Thick Ag Research Articles

An NiCr Alloy Piezoresistive Atmosphere Pressure Sensor based on Eutectic

Abstract In this paper, an nickel-chromium (NiCr) alloy piezoresistive atmosphere pressure sensor, based on eutectic bonding is presented. Compared with conventionally silicon piezoresistive pressure sensor, it has the advantages with low cost and easy fabrication processes. First, NiCr alloy (80:20 wt%) is used as the strain detecting material, with a smaller but acceptable sensitivity and simpler processes. Second, eutectic bonding technology based on silver-tin (Ag-Sn) alloy, which is 3.5%wt Ag and 20um thickness, is used as an alternative and easy bonding choice to complete the vacuum package. Bonding quality of eutectic bonding is evaluated by inspection through the deflection of diaphragm of silicon with more than 95% of the area successfully bonded. The Pressure-Voltage characteristic test results suggest a precision within 0.3% in square fitting. The temperature characteristics is also tested and theoretically analyzed. The temperature coefficient offset (TCO) is 620 ppm/(°C FSO).

Modulation of surface plasmons coupling for enhancement of optical transmittance of silver-coated alkaline-earth metal films

We enhanced the optical transmittance of silver-coated alkaline-earth metal films by modulation of surface plasmons (SPs) coupling. The result indicates that the optical transmittance of a metal film is controlled by the SPs coupling at the interface of the metal with a dielectric substrate. Because the SPs originate from the coupling between the free charge at the surface of the metal and the incident light, there exists the SPs coupling in an Ag layer with the dielectric substrate. These SPs lead to longitudinal surface charge density fluctuations that propagate along the substrate/Ag interface, resulting in the decreased transmittance property (47.9% in the visible region) of the 10 nm thick Ag layer on the dielectric substrate. Because both alkaline-earth metal and Ag have negative dielectric constants, the incident light cannot induce the SPs in the alkaline-earth metal/Ag double layer. Thus, inserting a thin alkaline-earth metal layer between Ag and the dielectric substrate could modulate the SPs coupling at the Ag/substrate interface and, hence, the optical transmittance of alkaline-earth metal/Ag films. Both alkaline-earth metal and Ag could be formed by thermal evaporation and in situ synchrotron radiation photoelectron spectroscopy results showed that the thermally evaporated alkaline-earth metal (Ca) film is composed of metallic (Ca) and metal-oxide (CaO) components. It is found that the SPs modulation optimized alkaline-earth metal/Ag (10 nm/10 nm) film has obtained a higher optical transmittance (69.8%) in the visible region than that of an Ag layer. This led to the enhanced maximum luminance of organic light emitting diodes with the alkaline-earth metal/Ag electrode from 24 300 cd m−2 to 32 700 cd m−2.

Long-term stability of Ag and Cu thin films on glass, LTCC and alumina substrates

Silver (Ag) and copper (Cu) are regarded as advanced material for metallization systems in microelectronic devices because of their high electrical conductivity and enhanced electromigration resistance. Typically, organic circuit boards as well as ceramic and glass–ceramic substrates use galvanic deposited Cu films or screen-printed metallization for this purpose. When applying the latter approach, however, the lateral resolution in the μm-region being required e.g. for novel high frequency applications can not be guaranteed. Hence, sputter deposition is envisaged for the realization of thin film metallization systems. The reliability of 300 nm thick Cu and Ag thin films is comparatively investigated under accelerated aging conditions, utilizing a test structure which consists of parallel lines stressed with current densities up to 2.5 × 106 A cm−² at temperatures up to 300°C on Si/SiO2, glass, LTCC (low temperature co-fired ceramics) and alumina substrates. To detect the degradation via the temporal characteristics of the current signal a constant voltage is applied according to the overall resistance of the test structure. Knowing the mean time to failure (MTF) and the activation energy at elevated temperatures conclusions on the migration mechanism can be drawn. Whereas on LTCC substrates the activation energy Ea is about 0.75 eV for both Ag and Cu thin films, the higher activation energies of about Ea ~ 1 eV measured for Cu on glass and alumina indicate a suppression of back diffusion especially at enhanced temperature levels. This effect is predominantly caused by a stable oxide layer which is formed at high temperatures and which acts as passivation layer. Therefore, the overall electromigration resistance is lower compared to Ag.

