Effect Of Passivation Layer Research Articles

RF 마그네트론 스퍼터링으로 증착된 AlOx봉지 박막을 갖는 OLED 소자의 수명 특성

We investigated the life time characteristics of OLED device with aluminium oxide (<TEX>$AlO_x$</TEX>) passivation film on glass substrate and polyethylene terephthalate (PET) substrate by RF magnetron sputtering for the transparent barrier film applied to flexible OLED device. Basic buffer layer was determined as <TEX>$Alq_3$</TEX>(500 nm)-LiF(300 nm)-Al(1200 nm), and the most suitable aluminium oxide (<TEX>$AlO_x$</TEX>) film have been formed when the partial volume ratio of oxygen was 20% and the sputtering power was 100 watt and the minimum thickness of buffer was <TEX>$2\;{\mu}m$</TEX>. <TEX>$AlO_x$</TEX>/epoxy hybrid film was also used as a effective passivation layer for the purpose of improving life time characteristics of OLED devices with the glass substrate and the plastic substrate. Besides, the simultaneous deposition of <TEX>$AlO_x$</TEX>/epoxy film on back side of PET could result in better improvement of life time.

Growth Kinetics of ZnO Nanocrystals in the Presence of a Base: Effect of the Size of the Alkali Cation

Following an earlier study (J. Am. Chem. Soc. 2007, 129, 4470) describing a very unusual growth kinetics of ZnO nanoparticles, we critically evaluate here the proposed mechanism involving a crucial role of the alkali base ion in controlling the growth of ZnO nanoparticles using other alkali bases, namely, LiOH and KOH. While confirming the earlier conclusion of the growth of ZnO nanoparticles being hindered by an effective passivating layer of cations present in the reaction mixture and thereby generalizing this phenomenon, present experimental data reveal an intriguing nonmonotonic dependence of the passivation efficacy on the ionic size of the alkali base ion. This unexpected behavior is rationalized on the basis of two opposing factors: (a) solvated cationic radii and (b) dissociation constant of the base.

C60:LiF Blocking Layer for Environmentally Stable Bulk Heterojunction Solar Cells

A nanocomposite of highly conductive C60 and insulating LiF (C60:LiF) is shown to function as both a highly effective passivation layer and hole blocking layer in polymer bulk heterojunction solar cells. C60:LiF composites with up to ≈80% LiF concentration dramatically increase the device stability and power conversion efficiency, enabling a new generation of high-performance and long lifetime organic photovoltaics on flexible substrates.

The effects of the band gap and defects in silicon nitride on the carrier lifetime and the transmittance in c-Si solar cells

In this paper, silicon nitride thin films with different silane and ammonia gas ratios were deposited and characterized for the antireflection and passivation layer of high efficiency single crystalline silicon solar cells. An increase in the transmittance and a recombination decrease using an effective antireflection and passivation layer can be enhanced by an optimized SiN x film in order to attain higher solar cell efficiencies. As the flow rate of the ammonia gas increased, the refractive index decreased and the band gap increased. Consequently, the transmittance increased due to the higher band gap and the decrease of the defect states, which existed for the 1.68 and 1.80 eV in the SiN x films. The interface trap density found in silicon can be reduced down to 1.0×10 10 cm −2 eV −1 for the SiN x layer deposited under the optimized silane to ammonia gas ratio. Reduction in the carrier lifetime of the SiN x films deposited using a higher NH 3/SiH 4 flow ratio was caused by the increase of the interface traps and the defect states in/on the interface between the SiN x and the silicon wafer. Silicon and nitrogen rich films are not suitable for generating both higher carrier lifetimes and transmittance. An improvement in the single c-Si solar cell parameters was observed for the cells with an optimal SiN x layer, as compared to those with non-optimal SiN x layers. These results indicate that the band gap and the defect states of the SiN x films should be carefully controlled in order to obtain the maximum efficiency for c-Si solar cells.

