Chamber Wall Surfaces Research Articles

Study of heat loss mechanism in argon-circulated hydrogen engine combustion chamber wall surface conditions

Hydrogen fuel in internal combustion engine gives a very big advantage to the transportation sector especially in solving the greenhouse emission problem. However, there are only few research discovered the ability of argon as a working gas in hydrogen combustion in internal combustion engine. The high temperature rises from the argon compression tend to result in heat loss problem. This research aims to study the heat loss mechanism on wall surface condition in the combustion chamber. Experiments were conducted to study the effects of different heat flux sensor locations and the effect of ignition delay on heat flux. Local heat flux measurement was collected and images were observed using high speed shadowgraph images. The ignition delay that occurred near the combustion wall will result in larger heat loss throughout the combustion process. Higher ambient pressure results in a bigger amount of heat flux value. Other fundamental characteristics were obtained and discussed, which may help in contributing the local heat loss data of an argon-circulated hydrogen engine in future engine operation.

Active Radiative Liquid Lithium Divertor for Handling Transient High Heat Flux Events

The extreme heat flux anticipated in fusion reactor divertor plasma facing components (PFCs) is perhaps the most challenging technology issue for fusion energy development. Most divertor PFCs are designed based on the maximum steady-state operational limits. Application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and reduction in the divertor peak heat flux while maintaining essentially Li-free core plasma operation even during H-modes. These promising Li results in NSTX and related modeling calculations motivated the passive and active radiative liquid lithium divertor concepts (RLLD and ARLLD) (Ono et al. in Nucl Fusion 53:113030, 2013; Fusion Eng Des 89:2838, 2014). This radiative process has the desired effect of spreading the localized divertor heat load to the rest of the divertor chamber wall surfaces, facilitating divertor heat removal with relatively small amount of lithium ~ few moles/s to handle the expected steady-state high divertor heat load. However, in addition to the high steady-state heat flux, the fusion reactor divertor PFCs could also experience significant transient heat flux such as ELMs and/or other magnetic reconnection events which can deposit large transient heat flux onto the divertor PFCs. If unprotected, it could damage the divertor PFC surfaces which could lead to a highly undesirable unplanned shutdown for PFC repair and/or replacement. In this paper, we explore feasibility of LLD and ARLLD concepts in handling such transient heat flux to protect the divertor PFCs from the extreme transient heat flux while maintaining the normal plasma operations. We also suggest a possible implementation technique using inductive pellet injector for the reactor PFC protection from transient heat flux which can be tested on NSTX-U.

An energy model of droplet impingement on an inclined wall under isothermal and non-isothermal environments

The study of spray-wall interaction is of great importance to understand the dynamics that occur during fuel impingement onto the chamber wall or piston surfaces in internal combustion engines. It is found that the maximum spreading length of an impinged droplet can provide a quantitative estimation of heat transfer and energy transformation for spray-wall interaction. Furthermore, it influences the air-fuel mixing and hydrocarbon and particle emissions at combusting conditions. In this paper, an analytical model of different droplet-wall impingement conditions is developed in terms of βm (dimensionless maximum spreading length, the ratio of maximum spreading length to initial droplet diameter) to understand the detailed impinging dynamic process. These conditions are grouped as: a single diesel droplet impinging on the wall with different inclined angles (α); cold wall - heated droplet and heated wall - cold droplet impingement when inclined angle of the wall is 0°, respectively. The analytical model is built up based on the energy conservation that considers kinetic energy, gravitation energy, and surface energy before impingement, as well as viscous dissipation, gravitation energy, adhesion energy, deformation energy, and heat energy after impingement. The experimental work of diesel droplet impinging on an inclined wall is performed at a certain range of the Weber number (We of 33 to 420) with various inclined angles (α of 0° to 45°), while for inclined angle is 0°, droplet and wall temperature are varied from 25°C to 150°C to study the effects of the inclined angle and temperature on the temporal evolution of the post-impingement characteristics (i.e. droplet spreading length, dynamic contact angle). The analytical model is validated and evaluated at the aforementioned experimental operating points. The validated model can be employed to predict maximum spreading length of the droplet impinged on the wall. It is further utilized to determine the transition from capillary regime to kinetic regime, then to viscous regime at different inclined angle of the wall.

