Copper (Cu) electroplating has been rising once again due to the giant industrial demands for metal interconnectors in the integrated circuit and the current collector in the lithium-ion battery. If the current acidic Cu(II) electroplating were replaced by the alkaline Cu(I) electroplating, it would reduce electricity consumption by at least 50%, not to mention the environmental friendliness. The bottleneck for alkaline electroplating is the complexation to stabilize the Cu(I) cations in solution. To this end, we developed a novel alkaline Cu(I) electroplating system and studied the complexation mechanism by both ex situ and in situ UV-visible spectroscopy. The results demonstrated that succinimide (SM) is a stronger complexant than sulfite and forms a stable [Cu(SM)2]- ion, which was further stabilized by maltose. The sulfite acted as no longer a complexant but a reductant. Thus, a high-quality Cu-plating layer was obtained with excellent metallographic structure and mechanical performance. The work demonstrates the vital capability of UV-visible spectroscopy in investigations on the action mechanisms of electroplating additives.

Solar energy is the ultimate power source for mass and energy conversions on this planet through photochemical reactions. Among these, photoinduced interfacial electron transfer (PIET) reactions are driven by photofield-induced Volta potentials, fundamentally different from classical electrochemical processes by directly applied potential through a potentiostat. Herein, we develop a colocated scanning electrochemical microscopy (SECM) approach─integrating with atomic force microscopy (AFM) and scanning Kelvin probe microscopy (SKPM)─to correlate the morphology, Volta potential, and PIET kinetics at the same located silver sheet/single-layer graphene (Ag/SLG) electrode. We reveal that illumination induces π-π* transitions in SLG and d-electron excitations in Ag, leading to a synchronous positive shift of the Fermi level of the Ag/SLG electrode, acting effectively as a photogenerated interfacial potential. More importantly, the Volta potential difference across the Ag/SLG boundary, determined by their electron work function, remains nearly constant. The synergy between the photoinduced Volta potential and the Volta potential difference across the Ag/SLG boundary underpins the enhanced PIET efficiency. This study provides a direct methodology to quantify physical-field-driven interfacial electron transfer and establishes a framework for the rational design of catalyst/carrier systems beyond conventional electrochemical paradigms.

Dielectric diffractive optical elements (DOEs) have attracted considerable interest for applications in semiconductor optics and optoelectronics owing to their efficient optical wavefront manipulation, ultra-low electromagnetic loss, and CMOS compatibility. We employ electrochemical nanoimprint lithography (ECNL) to directly fabricate holographic DOEs on dielectric gallium phosphide (GaP) wafers via confined electrochemical etching. By compensating systematic fabrication errors through mold design with reserved etching margins, ECNL achieves an ultra-high processing precision. We further demonstrate the advantages of ECNL in enabling efficient, controllable, and batch-compatible fabrication of holographic patterns. Moreover, the applicability of ECNL is validated across various semiconductor materials, establishing a scalable manufacturing pathway for dielectric DOEs.

High-precision, low-damage micro/nano-fabrication of gallium nitride (GaN) is essential for the performance and reliability of advanced GaN-based devices. Conventional dry etching inevitably induces surface and lattice damage. Meanwhile, wet etching is suffered from limited spatial resolution, complex interfacial chemistry, and poor in-situ controllability, leaving the localized etching kinetics of GaN under external physical fields insufficiently understood. Here we establish a microscopic research platform based on light-assisted scanning electrochemical probe lithography (SECPL) to investigate and modulate the localized anodic etching of GaN under coupled electric and optical fields. A well-defined metal/semiconductor/electrolyte (M/S/E) three-phase interface is confined at the micron-scale point contact between a microprobe and the GaN surface, enabling maskless, programmable direct-write etching in a gentle KOH/K2S2O8 electrolyte. Photoelectric synergistic effect markedly enhances the localized etching kinetics. By employing dual-potential modulation, we achieve an etching rate up to 2.92 mu m & sdot;min-1 while preserving strict spatial confinement. Comprehensive structural and chemical analyses confirm that the etching reaction is highly localized and does not induce any detectable lattice damage or chemical contamination. This work establishes a versatile platform for probing localized etching kinetics in widebandgap semiconductors under photoelectrical coupling, thereby offering insights for high-performance optoelectronic devices processing.

