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Journal of Physical Chemistry C
Volumn 111, Issue 11, 2007, Pages 4226-4234
Molecular self-assembly at bare semiconductor surfaces: Investigation of the chemical and electronic properties of the alkanethiolate-GaAs(001) interface
Author keywords

[No Author keywords available]
Indexed keywords

MOLECULAR SELF-ASSEMBLY; OCTADECANETHIOL; SEMICONDUCTOR SURFACES; TIME-OF-FLIGHT SECONDARY ION MASS SPECTROMETRY (TOF-SIMS);
EID: 34047274828     PISSN: 19327447     EISSN: 19327455     Source Type: Journal    
DOI: 10.1021/jp065173a     Document Type: Article
Times cited : (80)
References (110)
  • 75
    • 34047243783 scopus 로고    scopus 로고
    • The amount of time needed to mount the sample in the HRXPS spectrometer approximates the same amount of time taken to transfer samples from the NH 4OH solution into the glovebox where the sample is immediately exposed to a solution containing the SAM molecules
    • 4OH solution into the glovebox where the sample is immediately exposed to a solution containing the SAM molecules.
  • 76
    • 34047248017 scopus 로고    scopus 로고
    • Since the doublet identified in the Ga 3d spectra as the Ga oxide or surface component has a binding energy similar to that expected for a Ga-S component, we coarsely evaluated the As 3d and Ga 3d HRXPS weighted intensities to determine the relative concentrations. If we assume that As and Ga are oxidized to the same extent, then a comparison of the Ga oxide intensity minus that of the As oxide intensity reveals that the upper limit for the Ga-S bonds is 10-20% of all S-As/Ga bonds while As-S bonds make up the remainder, 80-90%.
    • Since the doublet identified in the Ga 3d spectra as the Ga oxide or surface component has a binding energy similar to that expected for a Ga-S component, we coarsely evaluated the As 3d and Ga 3d HRXPS weighted intensities to determine the relative concentrations. If we assume that As and Ga are oxidized to the same extent, then a comparison of the Ga oxide intensity minus that of the As oxide intensity reveals that the upper limit for the Ga-S bonds is 10-20% of all S-As/Ga bonds while As-S bonds make up the remainder, 80-90%.
  • 77
    • 34047270367 scopus 로고    scopus 로고
    • The S 2p doublet was fit with a 2:1 intensity ratio and a spin-orbit splitting of 1.18 eV.
    • The S 2p doublet was fit with a 2:1 intensity ratio and a spin-orbit splitting of 1.18 eV.
  • 81
    • 34047251797 scopus 로고    scopus 로고
    • We note that the ODT S 2p peaks are slightly broader (1.1 eV) than those of the DDT peaks (0.9 eV) and this can only mean a larger inhomogeneity of the adsorption site geometry and exact bonding conditions for the ODT film. Since the ODT film is densely packed, it can result in a stochastical, noncommensurate placing of the thiolate headgroup on the GaAs surface, resulting in a larger inhomogeneity of the respective adsorption sites as compared to the less densely packed DDT film
    • We note that the ODT S 2p peaks are slightly broader (1.1 eV) than those of the DDT peaks (0.9 eV) and this can only mean a larger inhomogeneity of the adsorption site geometry and exact bonding conditions for the ODT film. Since the ODT film is densely packed, it can result in a stochastical, noncommensurate placing of the thiolate headgroup on the GaAs surface, resulting in a larger inhomogeneity of the respective adsorption sites as compared to the less densely packed DDT film.
  • 93
    • 34047245580 scopus 로고    scopus 로고
    • Data not shown; see the Supporting Information
    • Data not shown; see the Supporting Information.
  • 95
    • 34047268704 scopus 로고    scopus 로고
    • We also note that, unlike the ODT and DDT SAMs, the Na 2S·9H2O treatment results in a nonuniform surface coating as seen by optical microscope imaging. Furthermore, initial Raman scans showed additional spurious peaks which gradually disappeared within 5-6 min of film formation and exposure to air. After approximately 5 min, the Na 2S·9H2O film reached a condition with invariant spectra. Our reported ILO/IL. ratios were determined after this point. Details are given in the Supporting Information
    • L. ratios were determined after this point. Details are given in the Supporting Information.
  • 102
    • 34047259634 scopus 로고    scopus 로고
    • This interpretation is different from the commensurate monolayer structure suggested by Nesher et al, see ref 25, where the thiolate molecules only bind to As atoms while the remaining Ga atoms are bound to interstitial oxygen atoms
    • This interpretation is different from the commensurate monolayer structure suggested by Nesher et al. (see ref 25), where the thiolate molecules only bind to As atoms while the remaining Ga atoms are bound to interstitial oxygen atoms.
  • 108
    • 34047253538 scopus 로고    scopus 로고
    • We note that a recent report of photoluminescence experiments on long chain alkanethiolate SAMs prepared on GaAs(001) by ambient-temperature solution deposition concluded there were only very small effects of the SAMs on the surface electronic properties compared to the native oxide; see ref 54. Again, however, since no detailed characterization data of the interfacial bonding and SAM structures were available, and a different electronic surface probe was used, direct comparisons and structure-property correlations are problematic
    • We note that a recent report of photoluminescence experiments on long chain alkanethiolate SAMs prepared on GaAs(001) by ambient-temperature solution deposition concluded there were only very small effects of the SAMs on the surface electronic properties compared to the native oxide; see ref 54. Again, however, since no detailed characterization data of the interfacial bonding and SAM structures were available, and a different electronic surface probe was used, direct comparisons and structure-property correlations are problematic.
  • 109
    • 34047252470 scopus 로고    scopus 로고
    • L. ratio decrease after SAM formation compared to the starting native oxide spectra. McGuiness, C. L.; Samarth, N.; Allara, D. L., unpublished results.
    • L. ratio decrease after SAM formation compared to the starting native oxide spectra. McGuiness, C. L.; Samarth, N.; Allara, D. L., unpublished results.

* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.