Adsorption and Desorption Kinetics for Chlorosilanes on Si(111) 7×7

1990 ◽  
Vol 204 ◽  
Author(s):  
P. Gupta ◽  
P.A. Coon ◽  
B.G. Koehler ◽  
M.L. Wise ◽  
S.M. George
Keyword(s):  
Activation Energy ◽  
Surface Coverage ◽  
Temperature Programmed Desorption ◽  
Desorption Kinetics ◽  
Sticking Coefficient ◽  
Temperature Dependent ◽  
Adsorption And Desorption ◽  
Desorption Activation Energy ◽  
Temperature Programmed ◽  
Sticking Coefficients

ABSTRACTThe adsorption and desorption kinetics for SiCl4 and SiCl2H2 on Si(111) 7×7 were studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. Both LITD and TPD experiments monitored SiCl2 as the main desorption product at 950 K at all coverages of SiCl4 and SiCl2H2 on Si(111) 7×7.HC1 desorption at 850 K and H2 desorption at 810 K were also observed following SiCl2H2 adsorption. Isothermal LITD measurements of SiCl4 and SiCl2H2) adsorption on Si(111) 7×7 revealed that the initial reactive sticking coefficient decreased with increasing surface temperature for both molecules. The temperature-dependent sticking coefficients were consistent with precursor-mediated adsorption kinetics. Isothermal LITD studies of SiC12 desorption revealed second-order SiCl2 desorption kinetics. The desorption kinetics were characterizedby a desorption activation energy of Ed = 67 kcal/mol and a preexponential of vd = 3.2 cm2/s. TPD studies observed that the HCI desorption yield decreased relative to H2 and SiCl2 desorption as a function of surface coverage following SiCl2H2 exposure. These results indicate that when more hydrogen desorbs as H2 at higher coverages, The remaining chlorine is forced to desorb as SiCl 2.

Adsorption of Styrene on Hydrochloric Acid-Modified Sepiolite

2012 ◽  
Vol 518-523 ◽  
pp. 2058-2063
Author(s):  
Zhao Du ◽  
Bin Bin Yang ◽  
Er Hong Duan ◽  
Bin Guo
Keyword(s):  
Activation Energy ◽  
Hydrochloric Acid ◽  
Surface Area ◽  
Temperature Programmed Desorption ◽  
Micropore Volume ◽  
Breakthrough Curves ◽  
Adsorption Capacities ◽  
Desorption Activation Energy ◽  
Temperature Programmed ◽  
Fixed Beds

In this work, the breakthrough curves of styrene in fixed beds packed separately with hydrochloric acid-modified sepiolite were determined. And the Temperature Programmed Desorption (TPD) method is applied to research the desorption activation energy on modified sepiolite and untreated sepiolite. The results showed that in compared with the original sepiolite, the hydrochloric acid-modified sepiolite had more surface basic groups, pore volume and higher surface area so that their adsorption capacities of styrene were improved. The sepiolite modified with 12% hydrochloric acid solution had more micropore volume and higher surface area than the other modified sepiolite, and thus its adsorption capacity of styrene was the highest. The activation energy for desorption of styrene on the modified is higher than on the original sepiolite, this show that using hydrochloric acid modified sepiolite can enhance its adsorption of styrene.

Adsorption and Decomposition of Trimethylarsenic on GaAs(100)

1988 ◽  
Vol 131 ◽  
Author(s):  
J. R. Creighton
Keyword(s):  
Activation Energy ◽  
Electron Irradiation ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Temperature Programmed Desorption ◽  
Methyl Radicals ◽  
Arsenic Compounds ◽  
Group V ◽  
Desorption Activation Energy ◽  
Temperature Programmed

