Ag Si Research Articles

Design and analysis of Si–Ag–graphene–HfO2 heterojunction based ultraviolet photodetector

Design and analysis of Si–Ag–graphene–HfO2 heterojunction based ultraviolet photodetector

Metastable phases of Ag–Si: amorphous Si and Ag-nodule mediated bonding

Metastable phases such as supersaturated solid solutions, supercooling, and amorphous phases are well-known in metallurgy. They are often composed in non-equilibrium states and can be transformed into a stable phase by overcoming an energy barrier with driving forces. Particularly, it has been widely used for material strengthening and heterogeneous nucleation of precipitates in solids is mainly induced by heat treatments for supersaturated solid solutions. However, little is known about the metastable phases of the Ag–Si alloy, although it is a well-known simple binary eutectic alloy. Here, we show that the metastable phases composed of amorphous Si and supersaturated Ag solid solution are induced by the eutectic reaction under rapid cooling of Ag–Si. Furthermore, the solute Si in the Ag matrix reacts with oxygen to precipitate Ag by-products, which grow as nodules. The Ag nodules have high crystallinity and robust interfacial structures, and the nodule growth leads to the formation of cross-links between the Ag–Si particles. We also demonstrate the Ag nodule-mediated bonding where the rapidly cooled Ag–Si ribbon is directly used as a bonding medium, indicating the possibility of using it as a high-temperature bonding material with low-temperature processes.

Insight of Effect of Silver Powders on Silver–Silicon Contacts of Crystalline Silicon Solar Cells through Analysis of Glass Structural Decay

Optimally designed silver–silicon (Ag–Si) contacts, based on silver (Ag) paste screen printing and the rapid sintering process, are widely utilized in mainstream crystalline silicon solar cells, enabling to reduce contact resistance and high photo‐conversion efficiency. Ag powder is the largest conductive component in Ag paste, but its impact on the formation of Ag–Si contacts lacks in‐depth research and comprehensive understanding. In this work, it is demonstrated that the oxygen adsorption capacity of silver powders affects the formation of Ag–Si contacts by enhancing the reactivity of Ag powders with glass frits, and has a significant effect on the performance of devices. The generation of Ag2O introduced by surface‐absorbed oxygen promotes the transformation of [TeO4] triangular bipyramidal into [TeO3] triangular pyramid, thus destroying the network structure of the glass frits. This structural decay accelerates the spreading of glass frits in the bulk, causing the glass frits to come into contact with SiNx layers earlier and facilitating the formation of the Ag–Si contacts. In this work, not only a complete picture of the interaction between Ag powder and glass frits but also a new direction is provided to optimize the Ag–Si contacts.

Thermodynamic modelling of Ag–Si nanophase diagram including shape effect

Thermodynamic modelling of Ag–Si nanophase diagram including shape effect

Investigation of the Ag–Si contact characteristics of boron emitters for n‐TOPCon solar cells metallized by laser‐assisted current‐injection treatment

Laser‐assisted current‐injection treatment, also known as Laser Enhanced Contact Optimization (LECO), has great potential to reduce the front contact resistance and metal‐induced recombination of n‐type tunnel oxide passivated contact (n‐TOPCon) solar cells, thereby improving the cell efficiency. Herein, we investigate the interfacial Ag–Si contact characteristics on boron‐doped p+ emitters and the electrical properties of industrial n‐TOPCon solar cells that feature a LECO treatment and a specific Ag paste and compare them with those of n‐TOPCon solar cells with a standard Ag/Al paste process. LECO causes some Current Fired Contacts (CFCs) that, when removed by sequential selective etching, leave bowl‐shaped imprints on the emitter, indicating that isotropic alloying behavior occurs between Ag and Si at these local positions during LECO. Unlike the standard Ag/Al metallization process, the LECO process does not significantly damage the passivation layer or emitter. More interestingly, the n‐TOPCon solar cells prepared with the specific Ag paste did not initially form an effective metal‐semiconductor contact, with an average efficiency of only 0.14%, which increased to 25.65% after LECO treatment, even 0.2%abs higher than that of the reference counterparts with standard Ag/Al electrodes. Ultimately, a physical model of LECO‐induced Ag–Si contact formation on boron emitters is proposed.This article is protected by copyright. All rights reserved.

