Showing papers on "Chamber pressure published in 2006"

On maintaining pressure equilibrium between a soil CO2 flux chamber and the ambient air

Abstract: [1] Pressure equilibrium between inside a soil CO2 flux chamber and the surrounding air outside the chamber must be maintained during a measurement if measured soil CO2 flux (FCO2) is to accurately represent the rate occurring naturally outside the chamber. In previous studies a simple vent tube connecting to the chamber has often been used to maintain pressure equilibrium. This approach, however, can be effective only under calm conditions. Under windy conditions, negative pressure excursions will occur inside the chamber that are artifacts resulting from wind passing over the vent tube's external open end, a phenomenon known as the Venturi effect. This causes anomalous mass flow of CO2-rich air from the soil into the chamber, leading to a significant overestimation of FCO2. In this present study, we found that negative chamber pressure excursions due to the Venturi effect cannot be observed unless the differential pressure measurement is made with the chamber resting on an impermeable base. Making pressure measurements with a chamber resting on porous soil can lead to the erroneous conclusion that an anomalous mass flow is not a problem precisely when it is causing serious artifacts. We also present a new vent design for a soil CO2 flux chamber capable of maintaining pressure equilibrium between inside the chamber and the ambient air outside the chamber under both calm and windy conditions. Differential pressure measurements from field experiments show that the pressures inside our newly designed vented chamber equal those outside the chamber when wind speed at a height of 0.5 m is up to 7 m s−1, thus virtually eliminating artifacts due to the Venturi effect. Our field data show that the problem of overestimation in measured FCO2 by a chamber with older vent designs under windy conditions can be avoided with our newly designed vented chamber.

A degassing plate with hydrophobic bubble capture and distributed venting for microfluidic devices

Abstract: This paper introduces a microfluidic wall plate that allows the removal of gas bubbles from a gas/liquid mixture in a distributed fashion, i.e., throughout the flow path, eliminating the need for discrete separators common in macroscopic practice. Integrated into a microfluidic system at critical locations, such a degassing plate prevents the build up of gas bubbles in microchannels so as to maximize the effective reaction area, decrease the flow resistance and keep the chamber pressure under check. Furthermore, the plate surface is designed to capture the gas bubbles preferentially on designated venting sites, so that the rest of the surface can be dedicated to other functions, such as the catalyst or electrodes. The mechanism of bubble capture is explained by surface energy minimization, and two types of bubble sinks are proposed and verified. Once captured, the bubbles can be vented out through hydrophobic venting holes small enough (e.g. sub-micron) to block the liquid by surface tension. By chemically generating CO2 inside a small chamber (30 mm ? 50 mm ? 1.5 mm) sealed by the degassing plate, the process of bubble capture and removal is visually demonstrated. A porous polypropylene membrane with ~0.2 ?m diameter holes shows that gas can be removed with only several kPa of internal pressure while water stays free of leakage even under 2.4 ? 105 Pa (35 psi). Venting is effective in any gravitational orientation, paving the way for portable microfluidic devices.

Spray Characteristics of a Multi-hole Injector for Direct-Injection Gasoline Engines:

Abstract: The sprays from a high-pressure multi-hole nozzle injected into a constant-volume chamber have been visualized and quantified in terms of droplet velocity and diameter with a two-component phase Doppler anemometry (PDA) system at injection pressures up to 200 bar and chamber pressures varying from atmospheric to 12 bar. The flow characteristics within the injection system were quantified by means of a fuel injection equipment (FIE) one-dimensional model, providing the injection rate and the injection velocity in the presence of hole cavitation, by an in-house three-dimensional computational fluid dynamics (CFD) model providing the detailed flow distribution for various combinations of nozzle hole configurations, and by a fuel atomization model giving estimates of the droplet size very near to the nozzle exit. The overall spray angle relative to the axis of the injector was found to be almost independent of injection and chamber pressure, a significant advantage relative to swirl pressure atomizers. Temporal droplet velocities were found to increase sharply at the start of injection and then to remain unchanged during the main part of injection, before decreasing rapidly towards the end of injection. The spatial droplet velocity profiles were jet-like at all axial locations, with the local velocity maximum found at the centre of the jet. Within the measured range, the effect of injection pressure on droplet size was rather small while the increase in chamber pressure from atmospheric to 12 bar resulted in much smaller droplet velocities, by up to four-fold, and larger droplet sizes by up to 40 per cent.