Investigation of the measurement characteristics of a multiple-ion-probe method for a propagating methane–oxygen–nitrogen flame

The multiple-ion-probe measurement method is a method to measure a propagating flame using ion probes installed on the wall surface of a combustion chamber. The dynamic behavior of the propagating flame along the wall surface can be regenerated from the dataset of flame signals from individual ion probes. Although this method only captures flames near the wall surface, the flame propagation behavior can be indirectly visualized. Because this method can attain very high temporal resolution, it can provide precise measurements of high-speed phenomena such as knocking in spark-ignition engines and detonation in detonation combustors. This study aimed to investigate the ability of a developed 64-channel multiple-ion-probe measurement system to characterize a propagating flame. To this end, three flames with substantially different propagation velocities were measured using the proposed multiple-ion-probe measurement system. During the experiments, methane–oxygen stoichiometric mixtures diluted with different amounts of nitrogen were used. The flame propagation velocity varied within the range of several m/s for a turbulent flame to 2.4 km/s for detonation by varying the dilution ratio of nitrogen. In the case where a mixture with a nitrogen mole fraction of 0.71 was used, a phenomenon of repeating stagnation and reacceleration of the propagating flame was observed. Furthermore, the phenomenon considered to be flame quenching was also observed near the wall. In the case of no dilution (nitrogen mole fraction = 0.00), multiple-ion probes with an installation interval of 1.5 mm indicated that the velocity fluctuated within the range of −500 m/s to +2000 m/s with respect to the Chapman–Jouguet detonation velocity of 2390 m/s. Experiments involving soot foil recording conducted in parallel confirmed that this velocity fluctuation was derived from the detonation cell structure and that micro-explosions in the detonation front could be captured using the multiple-ion-probe method.

Recombination coefficients for Cl on plasma-conditioned yttrium oxide chamber wall surfaces

Studies of power-modulated chlorine inductively coupled plasmas (ICPs) bounded by yttria-coated chamber walls are presented. Time-resolved optical emissions from Cl and Xe actinometry trace gas were recorded over the 740–920 nm region as power at 13.56 MHz was modulated between high power and no power. The intensity ratio of Cl-to-Xe emission, proportional to Cl number density, nCl, followed the modulation in power, allowing Cl heterogeneous loss coefficients, γCl, to be obtained from a simple time-resolved, 0-dimensional model of the afterglow period that best matched computed relative changes in nCl at the beginning and end of the powered period, with γCl as the only adjustable parameter. This approach only requires a treatment of diffusion and avoids complications introduced by attempting simulations of the full modulation period. Cl recombination coefficients were determined on the mostly yttria surfaces for Cl2 ICPs (a) immediately after NF3 plasma cleaning (γCl = 0.20), (b) during long exposure to the Cl2 plasma with no substrate bias (γCl = 0.11), and (c) during Si etching with substrate bias (γCl = 0.055-0.070). For Cl2/5% O2 ICPs, these values are 0.28, 0.17, and 0.030, respectively. These results compare favorably to qualitative behavior reported previously for continuous Cl2 and Cl2/O2 ICPs in this yttria-coated chamber.

Effects of Glow-Discharge Parameters on Silicon Coating Thickness Deposited on 316 Stainless Steel Samples

Silicon as a light element can be used as the tokamak first wall coating in order to protect the plasma from impurities which come from the wall. In this paper, we deposit an amorphous-silicon layer by the use of the glow discharge technique on the wall surface of the test chamber made from SS316. To do so, we employ silane as a source of silicon ions. The siliconization process is conducted at two time durations of 90 and 150 min. SEM image of the coated surface shows that the structure of the coated layer deposited by the 150-min is more compact in comparison with that of 90-min. Effect of current density on coating properties is evaluated by placing four samples at different locations on the wall surface which shows that the optimal values of current density are in the range of 14–20 μA/cm2 and the higher range of current density can damage the coating. The results confirm that by increasing the time of siliconization the coating thickness is increased successfully from 100 to 250 nm without appearance of any damage in coating.

