The Experts below are selected from a list of 18 Experts worldwide ranked by ideXlab platform

Koichiro Oshima - One of the best experts on this subject based on the ideXlab platform.

Rie Inoue - One of the best experts on this subject based on the ideXlab platform.

Webb, Lauren J. - One of the best experts on this subject based on the ideXlab platform.

  • High-Resolution Soft X-ray Photoelectron Spectroscopic Studies and Scanning Auger Microscopy Studies of the Air Oxidation of Alkylated Silicon(111) Surfaces
    'American Chemical Society (ACS)', 2006
    Co-Authors: Webb, Lauren J., Michalak, David J., Biteen, Julie S., Brunschwig, Bruce S., Chan, Ally S. Y., Knapp, David W., Meyer, Harry M., Nemanick, Eric J., Traub, Matthew C., Lewis, Nathan S.
    Abstract:

    High-resolution soft X-ray photoelectron spectroscopy was used to investigate the oxidation of alkylated silicon(111) surfaces under ambient conditions. Silicon(111) surfaces were functionalized through a two-step route involving radical chlorination of the H-terminated surface followed by alkylation with Alkylmagnesium Halide reagents. After 24 h in air, surface species representing Si^+, Si^(2+), Si^(3+), and Si^(4+) were detected on the Cl-terminated surface, with the highest oxidation state (Si^(4+)) oxide signal appearing at +3.79 eV higher in energy than the bulk Si 2p_(3/2) peak. The growth of silicon oxide was accompanied by a reduction in the surface-bound Cl signal. After 48 h of exposure to air, the Cl-terminated Si(111) surface exhibited 3.63 equivalent monolyers (ML) of silicon oxides. In contrast, after exposure to air for 48 h, CH_3-, C_2H_5-, or C_6H_5CH_2-terminated Si surfaces displayed

  • High-Resolution X-ray Photoelectron Spectroscopic Studies of Alkylated Silicon(111) Surfaces
    'American Chemical Society (ACS)', 2005
    Co-Authors: Webb, Lauren J., Michalak, David J., Biteen, Julie S., Brunschwig, Bruce S., Chan, Ally S. Y., Knapp, David W., Traub, Matthew C., Nemanick E. Joseph, Lewis, Nathan S.
    Abstract:

    Hydrogen-terminated, chlorine-terminated, and alkyl-terminated crystalline Si(111) surfaces have been characterized using high-resolution, soft X-ray photoelectron spectroscopy from a synchrotron radiation source. The H-terminated Si(111) surface displayed a Si 2p_(3/2) peak at a binding energy 0.15 eV higher than the bulk Si 2p_(3/2) peak. The integrated area of this shifted peak corresponded to one equivalent monolayer, consistent with the assignment of this peak to surficial Si−H moieties. Chlorinated Si surfaces prepared by exposure of H-terminated Si to PCl_5 in chlorobenzene exhibited a Si 2p_(3/2) peak at a binding energy of 0.83 eV above the bulk Si peak. This higher-binding-energy peak was assigned to Si−Cl species and had an integrated area corresponding to 0.99 of an equivalent monolayer on the Si(111) surface. Little dichloride and no trichloride Si 2p signals were detected on these surfaces. Silicon(111) surfaces alkylated with C_nH_(2n+1)^− (n = 1 or 2) or C_6H_5CH_2^− groups were prepared by exposing the Cl-terminated Si surface to an Alkylmagnesium Halide reagent. Methyl-terminated Si(111) surfaces prepared in this fashion exhibited a Si 2p_(3/2) signal at a binding energy of 0.34 eV above the bulk Si 2p_(3/2) peak, with an area corresponding to 0.85 of a Si(111) monolayer. Ethyl- and C_6H_5CH_2-terminated Si(111) surfaces showed no evidence of either residual Cl or oxidized Si and exhibited a Si 2p_(3/2) peak ∼0.20 eV higher in energy than the bulk Si 2p_(3/2) peak. This feature had an integrated area of ∼1 monolayer. This positively shifted Si 2p_(3/2) peak is consistent with the presence of Si−C and Si−H surface functionalities on such surfaces. The SXPS data indicate that functionalization by the two-step chlorination/alkylation process proceeds cleanly to produce oxide-free Si surfaces terminated with the chosen alkyl group

  • Chemical Characterization and Charge Carrier Dynamics of Crystalline Silicon(III) Surfaces Modified with Surface-Bound Organic Functional Groups
    2005
    Co-Authors: Webb, Lauren J.
    Abstract:

