Chemical ordering of alloy surfaces: Low-index versus vicinal surfaces

Abstract

Some A 3 B fcc alloys undergo a chemical order-disorder phase transition. During the ordering process, four types of domain appear within the bulk, separated by antiphase boundaries ͑APB's͒. As for chemical ordering in the presence of a surface, scanning tunneling microscopy and He diffraction studies consistently show a contrasting behavior between vicinals, where APB's emerge at the surface, and low-index surfaces, where no APB's emerge. These differences emphasize the role of the step density in surface chemical ordering.

Correlation between STM-induced photon emission and barrier height: The case of the Cu 3 Au alloy vicinal surface

“…The terminal plane composing the terraces of the paired-step surface (chemically ordered, figs. 2-3), is mixed (50% Au, 50% Cu) as demonstrated by previous experiments [11,18]. In agreement with the alternate Cu-CuAu concentration of (001) bulk planes and our STM observations, the concentration in Au atoms in terraces (CuAu) is twice as important as in paired-step edges (Cu 3 Au).…”

“…1. Long ordering time (t > 12 h) allows the formation of wide (L d > 40 nm) chemically-ordered domains [11,12]. Under UHV, the surface of the crystal was cleaned by cycles of Ar + bombardment at room temperature, followed by a short annealing at 800 K to restore the surface stoichiometry.…”

Characterization of antiphase boundary network inFe3O4(111)epitaxial thin films: Effect on anomalous magnetic behavior

“…The very same z =1/2 exponent has also been found both for bulk chemically ordered bimetallic alloys 30 and in the presence of a surface. 59,60 The limiting process of the domain coarsening is thus the chemical ordering process over the Fe sublattices ͑z =1/2͒. In addition, two distinct time scales ought to be considered in our case since domain coarsening takes place during film growth.…”

Theoretical study of the structure and vibrational dynamics of Cu3Au(511)

“…Such systematic studies of the environment-dependentcontribution to the local structural relaxations and vibrational free energy allows the determination of the role of local coordination in matters of surface and structural stability. We are further encouraged by experimental studies [5][6][7] of the vicinals of Cu 3 Au(100) which establish the stability of monoatomic and diatomic stepped surfaces of this alloy and provided us with avenues for comparison with our theoretical results.…”

“…The Cu 3 Au binary intermetallic alloy has often been selected as a model system because it exhibits a typical order-disorder transition. With the aim of obtaining a better understanding of this transition, a lot of work has been done both experimentally [1][2][3][4][5][6][7][8] and theoretically [9][10][11][12][13][14][15][16][17] in the area.…”