Cleaning Step Research Articles

Effect of the Cleaning Step on the Morphology of Gold Nanoparticles

The synthesis of unsupported spherical gold nanoparticles was performed using the water-in-oil microemulsion method. The surfactant stabilizing the particles was removed when performing electrochemical characterization. This step was carried out using either acetone or centrifugation. We demonstrate that the shape of the nanoparticles is affected by the cleaning procedure, which leads to the increase of the nanoparticles anisotropy. The application of acetone as a cleaning solvent results in a complete agglomeration of the nanocrystallites, whereas centrifugation preserves most of the spherical particles. This observation is confirmed by UV–vis as well as TEM measurements. Cyclic voltammetry characterization was performed by underpotential deposition of Pb on Au surfaces for the different materials obtained and provided an insight into the orientations of the low indexes Miller planes.

Spectrophotometric Flow Injection Analysis of Chromium(VI) Coupled with On-line Solid-phase Extraction with Anion-exchange Resin Cartridge Column

Trace amount of CrO4 2− in water sample was collected and concentrated on a cartridge type mini-column (4 cm in length and 2 mm i.d.) packed with anion-exchange resin, Toyopearl QAE-550C. The collection and concentration were carried out automatically using a sequential injection procedure. The handling sequence was the steps of cleaning, washing and conditioning of the resin, collection of CrO4 2− on the resin, and elution of CrO4 2− from the resin to a detection system. The CrO4 2− eluate was introduced into the photometric flow injection analysis system using 1,5-diphenylcarbazide as a derivatizing reagent. When an aliquot of 5.0 mL or 20 mL sample solution was treated, the sensitivity increased by 6.4 and 23 times, respectively. By combing the automated on-line pretreatment system with the photometric flow injection system, CrO4 2− at 10 mol L level was determined without expensive detectors such as ICP-AES. On the basis of the interference study, the proposed system was applied to the analysis of a river water sample. Concentration of CrO4 2− at 2.5x10 mol L was determined, and satisfactory results were also obtained with recovery tests.

Cleaning of GaN(2¯110) surfaces

The cleaning of GaN(2¯110) surfaces was investigated by x-ray photoelectron spectroscopy, scanning tunneling microscopy, and low-energy electron diffraction. Two different two-step cleaning methods, performed under ultrahigh-vacuum conditions, were carried out and compared. The first cleaning step of both methods is thermal degassing. The second step is either the deposition of metallic gallium followed by redesorption or an exposure to active nitrogen from a radio frequency nitrogen plasma source. Upon storage in a glovebox (N2 atmosphere) and transfer to ultrahigh vacuum under dry nitrogen, carbon and oxygen were identified as the major contaminants. A significant decrease in oxygen and carbon was achieved by thermal degassing at 750 °C under ultrahigh-vacuum conditions. By applying a subsequent Ga deposition/redesorption or N2-plasma cleaning step, a further reduction in oxygen and carbon could be achieved. In comparison, the Ga deposition/redesorption cleaning showed a better performance in oxygen removal, whereas the N2 plasma exhibits a better efficiency in carbon removal. Furthermore scanning tunneling microscopy and low-energy electron diffraction investigations showed a drastic improvement of the morphology and atomic structure of the clean surfaces in contrast to the sample surfaces after N2 storage and transfer.

Using Design of Experiments Approach to Optimize Custom Emitter Clean Process used in PV Manufacturing

