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.

Ftir Studies of Water and Ammonia Decomposition on Silicon Surfaces

1990 ◽  
Vol 204 ◽  
Author(s):  
A.C. Dillon ◽  
P. Gupta ◽  
M.B. Robinson ◽  
A.S. Bracker ◽  
S.M. George
Keyword(s):  
Silicon Surface ◽  
Silicon Oxide ◽  
High Surface ◽  
High Vacuum ◽  
High Surface Area ◽  
Ftir Spectra ◽  
Ultra High Vacuum ◽  
Silicon Surfaces ◽  
Surface Species ◽  
Surface Hydrogen

ABSTRACTFourier transform infrared (FTIR) transmission spectroscopy. was used to monitor the decomposition of H2O (D2O) and NH3(ND3) on silicon surfaces. Experiments were performed in-situ in an ultra-high vacuum (UHV) chamber using high surface area poroussilicon samples. The FTIR spectra revealed that H2O dissociates upon adsorption at 300K to form SiH and SiNH2 surface species. NH3 also issociates upon adsorption at 300 K to form SiH and SiOH2 species. Silicon samples with saturation exposures of H2O and NH3 were progressively annealed from 300 K to 860 K. The FTIR spectra of an H2O-saturated silicon surface revealed that the SiOH species decomposed to form a silicon oxide species and additional surface hydrogen between 460 K and 580 K. Likewise, the SiNH2 species decomposed between 540 K and 660 K to produce silicon nitride and additional surface hydrogen. In both cases, the Sill surface species decreased as H2 desorption from the silicon surface was observed above 700 K.

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.

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.

Effects of Hydrogen Coverage on Silicon Surface Reactivity

1992 ◽  
Vol 259 ◽  
Author(s):  
A.C. Dillon ◽  
M.B. Robinson ◽  
S.M. George ◽  
P. Gupta
Keyword(s):  
Porous Silicon ◽  
Silicon Surface ◽  
High Surface ◽  
Surface Cleaning ◽  
Surface Reactivity ◽  
Silicon Surfaces ◽  
Initial Surface ◽  
Hydrogen Passivation ◽  
Surface Species ◽  
Oxidation Rates

ABSTRACTHydrogen passivation of silicon surfaces plays an important role in silicon surface cleaning and preparation. To measure the effect of hydrogen passivation on silicon surface reactivity, Fourier transform infrared (FTIR) transmission spectroscopy was used to monitor the oxidation of silicon surfaces versus hydrogen coverage. Experiments were performed insitu in an ultrahigh vacuum (UHV) chamber using high surface area poroussilicon samples. Si-H stretching and bending vibrations and Si-O-Si stretching vibrations were employed to monitor the silicon surface species. Oxidation studies with O2 conducted versus various initial hydrogen coverages revealed that oxidation rates and apparent oxygen saturation levels on porous silicon decreased as a function of initial surface hydrogen coverage. Exceptional surface stability was observed when the porous silicon surface was passivated by both monohydride and dihydride surface species. In addition, new blue-shifted Si-H stretching and bending features were observed following the oxidation of partially hydrogen-passivated porous silicon which indicated the presence of Ox SiH species. Thermal annealing studies revealed that the thermal stability of these OxSiH species increased with increasing oxidation of the silicon surface. These results have important implications for silicon growth and surface cleaning because they indicate that hydrogen removal is more difficult when the silicon surface is contaminated with oxygen. These FTIR results have also been compared with earlier results of oxidation versus hydrogen coverage on Si(111) 7×7.

Functionalized Porous Silicon in a Simulated Gastrointestinal Tract: Modeling the Biocompatibility of a Monolayer Protected Nanostructured Material

2007 ◽  
Vol 1063 ◽  
Author(s):  
Daniel S. Albrecht ◽  
Jacob T. Lee ◽  
Nick Molby ◽  
Steven D. Rhodes ◽  
Hieu Minh Dam ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Porous Silicon ◽  
High Surface ◽  
High Surface Area ◽  
Surface Oxidation ◽  
Nanostructured Material ◽  
Synthetic Methods ◽  
Silicon Surfaces ◽  
Ambient Conditions ◽  
Chemical Attack