High efficient n‐type back‐junction back‐contact silicon solar cells with screen‐printed Al‐alloyed emitter and effective emitter passivation study

AbstractN‐type back‐junction back‐contact (BJ–BC) silicon solar cells have been successfully introduced in industry by Sunpower with efficiencies up to 23.4% and are being investigated by several research groups. For such n‐type bulk Si solar cells, the formation of the p+ emitter is still an issue. A traditional method is boron diffusion, which needs high temperature processes to form the emitter and to remove the silicate glass boron skin. In recent years, people have shown excellent results on n‐type front contact rear junction cells with a screen‐printed Al‐alloyed emitter. In this work, we demonstrate the use of such emitters on n‐type BJ–BC silicon solar cells. Different pitch sizes and emitter fractions have been studied. Clear trends of the short‐circuit current densities have been observed. Light beam induced current technique is used to investigate this phenomenon. Different front surface field (FSF) profiles were applied to our cells. The shallower FSF with a lower surface doping concentration results in lower front surface recombination, which results in the best cell performance. Efficiencies of 19.1% under 1 Sun on BJ–BC solar cells with an aperture area of 2 cm × 2 cm have been achieved on n‐type FZ and CZ silicon wafers. Good short‐circuit current densities and fill factors have been obtained. Compared to the boron‐diffused emitter BJ–BC solar cells, relatively low open‐circuit voltages were obtained. Better quality emitter with more effective cleaning process steps and passivation layers have been developed, to result in a further increase in cell efficiency in the future work. Copyright © 2010 John Wiley &amp; Sons, Ltd.

AlInN/AlN/GaN HEMT Technology on SiC With 10-W/mm and 50% PAE at 10 GHz

High-frequency high-electron-mobility transistors (HEMTs) were fabricated on AlInN/AlN/GaN heterostructures grown by low-pressure metal-organic chemical vapor deposition on a SiC substrate. The results presented in this letter confirm the high performance that is reachable by AlInN-based technology with an output power of 10.3 W/mm and a power-added efficiency of 51% at 10 GHz with a gate length of 0.25 ¿m. A good extrinsic transconductance value that is greater than 450 mS/mm and exceeding AlGaN/GaN HEMT results was also measured on these transistors. To our knowledge, these results are the best power results published on AlInN/GaN HEMTs. These good results were attributed to optimized heterostructure properties associated with low-resistance ohmic contacts and an effective passivation layer minimizing drain current slump in high-frequency operations.

Investigation of the major reduction reaction occurring during the passivation of galvanized steel rebars

The corrosion behaviour of zinc plates immersed in calcium hydroxide saturated solutions in the presence of oxygen, air and nitrogen, respectively, was studied. The corrosion resistance was monitored by potentials and corrosion rate measurements. The results obtained were confirmed by further data collected on galvanized rebars embedded in concrete and stored in different curing environments. The results clearly show that oxygen is the main oxidizing agent and indeed not water for the rapid formation of an effective passivation layer on zinc coating.

Effects of an anodic oxide passivation layer on mesa-type InGaAs (PIN) photodetectors

Because of the high density of surface states and large surface recombination velocity found in III–V materials, surface passivation remains a crucial processing step for the fabrication of mesa-type InGaAs photodetectors. It is required to find an easy and economical method to form an effective passivation layer on the surface of the detector. In this work, an oxide passivation layer formed by electrochemical anodization was proposed and a 256-element In0.78Ga0.22As photodetector array was fabricated. The dark current performance achieved is as low as 2 × 10−7 A (bias voltage of −0.1 V) at 300 K. The reduction of dark current indicates that the anodic oxide passivation layer is effective in reducing recombination at the exposed mesa surface.

Optimization of Surface Passivation for InAs-GaSb Infrared Photodetector

A type II indium arsenide / gallium antimonide (InAs-GaSb) strained layer superlattice (SLS) semiconductor is optimal for detecting long wavelength infrared (LWIR) signals for infrared imaging applications. However, as with all crystal structures dangling bonds at the surface of the semiconductor must be pacified with a passivant to maintain the integrity of the semiconductor. We report the most effective passivation layer for this III-V semiconductor by examining both the material and device characteristics of the devices pacified by silicon dioxide (SiO2), silicon nitride (SixNy), and zinc sulfide (ZnS). Our final reporting shows ZnS with a pre-passivation of ammonium sulfide ((NH4)2S) as being the most effective passivant.

Highly luminescent surface-passivated ZnS:Mn nanoparticles by a simple one-step synthesis

Highly luminescent surface-passivated ZnS:Mn nanoparticles were synthesized straightforwardly by a simple liquid-solid-solution method. Compared to the pristine Mn-doped zinc sulfide nanocrystals (quantum efficiency: ∼19%), the Li-added ZnS:Mn exhibited significantly enhanced luminescence properties (quantum efficiency: ∼43%). The surface passivation was investigated by x-ray photoelectron spectroscopy, transmission electron microscopy, and by the change in the radiative/nonradiative recombination rates. The photoluminescence enhancement is due to the formation of an effective passivation layer induced by lithium, and consequent suppression of the nonradiative recombination transitions.