Liquid lithium applications for solving challenging fusion reactor issues and NSTX-U contributions

Steady-state fusion reactor operation presents major divertor technology challenges, including high divertor heat flux both steady-state and transients. In addition, there are unresolved issues of long term dust accumulation and associated tritium inventory and safety concerns (Federici et al., 2001) [1]. It has been suggested that radiative liquid lithium divertor concepts with a modest lithium-loop could provide a possible solution for these outstanding fusion reactor technology issues, while potentially improving reactor plasma performance (Ono et al., 2013, 2014) [2,3]. The application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and reduction in the divertor peak heat flux while maintaining essentially Li-free core plasma operation even during H-modes. These promising results in NSTX and related modeling calculations motivated the radiative liquid lithium (LL) divertor (RLLD) concept (Ono et al., 2013) [2] and its variant, the active liquid lithium divertor concept (ARLLD) (Ono et al., 2014) [3], taking advantage of the enhanced non-coronal Li radiation in relatively poorly confined divertor plasmas. It was estimated that only a few moles/s of lithium injection would be needed to significantly reduce the divertor heat flux in a tokamak fusion power plant. By operating at lower temperatures ≤450°C than the first wall ∼600–700°C, the LL-covered divertor chamber wall surfaces can serve as an effective particle pump, as impurities generally migrate toward lower temperature LL divertor surfaces. To maintain the LL purity, a closed LL loop system with a modest circulating capacity of ∼1l/s (l/s) is envisioned to sustain the steady-state operation of a 1GW-electric class fusion power plant. By running the Li loop continuously, it can carry the dust particles and impurities generated in the vacuum vessel to outside where the dust/impurities are removed by relatively simple filter and cold/hot trap systems. Using a cold trap system, it can recover tritium (T) in real time from LL at a rate of ∼0.5g/s needed to sustain the fusion reaction while minimizing the T inventory. With an expected T fraction of ≤0.7%, an acceptable T inventory level can be achieved. In NSTX-U (Menard et al., 2012; Ono et al., 2015) [4,5], preparations are now underway to elucidate the physics of Li plasma interactions with a number of Li application tools and Li radiation spectroscopic instruments. The NSTX-U Li evaporator, which provides Li coating over the lower divertor plate, can offer important information on the RLLD concept, and the Li granule injector will test some of the key physics issues for the ARLLD concept. A LL loop is also being prepared off-line for prototyping future use on NSTX-U.

Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

Abstract. Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

Real-time dielectric-film thickness measurement system for plasma processing chamber wall monitoring

An in-situ real-time processing chamber wall monitoring system was developed. In order to measure the thickness of the dielectric film, two frequencies of small sinusoidal voltage (∼1 V) signals were applied to an electrically floated planar type probe, which is positioned at chamber wall surface, and the amplitudes of the currents and the phase differences between the voltage and current were measured. By using an equivalent sheath circuit model including a sheath capacitance, the dielectric thickness can be obtained. Experiments were performed in various plasma condition, and reliable dielectric film thickness was obtained regardless of the plasma properties. In addition, availability in commercial chamber for plasma enhanced chemical vapor deposition was verified. This study is expected to contribute to the control of etching and deposition processes and optimization of periodic maintenance in semiconductor manufacturing process.

10907 内部混合型回転デトネーションエンジンの成立条件に関する研究

In this study, operating conditions of a rotating detonation engine with internal mixing has been studied. Hydrogen and oxygen are supplied separately from gas storage tanks and mixed in an annular combustion chamber. The mixture is initiated by a spark discharge placed at the chamber wall surface. As a result, a strong deflagration after ignition is initially generated in the combustion chamber. The experimental results show that the following stages are involved to achieve stable propagation of the rotating detonation : i) a deflagration wave moves to the downstream, ii) a DDT process occurs in the downstream, iii) a detonation wave propagates in the upstream direction, iv) a rotating detonation is stabilized in the combustion chamber.

