IR Diagnostics of MOCVD Reaction Chemistry

1992 ◽  
Vol 282 ◽  
Author(s):  
Bruce H. Weiller
Keyword(s):  
Reaction Time ◽  
Gas Phase ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Flow Tube ◽  
Tube Reactor ◽  
Ftir Spectrometer ◽  
Ir Diagnostics ◽  
Trimethyl Aluminum ◽  
Phase Chemical

ABSTRACTThe gas-phase chemical reactions in the Metallorganic Chemical Vapor Deposition (MOCVD) of A1N and TiN have been studied using IR spectroscopy. The products formed from the reaction of trimethyl aluminum (TMA) and NH3 were compared to those from the reaction of TMAwith NF3 using a static gas-phase IR cell. Reaction with NH3 is rapid at 25 °C, and the IR spectrum of the product is consistent with the acid-base adduct (CH3)3Al-NH3. At 25 °C, no reaction between TMA and NF3 was observed. However, at 58 °C a slow reaction occurredto give (CH3)2AlF. The reaction of Ti(N(CH3)2)4 with NH3 was also studied using a flow-tube reactor with a sliding injector port that provides control over the reaction time between two reactive flows. By monitoring the disappearance of Ti(N(CH3)2)4 as a function of NH3 partial pressure and reaction time, we have obtained a preliminary estimate of the rate constant as ∼ 10−16 cm3 molecule−1 s−1 at 25 °C. This result confirms that the reaction is rapid even at room temperature and demonstrates the utility of the flow-tube reactor and FTIR spectrometer for studies of MOCVD chemistry.

Low Temperature CVD of TiN from Ti(NR2)4 and NH3: FTIR Studies of the Gas-Phase Chemical Reactions

1993 ◽  
Vol 335 ◽  
Author(s):  
Bruce H. Weiller
Keyword(s):  
Reaction Time ◽  
Gas Phase ◽  
Rate Constant ◽  
Chemical Vapor ◽  
Rate Limiting Step ◽  
Tube Reactor ◽  
Ftir Spectrometer ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Phase Chemical

AbstractThe gas-phase chemical reaction between Ti(NMe2)4 and NH3 is a critical step in the Metallorganic Chemical Vapor Deposition (MOCVD) of TiN at low temperatures. We have examined this reaction using a flow-tube reactor coupled to an FTIR spectrometer. A sliding injector provides control over the reaction time and the kinetics of reactive species can be measured as a function of the partial pressure of an added reagent. The disappearance of Ti(NMe2)4 was measured as a function of reaction time and NH3 pressure at 26°C. The resulting bimolecular rate constant is (1.1±0. 1) x 10-16 cm3molecules−1s−1 Dimethylamine is observed as a direct product from this reaction consistent with other studies. We have also measured the rate constant using ND3 and find a substantial isotope effect, kh/kd ≈2.4± 0.4. This indicates that H-atom transfer is involved in the rate limiting step. We show that these results can be explained by a mechanism comprised of transamination reactions with NH3.

Flow Tube Kinetics of Gas-Phase Cvd Reactions

1993 ◽  
Vol 334 ◽  
Author(s):  
Bruce H. Weiller
Keyword(s):  
Ir Spectra ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Rate Constant ◽  
Room Temperature ◽  
Flow Tube ◽  
Tube Reactor ◽  
Ftir Spectrometer ◽  
Kinetics Of ◽  
Phase Chemical

AbstractThis paper explores the use of a flow-tube reactor coupled to an FTIR spectrometer to study gas-phase chemical reactions in CVD systems. We show that our apparatus can generate reliable kinetics data by reproducing the literature rate constant for the reaction between O3 and isobutene. We present data from this apparatus on two technologically important systems: TiN from Ti(NMe2)4 (TDMAT) and NH3 and SiO2 from tetraethoxysilane (TEOS) and O3. The results presented include kinetics data for the reaction of Ti(NMe2)4 with NH3 and ND3 at room temperature and the IR spectra of the products from the reaction of TEOS with O3 at 175°C.

A gas-phase synthesis of Ag-centered phenylenediamine clusters

2020 ◽  
Vol 8 (30) ◽  
pp. 10325-10332
Author(s):  
Mengdi Guo ◽  
Baoqi Yin ◽  
Benben Huang ◽  
Haiming Wu ◽  
Zhixun Luo
Keyword(s):  
Gas Phase ◽  
Soft Landing ◽  
Flow Tube ◽  
Phase Synthesis ◽  
Gas Phase Synthesis ◽  
Tube Reactor

Gas-phase synthesis of Ag-centered phenylenediamine clusters is achieved by dual sources combined with a flow tube reactor, producing Raman-active soft-landing deposits.

scholarly journals Reaction of active nitrogen with oxygen

1967 ◽  
Vol 45 (22) ◽  
pp. 2837-2840 ◽  
Author(s):  
A. S. Vlastaras ◽  
C. A. Winkler
Keyword(s):  
Reaction Time ◽  
Oxygen Atom ◽  
Gas Phase ◽  
Rate Constant ◽  
Analytical Method ◽  
Order Rate Constant ◽  
Maximum Amount ◽  
Active Nitrogen ◽  
Tube Reactor ◽  
Different Levels

The maximum yields of oxygen atoms, estimated at different levels in a long-tube reactor by gas-phase "titration" with NO2, were equal for the reactions of active nitrogen with NO and O2. In this reactor, the maximum oxygen-atom production from the oxygen reaction, determined by the amount of N2O3 produced with excess NO2, was found to correspond to the NO "titration" value for the active nitrogen and not to the maximum amount of HCN produced in the active nitrogen – ethylene reaction. A second-order rate constant, [Formula: see text] [Formula: see text]was obtained for the active nitrogen – oxygen reaction.Experiments in a short reactor showed that the validity of the analytical method based on the trapping of N2O3 depended upon adequate reaction time for the NO + NO2 reaction to occur.

