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Micron

Volume 30, Issue 1
February 1999
Pages 13-20

PII: S0968-4328(98)00040-7
Copyright © 1999 Elsevier Science Ltd. All rights reserved.

Observations of reversible and irreversible structural transitions of cobalt on Si (1 1 1) with LEEM

R. J. Phaneufa, , Y. Hongb, S. Horchb and P. A. Bennettb

a Department of Physics and Astronomy, University of Maryland and Laboratory for Physical Sciences, College Park, MD 20742-4111, USA
b Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA

Received 2 February 1998; revised 27 May 1998; accepted 2 June 1998. Available online 4 March 1999.

Abstract

We present real time images of the evolution of the structure of the Si (1 1 1) surface during the deposition of cobalt at elevated temperatures, acquired using low-energy electron microscopy. The system follows a sequence of coexisting ordered and disordered phases, consistent with two-dimensional eutectic behavior. Reversible temperature driven transitions are observed between the ordered Si (1 1 1)¯(7×7) reconstructed phase and a disordered lattice gas of Co-containing ring-clusters (RC), indicating a local equilibrium between these structures. Only irreversible temperature driven transitions from an ordered (7×7)-RC phase to the disordered phase are observed. The nucleation and growth of stable islands, mostly CoSi2, depletes the Co-rich (7×7) structure of Co, resulting in the formation and growth of adjacent regions of the Co-poor disordered "(1×1)"-RC phase.

Author Keywords: Surfaces; Surface phase transitions; Surface phase separation; Silicides; Electron microscopy; Low-energy electron microscopy

Article Outline

1. Introduction
2. Materials and methods
3. Results and discussion
4. Conclusions
Acknowledgements
References


 (87K)
Fig. 1. LEEM images of Si (1 1 1) acquired during the deposition of Co showing a progression of structural phases. Temperature T=735°C. Incident flux FCo=0.0018 ML/s. Incident energy Ei=3.6 eV. Normal incidence. Scale bar shows 1 m. (a) Co=0.00 ML, the uniform (7×7) reconstructed phase appears as light gray at these imaging conditions, (b) Co=0.02 ML. The disordered "(1×1)"-RC appears as black at these conditions, along step edges and (7×7) domain boundaries, (c) Co=0.04 ML, (d) Co=0.10 ML, (e) Co=0.11 ML. The ordered (7×7)-RC phase appears as dark gray at these conditions, (f) Co=0.14 ML, (g) Co=0.18 ML, "(1×1)"-RC depletion zones appear as black circles, (h) Co=0.22 ML,CoSi2 islands visible as white regions within black "(1×1)"-RC depletion zones.

(19K)
Fig. 2. (sqrt7×sqrt7)-LEED pattern observed for the region of the Co/Si (1 1 1) surface shown in Fig. 1. Co=0.22 ML. Temperature quenched down to near room temperature. (a) Ei=6.7 eV. Reciprocal unit meshes for (7×7) R±19.1° are shown by dashed and dot-dashed lines, (b) Ei=15.7  eV. Integer-order beams, corresponding to bulk Si (1 1 1) periodicity, are labeled. Normal incidence for both panels. The elliptical appearance of the pattern is an electron-optical artifact produced by the mode in which the "magnetic prism" was operated. The diffuse intensity results from inelastically scattered electrons.

(48K)
Fig. 3. LEEM images of Co/Si (1 1 1) for Co=0.04 ML during heating and cooling experiments, after incremental deposition of 0.004  ML. Scale bar shows 1 m, Ei=3.6 eV. Normal incidence. (a) T=768°C (heating), (b) T=806°C (heating), (c) T=816°C (heating), (d) T=827°C (heating), (e) T=816°C (cooling), (f) T=768°C (cooling).

(5K)
Fig. 4. Measured temperature at which (7×7) regions (white in Fig. 3) disappear on heating (solid circles) and reappear on cooling (open squares) versus Co coverage.

(63K)
Fig. 5. LEEM images showing the irreversible transition of the ordered (7×7)-RC to the disordered "(1×1)"-RC phase on heating and cooling. Scale bar shows 1 m. Co=0.13 ML for all images. Incident flux turned off. Incident energy and angle and field of view as in Fig. 3. (a) T=670°C (heating), (b) T=725°C (heating), (c) T=740°C (heating), (d) T=745°C (heating), (e) T=725°C (cooling), (f) T=670 °C (cooling).

(57K)
Fig. 6. LEEM images showing the disappearance of the "(1×1)"-RC phase and regrowth of the (7×7)-RC phase during the deposition of Co at a constant temperature. Scale bar shows 1 m. T=670°C. Incident flux is 0.0003 ML/s. (a) Elapsed deposition time, te=0 s, Co=0.130 ML, (b) te=37 s, Co=0.141 ML, (c) te=57 s, 0.147 ML, (d) te=77 s, Co=0.153 ML, (e) te=97 s, Co=0.159 ML, (f) te=117 s, Co=0.165 ML.

References

Bartelt, N.C. and Tromp, R.M., 1996. Low-energy electron microscopy study of step mobilities on Si (0 0 1). Phys. Rev. B 54, p. 11731.

Bartelt, N.C., Theis, W. and Tromp, R.M., 1996. Ostwald ripening of two-dimensional islands on Si (0 0 1). Phys. Rev. B 54, p. 11741.