3D-CFD Code Based Numerical Analysis on Combustion Chamber Wall Surface Temperature Distributions in a Diesel Engine and their Effects on Heat Losses

3D-CFD Code Based Numerical Analysis on Combustion Chamber Wall Surface Temperature Distributions in a Diesel Engine and their Effects on Heat Losses

Active radiative liquid lithium divertor concept

Developing a reactor compatible divertor has been identified as a particularly challenging technology problem for magnetic confinement fusion. Application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and reduction in the divertor peak heat flux while maintaining essentially Li-free core plasma operation even during H-modes. These promising Li results in NSTX and related modeling calculations motivated the radiative liquid lithium divertor (RLLD) concept [1]. In the RLLD, Li is evaporated from the liquid lithium (LL) coated divertor strike point surface due to the intense heat flux. The evaporated Li is readily ionized by the plasma due to its low ionization energy, and the poor Li particle confinement near the divertor plate enables ionized Li ions to radiate strongly, resulting in a significant reduction in the divertor heat flux. This radiative process has the desired effect of spreading the localized divertor heat load to the rest of the divertor chamber wall surfaces, facilitating divertor heat removal. The modeling results indicated that the Li radiation can be quite strong, so that only a small amount of Li (∼a few mol/s) is needed to significantly reduce the divertor peak heat flux for typical reactor parameters. In this paper, we examine an active version of the RLLD, which we term ARLLD, where LL is injected in the upstream region of divertor. We find that the ARLLD has similar effectiveness in reducing the divertor heat flux as the RLLD, again requiring only a few mol/s of LL to significantly reduce the divertor peak heat flux for a reactor. An advantage of the ARLLD is that one can inject LL proactively even in a feedback mode to insure the divertor peak heat flux remains below an acceptable level, providing the first line of defense against excessive divertor heat loads which could result in damage to divertor PFCs. Moreover, the low confinement property of the divertor (i.e., <1ms for Li particle confinement time) makes the ARLLD response fast enough to mitigate the effects of possible transient events such as large ELMs.

Heat transfer coefficient on the combustion chamber wall surfaces in a naturally aspirated direct-injection diesel engine

Thin-film thermocouples were used to measure the instantaneous temperature at 100 points on all the combustion chamber wall surfaces in a naturally aspirated direct-injection diesel engine. Instantaneous heat flux at each measured point was also obtained through heat transfer analysis with the measured instantaneous wall surface temperature applied as a boundary condition. In addition, the instantaneous mass-averaged gas temperature in the combustion chamber was calculated through the equation of state of an ideal gas. As a result, the local and overall heat transfer coefficients were evaluated using the corresponding wall surface temperatures and heat fluxes. The overall heat transfer coefficients thus obtained were compared with those calculated with Eichelberg’s and Woschni’s empirical equations for five ignition timings and three engine speeds. As a result, it was revealed that an overall average heat transfer coefficient obtained through the authors’ experiments has characteristics different from those of the heat transfer coefficients calculated from the empirical equations proposed by Eichelberg and Woschni.

Recent progress in the NSTX/NSTX-U lithium programme and prospects for reactor-relevant liquid-lithium based divertor development

Developing a reactor-compatible divertor has been identified as a particularly challenging technology problem for magnetic confinement fusion. Application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and other plasma performance benefits. During the 2010 NSTX campaign, application of a relatively modest amount of Li (300 mg prior to the discharge) resulted in a ∼50% reduction in heat load on the liquid lithium divertor (LLD) attributable to enhanced divertor bolometric radiation. These promising Li results in NSTX and related modelling calculations motivated the radiative LLD concept proposed here. Li is evaporated from the liquid lithium (LL) coated divertor strike-point surface due to the intense heat flux. The evaporated Li is readily ionized by the plasma due to its low ionization energy, and the poor Li particle confinement near the divertor plate enables ionized Li ions to radiate strongly, resulting in a significant reduction in the divertor heat flux. This radiative process has the desired effect of spreading the localized divertor heat load to the rest of the divertor chamber wall surfaces, facilitating the divertor heat removal. The LL coating of divertor surfaces can also provide a ‘sacrificial’ protective layer to protect the substrate solid material from transient high heat flux such as the ones caused by the edge localized modes. By operating at lower temperature than the first wall, the LL covered large divertor chamber wall surfaces can serve as an effective particle pump for the entire reactor chamber, as impurities generally migrate towards lower temperature LL divertor surfaces. To maintain the LL purity, a closed LL loop system with a modest circulating capacity (e.g., ∼1 l s−1 for ∼1% level ‘impurities’) is envisioned for a steady-state 1 GW-electric class fusion power plant.