Exact Solution of the Bidirectional Vortex

Abstract: In this paper, we present an inviscid solution that describes the cyclonic motion of a bidirectional vortex in a cylindrical chamber. The study is prompted by the need to characterize the flowfield inside a swirl-driven thrust chamber. This chamber has the advantage of confining mixing and combustion to an inner vortex tube that remains separated from the chamber walls by virtue of an outer stream of swirling, low temperature oxidizer. Our model is based on nonreactive, steady, rotational, axisymmetric, incompressible, and inviscid flow conditions. Unlike other studies of columnar vortices where the axial dependence is not considered, the present model accounts for the chamber's finite body length. In fact, it incorporates the inlet and headwall conditions associated with a swirl-driven cyclone. Based on the resulting formulation, several flow features are captured. Among them is the location of the inner-outer vortex interface where the axial velocity vanishes.

Silicon oxynitride gate dielectric formation using multiple annealing steps

Abstract: A method for processing a semiconductor substrate in a chamber includes forming a silicon oxynitride film using a two-step anneal process. The first anneal step includes annealing the silicon oxynitride film in the presence of an oxidizing gas that has a partial pressure of about 1 to about 100 mTorr, and the second anneal step includes annealing the silicon oxynitride film with oxygen gas that has a flow rate of about 1 slm. The first anneal step is performed at a higher chamber temperature and higher chamber pressure than the second anneal step.

Drainage system for compressor separators

Abstract: A drainage system is for a compressor assembly that includes at least one separator with a chamber. The system includes a drain valve fluidly coupled with the separator chamber and adjustable between open and closed states. An actuator is operatively coupled with and adjusts the valve between the open and closed states or/and a sensor senses when the valve is open. A pressure sensor is configured to sense pressure within the chamber and a logic circuit is coupled with the pressure sensor and determines when the valve either has been or should have been adjusted to the open state. The logic circuit also generates an output signal or/and operates a device when the chamber pressure remains substantially constant or varies by less than a predetermined amount subsequent to the valve being opened and/or when the chamber pressure varies by at least the predetermined amount after the valve is opened.

Integrated Modeling and Analysis for a LOX/Methane Expander Cycle Engine: Focusing on Regenerative Cooling Jacket Design

Abstract: A fully integrated engine analysis methodology was created and employed to study a 25,000 pound-force thrust class expander cycle liquid oxygen/methane engine for Crew Exploration Vehicle applications. All major components for the engine were modeled, including the combustion thermal chemistry, the turbopump assembly, the regenerative cooling jacket and the injector. Significant attention was assigned to the regenerative cooling analysis with respect to varying channel geometry dimensions. Chamber pressures ranging from 500 to 1000 psia, were parametrically studied for varying aspect ratios of 4 to 8, channel widths of 0.020 to 0.080 inches, and 100 to 200 number of channels. Two of the three geometric parameters were held fixed, while trends in the third were studied at constant chamber pressures. The channel cross-section was held constant with respect to axial position in the engine. From the geometry cases studied, the initial baseline channel geometry was determined and chamber pressures were studied in detail from 500 to 1000 psia. A chamber pressure of 850 was determined as most favorable with respect to overall engine performance and design metrics. Using the initial baseline geometry, a constant cross-section and stepped channel design were compared. The performance for the stepped channel configuration is notably superior to the constant cross-section channel case with respect to pressure loss, and chamber mass metrics. Detailed results are presented for all engine components for the most favorable design.

