Studies on H-terminated Si(100) surfaces by second-harmonic generation

Jiang, HB; Liu, Y-H.; Xz, Lu; Wang, WC; Jb, Zheng; Zm, Zhang

doi:10.1103/physrevb.50.14621

Cited by 7 publications

(8 citation statements)

References 14 publications

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“…18 Unlike reflectance-difference ͑-anisotropy͒ spectroscopy ͑RDS/RAS͒, 19 the surface specificity of second-harmonic generation ͑SHG͒ does not depend on surface anisotropy, and thus can be applied to isotropic surfaces such as the oriented double-domain Si͑001͒-2ϫ1 surface used in the present study. SHG and SFG on silicon have thus been shown to be highly sensitive to hydrogen adsorption, desorption, and diffusion kinetics, 13,20 surface structural phase transitions, 14,21,22 and temperature-dependent changes in vibrational 15 and electronic 16 surface spectra.…”

Section: Introductionmentioning

confidence: 98%

“…11-14 and 16͒ corresponding to the fundamental and frequency-doubled output of pulsed Nd:YAG lasers. In such studies, surface spectroscopic information is either lacking, or at best acquired indirectly through temperature variation of the band structure, 16 which simultaneously changes other surface properties. Moreover, the quantitative relation between the SH signal and hydrogen coverage can usually be established only over limited coverage ranges at these wavelengths ͑e.g., 0-0.15 ML with 1.06-m fundamental 13 ͒.…”

Section: Introductionmentioning

confidence: 99%

“…[11][12][13][14][15][16][17] Optical probes, unlike electron-beam probes, are unperturbed by ambient gases, and thus can monitor the H-Si surface in real time during homoepitaxial and heteroepitaxial growth 11,12 by CVD. Moreover for centrosymmetric materials like Si, the second-order nonlinear optical response, unlike the linear optical response ͑e.g., in ellipsometry or infrared absorption͒, includes a highly surface-specific electric dipole component, but contains no bulk electric dipole component.…”

Section: Introductionmentioning

confidence: 99%

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Second-harmonic spectroscopy of a Si(001) surface during calibrated variations in temperature and hydrogen coverage

Dadap

et al. 1997

Phys. Rev. B

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The epitaxial growth of silicon films by chemical vapor deposition ͑CVD͒ is strongly affected by temperature and hydrogen ͑H͒ termination. We report measurements of p-polarized optical second-harmonic ͑SH͒ spectra generated in reflection from clean 2ϫ1-reconstructed and H-terminated epitaxial Si͑001͒ surfaces with no intentional doping by Ti:sapphire femtosecond laser pulses for SH photon energies 3.0р2បр3.5 eV near the bulk E 1 resonance. Temperatures were varied from 200 to 900 K and H coverages from 0 to 1.5 monolayers ͑ML͒. Increases in temperature at fixed H-coverage redshift and broaden the E 1 resonance, as observed in linear bulk spectroscopy. Increases in H coverage from 0 to 1 ML at fixed temperature strongly quench, redshift, and distort the lineshape of the E 1 resonance even though reflection high-energy electron diffraction shows that the surface maintains the dimerized 2ϫ1 reconstruction. The latter spectroscopic variations cannot be explained by vertical strain relaxation in the selvedge region, nor by bulk electric-field-induced SH ͑EFISH͒ effects. We instead attribute these variations to a monohydride-induced surface chemical modification, which we parametrize as a surface EFISH effect because submonolayer H strongly alters surface electric fields by redistributing charge from surface dimers into the bulk. The effects of vertical strain relaxation are weakly evident as a blueshift of the E 1 resonance accompanying dihydride termination ͑1.0-1.5 ML͒, which breaks the surface dimer bond. This modification is parametrized as a separate field-independent alteration to the surface dipole susceptibility surface (2) . Finally, guided by these SH spectroscopic studies, we demonstrate dynamic real-time ͑100-ms resolution͒ SH monitoring of H coverage ͑5% accuracy͒ during temperature programmed hydrogen desorption and CVD epitaxial growth of silicon from disilane. ͓S0163-1829͑97͒07144-0͔

