Structural studies of amorphous Ge-Au alloys

Edwards, Ann; Fairbanks, Mary C.; Newport, Robert J.

doi:10.1080/13642819108205950

Cited by 15 publications

(7 citation statements)

References 5 publications

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“…Furthermore, the Au that diffuses into the Ge layer satisfies the Ge dangling bonds in the void structure and the resulting reduction in free energy enhances the driving force for diffusion. Our observation of the formation of clusters of Au in the a-Ge layer is supported by the recent work of Edwards and co-workers 23 who have reported the formation of clusters of Au and intermetallic-type Au-Ge compound͑s͒ in an a-Ge matrix. The intermixing that occurs at the a-Ge/Au interface during annealing is conducive for the clustering of Au or possibly the formation of a metastable Au-Ge alloy on the a-Ge side of the interface.…”

Section: Discussionsupporting

confidence: 89%

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Au-mediated low-temperature solid phase epitaxial growth of a SixGe1−x alloy on Si(001)

Ramanath

Xiao

Lai

et al. 1996

Journal of Applied Physics

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The evolution of microstructure during Au-mediated solid phase epitaxial growth of a Si x Ge 1Ϫx alloy film on Si͑001͒ was investigated by in situ sheet resistance measurements, x-ray diffraction, conventional and high-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, and Rutherford backscattering spectrometry. Annealing amorphous-Ge/Au bilayers on Si͑001͒ to temperatures below 120°C caused changes primarily in the microstructure of the Au film. Near Ϸ130°C, Ge from the top layer diffused and crystallized along the grain boundaries of Au. The Ge that had reached the Au/Si ͑001͒ interface mixed with Si from the substrate, to form epitaxial Si x Ge 1Ϫx islands on Si ͑001͒. Si from the substrate had dissolved into Au before entering the growing epitaxial islands. Meanwhile, the Au that was displaced by Ge that filled the Au grain boundaries, diffused into the top layer along columnar voids in the amorphous Ge film. With increasing temperature, more Au was displaced to the top by the flux of Ge towards the substrate, facilitating further epitaxial growth and the coalescence of epitaxial Si x Ge 1Ϫx islands. At 310°C, the initial Au film was displaced completely to the top by a laterally continuous Si x Ge 1Ϫx epilayer of uniform composition ͑xϷ0.15͒. The epilayer thickness was limited by that of the initial Au film. Twins and residual amounts of Au trapped near the Si x Ge 1Ϫx /Si͑001͒ interface were the predominant defects observed in the completely strain-relaxed Si x Ge 1Ϫx epilayer.

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Section: Discussionsupporting

confidence: 89%

“…The observed temperature of Aumediated crystallization, is close to Ϸ0.6 T E ͑Au-Ge eutectic temperature-361°C͒ 20 in good agreement with earlier predictions. 24 The mechanism of Au-mediated crystallization may be related to the modification of the local structure of a-Ge 23 brought about by the presence of Au.…”

Section: Discussionmentioning

confidence: 99%

Au-mediated low-temperature solid phase epitaxial growth of a SixGe1−x alloy on Si(001)

Ramanath

Xiao

Lai

et al. 1996

Journal of Applied Physics

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“…Amorphous transition-metal-metalloid alloys are, for large ranges of concentration, composed of different amorphous phases [12][13][14][15][16][17][18][19][20][21][22][23][24], each with its own short-range order, a phenomenon called amorphous phase separation. Based on the two-phase model [8] with the two phases a-Cr 1−x A Si x A (≡phaseA) and a-Cr 1−x B Si x B (≡phaseB), in [1] the Seebeck coefficient of a-Cr 1−x Si x has been calculated with the approximation formula of [1] (equation (32) therein).…”

Section: Calculation Of the Seebeck Coefficient Of A-cr 1−x Si X Alloysmentioning

confidence: 99%

Thermoelectric power in alloys with phase separation (composites)

Sonntag¹

2009

J. Phys.: Condens. Matter

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A thermopower formula is derived for composites: [Formula: see text] (κ(i) and κ are the specific thermal conductivities, S(i) and S are the Seebeck coefficients of the phase i and the composite, respectively, and υ(i) is the volume fraction of the phase i). This formula can be applied for calculating the Seebeck coefficient (thermoelectric power) of amorphous transition-metal-metalloid alloys, for which amorphous phase separation occurs for large ranges of concentration. There are two contributions to S(i), a scattering term and a contribution due to electron transfer between the phases maintaining a common electrochemical potential μ. The theory predicts discontinuities in the concentration dependence of the Seebeck coefficient of metallic composites. It is argued that in amorphous composites these discontinuities occur very precisely at υ(i) = 1/3. This phenomenon can be used to characterize the crystallization kinetics of amorphous alloys. The theory is applied to a- Cr(1-x)Si(x) alloys for calculation of S versus x. Both the calculated S(x) dependence and the discontinuities agree very well with the experimental data, as long as x<0.67; the deviations at x>0.67 are interpreted to be caused by the p-d bonds at the phase boundaries.

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“…This subject has been investigated so intensively that it is impossible to give here a complete survey of all related studies of structure and transport properties of amorphous alloys in the vicinity of the MIT. Thus the following selection, listed according to the alloys investigated, contains merely the more important publications on low-temperature transport and, in some cases, structure: Ge-Al [27], Ge-Au [28][29][30], Ge-Co [31], Ge-Cu [32], Ge-Cr [31,[33][34][35], Ge-Fe [31,[36][37][38][39][40], Ge-Mn [31], Ge-Mo [40,41], Ge-Ni [31], Si-Au [42][43][44][45][46][47], Si-Cr [35,[48][49][50][51][52][53][54][55][56][57], Si-Fe [38,58,59], Si-Gd [60,61], Si-Mn [58,[62][63][64], Si-Nb …”

Section: Introductionmentioning

confidence: 99%

Metal–insulator transition in amorphous alloys

Möbius

1999

Current Opinion in Solid State and Materials Science

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We focus on the central problem of discriminating between metallic and insulating behaviour in amorphous alloys formed between a semiconductor and a metal. For this, the logarithmic temperature derivative of the conductivity, w = d ln σ/d ln T , has proved over recent years to be very helpful in determining the critical value x c of the metal content x for the metal-insulator transition (MIT). We show that, for various amorphous alloys, recent experimental results on w(T, x) are qualitatively inconsistent with the usual assumptions of continuity of the MIT at T = 0 and of σ(T, x c ) being proportional to a power of T . These results suggest that w(T, x c ) tends to 0 as T → 0, in which case the MIT should be discontinuous at T = 0 (but only there), in agreement with Mott's hypothesis of a finite minimum metallic conductivity. 71.30.+h,71.23.Cq, Typeset using REVT E X Abbreviations EDX: energy dispersive X-ray analysis MIT: metal-insulator transition MOSFET: metal oxide semiconductor field effect transistor RBS: Rutherford backscattering analysis

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Structural studies of amorphous Ge-Au alloys

Cited by 15 publications

References 5 publications

Au-mediated low-temperature solid phase epitaxial growth of a SixGe1−x alloy on Si(001)

Au-mediated low-temperature solid phase epitaxial growth of a SixGe1−x alloy on Si(001)

Thermoelectric power in alloys with phase separation (composites)

Metal–insulator transition in amorphous alloys

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