Fast Deposition Rate Research Articles

Action mechanism of different fibres on structure and property of plated coatings

This paper tentatively chooses polyester, bamboo fibre and cotton as solution carrier during the plating process. The morphology, deposition rate, phase structure, hardness, friction and wear properties of coatings is characterised. Water absorbency, heat dissipation and electrical conductivity of three different solution carriers are analysed in order to study their action mechanism. The results show that the bamboo fibre presents the smoothest and compacts surface morphology and good water absorbency, which can ensure the supplement of solution. It also features larger electricity resistance and lower deposition rate, but fine grain, high hardness and good wear-resistance, all of which result in the best comprehensive performance. Cotton, with the best water absorbency, characterises higher hardness but poor uniformity and wear-resistance. Polyester carries the worst water absorbency, fast deposition rate, low hardness and better wear-resistance.

GaN thin film deposition on glass and PET substrates by thermionic vacuum arc (TVA)

In this paper, GaN thin film production was realized by thermionic vacuum arc (TVA), a plasma deposition technique, for the first time. We present a new deposition mechanism for GaN thin films with a very short production time. Microstructure properties of samples were analyzed by X-ray diffractometry. The peak at 2θ = 72.88° corresponding to GaN (0004) was detected in XRD spectra. The surface morphology of the deposited GaN films was analyzed using field emission scanning electron microscopy and atomic force microscopy. The surface properties of the produced samples are quite different. The average roughness values were determined to be 0.48 nm for GaN/PET and 1.17 nm for GaN/glass. The optical properties (i.e., refractive index and reflection) were determined using an interferometer. Moreover, the obtained optical data were compared with bulk GaN materials. The refractive indexes were measured as 2.2, 3,0 and 2,5 for the GaN/glass, GaN/PET and bulk GaN, respectively. The transparencies of the different GaN-coated substrates are nearly the same. The obtained band gap values were measured in the energy range of 3.3–3.5 eV. TVA is a novel non-reactive plasma technique for the generation of metal organic thin films. The main advantage of this method is its fast deposition rate without any loss in the quality of the films.

Characterization of nanoparticle transport through quartz and dolomite gravels by magnetic resonance imaging

AbstractMagnetic resonance imaging (MRI) has tremendous potential for revealing transport processes in engineered and geologic systems. Here, we utilize MRI to image nanoparticle (NP) transport through a saturated coarse-grained system. Commercially available paramagnetically tagged NPs are used; the paramagnetic tag making the NP visible to MRI. NP transport was imaged as NPs migrated through packed columns of quartz and dolomite gravel. Changes in T2-weighted image intensity were calibrated to provide fully quantitative maps of NP concentration at regular time intervals (T2being the spin–spin relaxation time of1H nuclei). Transport of nanoparticles was significantly retarded in dolomite compared to quartz due to electrostatic attraction between nanoparticle and dolomite surfaces. NP concentration profiles were evaluated with the CXTFIT computer package to estimate nanoparticle transport parameters at multiple points along the length of the column. This provided temporally resolved parameters that standard breakthrough curve analysis cannot provide. Particle–surface interaction energy profiles were described through Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. While dispersion coefficients and fast deposition rate constant (kfast) were found to increase with distance, deposition rate constant (k) and collision efficiency (α) were found to decrease with distance. These length-dependant variations have significant scaling-up implications for transport models used to predict NP transport in natural and engineered coarse-grained systems, such as sustainable urban drainage systems and river beds.

Nanoparticle transport in saturated porous medium using magnetic resonance imaging

Transport study of nanoparticle (NP) through matrix flow dominated aquifer sand and soils have significant influence in natural systems. To quantify the transport behaviour, magnetic resonance imaging (MRI) was used to image the iron oxide based nanoparticle, Molday ION (carboxyl terminated) through saturated sandstone rock core. T2-weighted images were acquired and the changes in image intensity were calibrated to get a quantitative concentration profiles at various time intervals. These profiles were evaluated through CXTFIT transport model to estimate the transport parameters. These parameters are estimated at various points along the length of the column while classical breakthrough curve analysis cannot provide these details. NP–surface interactions were investigated using DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. The dispersion coefficients (2.55–1.21×10−7m2/s) were found to be decrease with distance, deposition rate constant k (6.70–9.13×10−4(1/s)) and fast deposition rate constant kfast (4.32–8.79×10−2(1/s)) were found to be increase with distance. These parameter variations over length will have a scaling up impact in developing transport models for environmental remediation and risk assessment schemes.