    Investigations of the chemical structure and charge carrier properties of alkylated crystalline silicon(111) surfaces are presented. Hydrogen-terminated Si(111) surfaces were alkylated with a series of saturated hydrocarbons through a chlorination/alkylation procedure and characterized using surface-sensitive techniques. High-resolution soft X-ray photoelectron spectroscopy (SXPS) identified 1 monolayer of H, Cl, and C on the H-, Cl- and CH3-terminated surfaces, respectively. Surfaces functionalized with bulkier alkyls showed Si 2p binding energy shifts that suggest that unalkylated Si atoms are bonded to hydrogen. Alkylated Si(111) surfaces were further characterized using transmission infrared spectroscopy (TIRS). The Si-Cl stretching and bending motions were identified at 583 and 528 cm-1, respectively. On the methyl-terminated Si(111) surface, a CH3 symmetrical bending vibrational mode at 1257 cm-1 polarized perpendicular to the surface was observed. On the C2H5-terminated surface, a Si-H stretching and bending motion at 2080 and 627 cm-1, respectively, were observed, confirming that unalkylated Si atoms are terminated with H atoms. Structural morphology of the CH3-terminated Si(111) surface was investigated by low energy electron diffraction (LEED), which found that this surface retained a flat, unreconstructed (1 x 1) structure. Scanning tunneling microscopy (STM) images of CH3-Si(111) were obtained at 4.7 and 77 K. The functionalized surface preserved the atomically flat morphology of freshly etched H-Si(111), and at 4.7 K individual methyl H atoms were clearly resolved for the first time. Electronic passivation of the alkylated Si(111) surface was investigated through measurement of surface charge carrier recombination velocities (S), through time-resolved radio frequency (rf) photoconductivity decay methods. While unpassivated H- and Cl-terminated surfaces reacted rapidly in an air ambient to yield S>1400 cm s-1, alkylated surfaces preserved S<200 cm s-1 even when exposed to air for a period of weeks. Finally, the two-step chlorination/alkylation route was compared to three other Si(111) surface functionalization techniques: (1) chlorination with Cl2(g) followed by alkylation with an Alkylmagnesium Halide reagent, (2) Lewis acid-mediated reduction of a terminal alkene, and (3) anodization of the H-terminated Si(111) surface in diethyl ether containing 3.0 M CH3MgI. The chemical properties and charge carrier recombination rates of each surface were measured as a function of time exposed to air.

Lewis, Nathan S. - One of the best experts on this subject based on the ideXlab platform.

  • High-Resolution Soft X-ray Photoelectron Spectroscopic Studies and Scanning Auger Microscopy Studies of the Air Oxidation of Alkylated Silicon(111) Surfaces
    'American Chemical Society (ACS)', 2006
    Co-Authors: Webb, Lauren J., Michalak, David J., Biteen, Julie S., Brunschwig, Bruce S., Chan, Ally S. Y., Knapp, David W., Meyer, Harry M., Nemanick, Eric J., Traub, Matthew C., Lewis, Nathan S.
    Abstract:

    High-resolution soft X-ray photoelectron spectroscopy was used to investigate the oxidation of alkylated silicon(111) surfaces under ambient conditions. Silicon(111) surfaces were functionalized through a two-step route involving radical chlorination of the H-terminated surface followed by alkylation with Alkylmagnesium Halide reagents. After 24 h in air, surface species representing Si^+, Si^(2+), Si^(3+), and Si^(4+) were detected on the Cl-terminated surface, with the highest oxidation state (Si^(4+)) oxide signal appearing at +3.79 eV higher in energy than the bulk Si 2p_(3/2) peak. The growth of silicon oxide was accompanied by a reduction in the surface-bound Cl signal. After 48 h of exposure to air, the Cl-terminated Si(111) surface exhibited 3.63 equivalent monolyers (ML) of silicon oxides. In contrast, after exposure to air for 48 h, CH_3-, C_2H_5-, or C_6H_5CH_2-terminated Si surfaces displayed

  • High-Resolution X-ray Photoelectron Spectroscopic Studies of Alkylated Silicon(111) Surfaces
    'American Chemical Society (ACS)', 2005
    Co-Authors: Webb, Lauren J., Michalak, David J., Biteen, Julie S., Brunschwig, Bruce S., Chan, Ally S. Y., Knapp, David W., Traub, Matthew C., Nemanick E. Joseph, Lewis, Nathan S.
    Abstract:

    Hydrogen-terminated, chlorine-terminated, and alkyl-terminated crystalline Si(111) surfaces have been characterized using high-resolution, soft X-ray photoelectron spectroscopy from a synchrotron radiation source. The H-terminated Si(111) surface displayed a Si 2p_(3/2) peak at a binding energy 0.15 eV higher than the bulk Si 2p_(3/2) peak. The integrated area of this shifted peak corresponded to one equivalent monolayer, consistent with the assignment of this peak to surficial Si−H moieties. Chlorinated Si surfaces prepared by exposure of H-terminated Si to PCl_5 in chlorobenzene exhibited a Si 2p_(3/2) peak at a binding energy of 0.83 eV above the bulk Si peak. This higher-binding-energy peak was assigned to Si−Cl species and had an integrated area corresponding to 0.99 of an equivalent monolayer on the Si(111) surface. Little dichloride and no trichloride Si 2p signals were detected on these surfaces. Silicon(111) surfaces alkylated with C_nH_(2n+1)^− (n = 1 or 2) or C_6H_5CH_2^− groups were prepared by exposing the Cl-terminated Si surface to an Alkylmagnesium Halide reagent. Methyl-terminated Si(111) surfaces prepared in this fashion exhibited a Si 2p_(3/2) signal at a binding energy of 0.34 eV above the bulk Si 2p_(3/2) peak, with an area corresponding to 0.85 of a Si(111) monolayer. Ethyl- and C_6H_5CH_2-terminated Si(111) surfaces showed no evidence of either residual Cl or oxidized Si and exhibited a Si 2p_(3/2) peak ∼0.20 eV higher in energy than the bulk Si 2p_(3/2) peak. This feature had an integrated area of ∼1 monolayer. This positively shifted Si 2p_(3/2) peak is consistent with the presence of Si−C and Si−H surface functionalities on such surfaces. The SXPS data indicate that functionalization by the two-step chlorination/alkylation process proceeds cleanly to produce oxide-free Si surfaces terminated with the chosen alkyl group

Hiroshi Shinokubo - One of the best experts on this subject based on the ideXlab platform.