Feature profile evolution during shallow trench isolation etching in chlorine-based plasmas. III. The effect of oxygen addition

The effect of oxygen addition to chlorine plasma during shallow trench isolation etching is quantified in this work. Specifically, the electron density and the electron temperature in an electron cyclotron resonance reactor were characterized by a Langmuir probe and were found to remain relatively constant upon O2 addition. The silicon etching rates were found to increase with the square root of the ion energy, suggesting the etching reaction is limited by the momentum transfer from ions to the surface. A relatively small amount of oxygen addition (&amp;lt;10%) to the chlorine plasma simultaneously changes the reactor wall conditions and surface kinetics, since oxygen becomes actively involved in the surface reactions. The change in the chamber wall conditions and surface kinetics leads to the change in both the amount of etch products and the etched feature profile. The incorporation of oxygen on the surface results in a significant change of the etched surface morphology and its composition. This work suggests a small amount of O2 addition to Cl2 plasmas in shallow trench isolation etching changes the etching behavior primarily through modifying the kinetics on etched surfaces. A multiscale etch model consisting of translating mixed layer and Monte Carlo modules for bulk and feature scale etching, respectively, was successfully applied to this case, demonstrating good agreement with the experimental results.

Method for Determining Instantaneous Temperature at the Surface of Combustion Chamber Deposits in an HCCI Engine

Homogeneous charge compression ignition (HCCI) combustion is widely regarded as an attractive option for future high efficiency gasoline engines. HCCI combustion permits operation with a highly dilute, well mixed charge, resulting in high thermal efficiency and extremely low NOx and soot emissions, two qualities essential for future propulsion system solutions. Because HCCI is a thermokinetically dominated process, full understanding of how combustion chamber boundary thermal conditions affect the combustion process are crucial. This includes the dynamics of the effective chamber wall surface temperature, as dictated by the formation of combustion chamber deposits (CCD). It has been demonstrated that, due to the combination of CCD thermal properties and the sensitivity of HCCI to wall temperature, the phasing of autoignition can vary significantly as CCD coverage in the chamber increases. In order to better characterize and quantify the influence of CCDs, a numerical methodology has been developed which permits calculation of the crank-angle resolved local temperature profile at the surface of a layer of combustion chamber deposits. This unique predictor-corrector methodology relies on experimental measurement of instantaneous temperature underneath the layer, i.e., at the metal-CCD interface, and known deposit layer thickness. A numerical method for validation of these calculations has also been devised. The resultant crank-angle resolved CCD surface temperature and heat flux profiles both on top and under the CCD layer provide valuable insight into the near wall phenomena, and shed light on the interplay between the dynamics of the heat transfer process and HCCI burn rates.

Reducing the deposition of fat and protein covered particles with low energy surfaces

Deposition behavior of spray dried full cream milk, skim milk and whey particles were observed in a pilot scale dryer. Particle surface dominated with fats exhibit gradual decrease in deposition fluxes when transition from the initial adhesion to the subsequent cohesion mechanism. Whey protein, however, displayed significant differences in the adhesion and cohesion fluxes. Reduction of particle deposition on low energy chamber wall surface is more significant for the hydrophobic whey particles. Further analysis shows that the reduction in droplet–wall contact energy is larger for the more hydrophobic droplet, delineating weaker adhesion interaction. The results suggest that the hydrophobicity of the depositing particles in an important consideration when using lower chamber wall with lower surface energy. This is in addition to the effect of particle rigidity and deposition strength as reported previously.

Cl atom recombination on silicon oxy-chloride layers deposited on chamber walls in chlorine–oxygen plasmas