Experimental investigation of phase equilibria in the Al–Ag–Si system

The phase equilibria of the Al-Ag-Si ternary system at 500 °C and 600 °C were investigated by X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA). Three two-phase regions ((Al) + (Si), (Si) + Ag2Al, and (Si) + (Ag)) and two three-phase regions ((Si) + (Ag) + Ag2Al and (Si) + (Ag) + Ag2Al) were observed at 500 °C. The (Si) + Ag2Al and (Si) + (Ag) two-phase regions and (Si) + Ag2Al + liquid and (Si) + (Ag) + Ag2Al three-phase regions were identified in the isothermal section at 600 °C. A vertical section of the Al–Ag–Si system along Al0.6Si0.4–Al0.8Ag0.2 was investigated using differential scanning calorimetry (DSC) from which the temperatures of the phase-transition reactions were determined. The isothermal and vertical sections obtained in this study provide fundamental data for the thermodynamics of the Al–Ag–Si system and knowledge of the thermodynamics associated with aluminium-based alloys.

Revisiting the effect of Ag additions on Ω precipitation and heat resistance of Al–Cu–Mg–Si–Ag alloys

In heat-resistant Al–Cu–Mg–Ag alloys, the presence of AgMg segregation layer on Ω phase ensures its high thermal stability. It was reported Ω precipitation would be inhibited when Si was added such that the Mg/Si mass ratio was lower than 2. However, in this work, it has been proved the notable increase in Ag content from 0.5% to 0.8% could still promote precipitation of Ω besides θ′ in an Al–Cu–Mg–Ag–Si alloy with a Mg/Si mass ratio around 1.7. The key point is to obtain an Ag/Mgexcess atomic ratio greater than 1 under the premise of W(Mg)/W(Si) > 1.4 in the supersaturated solid solution, where Mgexcess denotes the remaining Mg solutes after the formation of C/L phase. Although the fine precipitation of Ω in the 0.8 Ag alloy increases the total volume fraction of precipitates and yield strength, their quick coarsening at high temperature leads to a more pronounced strength loss. Such a comparison reveals the fully enveloped Ω precipitate is less stable than the θ′ precipitate with multiple interface phases. These findings update our knowledge on the systematic composition design for tunning Ω/θ′ precipitates' ratio and properties of Al–Cu–Mg–Ag–Si alloys.

Temperature and composition dependence of thermophysical properties within a wide temperature range for ternary Si–Ge–Ag alloys

The thermophysical properties of Si–Ge–Ag alloys in a broad temperature range are essential for the design of electronic devices. In this work, relationships between specific heat, thermal expansion, thermal conductivity and temperature, as well as chemical composition of Si–Ge–Ag alloys were clarified. Moreover, various thermophysical properties’ prediction strategies of multicomponent alloys from pure elements were evaluated. The specific heat of Ag–Si, Ag–Ge, Si–Ge, and Si–Ge–Ag alloys was determined by the differential scanning method. The results showed a significant increase with rising temperature at low temperatures followed by a gradual rise at high temperatures. The specific heat reached the maximum value when a small amount of Si/Ge was introduced to Ag. The coefficient of thermal expansion was obtained by a dilatometric method and increased slightly with the increasing temperature, while decreased linearly with the increase in the Si/Ge content. Furthermore, the thermal conductivity was investigated via a laser flash apparatus. It decreased with rising temperature when the Ag content is smaller than 50%, whereas it increased with rising temperature when the Ag content exceeds 50%. The thermal conductivity of Si–Ge alloys decreased with rising temperature and reached the local minimum for Si–Ge alloys with an equiatomic ratio of Si and Ge. More importantly, the experimental results reveal that the thermal expansion that is related to volume can be estimated approximately by pure metals in Si–Ge–Ag alloys. However, this rule cannot be applied to specific heat and thermal conductivity, which is due to the influence of lattice vibration, electronic scattering, and microstructure.

Narrow resonance line-widths and high figure of merits via composite nanopillar dimer array sensors

