X-ray scattering study of Ag/Si(111) buried interface structures

Hong, Hawoong; Aburano, R. D.; Lin, Deng-Sung; Chen, Haydn; Chiang, T.‐C.; Zschack, P.; Specht, E. D.

doi:10.1103/physrevlett.68.507

Cited by 53 publications

(22 citation statements)

References 13 publications

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“…Our experimental results differ from previously reported measurements 5,6 in which Ag films were deposited at about 320 K. 7 One possible reason for the contradiction is the difference in substrate temperature for the Ag deposition (320 K vs. 290 K). To confirm this, we prepared several samples at various substrate temperatures (290-370 K).…”

Section: Resultscontrasting

confidence: 99%

Interface Structure and Preferred Orientation of Ag/Si(111) Revealed by X-Ray Diffraction

et al. 1998

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We studied buried interface structures of Ag/Si (111) √ 3-Ag and Ag/Si(111)-(7 × 7) samples using grazing incidence X-ray diffraction with synchrotron radiation. We also measured the crystal orientation of the Ag overlayers of the samples. Of the numerous √ 3 structures, only boron-induced √ 3 structure has been detected in buried interfaces. We studied the buried interface superstructure of Ag(26 nm thick)/Si (111) √ 3-Ag, and detected a √ 3 fractional order reflection peak. This means that the √ 3 structure remained at the interface. Our results for the crystal orientation of the Ag overlayers of Ag/Si (111) √ 3-Ag showed that Ag{110}, Ag{100} and Ag{111} planes were grown on the surface. By measuring several samples prepared at various substrate temperatures, (290-370 K), we found a strong correlation between the appearance of interface √ 3 structure and the growth of the Ag{110} plane. In contrast, our results for the crystal orientation of the Ag overlayers of Ag(26 nm thick)/Si(111)-(7 × 7) showed that only the Ag{111} plane was grown on the surface.

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Section: Resultscontrasting

confidence: 99%

Interface Structure and Preferred Orientation of Ag/Si(111) Revealed by X-Ray Diffraction

et al. 1998

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“…The problem relates to more general issues concerning the differences between surface and interface structure. In particular, it is questionable whether the structure observed at monolayer coverages, which is accessible to many standard surface probes, is representative of the true interface between two materials [6]. The latter can only be studied with techniques that employ highly penetrating beams, such as x-ray diffraction and transmission electron microscopy (TEM).…”

mentioning

confidence: 99%

Structural transitions of theCaF2/Si(111) interface

1993

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We have used x-ray reflectivity and transmission electron microscopy to study the CaFi/SiCl 11) interface. The results are consistent with a reconstructed two-layer CaF interface which can be transformed to a diff'erent structure simply by increasing the thickness of the CaF2 overlayer. We are able to reconcile previous measurements of the interface structure and gain insight into the rich variety of phenomena that may be observed at heteroepitaxial interfaces.PACS numbers: 61.16. Bg, 68.35.Rh, 68.55.Jk CaF2/Si(lll) is a prototypical system for studying atomic and electronic structure at the ionic/covalent interface. As a consequence there has been a wide range of experiments aimed at determining the interface structure and a number of models have been proposed [1,2]. Despite this attention no consistent picture has emerged. Conflicting results have been attributed to differences in sample preparation and the varying sensitivity of experimental techniques [3][4][5]. The problem relates to more general issues concerning the differences between surface and interface structure. In particular, it is questionable whether the structure observed at monolayer coverages, which is accessible to many standard surface probes, is representative of the true interface between two materials [6]. The latter can only be studied with techniques that employ highly penetrating beams, such as x-ray diffraction and transmission electron microscopy (TEM). It is the structure of the buried interface that influences the electronic properties.In this Letter we present x-ray diffraction and TEM measurements of the CaFi/Sid 11) interface. The results are consistent with a reconstructed two-layer CaF interface between the top Si double layer and the "bulklike" CaF2 film. The interface structure is a metastable phase formed in the early stages of heteroepitaxy. By increasing the thickness of the CaF2 film it is possible to drive a transition to a single layer CaF interface. Our results are consistent with previous experiments and reconcile many of the differences in proposed interface models. The results indicate that the rich variety of phenomena observed at surfaces, e.g., reconstructions and phase transitions, may also be observed at buried interfaces.CaF2 was grown by molecular beam epitaxy (MBE) on well-oriented (miscut <0.5°) Si(lll) substrates in an ISA/Riber CBE 32P ultrahigh vacuum (UHV) system. The Shiraki etched Si substrates [7] were outgassed thoroughly and then heated to 880 °C to remove the protective oxide. Cooling to the growth temperature (720°C) routinely resulted in a sharp (7x7) reflection high-energy electron diffraction (RHEED) pattern. CaF2 was deposited by evaporation from an effusion cell at 1150°C. During deposition the pressure was typically ~1 xl0~^^ torr at a growth rate of ~ 1 CaF2 triple layer (TL) per 30 s. At 720 °C CaF2 films with a thickness of -7 TL's ( -22 A) were grown. This is below the critical thickness for strained layer growth (~12 TL's). The sample was then cooled to room temperature where, due t...

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“…7,14,15 Due to the lack of detailed structural data of the buried interface, it is not possible to offer a more fundamental understanding of the SBH at the Ag/Si interfaces; however, there are differences in buried interface structure. 27,44 Furthermore, growth, structure, morphology, 19,20,[24][25][26][27][28]45 and SBH distribution are distinctly different for each interface suggesting that these issues are intimately related. In that respect, one expects a similar behavior for other non reactive metals on Si since they all grow according to the Stranski-Krastanov mechanism and long-range atomic ordering appears to be limited due to structural and kinetic restraints.…”

Section: B Models For Schottky Barrier Formationmentioning

confidence: 99%

Inhomogeneous Schottky barriers at Ag/Si(111) and Ag/Si(100) interfaces

Weitering

Sullivan

Carolissen

et al. 1996

Journal of Applied Physics

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We have measured current-voltage and capacitance-voltage characteristics of epitaxial Si͑111͒7ϫ7-Ag, Si͑111͒͑ͱ3ϫͱ3͒R30°-Ag, Si͑100͒2ϫ1-Ag, and polycrystalline Ag/Si interfaces, using different doping levels for both n-and p-type silicon wafers. Our data strongly suggest that the Schottky barrier heights ͑SBHs͒ are spatially nonuniform. The distribution of local effective SBHs at the epitaxial interfaces is modeled by a summation of a single Gaussian, representing the spread in SBH for the majority of the contact, and two half-Gaussians which represent the high-and low-barrier tails of the full distribution. Despite the fact that the average SBHs of the epitaxial interfaces are hardly structure dependent, the SBH distributions are very broad and markedly different for each interface. The polycrystalline interfaces are characterized by a narrower SBH distribution centered at a substantially smaller mean. We argue that the electrical inhomogeneity is related to structural inhomogeneity at the interface which is a direct consequence of the kinetics and mode of growth of Ag on Si.

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X-ray scattering study of Ag/Si(111) buried interface structures

Cited by 53 publications

References 13 publications

Interface Structure and Preferred Orientation of Ag/Si(111) Revealed by X-Ray Diffraction

Interface Structure and Preferred Orientation of Ag/Si(111) Revealed by X-Ray Diffraction

Structural transitions of theCaF2/Si(111) interface

Inhomogeneous Schottky barriers at Ag/Si(111) and Ag/Si(100) interfaces

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