Abstract We describe a ‘Design of Experiment’ (DOE) technique used to optimize the process parameters of a new commercially available emitter clean solution aimed to enhance the output efficiency of the cell. Emitter etch solutions are known to substantially improve efficiency by reducing surface recombination of charge carriers and increasing the short circuit current of the cell. We have used a full factorial design of experiment with three variables kept at two levels. Appropriate randomization of the run order and three centre points were chosen in order to reduce experimental errors. Adjacent multicrystalline wafers chosen for this experiment were subjected to acid texturization, phosphorus doping, diffusion and phosphosilicate glass etching before the emitter clean step. We chose mean emitter sheet resistance (Rsheet) (average over 25 positions on each wafer) as the response of this experiment. The aim was to achieve an increment of 10% on Rsheet after emitter clean. Voc scan of the wafers were done to validate the Rsheet increments observed. The results showed that H2O2 concentration and temperature had statistically significant effects on change of Rsheet. Regression analysis was used to predict the optimized parameters that may achieve a 10% increase of Rsheet. A validation run was carried out with this recipe in an automated production line and solar cells fabricated from this run showed a 0.18% (absolute) increase in efficiency and 15% (relative) reduction of recombination current density (Jo2) compared to standard reference cells processed without emitter clean.

Automated determination of the optimal end pointof the 1st carbonatation

Based on laboratory trials on the optimal flocculating point, in which the variation of this command variable of the juice purification was demonstrated, a prototype for the automated determination was constructed. A measurement system, which is operated in the bypass of the industrial production, is used for an automatic stepwise carbonatation of main liming juice. Starting at pH = 11.2 carbonatation gas is injected to bring down the pH to 10.4 in 0.1 or 0.2 pH units per step. After every pH step, the sedimentation behavior of the juice is characterized by means of a turbidity measurement after a clarification time of 3.5 min. With the function of turbidity versus pH value the optimal end point of the1st carbonatation can be determined. All in all an analysis takes approximately 60 min. Afterwards, an automated cleaning step takes place. For the prototype, the control of every step as well as the interpretation of the results is carried out with a personal computer. Based on the good experiences a so-called industrial version of this measurement system was constructed.

Selective Epitaxial Growth of InP in STI Trenches on Off-Axis Si (001) Substrates

We report high quality InP layers selectively grown in shallow trench isolation structures on 6 degree offcut Si (001) substrates capped with a thin Ge buffer layer. The Ge layer was used to reduce the thermal budget for surface clean and double step formation. The atomic steps on the Ge surface were recovered after a bake at 680°C. Smooth nucleation layer was obtained at 420°C on the Ge surface. Baking the Ge surface in As ambient facilitates the InP nulceation and improves the InP crystalline quality. This improvement is attributed to the effective As adsorption on the Ge surface and the polar Ge:As surface prevents the islanding of InP seed layer. Stacking faults were found in the InP layers as a result of threading dislocation dissociation and high quality InP layers were obtained in trenches with aspect ratio greater than 2.

The potential of sonicated water in the cleaning processes of silicon wafers

The potential of using distilled water in environmental friendly and non-toxic ultrasonic cleaning step in crystalline Si wafer preparation is addressed. It is found that organic particle contaminants are effectively removed during the kHz-frequency sonication of wafers over the first 40–60 min, as evidenced by the disappearance of organic-related optical absorption peaks. Subsidiary effects of the sonication on electrical and photoelectrical behaviour of Si wafers are discussed. It is observed that, when treating the wafers less than 60 min, the dangling bonds at the air/oxide and oxide/wafer interface can be activated. That causes a decrease in the subsurface resistance against dislocation displacements (observed micro-hardness decrease). It affects barriers of the free carrier migration at the interfaces (revealed in the current–voltage characteristics), and acts as recombination centers, accelerating photovoltage decays. A healing of the bonds may occur at longer cleaning times (≈60–120 min), which partially recover the interfaces, thus reversing the observed changes. Although an exact mechanism is not yet clarified, the likely scenario behind the observed changes is proposed to involve oxygen and hydrogen molecules, which are decomposed in water and subsequently trapped at the silicon surface.

A method to prevent cross contamination during 2-DE by β-amyloid peptides

A method for the efficient decontamination of aluminium oxide ceramic 2-DE focusing trays from β-amyloid peptides (Aβ) is reported. As these contaminations were resistant to the standard cleaning procedures, additional harsh cleaning steps were necessary for their efficient removal. Our observations suggest that specific surface properties affect the degree of adsorption of the Aβ-peptides. "Surface catalysed amyloid aggregation" in the aluminium oxide ceramic trays is proposed as a possible underlying mechanism for the occurrence of proteinase K-resistant forms of Aβ.