scholarly journals Newly observed peroxides and the water effect on the formation and removal of hydroxyalkyl hydroperoxides in the ozonolysis of isoprene

2013 ◽  
Vol 13 (11) ◽  
pp. 5671-5683 ◽  
Author(s):  
D. Huang ◽  
Z. M. Chen ◽  
Y. Zhao ◽  
H. Liang
Keyword(s):  
Experimental Evidence ◽  
Gas Phase ◽  
Chemical Processes ◽  
Flow Tube ◽  
Tube Reactor ◽  
Criegee Intermediates ◽  
Long Lifetime ◽  
Laboratory Investigations ◽  
Range Of Values ◽  
Recent Laboratory

Abstract. The ozonolysis of alkenes is considered to be an important source of atmospheric peroxides, which serve as oxidants, reservoirs of HOx radicals, and components of secondary organic aerosols (SOAs). Recent laboratory investigations of this reaction identified hydrogen peroxide (H2O2) and hydroxymethyl hydroperoxide (HMHP) in ozonolysis of isoprene. Although larger hydroxyalkyl hydroperoxides (HAHPs) were also expected, their presence is not currently supported by experimental evidence. In the present study, we investigated the formation of peroxides in the gas phase ozonolysis of isoprene at various relative humidities on a time scale of tens of seconds, using a quartz flow tube reactor coupled with the online detection of peroxides. We detected a variety of conventional peroxides, including H2O2, HMHP, methyl hydroperoxide, bis-hydroxymethyl hydroperoxide, and ethyl hydroperoxide, and interestingly found three unknown peroxides. The molar yields of the conventional peroxides fell within the range of values provided in the literature. The three unknown peroxides had a combined molar yield of ~ 30% at 5% relative humidity (RH), which was comparable with that of the conventional peroxides. Unlike H2O2 and HMHP, the molar yields of these three unknown peroxides were inversely related to the RH. On the basis of experimental kinetic and box model analysis, we tentatively assigned these unknown peroxides to C2−C4 HAHPs, which are produced by the reactions of different Criegee intermediates with water. Our study provides experimental evidence for the formation of large HAHPs in the ozonolysis of isoprene (one of the alkenes). These large HAHPs have a sufficiently long lifetime, estimated as tens of minutes, which allows them to become involved in atmospheric chemical processes, e.g., SOA formation and radical recycling.

Gas Phase Adduct Reactions in MOCVD Growth of GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
A. Thon ◽  
T.F. Kuech
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Decomposition Temperature ◽  
Adduct Formation ◽  
Gas Phase Reactions ◽  
Flow Tube ◽  
Exponential Factor ◽  
First Order ◽  
Mocvd Growth ◽  
Tube Reactor

ABSTRACTGas phase reactions between trimethylgallium (TMG) and ammonia were studied at high temperatures, characteristic to MOCVD of GaN reactors, by means of insitu mass spectroscopy in a flow tube reactor. It is shown, that a very fast adduct formation followed by elimination of methane occurs. The decomposition of TMG and the adduct - derived compounds are both first order and have similar apparent activation energy. The pre-exponential factor of the adduct decomposition is smaller, and hence is responsible for the higher full decomposition temperature of the adduct relative to that of TMG.

scholarly journals The Caltech Photooxidation Flow Tube reactor: design, fluid dynamics and characterization

2017 ◽  
Vol 10 (3) ◽  
pp. 839-867 ◽  
Author(s):  
Yuanlong Huang ◽  
Matthew M. Coggon ◽  
Ran Zhao ◽  
Hanna Lignell ◽  
Michael U. Bauer ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Laminar Flow ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Reactor Design ◽  
Secondary Flows ◽  
Flow Profile ◽  
Flow Tube ◽  
Actual Performance ◽  
Tube Reactor

Abstract. Flow tube reactors are widely employed to study gas-phase atmospheric chemistry and secondary organic aerosol (SOA) formation. The development of a new laminar-flow tube reactor, the Caltech Photooxidation Flow Tube (CPOT), intended for the study of gas-phase atmospheric chemistry and SOA formation, is reported here. The present work addresses the reactor design based on fluid dynamical characterization and the fundamental behavior of vapor molecules and particles in the reactor. The design of the inlet to the reactor, based on computational fluid dynamics (CFD) simulations, comprises a static mixer and a conical diffuser to facilitate development of a characteristic laminar flow profile. To assess the extent to which the actual performance adheres to the theoretical CFD model, residence time distribution (RTD) experiments are reported with vapor molecules (O3) and submicrometer ammonium sulfate particles. As confirmed by the CFD prediction, the presence of a slight deviation from strictly isothermal conditions leads to secondary flows in the reactor that produce deviations from the ideal parabolic laminar flow. The characterization experiments, in conjunction with theory, provide a basis for interpretation of atmospheric chemistry and SOA studies to follow. A 1-D photochemical model within an axially dispersed plug flow reactor (AD-PFR) framework is formulated to evaluate the oxidation level in the reactor. The simulation indicates that the OH concentration is uniform along the reactor, and an OH exposure (OHexp) ranging from ∼ 109 to ∼ 1012 molecules cm−3 s can be achieved from photolysis of H2O2. A method to calculate OHexp with a consideration for the axial dispersion in the present photochemical system is developed.

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