Structure of GaAs(100)-<i>c</i>(8×2) determined by scanning tunneling microscopy

Skala, S. L.; Hubacek, J. S.; Tucker, J. R.; Lyding, Joseph W.; Chou, S. G.; Cheng, K. Y.

doi:10.1103/physrevb.48.9138

Cited by 99 publications

(36 citation statements)

References 18 publications

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“…1(c)], respectively. 8,9 A later STM study by Xue et al supports the ␤2 model. 10 However, Cerdá et al analyzed the three models by means of quantitative low-energy electron diffraction (LEED) and their analysis showed preference for the ␤ model.…”

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confidence: 71%

STM observation of Ga -dimers on a GaAs(001)-c(8×2)-Ga surface

Sun

et al. 2004

Phys. Rev. B

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Using in situ scanning tunneling microscopy (STM) we have obtained high-resolution empty-state images exhibiting triple-protrusion rows on GaAs͑001͒-c͑8 ϫ 2͒-Ga surface. We assign the middle protrusion rows to the surface Ga dimers in the model proposed by Lee et al. [Phys. Rev. Lett. 85, 3890 (2000)]. The surface Ga dimers, which are responsible for the c͑8 ϫ 2͒ periodicity, are the key feature of the structure and have never been imaged in previous STM studies. The current study provides direct evidence for the model, while all other existing models can be readily excluded from our STM images.The GaAs͑001͒ surface is of technological interest since it is an excellent substrate for both homoepitaxial and heteroepitaxial growth required in the fabrication of GaAs-based devices. GaAs͑001͒ is also a prototype surface in semiconductor surface physics owing to the large variety of surface reconstructions observed under different preparation conditions. 1 Numerous experimental and theoretical studies have been performed since the type of reconstruction is expected to have significant impact on the quality of the epitaxial layers. 2 Existing knowledge on (001) surfaces of III-IV group semiconductors often leads to dimer-based reconstruction models. Strong evidence, 3-5 however, does suggest that some of these surfaces reconstruct in a more complicated way, one example being the GaAs͑001͒-c͑8 ϫ 2͒-Ga surface.Since the observation of the GaAs͑001͒-c͑8 ϫ 2͒-Ga surface by Jona in 1965, 6 various structure models have been proposed for this surface. The first model, ␤ [cf. Fig. 1(a)], was proposed by Frankel et al. based on their high-resolution electron energy loss spectroscopy analysis. 7 From their scanning tunneling microscopy (STM) observations, Biegelsen et al. and Skala et al. suggested the ␤2 model [cf. Fig. 1(b)]and As-rich model [cf. Fig. 1(c)], respectively. 8,9 A later STM study by Xue et al. supports the ␤2 model. 10 However, Cerdá et al. analyzed the three models by means of quantitative low-energy electron diffraction (LEED) and their analysis showed preference for the ␤ model. 11 Recently, Lee et al. identified a structure [cf. Fig. 1(e)] from their firstprinciples calculations and quantitative LEED analysis. 3 An independent study by Kumpf et al. using surface x-ray diffraction (XRD) with direct methods has led to a structure basically the same as the structure. 4,12 The structure is no longer based solely on dimers like the models proposed previously. Instead, it is characterized by a mixed structure of sp 2 -bonded and dimerized Ga atoms, where the Ga dimers exist in both the surface and subsurface Ga layers. Recent studies by XRD, 13 reflection high-energy electron diffraction, 14 and noncontact atomic force microscopy 15 have offered support for the model. However, we note that it is the Ga dimers that produce the c͑8 ϫ 2͒ periodicity 4 and these Ga dimers have never been imaged by STM, as pointed out by Mishima et al. 5 Imaging Ga atoms requires the STM to operate in empty-state mode, i.e., positively...

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confidence: 71%

STM observation of Ga -dimers on a GaAs(001)-c(8×2)-Ga surface

Sun

et al. 2004

Phys. Rev. B

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“…1(a)] has been supported by the I-V curve analysis of low-energy electron diffraction (LEED), 2 but was found to be energetically unstable. 3 On the other hand, although it appears that the two-dimer model [ Fig. 1(b)] 4 and the top As-dimer model [ Fig. 1(c)] 5 are consistent with scanning tunneling microscopy (STM) images, both models failed in LEED test.…”

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confidence: 85%

Structure analysis of the Ga-stabilizedGaAs(001)−c(8×2)surface at high temperatures

et al. 2002

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Structure of the Ga-stabilized GaAs(001)-c(8x2) surface has been studied using rocking-curve analysis of reflection high-energy electron diffraction (RHEED). The c(8x2) structure emerges at temperatures higher than 600°C, but is unstable with respect to the change to the (2x6)/(3x6) structure at lower temperatures. Our RHEED rocking-curve analysis at high temperatures revealed that the c(8x2) surface has the structure which is basically the same as that recently proposed by Kumpf et al. [Phys. Rev. Lett. 86, 3586 (2001)]. We found that the surface atomic configurations are locally fluctuated at high temperatures without disturbing the c(8x2) periodicity.

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“…Scanning tunneling microscopy (STM) images were interpreted as the β2 (4 х 2) structure [21,22]. A distinctly different model for a reconstructed Ga-rich GaAs (001) (4 х 2) surface was put forward in [23]. Another geometry referred to as β3 (4 х 2) in accordance with the generally accepted notation was proposed in [24] on the basis of STM images.…”

Section: Theoretical Approaches Employed In Polar Surface Investigationsmentioning

confidence: 99%