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.

Germanium Deposition on Silicon: Surface Chemistry of (CH3CH2)2GeH2 and GeC14

1992 ◽  
Vol 282 ◽  
Author(s):  
P. A. Coon ◽  
M. L. Wise ◽  
A. C. Dillon ◽  
S. M. George
Keyword(s):  
Porous Silicon ◽  
Surface Chemistry ◽  
Silicon Surface ◽  
Atomic Layer ◽  
Silicon Surfaces ◽  
Desorption Kinetics ◽  
Surface Species ◽  
Adsorption And Desorption ◽  
Controlled Deposition ◽  
Sticking Coefficients

ABSTRACTDiethylgermane, (CH3CH2)2GeH2, and germanium tetrachloride, GeCl4 may be useful precursors for chemical vapor deposition (CVD) or atomic layer controlled deposition of germanium. To explore the surface chemistry of these alternative precursors, the adsorption and desorption kinetics of (CH3CH2)2GeH2 (DEG) and GeCl4 on Si(111) 7×7 have been examined using laser-induced thermal desorption (LITD), and temperature programmed desorption (TPD) techniques. Fourier transform infrared (FTIR) spectroscopy has also been employed to monitor the decomposition of DEG on porous silicon surfaces. The FTIR spectra revealed that DEG dissociatively adsorbs on porous silicon surfaces at 200 K to form SiH, GeH, and SiCH2CH3 surface species. No spectral features were observed for GeCH2CH3 surface species. The TPD studies following DEG exposures on Si(111) 7×7 observed CH2=CH2 and H2 desorption products at 700 and 800 K, respectively. The production of CH2=CH2 (ethylene) was consistent with a βhydride elimination mechanism from surface ethyl species, i.e. SiCH2CH3(ad) → SiH(ad) + CH2=CH2 (g). Similar TPD experiments following GeCl4 exposures monitored the desorption of only SiCl2 at approximately 920 K. Desorption of SiCl2 indicates that the chlorine on GeCl4 has transferred to the silicon surface. Atomic Ge was also observed to desorb at 1200 K following both DEG and GeCl4 adsorption. LITD experiments measured initial reactive sticking coefficients of So ∼0.05 for DEG and So ∼1.0 for GeCl4 at 200 K. As expected from a precursor-mediated adsorption model, the sticking coefficients decreased versus increasing surface temperature. The sticking coefficients for these germanium containing precursors were higher than the corresponding sticking coefficients for (CH3CH2)2SiH2 and SiCl4. Possible recipes for the CVD or atomic layer controlled deposition of germanium on silicon can be proposed based on the surface chemistry and adsorption and desorption kinetics for DEG and GeCl4.

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.

Growth of SiO2 on Si(111)7×7 Using SiCl4 and H2O

1992 ◽  
Vol 282 ◽  
Author(s):  
Michael L. Wise ◽  
Lynne A. Okada ◽  
Peter A. Coon ◽  
Steven M. George
Keyword(s):  
Thermal Desorption ◽  
Atomic Layer ◽  
Reaction Scheme ◽  
Layer Growth ◽  
Silicon Surfaces ◽  
Surprising Result ◽  
Dangling Bond ◽  
Sequential Reaction ◽  
Temperature Programmed ◽  
Kinetics Of

ABSTRACTThe controlled atomic layer growth of SiO2 insulating layers on silicon surfaces might be achieved through the sequential reaction of SiCl4 and H2O:(A) Si-Cl + H2O → Si-OH + HCl(B) Si-OH + SiCl4 → Si-O-SiCl3 + HCl.To explore this ABAB… binary reaction scheme, laser-induced thermal desorption, temperature-programmed desorption, and Auger electron spectroscopy techniques were utilized to measure the kinetics of H2O oxidation of a Si(111)7×7 surface that had been previously subjected to a saturation SiCl4 exposure. Reaction kinetics studies for the oxidation of the chlorinated surface revealed that the rate of oxygen gain and the rate of chlorine loss were equal at reaction temperatures between 200 K and 700 K. These results were consistent with a direct substitution reaction according to:(A) Si-Cl + H2O → Si-OH + HCl.Above 700 K, the amount of oxygen gain became progressively greater than the amount of chlorine loss. This behavior was associated with the thermal desorption of H2 and the resultant formation of new dangling bond sites for H2O adsorption. For all temperatures, the oxidation kinetics of the chlorinated surface were nearly equivalent to the kinetics for the oxidation of clean silicon. This surprising result indicates that chlorine sites and free dangling bond sites react with equal probability to H2O. The kinetics of SiCl4 deposition were also measured on a Si(111)7×7 surface previously exposed to a saturation H2O dose. This chlorination reaction occurred at a much slower rate and was not as amenable to UHV studies.