Optical emission spectroscopic studies and comparisons of CH3F/CO2 and CH3F/O2 inductively coupled plasmas

A CH3F/CO2 inductively coupled plasma (ICP), sustained in a compact plasma reactor, was investigated as a function of power (5–400 W) and feed gas composition, at a pressure of 10 mTorr, using optical emission spectroscopy and rare gas actinometry. Number densities of H, F, and O increased rapidly between 74% and 80% CO2, ascribed to the transition from polymer-covered to polymer-free reactor walls, similar to that found previously in CH3F/O2 ICPs at 48% O2. Below 40% O2 or CO2, relative emission intensity ratios were almost identical for most key species in CH3F/O2 and CH3F/CO2 ICPs except for higher OH/Xe (a qualitative measure of OH and H2O densities) over the full range of CH3F/O2 composition. The number density of H, F, and O increased with power in CH3F/CO2 (20%/80%) plasmas (polymer-free walls), reaching 4.0, 0.34, and 1.6 × 1013/cm3, respectively, at 300 W. The CO number density increased with power and was estimated, based on self-actinometry, to be 8.8 × 1013/cm3 at 300 W. The CO2 number density was independent of power below 40 W (where very little decomposition occurred), and then decreased rapidly with increasing power, reaching 2.8 × 1013/cm3 at 300 W, corresponding to 83% dissociation. Films deposited on p-Si, 10 cm from the open, downstream end of the plasma reactor, were analyzed by x-ray photoelectron spectroscopy. Between 10% and 40% CO2 or O2 addition to CH3F, film deposition rates fell and O content in the films increased. Faster deposition rates in CH3F/CO2 plasmas were ascribed mainly to a larger thermodynamic driving force to form solid carbon, compared with CH3F/O2 plasmas. Oxygen content in the films increased with increasing CO2 or O2 addition, but for the same deposition rate, no substantial differences were observed in the composition of the films.

Spatial atomic layer deposition on flexible substrates using a modular rotating cylinder reactor

Spatial atomic layer deposition (ALD) is a new version of ALD based on the separation of reactant gases in space instead of time. In this paper, the authors present results for spatial ALD on flexible substrates using a modular rotating cylinder reactor. The design for this reactor is based on two concentric cylinders. The outer cylinder remains fixed and contains a series of slits. These slits can accept a wide range of modules that attach from the outside. The modules can easily move between the various slit positions and perform precursor dosing, purging, or pumping. The inner cylinder rotates with the flexible substrate and passes underneath the various spatially separated slits in the outer cylinder. Trimethyl aluminum and ozone were used to grow Al2O3 ALD films at 40 °C on metallized polyethylene terephthalate (PET) substrates to characterize this spatial ALD reactor. Spectroscopic ellipsometry measurements revealed a constant Al2O3 ALD growth rate of 1.03 Å/cycle with rotation speeds from 40 to 100 RPM with the outer cylinder configured for one Al2O3 ALD cycle per rotation. The Al2O3 ALD growth rate then decreased at higher rotation rates for reactant residence times < 5 ms. The Al2O3 ALD films were also uniform to within <1% across the central portion of metallized PET substrate. Fixed deposition time experiments revealed that Al2O3 ALD films could be deposited at 2.08 Å/s at higher rotation speeds of 175 RPM. Even faster deposition rates are possible by adding more modules for additional Al2O3 ALD cycles for every one rotation of the inner cylinder.

Structural and electric properties of BaSn0.15Ti0.85O3 films on ITO/glass substrate by RF sputtering from powder target

BaSn0.15Ti0.85O3 (BTS) ferroelectric thin films have been deposited on the tin-doped indium oxide (ITO)/glass substrate by RF sputtering from a powder target, and the structural and electrical properties of the BTS film are also investigated at various deposition rates. The results indicate that leakage current of the BTS film is strongly related to the deposition rate, which decreases with increasing deposition rates. The leakage current density of the as-prepared film for a deposition rate of 40nm/min and thickness of 500nm is lower than 1.5×10−10A/cm2, while its dielectric tunability reaches 57.3% and dielectric loss remains only 0.01 at a bias voltage of 5V. From SIMS depth profiling of as-prepared BTS films, the lower leakage current density of the BTS film at a faster deposition rate may be attributed to the sharper BTS/ITO interface with a low inter-diffusion that results from the high deposition rate and shorter deposition time.