高輝度反射高速陽電子回折を用いたAg(111)薄膜表面上のBi,Pb原子位置のAg膜厚依存性の研究

高輝度反射高速陽電子回折を用いたAg(111)薄膜表面上のBi,Pb原子位置のAg膜厚依存性の研究

Influence of Ag thickness on electrical, optical and structural properties of nanocrystalline MoO3/Ag/ITO multilayer for optoelectronic applications

In this study, MoO3/Ag/ITO/glass (MAI) nano-multilayer films were deposited by the thermal evaporation technique and then were annealed in air atmosphere at 200 °C for 1 h. The effects of Ag layer thickness on electrical, optical and structural properties of the MoO3(45 nm)/Ag(5–20 nm)/ITO(45 nm)/glass nano-multilayer films were investigated. The sheet resistance decreased rapidly with increasing Ag thickness. Above a thickness of 10 nm, the sheet resistances became somewhat saturated to a value of 3(Ω/□). The highest transparency over the visible wavelength region of spectrum (85%) was obtained for 10 nm Ag layer thickness. Carrier mobility, carrier concentrations, transmittance and reflectance of the layers were measured. The allowed direct band-gap for an Ag thickness range 5–20 nm was estimated to be in the range 3.58–3.71 eV. The XRD pattern showed that the films were polycrystalline. X-ray diffraction has shown that Ag layer has a (111) predominant orientation when deposited. The figure of merit was calculated for MAI multilayer films. It has been found that the Ag layer thickness is a very important factor in controlling the electrical and optical properties of MAI multilayer films. The optimum thickness of the Ag layer for these films was determined. The results exhibit that the MAI transparent electrode is a good structure for use as the anode of optoelectronic devices.

The effect of Ag layer thickness on the properties of WO 3/Ag/MoO 3 multilayer films as anode in organic light emitting diodes

Transparent conductive WO 3/Ag/MoO 3 (WAM) multilayer electrodes were fabricated by thermal evaporation and the effects of Ag layer thickness on the optoelectronic and structural properties of multilayer electrode as anode in organic light emitting diodes (OLEDs) were investigated using different analytical methods. For Ag layers with thickness varying between 5 and 20 nm, the best WAM performances, high optical transmittance (81.7%, at around 550 nm), and low electrical sheet resistance (9.75 Ω/cm 2) were obtained for 15 nm thickness. Also, the WAM structure with 15 nm of Ag layer thickness has a very smooth surface with an RMS roughness of 0.37 nm, which is suitable for use as transparent conductive anode in OLEDs. The current density−voltage−luminance ( J− V− L) characteristics measurement shows that the current density of WAM/PEDOT:PSS/TPD/Alq 3/LiF/Al organic diode increases with the increase in thickness of Ag and WO 3/Ag (15 nm)/MoO 3 device exhibits a higher luminance intensity at lower voltage than ITO/PEDOT:PSS/TPD/Alq 3/LiF/Al control device. Furthermore, this device shows the highest power efficiency (0.31 lm/W) and current efficiency (1.2 cd/A) at the current density of 20 mA/cm 2, which is improved 58% and 41% compared with those of the ITO-based device, respectively. The lifetime of the WO 3/Ag (15 nm)/MoO 3 device was measured to be 50 h at an initial luminance of 50 cd/m 2, which is five times longer than 10 h for ITO-based device.

Angular distribution of thick-target bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on Ag

Experimental results are presented comparing the intensities of the bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on a thick Ag target, measured at forward angles in the range of 0\ifmmode^\circ\else\textdegree\fi{} to 55\ifmmode^\circ\else\textdegree\fi{}. When the data are corrected for attenuation due to photon absorption within the target, the results indicate that the detected radiation is distributed anisotropically only at photon energies $k$ that are approximately equal to the initial energy of the incident electrons ${E}_{0}$. The results of our experiments suggest that, as $k$/${E}_{0}$ \ensuremath{\rightarrow} 0, the detected radiation essentially becomes isotropic due primarily to the scattering of electrons within the target. A comparison to the theory of Kissel et al. [At. Data Nucl. Data Tables 28, 381 (1983)] suggests that the angular distribution of bremsstrahlung emitted by electrons incident on thick targets is similar to the angular distribution of bremsstrahlung emitted by electrons incident on free-atom targets only when $k$/${E}_{0}$ \ensuremath{\approx} 1. The experimental data also are in approximate agreement with the angular distribution predictions of the Monte Carlo program penelope.

