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

• Published in: Micron (Oxford, England : 1993) Vol. 30; no. 1; pp. 13 - 20
• Main Authors: Phaneuf, R.J., Hong, Y., Horch, S., Bennett, P.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-02-1999
• Subjects: Electron microscopy; Low-energy electron microscopy; Silicides; Surface phase separation; Surface phase transitions; Surfaces; Low-energy electron microscopy; Surfaces; Surface phase transitions; Surface phase separation; Silicides; Electron microscopy
• ISSN: 0968-4328; 1878-4291
• DOI: 10.1016/S0968-4328(98)00040-7

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 CoSi
2, 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.