Intrinsic and extrinsic parameters for controlling the growth of organic single-crystalline nanopillars in photovoltaics.

The most efficient architecture for achieving high donor/acceptor interfacial area in organic photovoltaics (OPVs) would employ arrays of vertically interdigitated p- and n- type semiconductor nanopillars (NPs). Such morphology could have an advantage in bulk heterojunction systems; however, precise control of the dimension morphology in a crystalline, interpenetrating architecture has not yet been realized. Here we present a simple, yet facile, crystallization technique for the growth of vertically oriented NPs utilizing a modified thermal evaporation technique that hinges on a fast deposition rate, short substrate-source distance, and ballistic mass transport. A broad range of organic semiconductor materials is beneficial from the technique to generate NP geometries. Moreover, this technique can also be generalized to various substrates, namely, graphene, PEDOT-PSS, ZnO, CuI, MoO3, and MoS2. The advantage of the NP architecture over the conventional thin film counterpart is demonstrated with an increase of power conversion efficiency of 32% in photovoltaics. This technique will advance the knowledge of organic semiconductor crystallization and create opportunities for the fabrication and processing of NPs for applications that include solar cells, charge storage devices, sensors, and vertical transistors.

Copper Electroless Process Optimization to Modify Boron Doped Diamond at Different Boron Levels

Composite of Cu/BDD (boron doped diamond) have the potential to use as solid electrode for application in environmental approaches. Among many Cu coating processes, the electroless plating has emerged in recent years due to its low cost, fast deposition rate, and good filling capability. In addition, its major advantage is its simplicity, where the processes can take place at room temperatures and pressures [1]. In the Cu electroless process, a hard pre-treatment is needed for cleaning the surface and for creating functional groups that can act as anchor points on the BDD samples. The pre-treatments can be obtained using different oxidation techniques. In this study the anodic electrochemical pre-treatment was carried out using 0.5 mol L-1 H2SO4 and a fixed potential of 3 V for 30 min. The present study was undertaken in order to investigate the influence of the BDD doping level in the electroless synthesis as well as the effect of some deposition parameters such as the solution pH and the deposition time, to obtain Cu/BDD composites. This material is very attractive for nitrate electroreduction related to environmental interest. BDD films were grown by hot filament-assisted chemical vapor deposition technique on the titanium substrate, activated by methane and hydrogen gas mixture with a pressure of 40 Torr, at 650ºC, for 24 h. Boron source was obtained by an additional hydrogen line passing through a bubbler containing B2O3 dissolved in methanol with a controlled B/C ratio that led to films with different doping level (5000 and 15000 ppm). Prior to the Cu electroless deposition, the sensitization on the BDD was achieved using a solution of 40 mL L-1 HCl containing 0.04 mol L-1 SnCl2 for 5 min and the activation was made using a solution containing 7x10-4 mol L-1 PdCl2 with 2.5 mL L-1 HCl for 5 min. Ultrasonic vibration was used for both steps. The electroless Cu deposition was carried out for different times (30, 60, 180 and 2400 s) at room temperature. The bath composition was 0.1 mol L-1 CuSO4 + 0.2 mol L-1 KNaC4H4O6 + 17.5 mL L-1 HCHO. The pH level was adjusted to 8, 10 and 12 by the addition of NaOH. The Raman scattering spectra showed the peak close to 1332 cm-1 corresponds to the vibration of a diamond first-order phonon, confirmed the quality of these BDD films. This peak decreased in intensity due to the boron incorporation in diamond films. The effect of boron doping is reflected in the spectral features. There is the appearance of the two bands located at 500 cm-1 and 1220 cm-1 attributed to B-B vibrations and B-C vibrations, respectively. According to Scanning Electron Microscopy images the Cu deposits showed an uniform particle distribution on the BDD surface for solution of pH 12. On the other hand, no Cu deposit was verified at pH 8 and at pH 10 in the range of time deposition from 30 to 180 s. However, for deposition time of 2400 s, the deposit presented low particle density. Similar experimental conditions for electroless Cu deposition on lightly doped diamond showed the same behavior as a function of pH. The Cu deposit rate increased with increasing the deposition time, for both BDD films. Comparing the highly and the lightly BDD electrode, higher deposition rate was observed in the highly doped electrode. This result can be attributed to the better conductivity of this electrode due to its higher boron content. It is noteworthy that the sensitization and activation processes are a crucial step for high quality coatings independently of the BDD doping level. Acknowledgments: Brazilian National Institute of Science and Technology (INCT) for Climate Change funded by CNPq Grant Number 573797/2008-0 e FAPESP Grant Number 2008/57719-9.