Computer-aided recording of automatic endoscope washing and disinfection processes as an integral part of medical documentation for quality assurance purposes.

BackgroundThe reprocessing of medical endoscopes is carried out using automatic cleaning and disinfection machines. The documentation and archiving of records of properly conducted reprocessing procedures is the last and increasingly important part of the reprocessing cycle for flexible endoscopes.MethodsThis report describes a new computer program designed to monitor and document the automatic reprocessing of flexible endoscopes and accessories in fully automatic washer-disinfectors; it does not contain nor compensate the manual cleaning step. The program implements national standards for the monitoring of hygiene in flexible endoscopes and the guidelines for the reprocessing of medical products. No FDA approval has been obtained up to now. The advantages of this newly developed computer program are firstly that it simplifies the documentation procedures of medical endoscopes and that it could be used universally with any washer-disinfector and that it is independent of the various interfaces and software products provided by the individual suppliers of washer-disinfectors.ResultsThe computer program presented here has been tested on a total of four washer-disinfectors in more than 6000 medical examinations within 9 months.ConclusionsWe present for the first time an electronic documentation system for automated washer-disinfectors for medical devices e.g. flexible endoscopes which can be used on any washer-disinfectors that documents the procedures involved in the automatic cleaning process and can be easily connected to most hospital documentation systems.

Investigating the fidelity of Mg/Ca and other elemental data from reductively cleaned planktonic foraminifera

[1] There has been considerable discussion about whether reductive cleaning can or should be used when samples are prepared for foraminiferal Mg/Ca analyses. The reductive solution causes considerable sample loss through dissolution, and the natural dissolution effect on planktonic foraminiferal Mg/Ca raises the question whether the shell chemistry might be affected during cleaning. We conducted a series of experiments to explore the effects of the reductive cleaning step on shell chemistry (Mg/Ca, Na/Ca, Sr/Ca, Fe/Ca, Mn/Ca, REE/Ca, and U/Ca) of two planktonic foraminiferal species. We then compare these results with natural dissolution in core top specimens from a range of varying natural dissolution intensity. Our results confirm previous experiments by Yu et al. (2007) that the citrate used in the reductive solution can play a larger role in decreasing some element/Ca ratios than hydrazine, the reductive agent, at least in samples that are not problematic to clean (i.e., have low Mn/Ca, Fe/Ca, and Al/Ca). Solutions containing varying concentrations of citrate yield lower Mg/Ca than those without citrate; however, Mg/Ca reaches an asymptotic value following a dilute application of citrate. Other element/Ca ratios are also lowered by citrate and tend toward an asymptotic value at increasing strengths of citrate. Mg/Ca data from experiments in which the duration of the reductive cleaning step was varied or repeated suggest that the standard reductive cleaning step should yield reproducible results for most elemental ratios. Our experiments suggest that the primary mechanism of dissolution by citrate is unlikely to be preferential removal of Mg from the lattice and also demonstrate that there are differences between natural and laboratory dissolution effects. Given that there are situations in which Mg/Ca data are improved by reductive cleaning, we conclude that it is acceptable to reductively clean samples before Mg/Ca analysis.

Effect of Pattern Layout and Dissolved Oxygen in CO2 Rinse Water on Cu Corrosion during Post-Etch Cleaning

When post-etch cleaning was carried out in Cu dual-damascene process, Cu at the bottom of isolated via was etched out especially in the wafer edge, and this would become a critical issue as device scale is shrunk. The corrosion was caused in the rinse step rather than chemical cleaning step because dissolved oxygen in rinse water from the air increased oxidation–reduction potential (ORP) and CO2 included in the rinse water for preventing wafer electrification decreased pH. The corrosion was found to be suppressed by increasing dummy pattern density and by controlling atmosphere and pH of the rinse water.