In this study, a series of tetrazolium derivatives i.e. iodonitrotetrazolium chloride, thiazolyl blue tetrazolium bromide, triphenyltetrazolium chloride, 2,3-(4-nitrophenyl)-5-phenyltetrazolium chloride, 2,3-(4-methoxyphenyl)-5-phenyltetrazolium chloride and 2,3-Bis(3-fluorophenyl)-5-phenyltetrazolium chloride are respectively employed as the leveler in acidic copper electroplating bath to elucidate the relationship between adsorption ability and their microvia filling performance. Microvia filling experiments and electrochemical measurements were conducted to evaluate their performance, complemented by density functional theory (DFT) simulations to elucidate adsorption mechanisms. The results reveal a volcano relationship between adsorption strength and filling performance: levelers with excessively weak adsorption cannot effectively compete adsorption with suppressor and accelerator, while those with excessively strong adsorption exhibit just uniform filling at both the via bottom and mouth, impeding bottom-up filling. Only those levelers with moderate adsorption capacity enable presenting the desired convection-dependent adsorption (CDA) behavior, facilitating void-free bottom-up filling. Furthermore, the adsorption capacity of a leveler molecule is significantly influenced by strong electron-withdrawing groups such as -NO2 and -F, suggesting that incorporating such substituents during molecule design of a leveler offers a viable strategy to modulate adsorption strength and achieve optimal filling performance. These findings provide definitive design principle for next-generation levelers in acidic copper electroplating.

Cyanide-free gold sulfite is a necessary and environmentally friendly salt for electrochemical preparation of Au deposits. This study reveals complex interfacial reactions of Au(SO3)23- ions under weak acidic conditions (pH 6). Introducing Bi3+ ions to regulate the processes can yield high-quality Au deposits and improve interface stability. Electrochemical surface-enhanced Raman spectroscopy (EC-SERS) and complementary electrochemical experiments demonstrate that SO3 2- ions are first reduced to S2O42- ions at-0.55 Von the Au electrode surface, followed by the electroreduction of Au(SO3)23- ions at -0.75 V. The reduced product S2O42- ions with strong reducing property chemically reduce Au(SO3)23- ions to Au nanoparticles, degrading the deposit quality and electroreduction stability. Bi3+ ions shift the reduction onset potential of Au(SO3)23- ions from -0.75 V to -0.48 V, preventing SO3 2- ions reduction and the undesired chemical reaction. Theoretical calculations attribute this depolarization of Bi3+ ions to their impact on the stability of the Au(SO3)23- ions, leading to alterations in their electronic structure. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) confirm that Bi3+ ions are not incorporated into gold deposits and the gold deposits obtained at a proper low current density of 0.5 A/dm2 features fine grains, compact structure, high purity, smoothness and brightness.

Surface-enhanced Raman spectroscopy (SERS) has evolved significantly over fifty years into a powerful analytical technique. This review aims to achieve five main goals. (1) Providing a comprehensive history of SERS's discovery, its experimental and theoretical foundations, its connections to advances in nanoscience and plasmonics, and highlighting collective contributions of key pioneers. (2) Classifying four pivotal phases from the view of innovative methodologies in the fifty-year progression: initial development (mid-1970s to mid-1980s), downturn (mid-1980s to mid-1990s), nano-driven transformation (mid-1990s to mid-2010s), and recent boom (mid-2010s onwards). (3) Illuminating the entire journey and framework of SERS and its family members such as tip-enhanced Raman spectroscopy (TERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and highlighting the trajectory. (4) Emphasizing the importance of innovative methods to overcome developmental bottlenecks, thereby expanding the material, morphology, and molecule generalities to leverage SERS as a versatile technique for broad applications. (5) Extracting the invaluable spirit of groundbreaking discovery and perseverant innovations from the pioneers and trailblazers. These key inspirations include proactively embracing and leveraging emerging scientific technologies, fostering interdisciplinary cooperation to transform the impossible into reality, and persistently searching to break bottlenecks even during low-tide periods, as luck is what happens when preparation meets opportunity.

Galvanostatic method based on the convection-dependent adsorption (CDA) model can be effectively utilized to predict the blind via filling performance but failed in evaluating the throwing power (TP) of an acidic copper plating solution for through hole (TH) thickening. In this work, another two factors of copper ions mass transfer and electric field distribution inside the TH are considered for further understanding the thickening mechanism of TH. Considering the copper ions mass transfer, forced convection is necessary to improve the undesirable gradient distribution of copper ions concentration inside the TH for the uniform thickening. Considering the uneven electric field distribution, a simple strategy for evaluating the TP of a plating solution by the electrochemical electrode kinetic parameters measured from linear scanning voltammetry (LSV) test is established. A larger value of Tafel slope (lower value of transfer coefficient) indicates that inside the TH, copper deposition rates at the hole center and hole mouth are more approaching thereby in favor of higher TP. The strategy, which is verified by three copper plating solutions and the finite element simulation, indicates the great reliability and applicability in TH thickening.