The Ag/Si/SiO2 composite nanopillar dimer array sensor is put forward to form a surface lattice resonance (SLR) with strong intensity and narrow resonance line-width. In the Ag/Si/SiO2 composite nanopillar dimer array, Ag nanopillar dimers sit on Si nanopillar dimers, and Si nanopillar dimers sit on SiO2 nanopillar dimers, which sit on a quartz substrate. Simulated results demonstrate that the line-width can be as narrow as 2.1 nm. This is mainly attributed to the coupling between the combination of single Ag nanopillar dimers' local surface plasmon quadrupole (Q) resonance and Si nanopillar dimers' Mie resonance with the array's diffraction waves. However, for the Ag/Si/SiO2 composite nanopillar array (without dimers), the SLR intensity is too weak for the sensing applications. Compared to the Ag/Si/SiO2 composite nanopillar array, the superiority of the Ag/Si/SiO2 composite nanopillar dimer array is that the near-field coupling in the dimer can further improve Ag nanopillar dimers' Q resonance and Si nanopillar dimers' Mie resonance. Therefore, SLR intensity can be significantly enhanced with only a slight increase in line-width, thus the sensing detection range is wider. The array's period, the height and diameter of Ag/Si/SiO2 nanopillars have notable effects on the SLR. Benefiting from the narrow line-width, the figure of merit (FOM) can reach a value of 226. This work is important to improve the optical sensor based on SLRs.

Three-Layered Thin Films for Simultaneous Infrared Camouflage and Radiative Cooling.

With the rapid advancements in aerospace technology and infrared detection technology, there are increasing needs for materials with simultaneous infrared camouflage and radiative cooling capabilities. In this study, a three-layered Ge/Ag/Si thin film structure on a titanium alloy TC4 substrate (a widely used skin material for spacecraft) is designed and optimized to achieve such spectral compatibility by combining the transfer matrix method and the genetic algorithm. The structure exhibits a low average emissivity of 0.11 in the atmospheric windows of 3-5 μm and 8-14 μm for infrared camouflage and a high average emissivity of 0.69 in 5-8 μm for radiative cooling. Furthermore, the designed metasurface shows a high degree of robustness regarding the polarization and incidence angle of the incoming electromagnetic wave. The underlying mechanisms allowing for the spectral compatibility of the metasurface can be elucidated as follows: the top Ge layer selectively transmits electromagnetic waves ranging from 5-8 μm while it reflects those in the ranges of 3-5 μm and 8-14 μm. The transmitted electromagnetic waves from the Ge layer are first absorbed by the Ag layer and then localized in the Fabry-Perot resonance cavity formed by Ag layer, Si layer and TC4 substrate. Ag and TC4 make further intrinsic absorptions during the multiple reflections of the localized electromagnetic waves.

Chemical Composition and Microstructure Characterization of High Purity CuMn Alloy for Integrated Circuit

High purity copper and copper alloy targets are the key supporting materials for the interconnection of integrated circuits in advanced processes. In this article, the chemical composition and microstructure of Cu-0.6wt%Mn alloy were characterized by means of Glow Discharge Mass Spectrometry, Inductive Coupled Plasma Emission Spectrometer, Optical Microscope and Scanning Electron Microscope. The results show that the total impurity content for Cu-0.69wt%Mn alloy is less than 1 ppm. The three key impurities contents of Ag and Fe and Si could meet the requirement of electronic materials for integrated circuits by use of high purity raw material and appropriate melting and casting methods. Mn content at different positions along the diameter direction fluctuates slightly between 0.66~0.72 wt%, and completely distributed uniformly in the Cu matrix without any trace of aggregation. Due to the influence of raw materials and casting technology, defects such as porosity and carbon inclusion are easy to appear in as-cast microstructure. Therefore, it is necessary to develop new casting mould and casting processing to improve the quality of ingots.

Highly strong interface in Ag/Si sintered joints obtained through Ag2O–Ag composite paste

In this study, the interfacial strength and fracture behavior of Ag/Si interfaces formed by a composite paste comprising Ag2O microparticles, Ag microflakes, and terpineol is demonstrated through microscale tensile testing. This paste induces a delayed reduction of Ag2O and subsequent interconnection between the Ag grains and Si substrate. This is owing to the interface formation by the direct bonding of Ag and a layer with Ag nanoparticles intermediated bonding using the newly generated Ag nanoparticles. This characteristic interface formation helps achieve a high joint strength (>30 MPa) at a bonding temperature of 250 °C, inducing a substrate fracture at 275 °C. Microscale tensile testing reveals the high-strength Ag/Si (>200 MPa) interface formation and intrinsic fracture morphology within the Ag layer at a nanoscale; the fracture occurs in the Ag layer and not at the interface.