Bauer, E., Mundschau, M. and Swiech, W., 1991. Low-energy electron microscopy of semiconductor surfaces. J. Vac. Sci. Technol. A 9, p. 1007. Abstract-INSPEC  | Full-text via CrossRef

Bauer, E., 1994. Low-energy electron microscopy. Rep. Prog. Phys. 57, p. 895. Abstract-INSPEC 

Bennett, P.A. and Webb, M.B., 1981. The Si (1 1 1) 7×7 to "(1×1)" transition. Surface Sci. 104, p. 74. Abstract-INSPEC 

Bennett, P.A., Copel, M., Cahill, D., Falta, J. and Tromp, R.M., 1992. Ring clusters in transition-metal¯silicon surface structures. Phys. Rev. Lett. 69, p. 1224. Abstract-INSPEC  | Full-text via CrossRef

Bennett, P.A., Devries, B., Robinson, I.K. and Eng, P.J., 1992. Layerwise reaction at a buried interface. Phys. Rev. Lett. 69, p. 2539. Abstract-INSPEC  | Full-text via CrossRef

Bennett, P.A., Cahill, D.G. and Copel, M., 1994. Initial precursor to silicide formation on Si (1 1 1)¯ (7×7). Phys. Rev. Lett. 73, p. 452. Abstract-INSPEC  | Full-text via CrossRef

Bennett, P.A., Lee, M.Y., Parikh, S.A., Würm, K. and Phaneuf, R.J., 1995. Surface phase transformations in the Ni/Si (1 1 1) system real time observations using LEEM and STM. J. Vac. Sci. Technol. A 13, p. 1728. Abstract-INSPEC  | Full-text via CrossRef

Chmelik, J., Veneklassen, L.H. and Marx, G., 1989. Comparing cathode lens configurations for low-energy electron microscopy. Optik 83, p. 155. Abstract-INSPEC 

Mundschau, M., Bauer, E. and Telieps, W., 1989. Atomic steps on Si (1 0 0) and step dynamics during sublimation studied by low-energy electron microscopy. Surface Sci. 223, p. 413. Abstract-INSPEC 

Nicolet, M.A. and Lau, S.S., 1983. Formation and characterization of transition-metal silicides. In: Einspruch, N. Editor, , 1983. VLSI Electronics: Microstructure Science 6 Academic Press, New York p. 330.

Phaneuf, R.J., Bartelt, N.C., Williams, E.D., Swiech, W. and Bauer, E., 1991. Low-energy electron microscopy investigations of orientational phase separation on vicinal Si (1 1 1) surfaces. Phys. Rev. Lett. 67, p. 2986. Abstract-INSPEC  | Full-text via CrossRef

Phaneuf, R.J., Bartelt, N.C., Williams, E.D., Swiech, W. and Bauer, E., 1992. Low-energy electron microscopy investigations of the domain growth of the (7×7) reconstruction on Si (1 1 1). Surface Sci. 268, p. 227. Abstract-INSPEC | Abstract-Compendex 

Phaneuf, R.J., Bartelt, N.C., Williams, E.D., Swiech, W. and Bauer, E., 1993. The crossover from metastable to unstable facet growth on Si (1 1 1). Phys. Rev. Lett. 71, p. 2284. Abstract-INSPEC  | Full-text via CrossRef

Phaneuf, R.J., Hong, Y., Horch, S. and Bennett, P.A., 1997. Two-dimensional phase separation for Co adsorbed on Si (1 1 1). Phys. Rev. Lett. 78, p. 4605. Abstract-INSPEC  | Full-text via CrossRef | APS full text

Phaneuf, R.J. et al., 1998, in preparation..

Reader, A.H., vanOmmen, A.H., Reis, P.J.W., Wolters, R.A.M. and Oostra, D.J., 1993. Transition metal silicides in silicon technology. Rep. Prog. Phys. 56, p. 1397. Abstract-INSPEC 

Swiech, W. and Bauer, E., 1991. The growth of Si on Si (1 0 0): a video-LEEM study. Surface Sci. 255, p. 219. Abstract-INSPEC | Abstract-Compendex 

Telieps, W. and Bauer, E., 1985. The (7×7) to (1×1) transition on Si (1 1 1). Surface Sci. 162, p. 163. Abstract-INSPEC 

Theis, W. and Tromp, R.M., 1996. Nucleation in Si (0 0 1) homoepitaxial growth. Phys. Rev. Lett. 76, p. 2770. Abstract-INSPEC  | Full-text via CrossRef | APS full text

Tu, K.N. and Mayer, J.W., 1978. Silicide formation Thin Films-Interdiffusion and Reactions. Wiley, New York p. 359.

Tung, R.T., 1992. Epitaxial CoSi2 and NiSi2 thin films. Materials Chem. Phys. 32, p. 107. Abstract-INSPEC | Abstract-Compendex 

Tung, R.T. and Batstone, J.L., 1988. Control of pinholes in epitaxial CoSi2 layers on Si (1 1 1). Appl. Phys. Lett. 52, p. 648. Abstract-INSPEC 

Veneklassen, L.H., 1991. Design of a spectroscopic low-energy electron microscope. Ultramicr. 36, p. 76.

Veneklassen, L.H., 1992. The continuing development of low-energy electron microscopy for imaging surfaces. Rev. Sci. Instrum. 63, p. 5513.

Weber, E., 1983. Transition metals in silicon. Appl. Phys. A 30, p. 1. Abstract-MEDLINE | Abstract-INSPEC | Abstract-Compendex 

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Micron
Volume 30, Issue 1
February 1999
Pages 13-20


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