Metal interconnection in integrated circuits (IC) is often obtained with electroplating copper in the high-aspect micronano vias. Electroplating additives are crucial for the void-free filling in order to overcome the nonuniform potential distribution and insufficient mass transfer inside the high-aspect micronano vias. However, revealing the molecular action mechanism of the additive is hindered for conventional spectroscopy techniques such as Raman spectroscopy due to the low operando concentration of these additives. Surface-enhanced Raman techniques such as shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) have shown promising results of revealing the interfacial adsorption behavior of a single additive. Here, an improved SHINERS configuration with a spectroelectrochemical flow cell and a water immersion objective is developed to obtain the in situ molecular information on the potential and convection dependent coadsorption of multiple coexisting additives in a novel acid copper sulfate electroplating solution. The results present a valuable in situ instrumental method to investigate the molecular action mechanism of electroplating additives.

In this study, we develop 4,7,10-trioxa-1,13-tridecanediamine (TTDDA) as a novel single-component additive for uniform thickening of micro through-hole (MTH) in acidic sulfate copper electroplating, replacing the traditional three-additives process. Chronopotentiometry and cyclic voltammetry (CV) reveal that TTDDA itself exhibits weak convection-dependent adsorption behavior and weak polarization effects during copper ions electroreduction. However, TTDDA can combine with Cl ions to significantly inhibit copper electrodeposition at the mouth of MTH, resulting in the similar electrodeposition rate with the center. Linear sweep voltammetry (LSV) demonstrates that TTDDA aids homogeneous copper deposition under non-uniform electric field distribution. Chronoamperometry highlights the critical role of forced convection in maintaining uniform copper ions distribution, further confirming that TTDDA and Cl ions inhibit deposition more at the mouth of MTH than at the center. Density functional theory (DFT) and in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) confirm that TTDDA can form TTDDA-Cu-Cl complex with copper ions and Cl ions, enhancing the adsorption of TTDDA on copper. The adsorption of TTDDA-Cu-Cl complex increases gradually with the negative potential shift, making copper ions electroreduction more difficult. The MTH copper electroplating experiments prove that TTDDA significantly increases the throwing power (TP) of MTH from 52.40 % to 92.59 % under the strong mass transfer condition.

On-line detection of additive concentrations in acidic copper (Cu) electroplating solution, including the suppressor, accelerator and leveler, is crucial for the industrial production of integrated circuit metal interconnections. For this purpose, a portable electrochemical microfluidic workstation (EMW) is developed. The polymer electrochemical microfluidic chip is designed and fabricated by 3D printing, in which a liquid mixer is integrated with an electrochemical microcell. The asymmetrically distributed herringbone microstructures in the microchannels (width: 400 mu m, height: 300 mu m, length: 4 cm) ensure the highly efficient mixture of solutions. In the electrochemical microcell, a 12.5 mu m radius platinum ultramicroelectrode (Pt UME) acts as the working electrode. Based on the suppressing or accelerating effects of the additives on Cu electroplating, the calibration curves can be obtained by the stripping charge of electrodeposited Cu. Thus, the concentration of each additive in the acidic Cu electroplating solution can be detected on line and adjusted in time. The solution volume needed for each additive is approximately 220 mu L. The detection error is lower than 10%, meeting the analytic requirements in industry. The automated EMW has the potential to replace the current manual cyclic voltammetry stripping (CVS) employed in lab analysis.Keywords: Electrochemical microfluidic workstation; On-line detection of additive concentration; Microfluidic chip; Ultramicroelectrode; Acidic copper electroplating.

Developing a highly efficient leveler in acid copper electroplating solution is one of the primary tasks necessary for achieving superconformal filling of microvias and interconnections in printed circuit boards (PCBs). Two triethylenediamine-based Gemini levelers, both with terminal quaternary ammonium groups, are synthesized and named as GL1 (C8) after reaction of triethylenediamine with 1,8-dichlorooctane and GL2 (C6 with two C–O linkages) after triethylenediamine with 1,2-bis(2-chloroethoxy) ethane. Electrochemical experiments indicate that at 100 rpm and 1000 rpm GL2 combines with a suppressor and accelerator to exhibit greater potential difference of 23 mV than GL1 in 9 mV for Cu2+ reduction, demonstrating that GL2 has a stronger synergistic convection-dependent adsorption (CDA) effect. Microvias copper electroplating experiments confirm that acid copper electroplating solution containing GL2 achieve more effective superconformal void-free filling as it results in FP = 96.1%, while the solution containing GL1 results in FP = 70%. Theoretical calculations indicate that adsorption energy of GL2 is −1037.54 kJ·mol−1, which is lower than GL1 (−1019.06 kJ·mol−1). GL2 displays lower electron density compared to GL1, which facilitates its displacement by accelerator at the bottom. The lower adsorption energy of GL2 suggests the weaker adsorption ability and the stronger CDA behavior.