ABSTRACTOwing to its photoluminescent properties and high surface area, porous silicon (por-Si) has shown great potential toward a myriad of applications including optoelectronics, chemical sensors, biocomposite materials, and medical implants. However, the native hydride-termination is only metastable with respect to surface oxidation under ambient conditions. Por-Si samples oxidize and degrade even more quickly when exposed to saline aqueous environments. Borrowing from solution phase synthetic methods, a selection of hydrosilylation reactions has been recently reported for functionalizing organic groups onto oxide-free, hydride-terminated porous silicon surfaces. Monolayers, bound through direct silicon-carbon bonds, are produced via thermal, microwave, Lewis acid, and carbocation mediated pathways. All of these wet, benchtop methods result in the formation of stable monolayers which protect the underlying silicon surface from ambient oxidation and chemical attack. However, no direct comparison of monolayer stability resulting from these diverse mechanisms has been reported. A variety of alkyl monolayers were prepared on porous silicon using the diverse hydrosilylation routes describe above and then immersed into a sequence of simulated gastric and intestinal fluids to replicate the conditions of potential por-Si biosensors or medicinal delivery systems in the human gastrointestinal tract. Degradation of the organic monolayers and oxidation of the underlying por-Si surfaces were monitored using both qualitative and semiquantitative transmission mode Fourier transform infrared spectroscopy (FTIR). Our initial results indicate that methods employing chemical catalysts often incorporate these species within the monolayer as defects, producing less robust surfaces compared to catalyst-free reactions. Regardless, monolayer protected por-Si samples demonstrated superior durability as opposed to the unfunctionalized controls.

Atomic Layer Controlled Deposition of Al2O3 Films Employing Trimethylaluminum (TMA) and H2O Vapor

1993 ◽  
Vol 335 ◽  
Author(s):  
A. C. Dillon ◽  
A. W. Ott ◽  
S. M. George ◽  
J. D. Way
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Silicon Surfaces ◽  
Controlled Growth ◽  
Alumina Membranes ◽  
Passivation Layers ◽  
Controlled Deposition ◽  
High Dielectric

AbstractSequential surface chemical reactions for the controlled deposition of Al2O3 films were studied using transmission Fourier transform infrared spectroscopy (FTIR). Experiments were performed in situ in an ultrahigh vacuum UHV chamber using high surface area alumina membranes. Trimethylaluminum [Al(CH3)3] (TMA) and H2O vapor were employed sequentially in an ABAB... binary fashion to achieve atomic layer controlled growth. An optimal Al2O3 growth procedure was established that employed TMA/H2O exposures at .3 Torr and 500 K. The experiments revealed that each reaction was self-terminating and atomic layer controlled growth was dictated by the surface chemistry. The controlled deposition of Al2O3 may be employed on silicon surfaces for the formation of high dielectric gate and passivation layers.

Conformal ZnO coatings on high surface area silica gel using atomic layer deposition

2008 ◽  
Vol 516 (18) ◽  
pp. 6158-6166 ◽  
Author(s):  
J.A. Libera ◽  
J.W. Elam ◽  
M.J. Pellin
Keyword(s):  
Atomic Layer Deposition ◽  
Surface Area ◽  
Silica Gel ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Layer Deposition

High-Surface Area Ceria-Zirconia Films Prepared by Atomic Layer Deposition

2017 ◽  
Vol 147 (6) ◽  
pp. 1464-1470 ◽  
Author(s):  
Tzia Ming Onn ◽  
Sheng Dai ◽  
Jiayao Chen ◽  
Xiaoqing Pan ◽  
George W. Graham ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Layer Deposition ◽  
Zirconia Films

scholarly journals Boron Nitride as a Novel Support for Highly Stable Palladium Nanocatalysts by Atomic Layer Deposition

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 849 ◽  
Author(s):  
Matthieu Weber ◽  
Cassandre Lamboux ◽  
Bruno Navarra ◽  
Philippe Miele ◽  
Sandrine Zanna ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Atomic Layer Deposition ◽  
Photoelectron Spectroscopy ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Average Diameter ◽  
Transmission Electron Microscopy Analysis ◽  
Layer Deposition ◽  
Palladium Nanocatalysts

The ability to prepare controllable nanocatalysts is of great interest for many chemical industries. Atomic layer deposition (ALD) is a vapor phase technique enabling the synthesis of conformal thin films and nanoparticles (NPs) on high surface area supports and has become an attractive new route to tailor supported metallic NPs. Virtually all the studies reported, focused on Pd NPs deposited on carbon and oxide surfaces. It is, however, important to focus on emerging catalyst supports such as boron nitride materials, which apart from possessing high thermal and chemical stability, also hold great promises for nanocatalysis applications. Herein, the synthesis of Pd NPs on boron nitride (BN) film substrates is demonstrated entirely by ALD for the first time. X-ray photoelectron spectroscopy indicated that stoichiometric BN formed as the main phase, with a small amount of BNxOy, and that the Pd particles synthesized were metallic. Using extensive transmission electron microscopy analysis, we study the evolution of the highly dispersed NPs as a function of the number of ALD cycles, and the thermal stability of the ALD-prepared Pd/BN catalysts up to 750 °C. The growth and coalescence mechanisms observed are discussed and compared with Pd NPs grown on other surfaces. The results show that the nanostructures of the BN/Pd NPs were relatively stable up to 500 °C. Consequent merging has been observed when annealing the samples at 750 °C, as the NPs’ average diameter increased from 8.3 ± 1.2 nm to 31 ± 4 nm. The results presented open up exciting new opportunities in the field of catalysis.

Sign in / Sign up

Export Citation Format

Share Document