Electroless Deposition of Cu-Mn Alloy

Interconnect scaling in semiconductor devices presents numerous challenges to the current dual-damascene process flow. One issue is the deteriorated Cu electromigration resistance, which shortens the device life. To address this problem, one approach is to dope the Cu interconnects with small amounts of manganese (Mn). The Mn segregates at the interface between Cu and the dielectric substrate and forms a barrier layer, thereby suppressing Cu diffusion. It was found that incorporation of ~2 at.% Mn increases the lifetime of Cu interconnects four-fold [1].Currently, the state-of-the-art method for depositing Cu-Mn alloys is sputter deposition with Mn content generally above a few atomic percent [2,3]. Compared to sputter deposition, electroless deposition has numerous advantages such as simplicity, low cost and faster deposition rate. Therefore, it is of great interest to develop an electroless process for depositing Cu-Mn alloy.In this study, we report electroless deposition of Cu-Mn. The Mn incorporated was found to be ‘mobile’, a prerequisite for its application in interconnect metallization. It was also observed that Mn was incorporated during electroless Cu-Mn deposition at potentials that are much more anodic to its standard reduction potential (-1.18 V vs. SHE). To further our understanding of the electroless Cu-Mn deposition, a combination of voltammetry and quartz crystal microbalance were used to unravel the Mn deposition mechanism.

Pulsed electrodeposition of CuSCN for superfilling of ZnO nanowire array electrodes

Pulsed electrodeposition at room temperature is shown to be a facile, simple and fast method for super-filling of CuSCN onto ZnO nanowire arrays for applications in transparent diodes and optoelectronic devices. Compared to previously suggested methods for CuSCN superfilling, it offers the advantages of low cost, room temperature deposition in a one-pot process, combined with fast deposition rates, making it highly accessible for lab-scale deposition as well as scale up for industrial processes. Each pulse consisted of a working time ton, at which the potential was -500mV vs. Ag/AgCl, and an off period toff, at which zero potential vs. Ag/AgCl was applied. The toff interval discharged the charged layer and regenerated the ion concentration near the cathode surface, resulting in denser nucleation and a more uniform coating. The pulse sequence controlled the deposition rate and the S/Cu ratio in the deposited CuSCN films, which was larger than in corresponding electrostatic depositions, due to higher SCN− concentration near the ZnO surface accomplished during the toff interval. Current-voltage characteristics showed excellent diode properties, significantly better than those of potentiostatic deposited CuSCN/ZnO diodes. We conclude that when high currents in transparent diodes are desirable, as in photovoltaic applications, pulsed electrodeposition and super-filling have significant advantages, with the pulse sequence ton=2sec, toff=1sec resulting in high deposition rates and optimized diode parameters.

Preparation of nickel-coated graphite by electroless plating under mechanical or ultrasonic agitation

In this paper, nickel-coated graphite powders were prepared by electroless plating. After a novel and facile pretreatment of graphite, electroless plating was carried out in an alkaline bath having nickel chloride (NiCl2) as a source of nickel and sodium borohydride (NaBH4) as a reducing agent. During the electroless nickel plating, mechanical or ultrasonic agitation was adopted to improve the properties of coating. The coated graphite powders were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The results show that two different morphologies of Ni–B coatings were achieved on the surface of graphite. Both coatings on graphite are continuous and uniform. For mechanical agitation process, the coating exhibits a sesame-seed slice-like structure which is composed of large spherical grains. The ultrasonic agitation process results in a faster deposition rate and a well-knit membrane-like structure coating free of voids. This is attributed to the easier nucleation and fine particle distribution of nickel nuclei under the ultrasonic agitation.