ABSTRACTAlkylated arsenic compounds have shown some promise as alternatives to arsine as the group-V source gas for GaAs MOCVD. However, little is known about the fundamental chemical interactions of these compounds with the GaAs surface. We have investigated the adsorption and reactivity of trimethylarsenic (TMAs) on GaAs(100) using temperature programmed desorption (TPD), Auger electron spectroscopy, and LEED. For the exposures and temperatures studied, TMAs did not pyrolytically decompose on the GaAs(100). TPD results indicate that TMAs chemisorbs, apparently non-dissociatively, and desorbs ≅330 K. Multilayers of TMAs desorb ≅140–160 K. Exposure of adsorbed TMAs to 70 eV electrons results in irreversible decomposition of the molecule. After electron irradiation, TPD shows that methyl radicals desorb at 660 K, which corresponds to a desorption activation energy of ≅40 kcal/mol. At higher temperatures, As2, H2, C2H2, and a smaller amount of methyl radicals desorb, and a small coverage of carbon remains on the surface.

Comparison of H2 Desorption Kinetics from Si(111)7×7 and Si(100)2×l

1990 ◽  
Vol 204 ◽  
Author(s):  
M. L. Wise ◽  
B. G. Koehler ◽  
P. Gupta ◽  
P. A. Coon ◽  
S. M. George
Keyword(s):  
Activation Energy ◽  
Preexponential Factor ◽  
Desorption Kinetics ◽  
Bond Energies ◽  
First Order ◽  
First Order Kinetics ◽  
Upper Limits ◽  
Desorption Activation Energy ◽  
Temperature Programmed ◽  
Kinetics Of

ABSTRACTThe desorption kinetics of hydrogen from the β1 H2 -TPD state on Si(111)7×7 and Si(100)2×l were studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. Isothermal LITD studies of H2 desorption from Si(111)7×7 revealed second-order kinetics with a desorption activation energy of Ed = 62 ±4 kcal/mol and a preexponential factor of Vd = 92 ±10 cm2 /s. In contrast, H2 desorption from Si(100)2×l revealed first-order kinetics with an activation energy of Ed = 58 ±2 kcal/mol and a preexponential factor of Vd = 5.5 ±0.5 × 1015 s−1. The desorption kinetics yield similar upper limits for the Si-H bond energies but different desorption mechanisms on Si(lll)7×7 and Si(100)2×l.

Adsorption and Decomposition of Diethylsilane on Silicon Surfaces

1990 ◽  
Vol 204 ◽  
Author(s):  
P.A. Coon ◽  
M.L. Wise ◽  
A.C. Dillon ◽  
M.B. Robinson ◽  
S.M. George
Keyword(s):  
Atomic Layer ◽  
Silicon Surfaces ◽  
Desorption Kinetics ◽  
Surface Species ◽  
Temperature Dependent ◽  
Hydrogen Elimination ◽  
Elimination Mechanism ◽  
Temperature Programmed ◽  
Sticking Coefficients ◽  
Kinetics Of

ABSTRACTDiethylsilane (DES), Si(C2H5)2H2, is a promising candidate for the atomic layer epitaxy of silicon. The adsorption and decomposition kinetics of DES on silicon surfaces were studied using laser-induced thermal desorption (LITD), temperature programmed desorption (TPD), and Fourier transform infrared (FTIR) spectroscopy. FTIR studies on porous silicon surfaces indicated that DES dissociatively adsorbs below 600 K and produces Si-H and Si-C2H5 surface species. The desorption products following DES adsorption on Si(111) 7×7 were C2H4 and H2 for all surface coverages using both LITD and TPD techniques. Ethylene and H2 desorption occurred at 700 and 810 K, respectively, during TPD experiments with a heating rate of β = 9 K/s. Ethylene desorption was consistent with a β-hydrogen elimination mechanism from the Si-C2H2 surface species. Isothermal LITD studies monitored the desorption kinetics of C2 H4 from Sl (111) 7×7 as a function of time following DES exposures. The first-order ethylene desorption kinetics were Ed = 36 kcal/mol and vd = 2.7 × 109 s−1. Additional LITD measurements determined that le initial reactive sticking coefficient of DES on Si(111) 7×7 decreased versus surface temperature. The temperature-dependent sticking coefficients suggested a precursormediated adsorption mechanism.