Single cell amperometry has proven to be a powerful and well-established method for characterizing single vesicular exocytotic events elicited at the level of excitable cells under various experimental conditions. Nevertheless, most of the reported characteristics are descriptive, being mostly concerned with the morphological characteristics of the recorded current spikes (maximum current intensities, released charge, rise and fall times, etc.) which are certainly important but do not provide sufficient kinetic information on exocytotic mechanisms due to lack of quantitative models. Here, continuing our previous efforts to provide rigorous models rationalizing the kinetic structures of frequently encountered spike types (spikes with unique exponential decay tails and kiss-and-run events), we describe a new theoretical approach enabling a quantitative kinetic modeling of all types of exocytotic events giving rise to current spikes exhibiting exponential decay tails. This model follows directly from the fact that the condensation of long intravesicular polyelectrolytic strands by high concentrations of monocationic neurotransmitter molecules leads to a matrix structure involving two compartments in constant kinetic exchanges during release. This kinetic model has been validated theoretically (direct and inverse problems) and its experimental interest established by the analysis of the amperometric spikes relative to chromaffin and PC12 cells previously published by some of us.

Surface-enhanced Raman spectroscopy (SERS) with its high sensitivity and interfacial specificity has been utilized to characterize interfacial species for obtaining in situ information on the composition, structure, and processes of solid–liquid interfaces. Herein, we provide a brief overview of the SERS methodology including the principles, the features, the methods, and experimental related issues of SERS for solid–liquid interfaces.

The detailed structure of the water layer in the inner Helmholtz plane of a solid/aqueous solution interface is closely related to the electrochemical and catalytic performances of electrode materials. While the applied potential can have a great impact, specifically adsorbed species can also influence the interfacial water structure. With the specific adsorption of p-nitrobenzoic acid on the Au(111) surface, a protruding band above 3600 cm(-1) appears in the electrochemical infrared spectra, indicating a distinct interfacial water structure as compared to that on bare metal surfaces, which displays a potential-dependent broad band in the range of 3400-3500 cm(-1). Although three possible structures have been guessed for this protruding infrared band, the band assignment and interfacial water structure remain ambiguous in the past two decades. Herein, by combining surface-enhanced infrared absorption spectroscopy and our newly developed quantitative computational method for electrochemical infrared spectra, the protruding infrared band is clearly assigned to the surface-enhanced stretching mode of water molecules hydrogen-bonded to the adsorbed p-nitrobenzoate ions. Water molecules, meanwhile, are hydrogen-bonded with themselves to form chains of five-membered rings. Based on the reaction free energy diagram, we further demonstrate that both hydrogen-bonding interactions and coverages of specifically adsorbed p-nitrobenzoate play an important role in determining the structure of the water layer in the Au(111)/p-nitrobenzoic acid solution interface. Our work sheds light on structural studies of the inner Helmholtz plane under specific adsorptions, which advances the understanding of structure-property relationships in electrochemical and heterogeneous catalytic systems.

Surface-enhanced Raman spectroscopy (SERS) was discovered in the mid-1970s and the development of SERS is parallel with the nanoscience, and in particular, SERS benefited considerably from new techniques for the preparation and characterization of SERS-active nanoparticles or nanostructures. SERS activity is closely related to the optical resonance property of the coinage metal nanomaterials, which can greatly enhance the local electromagnetic field, largely due to the excitation of surface plasmon resonance. In this article, we first generally review the development of SERS, and then the principles of SERS, followed by the preparation methods of SERS-active substrates and the strategies to expand the generality in SERS. In the “borrowing” SERS activity strategies, from coating transition metal onto SERS-active nanostructures, to tip-enhanced Raman spectroscopy (TERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), enormous efforts have been dedicated to overcoming the long-standing limitations of material and surface generalities in traditional SERS in the past decades. In the final section, we present a perspective with emphasis on the exploration of new nanomaterials suitable for the applications of SERS in a wider spectral region, as well as the design of new nanostructures to probe weakly SERS-active or SERS-inactive substrates.

