Temperature-dependent structure, elasticity, and entropic stability of Bi phases on Cu{111}

Abstract

We have used low energy electron microscopy (LEEM) to characterize the structure and stability of Bi phases on Cu{111}. As a function of temperature we find that the Cu{111}(• -Bi surface alloy phase gradually dealloys and is fully depleted from Bi at a temperature of 803 K. The dealloying leads to a defect induced change of its elastic properties. The Bi surface alloy phase coexists with a Bi overlayer phase that exhibits a sharp decrease in density in a narrow temperature interval just below the temperature where the surface alloy phase has fully dealloyed. LEEM is used to directly evaluate the structure as well as the entropic contributions that determine the stability of each of the phases.

Surface and grain boundary complexions in transition metal – Bismuth alloys

“…Bi forms various monolayer structures on Ni and Cu surfaces [21,22,23,24,25,26,27,28]. In multilayer surface complexions (∼1 nm), Bi exhibits allotropic transformations from puckered pseudocubic films to bulk-like rhombohedral films on Si(111) and on some quasicrystal surfaces [29,30].…”

Large spin-mixing conductance in highly Bi-doped Cu thin films

“…There are no extra-spots corresponding to Bi on a Cu surface, i.e., the Bi atoms are either not on the Cu surface or they do not form an ordered structure. However, when Cu and Bi are co-evaporated at a higher temperature (100 • C) (Figure 1.b) additional LEED spots appear that can be related to a ( √ 3 × √ 3) R30 • reconstruction, which is characteristics of a Bi monolayer on the surface of a Cu(111) 16 . From the LEED pattern, it is clear that, when growing at high temperature, Bi segregates to the surface whereas no segregation is observed at RT.…”

Critical vacancy density for melting in two-dimensions: the case of high density Bi on Cu(111)

“…A Cu(111) surface 5 was prepared by cycles of 1 keV Ar + ion bombardment and annealing to 1100 K until good quality LEED patterns were obtained and no contaminations were detected with Auger electron spectroscopy. The nominal orientation was approximately 0.1°(see also [11]).…”

“…Bi surface alloys and ultra-thin Bi films on the Cu(111) substrate have shown a rich mixture of various physical effects [5][6][7][8][9], including order-disorder transitions [6], a gradual de-alloying [5], and even a liquid-tolattice gas phase transition [5]. One of the effects that was predicted in the phase diagram of the Bi/Cu(111) system after the original structure determination [8], was the occurrence of a Bi coverage dependent melting temperature of the [2012] overlayer phase which forms in this system.…”