Competitive Pairing and the Chemistry of Coadsorbed Hydrogen and Halogens on Ge(100)

1992 ◽  
Vol 282 ◽  
Author(s):  
Yuemei L. Yang ◽  
Stephen M. Cohen ◽  
Mark P. D'Evelyn
Keyword(s):  
Epitaxial Growth ◽  
Atomic Layer ◽  
Temperature Programmed Desorption ◽  
Model System ◽  
Atomic Layer Epitaxy ◽  
Desorption Kinetics ◽  
First Order ◽  
First Order Kinetics ◽  
Temperature Programmed ◽  
Kinetics Of

ABSTRACTThe chemistry of coadsorbed H and X (X=C1, Br) on semiconductor surfaces is important in epitaxial growth of silicon from chlorosilanes and of SixGe1−x alloys, in hydrogenating/ halogenating cycles in atomic layer epitaxy, and also provides an interesting model system, yet has received little attention to date. We have investigated the interaction of HC1 and HBr with Ge(100) by temperature-programmed desorption, and find that H2, HCl and HBr each desorb with near-first-order kinetics near 570–590 K and that GeCl2 and GeBr2 desorb with near-second-order kinetics near 675 K and 710 K, respectively. Analysis of the desorption kinetics of H2 and HX provides evidence that adsorbed H and X atoms pair preferentially in a qualitatively similar way as H atoms adsorbed alone on Ge(100)2×1 or Si(100)2×1 and that pairing of H+X occurs in competition with pairing of H+H.

scholarly journals Engineering of TMDC-OSC Hybrid Interfaces: The Thermodynamics of Unitary and Mixed Acene Monolayers on MoS2

2020 ◽  
Author(s):  
Stefan R. Kachel ◽  
Pierre Martin Dombrowski ◽  
Tobias Breuer ◽  
Michael Gottfried ◽  
Gregor Witte
Keyword(s):  
Monte Carlo ◽  
Molecular Mobility ◽  
Temperature Programmed Desorption ◽  
Model System ◽  
Desorption Kinetics ◽  
Temperature Programmed ◽  
Kinetics Of

Here, we use temperature-programmed desorption (TPD) and Monte Carlo (MC) simulations<br>of TPD traces to characterize the desorption kinetics of pentacene (PEN) and perfluoropentacene (PFP) on MoS2 as a model system for OSCs on TMDCs. We show that the monolayers of PEN and PFP are thermally stabilized compared to their multilayers, which allows to prepare nominal monolayers by selective desorption of multilayers. This stabilization is, however, caused by entropy due to a high molecular mobility rather than an enhanced molecule-substrate bond. Consequently, the nominal monolayers are not densely packed films.

scholarly journals Engineering of TMDC-OSC Hybrid Interfaces: The Thermodynamics of Unitary and Mixed Acene Monolayers on MoS2

2020 ◽  
Author(s):  
Stefan R. Kachel ◽  
Pierre Martin Dombrowski ◽  
Tobias Breuer ◽  
Michael Gottfried ◽  
Gregor Witte
Keyword(s):  
Monte Carlo ◽  
Molecular Mobility ◽  
Temperature Programmed Desorption ◽  
Model System ◽  
Desorption Kinetics ◽  
Temperature Programmed ◽  
Kinetics Of

Here, we use temperature-programmed desorption (TPD) and Monte Carlo (MC) simulations<br>of TPD traces to characterize the desorption kinetics of pentacene (PEN) and perfluoropentacene (PFP) on MoS2 as a model system for OSCs on TMDCs. We show that the monolayers of PEN and PFP are thermally stabilized compared to their multilayers, which allows to prepare nominal monolayers by selective desorption of multilayers. This stabilization is, however, caused by entropy due to a high molecular mobility rather than an enhanced molecule-substrate bond. Consequently, the nominal monolayers are not densely packed films.