Method of controlling a chamber based upon predetermined concurrent behavoir of selected plasma parameters as a function of selected chamber paramenters

Abstract: The invention involves a method of processing a workpiece on workpiece support pedestal in a plasma reactor chamber in accordance with user-selected values of plural (i.e., N) plasma parameters by controlling plural chamber parameters. The plasma parameters may be selected from of a group including ion density, wafer voltage, etch rate, wafer current and possibly other plasma parameters. The chamber parameters may be selected from a group including source power, bias power, chamber pressure, magnet coil current of different coils, gas flow rate in different gas injection zones, gas species composition in different gas injection zones, and possibly other chamber parameters. The method begins with a first step carried out for each one of the selected plasma parameters. This first step consists of fetching from a memory a relevant surface of constant value corresponding to the user-selected value of the one plasma parameter, the surface being defined in a N-dimensional space of which each of the N chamber parameters is a dimension. This step further includes determining an intersection of these relevant surfaces, the intersection corresponding to a target value of each of the N chamber parameter. The method further includes setting each of the N chamber parameters to the corresponding target value.

Critical flow based mass flow verifier

Abstract: A flow verifier for verifying measurement by a fluid delivery device under test (DUT) includes a chamber configured to receive a flow of the fluid from the DUT, at least one temperature sensor to provide gas temperature in the chamber, at least one pressure transducer to provide gas pressure in the chamber, and a critical flow nozzle located upstream of the chamber along a flow path of the fluid from the DUT to the chamber. The critical flow nozzle and the flow verification process are configured to maintain the flow rate of the fluid through the nozzle at the critical flow condition such that the flow rate through the nozzle is substantially constant and substantially insensitive to any variation in pressure within the chamber downstream of the nozzle. Therefore, the varying chamber pressure during the flow verification period has substantially no impact on the downstream pressure of the DUT, and the external volume between the flow verifier and the DUT is substantially irrelevant to the flow verification calculation.

Effect of reverse flow by differential pressure on the protection of critical surfaces against particle contamination

Abstract: Mask protection from particulate contaminants is one of the most serious concerns for the success of deploying extreme ultraviolet lithography (EUVL) technology for future semiconductor manufacturing. Standard pellicles are not applicable for an EUVL mask surface because of the high absorption of the EUV beam by any material. Therefore, methods such as thermophoresis and electrophoresis are desirable for protection, instead of using organic membrane pellicles. A reverse flow concept by introducing differential pressure between different operating zones (mask zone with higher pressure and optics zone with lower pressure) is introduced for protection of critical surfaces against particulate contamination. In this study, we show systematic investigations of the differential pressure effect on the protection of critical surfaces using 125nm polystyrene latex spheres at a chamber pressure of 50mTorr, whereas the critical surface zone pressure was varied up to 550mTorr. We found that a higher particle speed nee...

Dissociation of Natural Gas Hydrates Observed by X-ray CT Scanner

Abstract: Core samples containing pore-space gas hydrate within granular sands were collected from 913.76 m of the research well named JAPEX/JNOC/GSC Mallik 2L-38. X-ray CT images of the core were acquired while warming from −18 to 4°C, and subsequently during stepped decreases of 0.1 MPa in the chamber pressure below the methane hydrate equilibrium pressure. Discharged gas flows and sample temperatures were monitored continuously. Changes in CT values indicated that gas hydrate dissociated simultaneously both on the exposed surfaces and within the pore spaces of the sample in response to pressure changes. This suggested that pressure reductions were effectively transmitted through the sample most likely because the samples contained some amount of fluids. The result of gas flow measurements indicated that a larger pressure drawdown caused a higher dissociation rate.

Plasma reactor control by translating desired values of m plasma parameters to values of n chamber parameters

Abstract: The invention concerns a method of processing a wafer in a plasma reactor chamber by controlling plural chamber parameters in accordance with desired values of plural plasma parameters. The method includes concurrently translating a set of M desired values for M plasma parameters to a set of N values for respective N chamber parameters. The M plasma parameters are selected from a group including wafer voltage, ion density, etch rate, wafer current, etch selectivity, ion energy and ion mass. The N chamber parameters are selected from a group including source power, bias power, chamber pressure, inner magnet coil current, outer magnet coil current, inner zone gas flow rate, outer zone gas flow rate, inner zone gas composition, outer zone gas composition. The method further includes setting the N chamber parameters to the set of N values.