Chlorine atom recombination coefficients were measured on silicon oxy-chloride surfaces deposited in a chlorine inductively coupled plasma (ICP) with varying oxygen concentrations, using the spinning wall technique. A small cylinder embedded in the walls of the plasma reactor chamber was rapidly rotated, repetitively exposing its surface to the plasma chamber and a differentially pumped analysis chamber housing a quadruple mass spectrometer for line-of-sight desorbing species detection, or an Auger electron spectrometer for in situ surface analysis. The spinning wall frequency was varied from 800 to 30 000 rpm resulting in a detection time, t (the time a point on the surface takes to rotate from plasma chamber to the position facing the mass or Auger spectrometer), of ∼1–40 ms. Desorbing Cl2, due to Langmuir–Hinshelwood (LH) Cl atom recombination on the reactor wall surfaces, was detected by the mass spectrometer and also by a pressure rise in one of the differentially pumped chambers. LH Cl recombination coefficients were calculated by extrapolating time-resolved desorption decay curves to t = 0. A silicon-covered electrode immersed in the plasma was either powered at 13 MHz, creating a dc bias of −119 V, or allowed to electrically float with no bias power. After long exposure to a Cl2 ICP without substrate bias, slow etching of the Si wafer coats the chamber and spinning wall surfaces with an Si-chloride layer with a relatively small amount of oxygen (due to a slow erosion of the quartz discharge tube) with a stoichiometry of Si:O:Cl = 1:0.38:0.38. On this low-oxygen-coverage surface, any Cl2 desorption after LH recombination of Cl was below the detection limit. Adding 5% O2 to the Cl2 feed gas stopped etching of the Si wafer (with no rf bias) and increased the oxygen content of the wall deposits, while decreasing the Cl content (Si:O:Cl = 1:1.09:0.08). Cl2 desorption was detectable for Cl recombination on the spinning wall surface coated with this layer, and a recombination probability of γCl = 0.03 was obtained. After this surface was conditioned with a pure oxygen plasma for ∼60 min, γCl increased to 0.044 and the surface layer was slightly enriched in oxygen fraction (Si:O:Cl = 1:1.09:0.04). This behavior is attributed to a mechanism whereby Cl LH recombination occurs mainly on chlorinated oxygen sites on the silicon oxy-chloride surface, because of the weak Cl–O bond compared to the Cl–Si bond.

Study of OH-initiated degradation of 2-aminoethanol

Abstract. The degradation of 2-aminoethanol (MEA) by the hydroxyl radical (OH) was studied in the European Photoreactor (EUPHORE), a large outdoor environmental chamber. High-Temperature Proton-Transfer-Reaction Mass Spectrometry (HT-PTR-MS) and Fast Fourier Transform Infrared (FT-IR) were used to follow concentrations of reactants in the gas phase. Aerosol mass concentrations were tracked with Aerosol Mass Spectrometry (AMS). The chamber aerosol model MAFOR was applied to quantify losses of MEA to the particle phase. The rate constant k(OH + MEA) was determined relative to the rate constant of the 1,3,5-trimethylbenzene reaction with OH and was found to be (9.2 ± 1.1) × 10−11 cm3 molecule−1 s−1, and thus the reaction between OH radicals and MEA proceeds a factor of 2–3 faster than estimated by structure-activity relationship (SAR) methods. Main uncertainty of the relative rate determination is the unknown temporal behaviour of the loss rate of MEA to chamber wall surfaces during the sunlit experiments. Nucleation and growth of particles observed in the experiments could be reproduced by the chamber model that accounted for condensation of gaseous oxidation products, condensation of ethanolaminium nitrate and nucleation involving MEA and nitric acid.

Control of active nitrogen species used for PA-MBE growth of group III nitrides on Si

A new spiral parallel mesh electrode (PME) is presented to control active nitrogen species in plasma-assisted molecular beam epitaxial (PA-MBE) growth of group III nitrides and their alloys. Direct flux of active nitrogen from radio frequency inductive coupled plasma (rf-ICP) discharge was able to be measured using a mesh electrode for filtering charge particles and electron emission due to the self-ionization of nitrogen atoms on a negatively biased electrode. In situ measurement of direct nitrogen atom fluxes using the spiral PME during PA-MBE growth of GaN and AlN on Si substrates is investigated. A linear rf power dependence of direct flux of active species on atoms such as nitrogen (N+N⁎), where N and N⁎ were ground and excited atoms, respectively, from a rf-ICP was confirmed by the spiral PME. An indirect flux of nitrogen adsorbed (ADS) atoms (N+N⁎) during discharge was also monitored by the spiral PME and received influence of the wall surface of the growth chamber. ADS nitrogen atoms are able to be used for nitridation of Si surface to grow a double buffer layer (DBL) AlN/β-Si3N4/Si.