Extended lifetime of pentacene thin-film transistor with polyvinyl alcohol (PVA)/layered silicate nanocomposite passivation layer

We prepared a novel organic passivation material to protect organic thin-film transistors (OTFTs) from H 2O and O 2 using a polyvinyl alcohol (PVA)/hydrophilic layered silicate (HLS) nanocomposite system. Using up to a 3 wt% layered silicate to PVA weight concentration, a highly homogeneous nanocomposite solution was prepared. In addition, a PVA/HLS nanocomposite solution formed a smooth film layer by the spin-coating method with RMS surface roughness of about 1 nm. An OTFT device with PVA passivation showed a decrease of 23% in field effect mobility after passivation. However, a pentacene TFT device with PVA/HLS nanocomposite passivation showed no significant initial performance drop after passivation, and mobility was even slightly improved. Pentacene TFT-passivated PVA/HLS showed 2860 h of TFT lifetime (the time required to reduce the mobility by one-half of the initial mobility after passivation), which is almost twice the lifetime of pentacene TFT with PVA passivation (1320 h). We propose that a layered silicate containing PVA nanocomposite film can be used as an effective organic passivation layer in an OTFT.

5-Phenyl-1-H-Tetrazole as a Low-pH Passivating Agent for Copper Chemical Mechanical Planarization

The introduction of porous low- dielectric materials into semiconductor devices requires the development of low downforce Cu chemical mechanical planarization (CMP). An alternative passivation agent, 5-phenyl-1H-tetrazole (PTA), is proposed here that is effective at lower pH than the traditional CMP passivation agent, benzotriazole (BTA). PTA has previously been reported as a low-pH Cu corrosion inhibitor, but has not been explored for Cu CMP. Cu CMP removal rates and Cu static etch rates are measured for slurries containing , glycine, colloidal silica, and PTA concentrations ranging from . At pH 3 and PTA concentrations of , PTA provides both effective passivation and Cu removal rates of . Fourier transform-infrared and electrochemical studies are consistent with the formation of an effective passivation layer on Cu in CMP slurries containing PTA concentrations ranging from , with the effectiveness of passivation increasing with PTA concentration. The improved low-pH passive film formation for PTA in Cu CMP slurries relative to BTA is most likely due to its much lower pKa (4.3), with a much larger fraction of PTA in the anionic form at low pH.

Growth Kinetics of ZnO Nanocrystals: A Few Surprises

Using extensive state-of-the-art experiments over a wide range of synthesis parameters, such as the temperature and concentrations of different reactants, we establish qualitatively different growth kinetics for ZnO nanocrystals compared to all growth kinetics of semiconductor nanocrystals, including ZnO, discussed so far in the literature. The growth rate is shown to be strongly dependent on the concentration of (OH)- in an intriguing nonmonotonic manner as well as on temperature and is almost invariably much slower than well-known and generally accepted growth mechanisms based on a diffusion-controlled Ostwald ripening process or that expected in the surface reaction controlled regime. We show that these qualitatively different results arise from the unexpected role played by a part of the reactants by inhibiting rather than facilitating the reaction; we explain this extraordinary result in terms of an effective passivating layer around the growing nanocrystals formed by a virtual capping shell of Na+ ions.

Influence of gate oxide thickness on Sc 2O 3/GaN MOSFETs

The influence of Sc 2O 3 gate dielectric thickness and of gate length of GaN metal–oxide–semiconductor field effect transistor (MOSFETs) on saturation current, gate current, gate breakdown voltage and threshold voltage were examined using a drift–diffusion model. The threshold voltage was directly proportional to Sc 2O 3 thickness and only modestly dependent on dielectric thickness. The saturation drain current was <10 −2 A μm −1 for all gate lengths in the range 0.5–1.0 μm devices with oxide thickness < 800 Å. Gate current is <10 −6 A μm −1 at 300 K even at 100 V gate bias for 0.5 μm gate lengths and dielectric thicknesses < 800 Å. The gate breakdown voltage was directly proportional to dielectric thickness. The Sc 2O 3 also performs as an effective surface passivation layer, mitigating the effects of virtual gates created in the gate–drain region by surface states.

Direct determination of epitaxial interface structure in Gd2O3 passivation of GaAs.