Plasmonic Ring Resonator Sensor With High Sensitivity and Enhanced Figure of Merit Using an Ag–Si–Ag Bus Waveguide

A plasmonic miniaturized ring resonator based on Ag-analyte-Ag ring cavity coupled with an Ag-Si-Ag input bus waveguide has been numerically analyzed for bulk refractive index and surface adlayer sensing applications. The opto-geometric parameters of the sensor structure have been thoroughly optimized to maximize field confinement in the sensing zone, which significantly improves the sensitivity. Using an Ag-Si-Ag input bus waveguide results in the reduction of propagation loss which offers an improved quality factor and figure of merit due to narrowing of full width at half maximum (FWHM) of the transmission spectrum. The average bulk refractive index sensitivity over biologically relevant refractive index range (1.33-1.38 RIU) and gas-sensitivity (1-1.01 RIU) values are 1757.71 nm/RIU with an FWHM of 37 nm, and 1787.14 nm/RIU with an FWHM of 24 nm, respectively. We have also investigated the optimized sensor's performance as an adlayer biosensor and the maximum adlayer sensitivity obtained is 2.72 nm/nm. We have also analyzed the sensor's optical tolerance by incorporating a 10% change in Ag's and Si's real part of dielectric constants. Owing to excellent sensitivity and high figure of merit the proposed sensor may find applications in designing highly sensitive on-chip nano-sensors with improved detection limit.

Broadband absorption of modified conical nanowires for photovoltaic applications

In this paper, modified conical nanowires (CNWs) with different top diameters are suggested to break the structure mirror symmetry and increase the light absorption. The proposed arrangement consists of 2 × 2 periodic CNWs with top different conical diameters where the light reflection is reduced and therefore the absorption efficiency is enhanced. The optical characteristics of the suggested CNWs are numerically simulated using three-dimensional 3-D finite-difference time-domain (FDTD) method. The numerical results show that a good coupling of the scattered light is achieved through the proposed NWs with multiple resonant wavelengths. In this context, the Mie resonances are improved and strengthened over a wide range of wavelengths by optimizing the top cone diameters. The reported design offers an ultimate efficiency (η) of 39.8 % and short circuit current density (Jsc) of 35.2 mA/cm2 with an enhancement of 28.8 % compared to the conventional CNWs. When a bottom Si substrate and Ag back reflector are used, the η and Jsc are improved to 42.1 % and 37.4 mA/cm2, respectively. This is owing to the coupling between the supported modes in the NWs and those excited in the Si substrate. The maximum power conversion efficiency (PCE) in the axial junction of the modified CNWs structure is equal to 18 % compared to 15.5 % for the conventional CNWs design with an enhancement of 16 % in the ideal passivation.

Silicene’s pervasive surface alloy on Ag(111): a scaffold for two-dimensional growth

Silicene, the two-dimensional (2D) allotrope of silicon, is a promising material for electronics. So far, the most direct synthesis strategy has been to grow it epitaxially on metal surfaces; however, the effect of the strong silicon-metal interaction on the structure and electronic properties of the metal-supported silicene is generally poorly understood. In this work, we consider the -silicene monolayer (ML) grown on Ag(111), probably the most illustrious representative of the 2D silicon family, and show that our experimental results refute the common interpretation of this system as a simple buckled, honeycomb ML with a sharp interface to the Ag substrate. Instead, the presented analysis demonstrates the pervasive presence of a second silicon species, which we conclude to be a Si–Ag alloy stacked between the 2D silicene and the silver substrate and scaffolding the 2D silicene layer. These findings question the current structural understanding of the silicene/Ag(111) interface and may raise expectations of analogous alloy systems in the stabilization of other 2D materials grown epitaxially on metal surfaces.

Simulation of Mushroom Nanostructures with Ag Nanoparticles for Broadband and Wide-Angle Superabsorption

Metal nanoparticles (NPs) concentrate the energy of incident photons through plasmon resonance excitation, which allows scattering into a substrate with a high refractive index, and the radiated energy from this excitation significantly increases the optical absorption of the substrate. In this work, the effect of Ag NPs on the absorption capacity of mushroom-nanostructured Si metasurfaces was analyzed using the finite-difference time-domain method. It was observed that the absorbance in the metasurfaces with Ag NPs increased from 90.8% to 98.7% compared with nanostructured Si metasurface without NPs. It was shown that the plasmon resonance effect of Ag NPs enlarged the range of the FP cavity by about 10 times, and the electric field strength E2 increased by about four times through the combination of Ag NP and Si absorbers. Meanwhile, the effect of randomly distributed nanostructures on the absorption properties of Si metasurfaces was simulated. Additionally, the nanostructured surface with Ag NPs was insensitive to angle, which encourages the design of broadband and wide-angle superabsorption nanostructures.