Simple methods for characterization of metals in historical textile threads

Characterization of metal threads on historical textile materials is important for preservation of valuable cultural heritage. Obtained results dictate decisions on cleaning, conservation and restoration steps. The most important part of characterization is chemical analysis of originally applied materials, since this enables understanding the nature of chemical and physical degradation and determines the cleaning methods. Methods applied should be non-destructive and sensitive enough to detect trace elements in small sample amounts. The goal of this research was to describe the most useful procedures for fast and simple determination of specific metals of interest. Therefore we propose application of scanning electron microscopy equipped with EDS detector (SEM-EDS) for sample surface analysis and inductively coupled plasma-optical emission spectroscopy (ICP-OES) for chemical analysis of metals threads. For quality insurance reasons, a comparative method applied for chemical analysis was atomic absorption spectrometry (AAS). This combination of methods has proven to be very useful in analysis of historical samples, since SEM-EDS was a simple and non-destructive method which provided information on chemical composition of sample surfaces, while ICP-OES and AAS enabled the full insight into the average chemical composition of samples. Nevertheless, both ICP-OES and AAS were destructive methods which demanded dissolving of samples prior to the analysis. In this work nine different metal fibers collected from historical textile materials were characterized. Proposed methods enabled obtaining information on sample constitution, morphology, topology and chemical composition.

Preparation of Conjugated Polymers Inside Assembled Solid‐State Devices

Soluble precursor polymers are processed and assembled into solid-state devices and subsequently converted in the devices to conjugated electrochromic materials. This method, termed in situ conversion, requires no rigorous cleaning step for the electrode substrate. It eliminates the use of a costly electrolyte bath during the assembly process. This methodology results in high yields for the resultant conjugated system.

Plasma doping two-dimensional characterization using low energy x-ray emission spectroscopy and full wafer secondary ion mass spectrometry/angle-resolved x-ray electron spectroscopy techniques

Several metrologies may be used to analyze plasma doping (PLAD) [S. Qin and A. McTeer, IEEE Trans. Electron Devices 54, 2497 (2007)] results, each with its own advantages and disadvantages. An investigation into the available characterization methods has been performed in order to reduce costs associated with the current qualification process, such as additional clean and annealing steps. This article will introduce an improved analytical method developed at Micron and demonstrate results of a correlation study between characterization techniques for B doped PLAD. The combined secondary ion mass spectrometry/angle-resolved x-ray electron spectroscopy two-dimensional (2D) dose mapping data provide excellent confirmation of the low energy x-ray emission spectroscopy (LEXES) 2D dose mapping data, and the nonuniformity from annealing can be deconvoluted from nonuniformities due to the implantation process. The data demonstrate that LEXES may replace the thermally processed RS measurement for tool and/or process qualifications.

耳鼻咽喉科における内視鏡の洗浄・消毒方法の検討

To compare conventional and automatic flexible nasopharyngeal fiberscope (NFS) sterilizer effectiveness and required time, we studied the NFS handle and tip before and after sterilization in clinical use in 9 cases each. Two bacterial strains were infused into 6 NFS channels then washed them with each method, recording all required cleaning and sterilization time and steps. Automatic sterilization yielded no bacteria on the NFS handle, tip, or channnel of the scope in any case. Conventional sterilization yielded bacteria on the handle in 5 of 9 cases, although none on the channel or tip. Average automatic sterilization took 12 minutes 43 seconds, significantly shorter than the conventional 23 minutes 7 seconds. We found automatic sterilization to be more bactericidaliy effective and efficacious than conventional sterilization.

Update on the Performance of the SUERC In Situ Cosmogenic 14C Extraction Line

In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ14C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ14C standard (PP-4). The SUERC in situ14C extraction system was built in 2001 and is based on a combustion technique following the design of the extraction system at the University of Arizona. Our preliminary results suggest that the continuous running of the extraction system and the monitoring of gas collecting time and of the temperature of the cryogenic traps used in the gas cleaning steps are key to maintaining low and stable system blanks. Our latest average system blank is 2.02 ± 0.23 x 10514C atoms. This is consistent with those recently published by the University of Arizona and ETH in situ14C labs. Measurements of in situ14C concentrations in sample PP-4 yield an average of 3.82 ± 0.23 x 105 atoms g–1 quartz, again consistent with published values.

