Surface segregation at the binary alloy CuAu (100) studied by low-energy ion scattering

Abstract

We present results from an experimental study of segregation at the CuAu (100) surface. It is shown that Au enrichment in the top surface layer persists up to temperatures far beyond the bulk order-disorder transition temperature. From the gradual desegregation at higher temperatures a segregation energy of -0.30 eV was determined. Our results are in quantitative agreement with calculations by Tersoff predicting oscillatory concentration depth profiles with decreasing amplitudes at higher temperatures. For the layer selective surface analysis we used low-energy He + and Na + scattering. Data interpretation and quantification was supported by numerical simulations with the MARLOWE code to which we had added the special features of trajectory resolved analysis and anisotropic thermal vibrations of surface atoms.

Segregation and preferential sputtering of Cr in WCrY smart alloy

“…Two representative LEIS spectra for the investigation of the thermally activated segre- The segregation enthalpy, ∆H, can be determined from the data shown in figure 3. For the analysis of the Cr segregation we follow the procedure described in [18]. The surface concentration of the segregating species, here Cr, is described by a Langmuir-McLean…”

Surface Segregation Across Ternary Alloy Composition Space: CuxAuyPd1–x–y

“…On Cu 3 Au(110), some intermixing was observed 84 between first and second atomic layers and θ Au ≈ 0.4 at around 500−600 K. A low-energy electron diffraction study 85 shows no segregation of Au on the Cu 3 Au(111) surface. On CuAu(100), a top-most layer Au composition of θ Au = 0.93 was measured by LEIS at 400−700 K. 69,70 Figure 9 shows segregation profiles obtained in this work at 500 and 600 K, revealing excess Au at all surface compositions and low temperature dependence. However, it is quite clear that the degree of surface segregation over the bulk Au composition range 0.2 < x Au < 0.5 is relatively low.…”

“…Over the region of the ternary space in which the B2 phase is expected, the analysis points are spaced to yield ∼5% composition resolution. Also, Figure shows the bulk compositions at which previous quantitative LEIS measurements of segregation have been made and reported. ,,,,,, These are bulk compositions along each binary axis (blue, green, and purple symbols) and in a small region of ternary alloy compositions (solid red downward triangles). Figure demonstrates that this study of ternary alloy segregation is far more comprehensive than any prior study of the Cu x Au y Pd 1– x – y system and, to the best of our knowledge, any other ternary alloy.…”

“…Also, Figure 2 shows the bulk compositions at which previous quantitative LEIS measurements of segregation have been made and reported. 7,10,22,59,60,69,70 These are bulk compositions along each binary axis (blue, green, and purple symbols) and in a small region of ternary alloy compositions (solid red downward triangles). Figure 2 demonstrates that this study ■ ).…”

“…On Cu 3 Au­(110), some intermixing was observed between first and second atomic layers and θ Au ≈ 0.4 at around 500–600 K. A low-energy electron diffraction study shows no segregation of Au on the Cu 3 Au­(111) surface. On CuAu(100), a top-most layer Au composition of θ Au = 0.93 was measured by LEIS at 400–700 K. , …”