Characterization of microstructure, corrosion, and tribological properties of a multilayered friction surfaced Al–Mg–Si–Ag alloy

Characterization of microstructure, corrosion, and tribological properties of a multilayered friction surfaced Al–Mg–Si–Ag alloy

Preparation and optical properties of sulfur-doped silicon oxide microbelts and microrods

Amorphous S-doped and non-doped silicon oxide (SiO 2 ) one-dimensional structures with various morphologies are synthesized on Si substrates by vapor deposition with Ag 2 S as the precursor in a horizontal tube furnace. Curved microwires, grass-like microwires, S-doped microbelts, and straight S-doped microrods are obtained at the downstream of the furnace with different deposition temperatures in sequence. The microwires and microbelts are formed by the direct vapor-solid mechanism. The morphologies of microwires are largely determined by the inherent isotropy of their amorphous structure and the competitive growth in vapor phase. The microbelts are formed by the lateral growth of small microwires and the doped S played a critical role in their formation. However, the Ag–Si–S–O nanoparticles located at the growth ends suggests that the formation of S-doped SiO 2 microrods should be controlled by the vapor-liquid-solid mechanism. Both curved and grass-like microwires have similar photoluminescence behavior with strong blue/green/yellow bands and weak violent/red bands. However, S-doped microbelts exhibit strong violet/blue bands and relative strong a red band, and S-doped microrods exhibit low violet/blue bands and a strong red band. The obvious shifts in the intensities and wavelengths of the violet/blue/yellow bands are attributed to the morphology/size effects of microwires and microbelts, while the improved red-light emission is assigned to the doped S in microbelts and microrods. • S-doped SiO 2 nanobelts and nanorods are synthesized by vapor deposition. • S-doped SiO 2 nanobelts and nanorods are twist-free and straight. • Doped S determines the formation and morphology of the nanobelts. • Doped S can tune the optical properties of the nanobelts and nanorods.

High-density Si nanopillars modified with Ag nanoislands: Sensitive SALDI-MS chip for sulfonamides

In recent years, the abuse of antibiotics has brought adverse effects on water environment and food safety, to monitor the antibiotic content in water and foodstuffs is imperative for environmental protection and human health. In this work, a chip, composed of high-density Si nanopillars and Ag nanoislands, is prepared for sensitive detection of sulfonamides with surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). In this chip, the high-density Si nanopillars can absorb laser energy efficiently and promote electron transfer as antennas; the Ag nanoislands can enhance the thermal effect; the formation of the Schottky barrier and the conductive nanolayer between Si/Ag can extend the lifetime of electrons and promote electron tunneling effect. Therefore, the heterostructure presents high detection sensitivity (the limit of detection of sulfamethazine is as low as 3 amol); in addition, the satisfactory coefficients of determination (> 0.99) show that the chip is applicable for rapid quantification of sulfonamides. Further, the sulfacetamides spiked in milk and lake water can be sensitively identified and rapidly quantified. The prepared chip presents a considerable potential for food and environment monitoring.

An Alternative to Compound Semiconductors Using a Si-Based IR Detector

Though infrared (IR) photodetection is popular, it faces several problems. First, the main materials, compound semiconductors, require high temperature, low pressure, and high energy consumption facilities. Second, compound semiconductor elements are rare on earth. Third, compound semiconductors are difficult to integrate with Si-based integrated circuit (IC) manufacturing process. To overcome these problems, we utilized a Si-based Schottky junction and internal photoemission to break the detection limit of a Si photodetector. The spectral detection limit extends from 1100 nm, the bandgap wavelength of Si, to ca. 1600 nm, the Schottky barrier wavelength of the metal/Si junction. The Schottky junction is composed by Ag and n-type Si through simple thermal evaporation. The light incident direction, metal thickness, and device temperature were analyzed. As a result, under normal temperature and pressure, the Schottky barrier height of the Ag/Si junction is 0.742 eV. The detection limit is 1670 nm. If the 1550-nm laser is a detected light source illuminating from the metal film, the responsivity is 0.02122 mA/W. If the same detected light source illuminates from the Si substrate, the responsivity improves to 0.04567 mA/W due to the light absorption enhancement. Furthermore, if the metal thickness is increased to 100 nm, the responsivity increases to 1.242 mA/W, which is about 585.3% of the original value. In addition, the influence of the temperature on the electric properties of the devices indicates that a Ag/Si Schottky device could be a candidate for temperature detection.