Improvement in Device Performance and Reliability of Organic Light-Emitting Diodes through Deposition Rate Control

We demonstrated a fabrication technique to reduce the driving voltage, increase the current efficiency, and extend the operating lifetime of an organic light-emitting diode (OLED) by simply controlling the deposition rate of bis(10-hydroxybenzo[h]qinolinato) beryllium (Bebq2) used as the emitting layer and the electron-transport layer. In our optimized device, 55 nm of Bebq2was first deposited at a faster deposition rate of 1.3 nm/s, followed by the deposition of a thin Bebq2(5 nm) layer at a slower rate of 0.03 nm/s. The Bebq2layer with the faster deposition rate exhibited higher photoluminescence efficiency and was suitable for use in light emission. The thin Bebq2layer with the slower deposition rate was used to modify the interface between the Bebq2and cathode and hence improve the injection efficiency and lower the driving voltage. The operating lifetime of such a two-step deposition OLED was 1.92 and 4.6 times longer than that of devices with a single deposition rate, that is, 1.3 and 0.03 nm/s cases, respectively.

Characteristiscs of Nanocrystalline Silicon Films Deposited by Cat-CVD below 100 °C

Nanocrystalline Silicon (nc-Si) films were deposited by catalytic chemical vapor deposition (Cat-CVD) at a low substrate temperature (100 °C) for use as an active layer in bottom-gate thin-film transistors (TFTs). Hydrogen dilution technique was attempted to increase the crystalline volume fraction (Xc). The hydrogen dilution ratio, RH = [H2]/[SiH4], was varied from 44 to 74. In order to obtain nc-Si film with a high XC, a thin incubation layer and a fast deposition rate simultaneously, we varied RH and pressure as the deposition proceeded. When the pressure was set to 50 mTorr during the initial stage and changed to 60 mTorr for the rest of the deposition, the incubation layer thickness was suppressed to 4 nm.

Surface engineering characteristics of ultrasound assisted hypophosphite electroless plating baths

This article addresses the characteristics of metallic skin layer and the performance of hypophosphite based ultrasonic electroless plating baths during the fabrication of nickel/ceramic microfiltration membranes. The process performance was evaluated in terms of overall conversion and metal plating efficiency, and the metal film was characterised in terms of average film pore size, average effective porosity, film thickness and per cent pore densification. Parametric investigations were carried out for a wide range of initial nickel solution concentrations (0·04–0·16 mol L−1) at two different loading ratios (196 and 393 cm2 L−1) for sonication coupled electroless plating. A simple mass transfer model was developed to provide insights with respect to the pertinent mass transfer limitations. Sonication resulted in faster deposition rate, better efficiency and improved surface morphology. In comparison with conventional and agitated electroless plating baths, ultrasound assisted electroless plating provided the best combination of process as well as performance characteristics.

Plasma‐Enhanced Atomic Layer Deposition of Ultrathin Oxide Coatings for Stabilized Lithium–Sulfur Batteries

AbstractOne of the most challenging problems in the development of lithium–sulfur batteries is polysulfide dissolution, which leads to cell overcharge and low columbic efficiency. Here, we propose the formation of a thin conformal Li‐ion permeable oxide layer on the sulfur‐carbon composite electrode surface by rapid plasma enhanced atomic layer deposition (PEALD) in order to prevent this dissolution, while preserving electrical connectivity within the individual electrode particles. PEALD synthesis offers a fast deposition rate combined with a low operating temperature, which allows sulfur evaporation during deposition to be avoided. After PEALD of a thin layer of aluminium oxide on the surface of electrode composed of large (ca. 10 μm in diameter) S‐infiltrated activated carbon fibers (S‐ACF), significantly enhanced cycle life is observed, with a capacity in excess of 600 mA·h·g−1 after 300 charge–discharge cycles. Scanning electron microscopy (SEM) shows a significant amount of redeposited lithium sulfides on the external surface of regular S‐ACF electrodes. However, the PEALD alumina‐coated electrodes show no lithium sulfide deposits on the fiber surface. Energy dispersive spectroscopy (EDS) studies of the electrodes’ chemical composition further confirms that PEALD alumina coatings dramatically reduce S dissolution from the cathodes by confining the polysulfides inside the alumina barrier.

