Surface melting on spherically shaped copper crystals

Stock, K. D.; Menzel, E.

doi:10.1016/0039-6028(76)90419-2

Cited by 42 publications

(6 citation statements)

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“…Furthermore, one can use the observed T R =600°C to calculate what is expected for the more closely packed (111) and (100) faces and for the (100) vicinal faces, using the result that T R scales with d 1 . The expected T R for the (111) and (100) faces is above T m , in agreement with the ECS, 5 and I find that 7*013) =360°C, which is within the range of values allowed by experiment. 6 However, the values calculated for the (115) and (117) faces, 290 and 140 K, respectively, are too low.…”

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confidence: 82%

“…The choice of copper was motivated in part by extensive studies of the ECS of small (5-jum) metal crystals. 4,5 Specifically, it is known that the (110) face of copper is absent from the ECS immediately below its melting temperature (T m =1083 o C). 5 In addition, the He-diffraction measurements of Lapujoulade and coworkers 6 on faces of copper vicinal to the (100) suggest that the (113), (115), and (117) faces undergo roughening transitions.…”

mentioning

confidence: 99%

“…4,5 Specifically, it is known that the (110) face of copper is absent from the ECS immediately below its melting temperature (T m =1083 o C). 5 In addition, the He-diffraction measurements of Lapujoulade and coworkers 6 on faces of copper vicinal to the (100) suggest that the (113), (115), and (117) faces undergo roughening transitions. A comparison between the behavior of the (110) face and these stepped surfaces may lead to a better general understanding of the orientation dependence of metal surface stiffness.…”

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confidence: 99%

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Thermal roughening of the copper (110) surface: An x-ray diffraction experiment

Mochrie

1987

Phys. Rev. Lett.

131

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The roughness of the (110) surface of face-centered-cubic copper has been measured between 200 and 700 °C, by x-ray diffraction. The changes observed are reversible and suggest a roughening temperature of TR-600°C. This value is compared with simple theoretical estimates and found to be in satisfactory agreement.PACS numbers: 61.50. Cj, 64.60.Cn, 68.35.Bs A fundamental understanding of crystal surfaces and interfaces is a goal with many applications in physics, chemistry, and metallurgy, ranging from surface reconstructions to wetting and adhesion, catalysis, crystal growth, and sintering. Perhaps the simplest interface one can conceive is an atomically smooth, low-index facet that separates a crystallizing element from its vapor. However, a recurrent theoretical idea of the last thirty years is that of a surface-roughening transition, 1 which may occur at a much lower temperature than bulk melting. Below the roughening-transition temperature (TR), the interface corresponds more or less to the ideal, but for T>TR, its behavior is determined by surface stiffness. Therefore, capillary waves cause the interfacial position to fluctuate. Microscopically, this is achieved through the proliferation of atomic steps. The transition has attracted attention recently in the context of the equilibrium crystal shapes (ECS), 2 especially of 4 He crystals. 3 The connection is that, for a particular facet to occur on the ECS, the temperature must be below TR for that face. However, there have been few experimental studies of the microscopic aspects of interfacial roughening.Here, I report the results of an x-ray-diffraction study of the (110) face of face-centered-cubic (fee) copper, for temperatures between 200 and 700 °C. It is shown that the root mean square roughness ((w 2 ) l/2 ) of this surface changes reversibly with temperature, by measurements of the Bragg reflectivity far from Bragg peaks. From the temperature dependence of (w 2 ) 1/2 , T R -600°C is deduced. Finally, the values of both (u 2 ) l/2 and TR are compared favorably to simple theoretical estimates. These experiments provide the first direct observation of a roughening transition of a low-index face of a metal crystal. The choice of copper was motivated in part by extensive studies of the ECS of small (5-jum) metal crystals. 4,5 Specifically, it is known that the (110) face of copper is absent from the ECS immediately below its melting temperature (T m =1083 o C). 5 In addition, the He-diffraction measurements of Lapujoulade and coworkers 6 on faces of copper vicinal to the (100) suggest that the (113), (115), and (117) faces undergo roughening transitions. A comparison between the behavior of the (110) face and these stepped surfaces may lead to a better general understanding of the orientation dependence of metal surface stiffness. Finally, it is worth mentioning that while the techniques of microscopy and atom diffraction probe significantly different length scales-microns in the former case and several tens of angstroms in the latter-one advantage of x-ray...

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Thermal roughening of the copper (110) surface: An x-ray diffraction experiment

Mochrie

1987

Phys. Rev. Lett.

131

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“…Observation of small copper crystals immediately below their melting point ͑T m = 1083°C͒ demonstrates that the ͑110͒ facet is absent from the equilibrium crystal shape ͑ECS͒ at this temperature. 20 This requires that either the ͑110͒ surface has a roughening transition at a temperature ͑T R ͒ below T m or the ͑110͒ surface is not a stable facet at any temperature. By using surface x-ray diffraction techniques, Mochrie et al have investigated the thermodynamic stability of the Cu͑110͒ surface and demonstrated that the ͑110͒ facet of Cu is a stable equilibrium facet at low temperatures and becomes unstable ͑roughening or faceting transition͒ at higher temperatures ͑ϳ700°C͒.…”

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confidence: 99%

Effects of surface topology on the formation of oxide islands on Cu surfaces

Zhou

Wang

Yang

2005

Journal of Applied Physics

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We examined the effects of surface topology on the nucleation and growth of Cu 2 O oxide islands during the initial oxidation stages of Cu͑100͒ and Cu͑110͒ surfaces by in situ ultrahigh vacuum transmission electron microscopy and ex situ atomic force microscopy. Our observations indicate that nucleation of three dimensional oxide islands on single crystal surfaces is homogenous, surface defects and dislocations play a very limited role as preferential sites for oxide nucleation. On the other hand, grain boundaries are the preferential sites for oxide nucleation and the oxide islands formed along the grain boundaries show a faster growth rate than that on flat Cu surface. The oxidation on the faceted Cu͑110͒ surface results in heterogeneous nucleation of oxide islands in the facet valleys and one-dimensional growth along the intersection direction of the facets.

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“…In the now accepted opinion, melting of a solid starts at the surface at temperature appreciably lower than the bulk melting point This so-called surface premelting (already suggested long ago by Faraday [1] to explain the properties of ice) has been confirmed and studied in detail using modern techniques of surface science. Premelting was detected (i) on physisorbed layers (Ar/graphite, CH4/MgO) by measuring their heat capacities [2] or by quasi-elastic neutron scattering [3] ; (ii) on organic crystals (biphenyl) by ellipsometry [4] and (iii) on metallic crystals (Cu, Au, Pb, In) by optical emissivity [5], by ion scattering [6,19] by Leed [7] and by observation of the equilibrium shape of crystallites [8,9].…”

Section: Introductionmentioning

confidence: 99%

The overheating of lead crystals

Métois

Heyraud

1989

J. Phys. France

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Overheating of crystals has scarcely been reported unlike undercooling which is frequently observed. Admittedly the absence of overheating is the consequence of the crystal surface being covered by a liquid film (surface premelting) well under the bulk melting temperature. In the present letter we show that overheating is possible, and is actually observed (ΔT ∼ 3°C), when the crystals are bounded by non wettable facets ({111} facets) separated by relatively small curved regions covered by their melt

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Surface melting on spherically shaped copper crystals

Cited by 42 publications

References 5 publications

Thermal roughening of the copper (110) surface: An x-ray diffraction experiment

Thermal roughening of the copper (110) surface: An x-ray diffraction experiment

Effects of surface topology on the formation of oxide islands on Cu surfaces

The overheating of lead crystals

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