Highly flexible transparent and conductive ZnS/Ag/ZnS multilayer films prepared by ion beam assisted deposition

ZnS/Ag/ZnS (ZAZ) multilayer films were prepared on polyethene terephthalate (PET) by ion beam assisted deposition at room temperature. The structural, optical and electrical characteristics of ZAZ multilayers dependent on the thickness of silver layer were investigated. The ZAZ multilayers exhibit a low sheet resistance of about 10Ω/sq., a high transmittance of 92.1%, and the improved resistance stabilities when subjected to bending. When the inserted Ag thickness is over 12nm, the ZAZ multilayers show good resistance stabilities due to the existence of a ductile Ag metal layer. The results suggest that ZAZ film has better optoelectrical and anti-deflection characteristics than conventional indium tin oxide (ITO) single layer.

Flexible ZnSnO3/Ag/ZnSnO3 multilayer electrodes grown by roll-to-roll sputtering on flexible polyethersulfone substrates

The authors report on the characteristics of flexible ZnSnO3 (ZTO)/Ag/ZTO multilayer electrodes sputtered on a flexible polyethersulfone substrate using roll-to-roll sputtering at room temperature. The sheet resistance and optical transmittance of the flexible ZTO/Ag/ZTO multilayer were mainly affected by the thickness and morphology of the Ag layer inserted between the ZTO layers. Dependence of photoluminescence peak intensity on the Ag thickness indicates that the high transmittance of the flexible ZTO/Ag/ZTO electrode can be explained by surface plasmon resonance as well as antireflection effects. At the optimized Ag thickness (10 nm), the flexible ZTO/Ag/ZTO exhibited a resistivity of 4.15 × 10−5 Ω-cm, an optical transmittance of 86.03%, and a figure of merit value of 42.83 × 10−3 Ω−1 comparable to those of conventional crystalline ITO electrodes. In addition, the optimized ZTO/Ag/ZTO sample showed constant resistance change (ΔR/R) during repeated bending cycles, indicating the robustness of the ZTO/Ag/ZTO electrode as a flexible electrode for cost efficient-flexible displays and photovoltaics.

Ag surfactant effects of TiO 2 films prepared by sputter deposition

The surfactant effect of Ag on the thin film structure of TiO 2 by radio frequency magnetron sputtering has been investigated. Comparisons between the atomic force microscopy images revealed that the surface roughness of TiO 2 film mediated by Ag was smaller than that of the TiO 2 film without Ag. The surface segregation effect of Ag was confirmed using X-ray photoelectron spectroscopy. The results of X-ray diffraction revealed that the initial deposition of a 0.4 nm thick Ag surfactant layer onto a Fe buffer layer prior to the deposition of the TiO 2 film reduced the rutile (110) growth and enhanced the anatase (100) growth. It was concluded that Ag was an effective surfactant for changing the thin film structure of TiO 2 on the Fe buffer layer. The photocatalytic effect of the fabricated TiO 2 film was also investigated using the remote oxidation process. TiO 2 films with the Ag surfactant exhibited higher photocatalytic activity than conventionally deposited TiO 2 films.

Fluxless Bonding of Bismuth Telluride Chips to Alumina Using Ag–In System for High Temperature Thermoelectric Devices

Bismuth telluride (Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) and its alloys are the most commonly used materials for thermoelectric devices. In this paper, the fluxless bonding process was developed to bond Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> chips to alumina substrates for high temperature applications. The silver-indium (Ag-In) system was chosen for the process development. To work with this system, the Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> chips were coated with 100 nm titanium (Ti) and 100 nm gold (Au) as barrier layer and plated with 10 μm Ag layer. The Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> samples were annealed at 250 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C for 200 h. No interdiffusion between Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and Ag was detected. The Ti/Au barrier layer was not affected either. It showed exceptional step coverage on the rough Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> surface even after the annealing process. To prepare for bonding, alumina substrates with 40 nm TiW and 2.5 μm Au were plated with 60 μm Ag, followed by 5 μm In and thin Ag cap layer for oxidation prevention. The Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> chips were bonded to alumina substrates at 180 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. No flux was used. The resulting void-free joint consists of five regions: Ag, (Ag), Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In, (Ag) and Ag. (Ag) is Ag-rich solid solution. The joint has a melting temperature higher than 660 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. Due to the thick ductile Ag layer on alumina, the Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> chip did not break after bonding despite its significant coefficient of thermal expansion mismatch with alumina.

