.g., solar cell) and storage (e.g., lithium-ion battery) devices, gas sensors, medical diagnostics, drug delivery. The SiNWs-based devices have optical, electronic, and physical properties that can outperform their traditional counterparts in various ways because the SiNWs have a high surface Si area to volume ratio and unique quasi-one-dimensional electronic structure. The metal-assisted chemical etching (MACE) produces the SiNWs using an electrolyte composed of hydrofluoric acid (HF), hydrogen peroxide (H2O2), and a metal salt. Effect of MACE parameters, such as H2O2 concentration (i.e., 0.1 M to 0.3 M), etching time (i.e., 30 minutes to 60 minutes), Si wafer resistivity, HF concentration (i.e., from 0.48M to 9.6M), and etching temperature (i.e., 25℃ to 85℃), on the morphological characteristics (especially length) of SiNWs are compared and thoroughly discussed. Additionally, MACE parameters on the length of SiNWs using Si and porous Si substrates are discussed. The cross-sectional view of FESEM confirms the variation of the length of SiNWs for the variation of MACE parameters. The Raman line broadening and peak shift are due to FANTUM (FANo + quanTUM) effect (i.e., Fano effect and quantum confinement effect), amorphous content (⁓15-20%), and stress in the SiNWs. The tensile strain remains ⁓0.25%, and the crystallinity volume fraction of ⁓80% provides a range of MACE parameter variation to fabricate the SiNWs according to various device applications. The SiNWs, however, need to be transferred to a better substrate for additional flexibility, lesser cost, and transparency compared to Si substrate resulting in improved device functionality. This part explores, optimizes, and compares two techniques to transfer SiNWs to glass: the gluing technique and the two-step electro-assisted technique. The objective is to preserve the length of nanowires on a larger transfer area. Gluing technique spin-coats an adhesive layer made of polyvinyl acetate (PVAc) and methanol solution. The gluing method studies the effect of variation in MACE time on the percentage transfer ratio for the optimized PVAc layer. The electro-assisted technique detaches the vertically aligned SiNWs array with the aid of a sacrificial porous Si layer for variation in anodization time. The yield of the gluing and electro-assisted technique is optimized for MACE and anodization time. The transferred layer is characterized by various parameters, such as the percentage transferred length (%TRL), total transfer area, crystallinity, strain, and morphology of the SiNWs. For optimized values, the gluing method achieved %TRL = 68.2% while transferring 0.95 cm2 of the film area, whereas the electro-assisted technique achieves %TRL = 7.4% for an area of 19 cm2

Fabrication and Characterization of Silicon Quantum Dots by Sputtering Method

Solar energy spectrum ranges from 0.5 eV to 3.5 eV. In the single junction solar cell, a single bandgap energy (e.g Eg=1.12 eV for Si) is converted to electron-hole pair (EHP) and which further helps in current conduction. The third-generation solar cell comes into picture when it is required to convert a range of solar energy spectrum into electric current with reduced cost. The third-generation PV solar cell is based on QDs. A semiconductor material will show quantum confinement effect when the Bohr's radius of that material is less than around 10 nm. The quantum confinement effect is used to tune the bandgap in QDSC. Control of physical parameters and morphology of thin film layer are essential for the synthesis of the quantum dots PV solar cell. Fabrication of the third generation photovoltaic (PV) solar cell uses thin film deposition technique to deposit dielectrics such as SiO2, Si3N4, SiC, and SiOx. The layer works as a barrier layer, passivation layer, capping layer, tunneling medium, and an intermediate (i)- layer in the p-i-n structure solar cell. The presented work use radio frequency (RF) sputtering as deposition technique to fabricate the silicon rich oxide (SRO) and silicon dioxide (SiO2) layers on controlling the deposition parameters such as RF sputtering power, the proportion of sputtering gas flow rate, and sputtering deposition time. The fabricated device is examined for physical and optical properties using spectroscopic techniques such as a surface profiler, EDS-SEM, XRD, FTIR, UV-Vis, and PL

Integration of silicon nanowires in solar cell structure for efficiency enhancement: A review

Silicon nanowires (SiNWs) are a one-dimensional semiconductor, which shows promising applications in distinct areas such as photocatalysis, lithium-ion batteries, gas sensors, medical diagnostics, drug delivery, and solar cell. From an implementation point of view, SiNWs are fabricated using either a top-down or bottom-up approach, and SiNWs are both optically and electronically active. SiNWs enhances the efficiency of the solar cell due to better electronic, optical, and physical properties that can be controlled by tuning the physical dimensions of SiNWs. The SiNWs shows an inherent capability to be utilized in radial or coaxial p-n junction solar cells, to stipulate orthogonal photon absorption, anti-reflection, and enhanced carrier collection. This paper reviews property-control of SiNWs, their various types of incorporation in a solar cell, and the reasons behind enhanced efficiency. Keywords: Optical, Electronic and physical properties, Axial solar cell, Radial solar cell, Anti-reflection coating, Silicon nanowires solar cel