MONTE CARLO SIMULATION OF TEMPERATURE-PROGRAMMED DESORPTION CO/Cu(110) AND CO2/Cu(100) SYSTEMS

2004 ◽  
Vol 11 (02) ◽  
pp. 137-143 ◽  
Author(s):  
KH. ZAKERI ◽  
A. DASHTI
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Excellent Agreement ◽  
Temperature Programmed Desorption ◽  
High Order ◽  
Kinetics And Mechanism ◽  
Lateral Interaction ◽  
Desorption Rate ◽  
Temperature Programmed

In this investigation, we have studied the kinetics and mechanism of desorption of CO from the Cu (110) surface using a new Monte Carlo simulation and putting emphasis on high order lateral interaction. According to our simulated TPD spectra, for β=10 K/s the maximum desorption rate occurs at Tm=218.6 K. Furthermore, analysis of simulated TPD spectra of CO desorption shows that it is strongly lateral-interactive and results an activation energy of CO desorption from Cu (110) that is Ed=66.6 Kj/mol. These simulated results are compared with other reported results and show excellent agreement. After that we have investigated the kinetics and mechanism of desorption of CO 2 from the Cu (100) surface using a Monte Carlo simulation. According to our simulated TPD spectra, for β=0.5 K/s the maximum desorption rate occurs at Tm=89.7 K. Analysis of simulated TPD spectra of CO 2 desorption shows that it is not strongly lateral-interactive and results in an activation energy of CO desorption from Cu (100) that is Ed=25.2 Kj/mol. Finally, the CO / Cu (110) system is compared with the CO 2/ Cu (100) system.

Adsorption of Silicon Tetrachloride on Si(111) 7×7

1988 ◽  
Vol 131 ◽  
Author(s):  
P. Gupta ◽  
P. A. Coon ◽  
B. G. Koehler ◽  
S. M. George
Keyword(s):  
Surface Temperature ◽  
Thermal Desorption ◽  
Temperature Programmed Desorption ◽  
Silicon Tetrachloride ◽  
Sticking Coefficient ◽  
Adsorption Model ◽  
Temperature Programmed ◽  
Kinetics Of

ABSTRACTThe kinetics of SiCl4 adsorption on Si(lll) 7×7 were studied using laser induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The initial reactive sticking coefficient of SiCl4 on Si(lll) 7×7 was observed to decrease with increasing surface temperature. This decrease was consistent with a precursor-mediated adsorption model. Both LITD and TPD experiments monitored SiCl2 as the main desorption product. These results suggest that SiC12 may be the stable chlorine species on the Si(lll) 7×7 surface.

Thermal Stability of Z-Type Perfluoro Poly Ether Lubricant Polymers: A Combined Thermogravimetric and Temperature Programmed Desorption Study

2003 ◽  
Author(s):  
Paul M. Jones ◽  
Lei Li ◽  
Yiao-Tee Hsia
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Temperature Programmed Desorption ◽  
Kcal Mole ◽  
Three Samples ◽  
Desorption Study ◽  
Polymer Decomposition ◽  
Temperature Programmed ◽  
Decomposition Chemistry ◽  
Thermal Stability Of

The thermal stability of Zdol 4000, 7800 and Ztetraol perfluoropolyethers (PFPE) have been studied in both the bulk with thermogravimetric analysis (TGA) and in thin film form with temperature programmed desorption spectroscopy (TPD). The TGA results have been interpreted to yield an evaporation activation energy for both Zdol 4000 (13 kcal/mole) and Zdol 7800 (19 kcal/mole). A larger activation energy is also found for all three samples investigated that is consistent with polymer decomposition (22, 27 and 21 kcal/mole respectively). The TPD threshold has been found to be approximately similar all three samples (∼500 K). The temperature of decomposition was also found to be similar for all three samples and was dominated by the CF2O+ mass fragment at ∼660 K. Two desorption maximums were observed for both Zdol 4000 and Ztetraol indicating the similarity in their decomposition chemistry. In contrast only one desorption peak was observed from Zdol 7800 (675 K). A CF3+ fragment was not observed in any of the TPD spectra indicating the absence an acidic decomposition path for all of the Fomblin Z polymers studied.

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