Enhancement of electric field and Raman scattering by Ag coated Ni nanotips

Localization and enhancement of electric field by Ag-coated vertical Ni nanotip arrays were studied by using finite-different time domain calculations. With the 30 nm thick Ag coating, the nanotips can localize and enhance the electric field to more than 103 times under the excitation of TE-polarized light with a 532 nm wavelength. Nanotip-enhanced Raman scattering of cytochrome-c protein was demonstrated in a confocal Raman microscope. Significant enhancement of Raman spectrum was achieved at 1 × 10−9 mol/l concentration of the proteins.

Organic solar cells using a multilayer structure MoO3/Ag/MoO3 as anode

Abstract MoO3/Ag/MoO3 structures have been grown and characterized. It is shown that the transmittance of the films increases when the silver thickness increase from 8 to 10 nm, whereas further increase induces transmittance decrease. The study of the variation of the conductivity vs. Ag thickness shows that the MoO3/Ag/MoO3 structures become highly conductive when the Ag thickness reaches 10 nm. Therefore, the optimum structure is obtained when the silver thickness is 10 nm. These MoO3/Ag/MoO3 structures have been used as anode in glass/anode/CuPc (35 nm)/C60(40 nm)/Alq3 (9 nm)/Al (120 nm) organic solar cells. These anodes permit achievable promising results, even if their efficiencies stay slightly smaller than that achieved with ITO based devices.

Quantum Interference of Rashba-Type Spin-Split Surface State Electrons

We studied the quantum interference of electrons in the Bi (p(x), p(y)) orbital-derived j = 1/2 spin-split surface states at Bi/Ag(111)√3 × √3 surfaces of 10 monolayer thick Ag(111) films on Si(111) substrates. Surface electron standing waves were observed clearly at the energy (E) below the intersection of the two spin-split downward dispersing parabola bands (E(x)). The E dependence of the standing wave pattern reveals the dispersion as the average of the two spin-split surface bands due to the interference between |(k + Δ), ↑> and |-(k - Δ), ↑> [or (|(k - Δ), ↓>) and |-(k + Δ), ↓>] states. In contrast, it was impossible to deduce the dispersion from the standing wave pattern at E ≥ E(x) because the surface electron cannot find its backscattered state with the same spin polarization.

Valence band circular dichroism in non-magnetic Ag/Ru(0001) at normal emission

For the non-magnetic system of Ag films on Ru(0001), we have measured the circulardichroism of photoelectrons emitted along the surface normal, the geometry typically usedin photoemission electron microscopy. Photoemission spectra were acquired frommicrometer-sized regions having uniformly thick Ag films on a single, atomically flat Ruterrace. For a single Ag layer, we find a circular dichroism that exceeds 6% at thed-derived band region around 4.5 eV binding energy. The dichroism decreases as theAg film thickness increases to three atomic layers. We discuss the origin of thecircular dichroism in terms of the symmetry lowering that can occur even in normalemission.

Flexible Visible–Infrared Metamaterials and Their Applications in Highly Sensitive Chemical and Biological Sensing

Flexible electronic and photonic devices have been demonstrated in the past decade, with significant promise in low-cost, light-weighted, transparent, biocompatible, and portable devices for a wide range of applications. Herein, we demonstrate a flexible metamaterial (Metaflex)-based photonic device operating in the visible-IR regime, which shows potential applications in high sensitivity strain, biological and chemical sensing. The metamaterial structure, consisting of split ring resonators (SRRs) of 30 nm thick Au or Ag, has been fabricated on poly(ethylene naphthalate) substrates with the least line width of ∼30 nm by electron beam lithography. The absorption resonances can be tuned from middle IR to visible range. The Ag U-shaped SRRs metamaterials exhibit an electric resonance of ∼542 nm and a magnetic resonance of ∼756 nm. Both the electric and magnetic resonance modes show highly sensitive responses to out-of-plane bending strain, surrounding dielectric media, and surface chemical environment. Due to the electric and magnetic field coupling, the magnetic response gives a sensitivity as high as 436 nm/RIU. Our Metaflex devices show superior responses with a shift of magnetic resonance of 4.5 nm/nM for nonspecific bovine serum albumin protein binding and 65 nm for a self-assembled monolayer of 2-naphthalenethiol, respectively, suggesting considerable promise in flexible and transparent photonic devices for chemical and biological sensing.