Method of characterizing a chamber based upon concurrent behavior of selected plasma parameters as a function of plural chamber parameters

Abstract: The invention involves a method of characterizing a plasma reactor chamber through the behavior of many selected plasma parameters as functions of many selected chamber parameters. The plasma parameters may be selected from a group including ion density, wafer voltage, etch rate and wafer current or other plasma parameters. The chamber parameters are selected from a group including source power, bias power, chamber pressure, magnetic coil current in different magnetic coils, gas flow rates in different gas injection zones and species composition of the gas in different gas injection zones.

Microwave Electrothermal Thruster Chamber Temperature Measurements and Performance Calculations

Abstract: The microwave electrothermal thruster (MET) uses microwave frequency energy to create and sustain a resonant cavity plasma to heat a propellant. A 2.45-GHz aluminum cylindrical thruster with converging copper-alloy nozzles was used for this study. A spectroscopic system was used to collect light emitted through a window in the plasma chamber. A Schumann-Runge oxygen-emission model was developed assuming an anharmonically vibrating, nonrigid rotating oxygen molecule. The commercially available LIFBASE software was used to model the ionized molecular nitrogen first negative system emission from the nitrogen plasmas. Experimental data were compared to the temperature-dependent models using least-squared difference summation schemes. Oxygen rotational temperatures of 2000 K and ionized nitrogen rotational temperatures of 5500 K were measured. These measurements were nearly constant for all chamber pressures and investigated absorbed specific powers. CEA2 code equilibrium thermochemical calculations show the relationship among enthalpy addition, temperature, and specific impulse for realistic operating conditions. Nitrogen was found to be an excellent choice as a propellant or propellant component, whereas oxygen was found to be a poor choice because of the temperatures achieved for the respective gases in the MET chamber.

Enhanced Surface Spary Cooling With Embedded and Compound Extended Surface Structures

Abstract: Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of embedded structures (dimples, pores, and tunnels) and compound extended surface enhancements (straight fins, cubic pin fins and dimples) machined on and within the top surface of copper heater blocks. Each copper block had a projected cross-sectional area of 2.0 cm2. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2times2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N2 gas at 101 kPa) with a bulk fluid temperature of 20.5 degC. Results for both the nominally degassed and gassy cases show that the highest critical heat flux (CHF) was attained using straight fins and porous tunnels. For the nominally degassed case, both had a CHF of ap142 W/cm2 while for the gassy case their CHF values increased to 175 W/cm2 . This gave an enhancement relative to the respective flat surface degassed/gassy cases of ap 77% and 62% respectively

Maintaining disinfection of medical equipment

Abstract: A method is provided for maintaining the disinfection of medical equipment, in particular medical endoscopes (10), following processing. The method comprises placing the disinfected equipment (10) in a sealed chamber (12), and subsequently reducing the pressure within the sealed chamber (12) to cause evaporation of residual moisture. Gas scavenger sachets (21) are also provided within the sealed chamber (12) to remove atmospheric oxygen, thus causing a further reduction in the chamber pressure. The method may optionally include a further step of charging the sealed chamber (12) with a disinfectant gas or vapor. The processed medical equipment (10) is then maintained at the desired level of disinfection within the controlled biostatic environment in the sealed chamber (12).

Method of controlling a chamber based upon predetermined concurrent behavior of selected plasma parameters as a function of source power, bias power and chamber pressure

Abstract: For each one of plural plasma parameters, such as ion density, wafer voltage, etch rate, wafer current, a relevant surface of constant value is fetched from a memory. The relevant surface of constant value corresponds to a user-selected value of one of the plasma parameters, the surface being defined in a space of which each one of plural, chamber parameters (e.g., source power, bias power and chamber pressure) is a dimension. An intersection of these relevant surfaces is found, the intersection corresponding to a target value of source power, bias power and chamber pressure. The source power, the bias power and the chamber pressure, respectively, are set to their corresponding target values.

