Surface alloying of immiscible metals induced by surface state shift

Generation of nanoparticles by spark discharge

“…Equilibrium phases in the phase diagram of bulk Cu-W calculated from a thermodynamic model include the fcc terminal solid solution (Cu) with extremely limited solid solubility of W, and the bcc terminal solid solution (W) with extremely limited solid solubility of Cu . On the basis of first principles calculations, Shu et al (2003) suggested that the noble metal atoms (Ag, Au, Cu) would like to occupy the vacancy sites of the W(001) surface to form the substitutional surface alloys despite the fact that they hardly form an alloy in the bulk. Dirks et al (1985) produced Cu-W alloy films by simultaneous vapour deposition of the elements on unheated substrates.…”

Controlling magnetic interfaces using ordered surface alloys

“…Similar charge transfer that occurs to select metal adsorbates is believed to be sufficient for the stabilization of the vacancy array in which the metal atoms take up residence in the surface alloys [30][31][32]. Surface state shifts that occur during alloy formation are also believed to contribute to the stability of the surface alloys [32].…”

“…The energetic and kinetic requirements for the formation of surface alloys are met in a significant number of adsorbate-substrate systems. The stability of surface alloys has also received * huang.l@sustc.edu.cn † phaltman@ust.hk particular attention because they are known to form even between many elements that are immiscible in bulk [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Whether for reasons of bulk immiscibility, energetics of the surface alloy configuration, or even kinetic limitations to the formation of more deeply penetrated alloys, alloying is very frequently confined to the topmost atomic layer.…”

“…These alloys are part of a larger class of noble metal-induced (Au, Ag, Cu, Pt, Pd) c(2 × 2) surface alloys that form on W(100) and Mo(100) refractory metal surfaces [21][22][23][24][25][26][27][28][29][30][31][32]. In the c(2 × 2) alloy structure, noble metal atoms substitute for surface Mo or W atoms in a checkerboard pattern, with an optimal metal coverage of 0.5 monolayer (ML).…”

“…Local density approximation calculations have shown that electron depletion induced by an applied electric field can stabilize c(2 × 2) vacancy arrays on Mo(100) and W(100) surfaces [30,31]. Similar charge transfer that occurs to select metal adsorbates is believed to be sufficient for the stabilization of the vacancy array in which the metal atoms take up residence in the surface alloys [30][31][32]. Surface state shifts that occur during alloy formation are also believed to contribute to the stability of the surface alloys [32].…”