Minimize MicrofiItration Membrane Maintenance

This article discusses a system design to minimize microfiltration membrane maintenance at the Westchester Joint Water Works in Mamaroneck, New York. Several cleaning steps were used to remove contaminants from membrane fibers and keep them free of fouling. Frequent air agitation, backpulsing, and deconcentration were used to remove solids from the fibers. More aggressive cleaning programs‐‐ maintenance and recovery cleaning‐‐ were used with chemicals to remove fouling. The wastes produced from each of these steps must be handled carefully and within the constraints of local utilities, available property, and capital/operational costs.

Optimization of a surfactant free polyol method for the synthesis of platinum–cobalt electrocatalysts using Taguchi design of experiments

A design of experiments (derived from the Taguchi method) was implemented to optimize experimental conditions of a surfactant free polyol method for the synthesis of PtCo electrocatalysts. Considered responses were the active surface area and the catalytic activity toward oxygen reduction reaction. Metallic salt concentration, pH, temperature ramp, addition order of reactants and particle cleaning step were chosen as main parameters according to considerations coming from literature and previous experiments. Matrix models describing the behaviour of the synthesis system was elaborated taking into account the effects of each considered parameter and their interactions. From this model, an optimized PtCo/C catalyst, in terms of active surface area and activity towards the oxygen reduction reaction, was synthesized. Both the measured values of the active surface area and the electrocatalytic activity are in very good agreement with the calculated ones from the matrix model. Furthermore, actions of parameters and interactions between parameters can be better understood using this method.

Interplay between Dry Etch and Wet Clean in Patterning La2O3/HfO2 Containing High-k/metal Gate Stacks

A dry-wet patterning process for La2O3/HfO2-containing high-κ/ metal gate stacks was successfully developed. The process meets the stringent requirements of complete removal of the high-κ layers and metal-containing sidewall residues without inducing silicon recess or undercut. The interaction between the dry etch and wet clean steps was studied. Use of a BCl3-based plasma process facilitated the cleaning process as it damages and modifies the high-κ layers in the active area. When the dry etch process ends with a BCl3-step, La-containing residues were formed inhomogeneously over the wafer within the time scale of hours. These residues could no longer be removed with a wet clean, but were not observed when the dry etch and wet clean processes were integrated. This demonstrates that an integrated etch-clean process enlarges the process window.

Reproducibility and Efficiency of Carbon Nanotube End‐Group Generation and Functionalization

AbstractIn a systematic fashion, several methods for esterification and amidation of single‐walled carbon nanotubes have been evaluated with focus on efficiency and reproducibility in forming covalently functionalized products soluble in organic media. The outcome of transformations was determined using IR, Raman and NMR spectroscopy and by thermogravimetric analysis (TGA). Amidation proceeding via a SWNT‐(COCl)n intermediate yielded the expected covalent product, whereas carboxylate salt formation dominated with other attempted methods. Esterification was achieved via the acyl chloride method and via alkylation of SWNT‐(COO–)n, the latter being the more efficient method. A non‐covalent solubilizing interaction was obtained for RNH2 but not for ROH (R = octadecyl), proving that the most important non‐covalent interaction between oxidatively cleaned SWNTs and octadecylamine is a salt formation. The outcome of the secondary functionalization of carboxyl units is highly reproducible for experiments carried out on the same batch of SWNT‐(COOH)n. Normalization of the outcome of the secondary functionalization to the composition of the different batches of starting materials reveals an overall high reproducibility of the secondary functionalizations. The differences in outcome related to different commercial SWNT batches from the same synthetic procedure is negligible compared to that resulting from differences in overall carboxyl content after the primary HNO3 oxidative cleaning step. Hence, the composition of purified SWNT starting materials always needs to be assessed, in particular before drawing any conclusions concerning differences in outcome from reaction systems involving different sources of SWNT material. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)