Computational Study of Surface Deposition and Gas Phase Powder Formation during Spinel Chemical Vapor Deposition Processes

Chemical vapor deposition (CVD) processes are often employed to produce high quality materials. In some applications, a relatively fast deposition rate is required to produce thick pieces of material, e.g., on the order of centimeter, in an economical manner. However, in some processes the formation of solid nuclei or powder in the gas phase can be a major obstacle to increasing the deposition rate. The homogeneous powder formation reaction can compete with the surface deposition reaction and consume the gas phase reactants, thus reducing the available material to grow on the substrate surface. Understanding the thermodynamics as well as kinetics of these two competing reactions helps elucidate the reaction conditions that best reduce powder formation and increase deposition rate. As an example where gas phase powder formation can significantly limit the surface deposition rate CVD growth of spinel (MgAl2O4) is investigated. In this CVD process, reverse water gas shift (rWGS) is employed to generate water...

Electrochemical properties of an as-deposited LiFePO4 thin film electrode prepared by aerosol deposition

Prepared by the deposition of a solid electrode and electrolyte, all-solid-state batteries are a promising next generation battery system. Aerosol deposition (AD) offers many advantages compared to the conventional thin film deposition methods, including the deposition of a crystallized thin film with no heat treatment and a fast deposition rate. In this study, a LiFePO4/C composite thin film is directly fabricated using a LiFePO4/C composite raw powder. SEM and EDS results show the successful deposition of a LiFePO4/C composite thin film on a stainless steel substrate and X-ray diffraction patterns reveal that the as-deposited thin film has a crystalline structure, corresponding to the olivine phase, without any heat treatment. In a CV test, oxidation and reduction peaks appear at 3.51 and 3.36 V, corresponding closely to the peaks of bulk olivine LiFePO4. Furthermore, the profiles of the charge and discharge curves are similar to those of the bulk electrode and the discharge capacity is 31.1 μAh cm−2 μm−1 in the first cycle. After 20 cycles of 10.65 and 106.5 μA cm−2 μm−1, the capacity is recovered to 30.7 μAh cm−2 μm−1. Aerosol deposition can potentially be used in the fabrication of all-solid-state batteries.

High performance PbS Quantum Dot Sensitized Solar Cells exceeding 4% efficiency: the role of metal precursors in the electron injection and charge separation

Here we report the preparation of high performance Quantum Dot Sensitized Solar Cells (QDSCs) based on PbS-CdS co-sensitized nanoporous TiO2 electrodes. QDs were directly grown on the TiO2 mesostructure by the Successive Ionic Layer Absorption and Reaction (SILAR) technique. This method is characterized by a fast deposition rate which involves random crystal growth and poor control of the defect states and lattice mismatch in the QDs limiting the quality of the electrodes for photovoltaic applications. In this work we demonstrate that the nature of the metallic precursor selected for SILAR has an active role in both the QD's deposition rate and the defect's distribution in the material, with important consequences for the final photovoltaic performance of the device. For this purpose, acetate and nitrate salts were selected as metallic precursors for the SILAR deposition and films with similar absorption properties and consequently with similar density of photogenerated carriers were studied. Under these conditions, ultrafast carrier dynamics and surface photovoltage spectroscopy reveal that the use of acetate precursors leads to higher injection efficiency and lower internal recombination due to contribution from defect states. This was corroborated in a complete cell configuration with films sensitized with acetate precursors, achieving unprecedented photocurrents of ~22 mA cm(-2) and high power conversion efficiency exceeding 4%, under full 1 sun illumination.

Pd@Au core–shell nanocrystals with concave cubic shapes: kinetically controlled synthesis and electrocatalytic properties

A new type of concave cubic Pd@Au core-shell nanocrystals is synthesized through a kinetically controlled growth process. Pd nanocubes of 56 nm are used as the inner core, and CTAC and Br(-) are used as the capping agent and selective adsorbent, respectively. A suitable ratio of HAuCl4 and cubic Pd seeds and the presence of Br(-) anions are critical to the growth of the concave cubic Pd@Au core-shell nanocrystals. The fast deposition rate on the corners of the cubic Pd seeds promotes the overgrowth of the Au outer shell along the <111> direction, leading to the formation of concave cubic nanostructures. The reduction process is monitored by the surface plasmon resonance spectra of the nanocrystals, and the extinction band became broader and red shifted as the nanocrystals became larger. The electrocatalytic properties of the concave cubic Pd@Au core-shell nanocrystals were investigated with the cathodic electrochemiluminescence reaction of luminol and H2O2. A possible electrocatalytic mechanism was proposed and analyzed.