Obtaining accurate structural information on epitaxial films and interfaces is nowhere more critical than in semiconductor passivation layers, where details of the atomic structure and bonding determine the nature of the interface electronic states. Various non-destructive methods have been used to investigate the structure of films and interfaces, but their interpretation is model-dependent, leading occasionally to wrong conclusions. We have developed a new X-ray method for the direct determination of epitaxial structures, coherent Bragg rod analysis (COBRA). The usefulness of our technique is demonstrated by mapping, with atomic precision, the structure of the interfacial region of a Gd2O3 film grown epitaxially on a (100) GaAs substrate. Our findings reveal interesting behaviour not previously suggested by existing structural methods, in particular a lock-in of the in-plane Gd atomic positions to those of the Ga/As atoms of the substrate. Moreover, we find that the bulk stacking of the Gd2O3 atomic layers is abandoned in favour of a new structure that is directly correlated with the stacking sequence of the substrate. These results have important implications for Gd2O3 as an effective passivation layer for GaAs (ref. 7). Our work shows that the COBRA technique, taking advantage of the brilliance of insertion device synchrotron X-ray sources, is widely applicable to epitaxial films and interfaces.

Use of carbon films for passivation and environmental protection of superconducting YBa2Cu3O7−x

Electronic device applications of high-temperature superconducting cuprates require the production of patterned thin films that are stable and inert in various processing and operating environments; however, the superconducting rare-earth barium cuprates have been shown to decompose in water and to degrade in superconducting properties in a humid atmosphere. The thermodynamics that forms the driving force for the degradation is reviewed. Protective coatings or removable protective films can realize many applications and facilitate processing of superconducting devices. Diamondlike carbon films as well as amorphous carbon films are investigated as possible protective layers for YBa2Cu3O7−x (YBCO). Amorphous carbon (a-carbon) films deposited by evaporation are shown to protect superconducting YBCO films from degradation by humidity. The YBCO films with a-carbon coatings have been shown to have critical current densities four orders of magnitude higher than the uncoated YBCO films after 2 h at a stressing of 100% relative humidity (RH). A similar stressing for 44.5 h has conducting YBCO films but no longer has a measurable critical current density. The a-carbon coating is an effective passivation layer for short-term storage (with time &amp;lt;2 h and 100% RH and time ≳4 h at 50% RH) at room temperature. The critical current is shown to be a better indicator for the degree of degradation, since the transition temperature remains relatively constant as long as there is enough superconducting YBCO to provide a percolation path for the supercurrent. Degrees of degradation were also assessed by scanning electron microscopy. The versatility of these carbon films lies in that their deposition and removal by plasma oxidation at room temperature are compatible with YBCO films.

Electronic and atomic structure of arsenic terminated Si(100)

A comparison between angle resolved photoemission data and ab initio pseudopotential calculations for a structural model of the As covered Si(100) surface is presented. After a coverage of one monolayer the Si(100):As surface shows a 2×1 low energy electron diffraction pattern. The arsenic acts as an effective passivating layer and the adsorption of further arsenic is highly reduced. We propose a symmetric As–As dimer model for the Si(100):As 2×1 surface derived from energy minimization calculations. The major feature of the electronic structure of this model is the occurrence of occupied π and π* surface state bands derived from bonding and antibonding combinations of the dangling hybrids on the As atoms. The calculated dispersions for the π and π* bands are found to be in very good agreement with the experimental surface state dispersions. The results discussed provide an example of how angle resolved photoemission in combination with ab initio pseudopotential calculations can lead to a conclusive determination of the electronic and atomic structure of surfaces.

The electrolytic and chemical polishing of metals in research and industry : W. J. McG. Tegart. 2 ed. 139 pp. 1959. Pergamon Press, New York

With the rapid increase of data storage density on computer hard disk drives (HDDs), the operation distance between read/write head and disk surface has fallen to just a few nanometers. Chemical mechanical planarization (CMP) has been selected as the best process to produce high quality surface finish during the manufacturing of Ni–P alloy substrates for HDD applications. Herein we report, for the first time, the use of benzotriazole (BTA) as a passivating agent in CMP slurries to decrease the surface roughness (Ra). Results show that the average Ra of the polished surfaces is decreased to 0.2 nm in a 5 μm × 5 μm scan area with the adding of 2 mM BTA. X-ray photoelectron spectroscopy (XPS) and electrochemical studies results further prove the interaction between BTA and Ni–P surface and the formation of an effective passivating layer on Cu in CMP slurries containing BTA.