Multihole injectors for direct-injection gasoline engines

Abstract: High-pressure multi-hole nozzles, carrying a Diesel-derived technology, are believed to be promising Fuel Injection Equipment (FIE) for Direct-Injection (DI) Spark Ignition (SI) gasoline engines. Having explored thoroughly swirl pressure atomisers and their spray behaviour, multi-hole nozzles represent the second-generation injectors. Thus, complete investigation of multi-hole nozzle flow, spray characteristics and their engine performance is a vital part of development of future DI gasoline engines. The internal nozzle flow of an enlarged transparent multi-hole injector was investigated for different flow rates and needle lifts under steady state flow conditions. High-resolution CCD camera and high speed digital video systems were employed to visualize the nozzle flow patterns and cavitation development. The images identified the onset of cavitation in multi-hole gasoline nozzles and revealed the transition from pre-film to film stage cavitation. Cavitation strings were also visualized inside the injection hole that could extend to the needle face. However, these structures are highly unstable and directly affected by needle lift and cavitation number, although it appeared to be independent of the Re, in a behaviour similar to that of multi-hole diesel injectors. The sprays from various high-pressure multi-hole nozzle designs injected into a high-pressure/temperature constant-volume chamber have been visualised and quantified in terms of droplet velocity and diameter with a two-component phase-Doppler Anemometry (PDA) system at injection pressures up to 200bar and chamber pressures varying from atmospheric to 12bar. The overall spray angles relative to the axis of the injector were found to be almost independent of injection and chamber pressure, a significant advantage relative to swirl pressure atomisers. Within the measured range, the effect of injection pressure on droplet size was rather small while the increase in chamber pressure from atmospheric to 12bar resulted in much smaller droplet velocities, by up to fourfold, and larger droplet sizes by up to 40%. The effect of chamber temperature on multi-hole sprays confirmed the expected trends that dictate smaller droplet size distributions as temperature rise from 50 to 90 and 120°C. Additionally, multiple-injection proved to have similar dependencies to the single injection with certain operating limits. Laser-induced fluorescence has been mainly used to characterise the two-dimensional fuel vapour concentration inside the cylinder of a multi-valve twin-spark ignition engine equipped with high-pressure multi-hole injectors. The effects of injection timing, in-cylinder charge motion and injector tip layout have been quantified. The flexibility in nozzle design of the multi-hole injectors has proven to be a powerful tool in terms of matching overall spray cone angle and number of holes to specific engine configurations. Injection timing was found to control spray impingement on the piston and cylinder wall, thus contributing to quick and efficient fuel evaporation. Multipleinjection performed well under certain operating conditions and proved to be a powerful tool in the hands of engine manufacturers. It was confirmed that in-cylinder charge motion plays a major role in engine's stable operation by assisting in the transportation of the air-fuel mixture towards the ignition locations (i.e. spark-plugs) in the way of a uniformly distributed charge or by preserving stratification of the charge depending on operating mode of the engine.

Method and apparatus for pressure control and flow measurement

Abstract: A method and apparatus for gas control is provided. The apparatus may be used for controlling gases delivered to a chamber, controlling the chamber pressure, controlling the delivery of backside gas between a substrate and substrate support and the like. In one embodiment, an apparatus for controlling gas control includes at least a first flow sensor having a control valve, a first pressure sensor and at least a second pressure sensor. An inlet of the first flow sensor is adapted for coupling to a gas supply. A control valve is coupled to an outlet of the flow sensor. The first pressure sensor is adapted to sense a metric indicative of the pressure upstream of the first flow sensor. The second pressure sensor is adapted to sense a metric indicative of the pressure downstream of the control valve.