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Second-harmonic spectroscopy of a Si(001) surface during calibrated variations in temperature and hydrogen coverage

Dadap

et al. 1997

Phys. Rev. B

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“…AKT is the downstream target of PI3K, which controls angiogenesis and tumor growth. 53 The PTEN genesis is frequently mutated or inactivated in a high proportion of human cancers, including up to 30% of breast cancers, resulting in hyper-activation of the PI3K/Akt signaling pathway. 54 Increasing PTEN expression and down-regulating PTEN phosphorylation are important steps in retarding tumor growth.…”

Section: Western Blot Analysismentioning

confidence: 99%

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway

et al. 2014

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A series of imidazo[1,5-a]pyridine-benzimidazole hybrids (5a–aa) were prepared and evaluated for their cytotoxic activity against a panel of sixty human tumor cell lines. Among them compounds 5d and 5l showed significant cytotoxic activity with GI50 values ranging from 1.06 to 14.9 μM and 0.43 to 7.73 μM, respectively. Flow cytometric analysis revealed that these compounds arrest the cell cycle at G2/M phase and induced cell death by apoptosis. The tubulin polymerization assay (IC50 of 5d is 3.25 μM and 5l is 1.71 μM) and immunofluorescence analysis showed that these compounds effectively inhibited the microtubule assembly in human breast cancer cells (MCF-7). Further, the apoptotic effects of compounds were confirmed by Hoechst staining, mitochondrial membrane potential, cytochrome c release, ROS generation, caspase 9 activation and DNA fragmentation analysis. After treatment with these compounds for 48 h, p-PTEN and p-AKT levels were markedly decreased. Moreover, these compounds did not significantly inhibit the normal human embryonic kidney cells, HEK-293. The molecular docking simulations predicted the binding interactions of 5d and 5l with colchicine binding site of the tubulin, which is in compliance with the antiproliferative activity data.

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“…One of the most widespread applications of SHG has been the monitoring of adatom interactions with semiconductor surfaces, which underlie such key technological processes as epitaxial film growth and etching. For example, singlewavelength SHG has been used to monitor adsorption and desorption 43,54,141 -143 and surface diffusion 144 -147 of H, 54,55,143,148,149 Ge, 150 -152 B, 58 O, 43 Sb, 145,153 In, 146 Ga, 154 Cl 2 and XeF 2 155 on various semiconductor surfaces. Adsorbate effects on spectroscopic SHG have been reported for a few semiconductor surfaces, including H, 54 C 10 H 21 134 :Si(111) and H, 53 -55 Ge, 133 B, 58 Sb, 153 As 128 : Si(001).…”

Section: The Shg Spectra Of Adsorbate-covered Semiconductor Surfacesmentioning

confidence: 99%

Optical second harmonic spectroscopy of semiconductor surfaces: advances in microscopic understanding

Downer

Mendoza

Гавриленко³

2001

Surface & Interface Analysis

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Even-order non-linear optical spectroscopy has emerged as an unusually sensitive technique for noninvasive analysis of surfaces and buried interfaces of centrosymmetric materials. The forefront challenges are: to develop reliable microscopic computational methods for calculating and interpreting measured surface non-linear spectra; to relate non-linear surface spectra quantitatively to linear optical surface probes such as reflectance-difference spectroscopy (RDS); and to develop convenient methods for acquiring nonlinear optical spectra over bandwidths (several electron-volts) that encompass multiple electronic surface resonances. We review recent advances in both calculation and measurement of non-linear spectra, with emphasis on reconstructed and adsorbate-covered silicon surfaces in epitaxial growth environments.

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Studies on H-terminated Si(100) surfaces by second-harmonic generation

Cited by 7 publications

References 14 publications

Second-harmonic spectroscopy of a Si(001) surface during calibrated variations in temperature and hydrogen coverage

Second-harmonic spectroscopy of a Si(001) surface during calibrated variations in temperature and hydrogen coverage

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway

Optical second harmonic spectroscopy of semiconductor surfaces: advances in microscopic understanding

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