The Fabrication of Ag Nanostructure Array Integrated with Microfluidics for Surface Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) with enormous enhancements has shown great potential in single-molecule detection, however, the fabrication of large-scale, controllable and reproducible substrates with high SERS activity is a major limitation. This paper provides method to create wafer level SERS substrate with tunable nanoparticle sizes and interparticle gaps. Silver films with different thicknesses were deposited by electron beam evaporation (EBE) and annealed at 260 °C for 15min in nitrogen gas. When annealed, the thin Ag films break up under surface tension to form isolated nanoparticle. The nanoparticle size, density, and shape are found to be dependent on the thickness of Ag and the condition of annealing. The selective deposition of Ag nanoparticle on the silicon substrate is applied to create SERS active sites before the integration with a PDMS microfluidic chip which functions as a sample delivery device and a transparent optical window for SERS. Detections of Rhodamine 6G SERS spectra are accomplished by using a 633nm laser with 300W excitation power. The results show that the fabrication protocol of such a SERS substrate is low-cost, easy-fabrication and inexpensive. Therefore, this substrate may anticipate a wide range of applications in SERS-based sensors.

Microstructure and Surface Treatment of 304 Stainless Steel for Electronic Packaging

A fundamental study is carried out to investigate the microstructure and surface treatment possibilities of 304 stainless steel (304SS) substrates. To expose the microstructure, mirror-finished 304SS is applied with a self-mixed etchant containing ammonium sulfite ((NH4)2SO3), iron chloride (FeCl3), hydrochloric acid (HCl), and nitric acid (HNO3). Scanning electron microscope (SEM) images exhibit quite clear rocky-wall-like structure. Grain boundaries are clearly observed. Each grain contains many subgrains and the average grain size is 10 μm. Energy dispersive X-ray analysis determines the composition as 69 wt. % iron (Fe), 19 wt. % chromium (Cr), 10 wt. % nickel (Ni), around 2 wt. % manganese (Mn), and less than 0.08 wt. % carbon (C), which agrees well with the data provided by the manufacturer. Diffraction peaks produced by X-ray diffraction (XRD) are able to correspond to profiles found in XRD database, showing that 304SS has face-centered cubic crystal lattice. The Ni strike technique is used as surface treatment to make 304SS bondable to other metals, such as silver (Ag), copper (Cu), and gold (Au), commonly used in electronic packaging. Cross section SEM images show that thick Ag, Cu, up to 50 μm, and Au, up to 70 μm, were successfully plated over the thin Ni layer that was plated on 304SS.

Publisher’s Note: Angular dependence of bremsstrahlung produced by 17.5-keV electrons incident on thick Ag [Phys. Rev. A83, 022712 (2011)

Publisher’s Note: Angular dependence of bremsstrahlung produced by 17.5-keV electrons incident on thick Ag [Phys. Rev. A<b>83</b>, 022712 (2011)

Clinical investigations of a CVD diamond detector for radiotherapy dosimetry

X-ray detectors based on single crystal diamond film made via chemical vapor deposition were investigated to evaluate their performance under clinically relevant conditions for radiotherapy dosimetry. Studies focused on repeatability, dose rate dependence, tissue phantom ratios, output factors and beam profiling. Repeatability experiments revealed a temporary loss in sensitivity due to charge detrapping effects following irradiation, which was modeled to make corrections that improved short-term precision. Dose rate dependence was observed (Fowler fitting parameter Δ = 0.96 ± 0.2) using dose rates up to ∼2 Gy min^−1. The detector statistically distinguished (n = 5, P < 0.05) between dose values separated by 7.7 × 10^−3 Gy (1 MU). Depth dose measurements from 1 to 15 cm and output factors using 3 × 3 to 10 × 10 cm^2 field sizes compared well with a Farmer ion chamber (<1.3% difference). Output factor measurements indicate encouraging results for fields sizes <4 × 4 cm^2. Off-axis measurements showed that perturbation of the beam could be reduced when the detector is used in the edge-on orientation due to its thin-film sandwich configuration and ∼200 nm thick Ag contacts. This relatively inexpensive detector has potential to be used for routine dosimetry using conventional radiotherapy instrumentation.