Surface-enhanced Raman spectroscopy (SERS) has manifested its power in clinical applications, benefitted from the ability to provide fingerprint information even down to single-molecule level. In this chapter, we will guide you through the principles of SERS, including the electromagnetic field enhancement and chemical enhancement, with emphasis on the surface plasmon resonance effect. Some practical issues, such as spectral analysis and selection of SERS substrates, will also be briefed from the mechanistic understanding. The main purpose of this chapter is to provide you the necessary background to understand the literatures and start your own journey of applying SERS for clinical diagnosis.

The fundamental structure-biofunction relationship of calcium phosphates (CaPs) remains unclear despite their clinical successes as important biomaterials. Herein, a series of CaP coatings with gradual change of topography and crystallinity is constructed by electrochemical deposition, and the roles of the two basic physicochemical properties are scrutinized for further understanding the mechanism behind the superior bioactivities of octacalcium phosphate (OCP). We observe a distinct modulation on cell proliferation on the prepared CaP coatings for different cells. The magnitude of the modulation seems to depend on the cellular size, and the effect is attributed mainly to the microstructure of the coatings. On the other hand, the crystallinity manifests its significance for the osteogenic property of the OCP coatings. Further transmission electron microscopy analysis and density functional theory calculations reveal a surface rich in HPO4 2- for the high-crystalline OCP nanocrystals. The results highlight that the nanocrystal surface properties of the OCP coatings, including the periodic structure and the HPO4 2- composition, may play significant roles surpassing the ion release effect in determining its osteogenic property, probably via surface spatial and/or chemical recognitions. The present findings shed light on the fundamental understanding of the structure-biofunction relationship for CaP biomaterials.

Surface structures and physicochemical properties critically influence osseointegration of titanium (Ti) implants. Previous studies have shown that the surface with both micro- and nanoscale roughness may provide multiple features comparable to cell dimensions and thus efficiently regulate cell-material interaction. However, less attention has been made to further optimize the physicochemical properties (e.g., crystalline phase) and to further improve the bioactivity of micro/nanostructured surfaces. Herein, micro/nanostructured titania surfaces with different crystalline phases (amorphous, anatase and anatase/rutile) were prepared and hydroxyapatite (HA) nanorods were deposited onto the as-prepared surfaces by a spin-assisted layer-by-layer assembly method without greatly altering the initial multi-scale morphology and wettability. The effects of crystalline phase, chemical composition and wettability on osteoblast response were investigated. It is noted that all the micro/nanostructured surfaces with/without HA modification presented superamphiphilic. The activities of MC3T3-E1 cells suggested that the proliferation trend on the micro/nanostructured surfaces was greatly influenced by different crystalline phases, and the highest proliferation rate was obtained on the anatase/rutile surface, followed by the anatase; but the cell differentiation and extracellular matrix mineralization were almost the same among them. After ultrathin HA modification on the micro/nanostructured surfaces with different crystalline phases, it exhibited similar proliferation trend as the original surfaces; however, the cell differentiation and extracellular matrix mineralization were significantly improved. The results indicate that the introduction of ultrathin HA to the micro/nanostructured surfaces with optimized crystalline phase benefits cell proliferation, differentiation and maturation, which suggests a favorable biomimetic microenvironment and provides the potential for enhanced implant osseointegration in vivo.

In-situ electrochemical infrared (EC-IR) and Raman (EC-Raman) spectroscopies are powerful tools for characterizing electrochemical interfacial structures. However, the electrochemical interfaces even for model systems such as single-crystal electrode/electrolyte interfaces are usually very complexly related to the applied potential, adsorbates, electrolyte ions and solvent. As a result, the observed EC-IR and-Raman spectra including the potential-dependent vibrational frequencies and spectral intensities are difficult to be unambiguously interpreted for over four decades. By combining vibrational spectra simulations with electrochemical interface models, we developed a computational method capable of quantitatively simulating EC-IR and EC-Raman spectra observed in the classic metal single-crystal electrochemical systems. In this work, we introduce in detail the theoretical derivation and the optimization of computational parameters for the method. The selections of applied potential, vibrational model, as well as electrode surface configuration are further elaborated for the exact simulation of electrochemical infrared and Raman spectra of the ordered CO adstructures at the Pt (111) electrode/0.1 M perchloric acid solution interface. The developed method can be expanded to simulate the spectral features in different specific adsorption systems for understanding more complicated materials and interface structures.