Decomposition of Alkylsilanes on Silicon Surfaces Using Transmission Ftir Spectroscopy

1991 ◽  
Vol 222 ◽  
Author(s):  
A. C. Dillon ◽  
M. B. Robinson ◽  
M. Y. Han ◽  
S. M. George
Keyword(s):  
Porous Silicon ◽  
Silicon Surface ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Silicon Surfaces ◽  
Surface Species ◽  
Reaction Products ◽  
Molecular Precursors ◽  
Hydride Elimination

ABSTRACTFourier transform infrared (FTIR) transmission spectroscopy was used to monitor the decomposition of alkylsilanes such as diethylsilane (DES) [(CH3 CH2)2SiH2], di-t-butylsilane (DTBS) [((CH3)3C)2SiH2] and ethylsilane (ES) [CH3CH2SiH3 on high-surface-area porous silicon samples. The FTIR spectra revealed that tKe akylsilanes dissociatively adsorb on porous silicon at 300 K to form SiH and Si-alkyl species. As the silicon surface was progressively annealed, the Si-alkyl species decomposed and produced gas phase ethylene (DES,ES) or isobutylene (DTBS). The decomposition of the alkyl group was accompanied by the growth of additional SiH surface species. These reaction products were consistent with a [β-hydride elimination reaction. Above 700 K, the SiH surface species decreased concurrently with the desorption of H2 from the porous silicon surface. The uptake of surface species was also monitored at various adsorption temperatures to determine the optimal exposure temperatures for carbon-free silicon deposition. Carbon contamination was not detected at adsorption temperatures below 640 K prior to H2 desorption. Because the alkylsilane adsorption process is self-limiting at temperatures below 640 K, alkylsilanes may be useful molecular precursors for the atomic layer epitaxy (ALE) of silicon.

Comparison of Trichlorosilane and Trichlorogermane Decomposition on Silicon Surfaces Using FTIR Spectroscopy

1992 ◽  
Vol 282 ◽  
Author(s):  
A. C. Dillon ◽  
M. B. Robinson ◽  
S. M. George
Keyword(s):  
Porous Silicon ◽  
High Surface ◽  
High Vacuum ◽  
Atomic Layer ◽  
Layer Growth ◽  
Ultra High Vacuum ◽  
Silicon Surfaces ◽  
Absorption Feature ◽  
Surface Species ◽  
Thermal Stabilities

ABSTRACTFourier transform infrared (FTIR) transmission spectroscopy was used to compare the decomposition of trichlorosilane (SiHCl3) and trichlorogermane (GeHCl3) on silicon surfaces. Chlorosilanes, such as SiHCl3 are employed in silicon chemical vapor deposition (CVD). Chlorosilanes and chlorogermanes are also possible molecular precursors for the controlled atomic layer growth of silicon and germanium. GeHCl3 may be useful for the deposition of germanium on silicon surfaces and the growth of Si1−xGex heterostructures. The FTIR studies were performed in-situ in an ultra-high vacuum chamber on high surface area, porous silicon samples. The FTIR spectra revealed that SiHCl3 dissociatively adsorbs at 200 K to form SiH, SiClx, ClSiH and Cl2SiH surface species. The presence of ClxSiH species is revealed by ClxSiH stretching (2196 cm−1) and bending (775, 744 cm−1) vibrations. The presence of these modes indicates that there is incomplete decomposition of SiHCl3 upon adsorption at 200 K. GeHCl3 also dissociatively adsorbs at 200 K to form SiH and SiClx species. An infrared absorption feature in the Ge-H stretching region (1970–1995 cm−1) was not detected in the FTIR spectrum. The absence of a Ge-H absorption feature argues that there is a complete transfer of hydrogen from germanium to surface silicon atoms at 200 K. The thermal stabilities of the surface species were studied with annealing experiments. The Clx SiH formed upon initial SiHCl3 exposures at 200 K were observed to decompose between 200–590 K and form additional surface SiH and SiCl species. For both GeHCl3 and SiHCl3 dissociative adsorption on porous silicon, the SiCL. (x = 2 or 3) surface species were converted to silicon monochloride surface species between 200–600 K. In addition, SiH surface species were lost upon annealing between 680–780 K as H2 desorbed from the surface. The adsorption kinetics of SiHCl3 and GeHCl3 were also monitored on porous silicon at various isothermal temperatures. These experiments provide insight into the surface chemistry of chlorosilanes and chlorogermanes during CVD and atomic layer controlled growth.

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