Performances of a Rocket Chamber for the Combined-cycle Engine at Various Conditions

Abstract: A gaseous hydrogen/gaseous oxygen rocket chamber was designed to fit in a rocketramjet combined-cycle engine model, and its performance was evaluated experimentally. Such a rocket chamber is required to operate in very wide ranges of chamber pressure (Pc) and mixture ratio (O/F). For stable operation, the injector has a choking point and a diffuser in the downstream portion. The design point of the injector is Pc = 5.0 MPa and O/F = 7 when the injection pressure of both the fuel and the oxidizer is 7 MPa. Stable operation and a C-star efficiency of 0.91 were attained in the rocket mode operation at O/F = 6.5 - 7.5 and Pc = 3 - 5 MPa. Stable operation and a C-star efficiency of 0.93 were attained in the ramjet mode operation at O/F = 4.5 - 7 and Pc= 0.6. This stable operation was attained by supplying oxygen from two, three or four of eight injectors. The C-star efficiency was 0.94 with four oxygen injector elements at O/F = 0.89, and 0.92 with three oxygen injector elements at O/F = 0.49. No thermal damage was observed on the oxygen post and faceplate with flush face oxygen post in all operating conditions. The fundamental design of the rocket chamber and injector for the combined-cycle engine was completed in this study.

Fuel injection apparatus for internal combustion engine

Abstract: A fuel injection valve has a sac chamber filled with high-pressure gaseous fuel, an injection hole communicated with the sac chamber, and a nozzle needle that slidably moves to allow and interrupt a supply of the high-pressure gaseous fuel into the sac chamber. The fuel injection valve performs an injection of the high-pressure gaseous fuel directly into a combustion chamber of the internal combustion engine in accordance with a movement of the nozzle needle. The injection hole has an outlet portion with a divergently formed inner surface as coming toward an outlet end of the injection hole. The driving portion controls the movement of the nozzle needle to change a sac chamber pressure of the high-pressure gaseous fuel in the sac chamber so as to switch a jet flow speed of the high-pressure gaseous fuel injected through the injection hole between a subsonic speed and a supersonic speed.

Parameter study of the axisymmetric hydromechanical deep drawing process

Abstract: In this paper, hydromechanical deep drawing and the effect of process parameters on the process have been studied using the finite element (FE) method. In order to verify the results of FE simulations, a study has also been carried out using experimental tooling. Numerical results indicate a working zone with a maximum chamber pressure in which the maximum limit drawing ratio (LDR) can be achieved and where the effect of chamber pressure on the process can be shown. Also, the effect of parameters such as initial chamber pressure, die profile radius, blank thickness, and friction effect has been investigated. It is shown that initial chamber pressure has an optimum value in which the maximum LDR can be achieved. Increasing the die profile radius increases the LDR at lower chamber pressures but has no marked effect at higher pressures. The numerical result also shows that increasing the friction between blank and die or blank and blank-holder decreases the LDR value, while increasing the friction between blank and punch increases the LDR value.

Reduction of Power Losses in Bearing Chambers Using Porous Screens Surrounding a Ball Bearing

Abstract: Trends in aircraft engine design have caused an increase in mechanical stress requirements for rolling bearings. Consequently, a high amount of heat is rejected, which results in high oil scavenge temperatures. An RB199 turbofan bearing and its associated chamber were modified to carry out a survey aiming to reduce power losses in bearing chambers. The test bearing was a 124 mm PCD ball bearing with a split inner ring employing under-race lubrication by two individual jets. The survey was carried out in two parts. In the first part, the investigations were focused on the impact on the power losses in the bearing chamber of the operating parameters, such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed. In the second part, the investigations focused on the reduction of the dwell time of the air and oil mixture in the bearing compartment and its impact on the power losses. In this part, porous screens were introduced around the bearing. These screens would aid the oil to flow out of the compartment and reduce droplet-droplet interactions as well as droplet-bearing chamber wall interactions. The performance of the screens was evaluated by torque measurements. A high-speed camera was used to visualize the flow in the chamber. Considerable reduction in power loss was achieved. This work is part of the European Research programme GROWTH ATOS (Advanced Transmission and Oil Systems).

Apparatus and method for dispensing frozen carbonated beverages

Abstract: Frozen carbonated beverage apparatus and method is illustrated, and has a freeze chamber in which beverage is frozen wherein the addition of beverage to the freeze chamber is controlled in response to pressure in the freeze chamber. Controlling the addition of unfrozen beverage to the freeze chamber in response to the pressure provides a method of controlling the beverage in the freeze chamber. As freeze chamber pressure falls to a pre-determined lower pressure, beverage is added to the freeze chamber until a pre-determined upper pressure. Beverage may be added to the freeze cylinder at a rate that matches the cooling rate of the beverage within the freeze chamber so that unfrozen beverage added to the freeze chamber is rapidly frozen and does not significantly alter the viscosity (consistency) of the frozen carbonated beverage.

Computational Simulation of High Enthalpy Arc Heater Flows

Abstract: The flowfields in segmented constrictor-type arc heaters are simulated using a new Navier-Stokes code named ARCFLO3. The validity of the radiation and turbulence modeling employed in ARCFLO3 is assessed by comparing the calculated results with the existing experimental data obtained in the 20 and 60 MW arcjet facilities at NASA Ames Research Center. Comparison is made between the calculated and the measured data for arc voltage, heater efficiency, mass-averaged enthalpy, chamber pressure, heat flux at wall, and total enthalpy in the centerline region of an arcjet flow

Indentation fracture of a-C:H thin films from chemical vapour deposition

Abstract: Thin films of a-C:H were produced by chemical vapour deposition from butene and butadiene gases on silicon. Hardness, elastic modulus and residual stress of the films vary depending on the voltage bias and chamber pressure during deposition. Films obtained with voltage bias of −200 V and chamber pressure of 8 Pa for the two precursor gases were analyzed. Film thicknesses were about 900 nm and hardness was 6.6 GPa for film from butadiene gas and 7.9 GPa for butene gas. Cube-corner and Berkovich indenters were used to produce indentation fracture on these films. Crack initiation, delamination and chipping were correlated to modifications of load versus displacement curves. Fractography of cracks was made by scanning electron microscopy and atomic force microscopy. Cracks generated by indentation with cube-corner and Berkovich indenters were compared. Delamination could be analyzed from the derivative of load versus displacement curves. Samples that present higher hardness values do not show chipping. Indent...

The effect of some instrument operating conditions on the x-ray microanalysis of particles in the environmental scanning electron microscope

Abstract: The objective of this investigation was to evaluate the practical effects of electron beam broadening in the environmental scanning electron microscope (ESEM) on particle x-ray microanalysis and to determine some of the optimum operating conditions for this type of analysis. Four sets of experiments were conducted using a Faraday cage and particles of copper, glass, cassiterite, andrutile. The accelerating voltage and chamber pressure varied from 20 to 10 kV and from 665–66 Pa (5.0 to 0.5 torr), respectively. The standard gaseous secondary electron detectors (GSED) and the long environmental secondary dectectors (ESD) for the ESEM were evaluated at different working distances. The effect of these parameters on the presence of artifact peaks was evaluated. The particles were mounted on carbon tape on an aluminum specimen mount and were analyzed individually and as a mixture. Substrate peaks were present in almost all of the spectra. The presence of neighboring particle peaks and the number of counts in these depended upon the operating conditions. In general, few of these peaks were observed with the long ESD detector at 19 mm working distance and at low chamber pressures. More peaks and counts were observed with a deviation from these conditions. The most neighboring peaks and counts were obtained with the GSED detector at 21.5 mm working distance, 10 kV accelerating voltage, and 665 Pa (5.0 torr) chamber pressure. The results of these experiments support the idea that the optimum instrumental operating conditions for EDS analysis in the ESEM occur by minimizing the gas path length and the chamber water vapor pressure, and by maximizing the accelerating voltage. The results suggest that the analyst can expect x-ray counts from the mounting materials. These tests strongly support the recommendation of the manufacturer to use the long ESD detector and a 19 mm working distance for EDS analysis. The results of these experiments indicate that neighboring particles millimeters from the target may contribute x-ray counts to the spectrum.