Thermal stability, atomic vibrational dynamics, and superheating of confined interfacial Sn layers inSn∕Simultilayers

Abstract

Multilayers composed of materials with low ͑Sn͒ and high ͑Si͒ bulk melting points were grown at room temperature by ultrahigh vacuum deposition. 119 Sn Mössbauer spectroscopy has been used to investigate the temperature dependence of the Debye-Waller factor f, the mean-square displacement, and the mean-square velocity of 119 Sn nuclei in ultrathin ͑10 Å thick͒ ␣-like Sn layers embedded between 50 Å thick Si layers. The f factor was found to be nonzero with a value of 0.036± 0.009 even at 450°C. This provides unequivocal proof of the solid state of the confined ␣-like Sn layers at least up to 450°C. Melting can only be achieved by superheating to T Ͼ 450°C. This temperature is significantly higher than the melting temperature of bulk ␤-Sn ͑231.9°C͒ and of a nonconfined epitaxial ␣-Sn single layer grown on InSb͑111͒ ͑170°C͒ previously reported in the literature ͓T. Osaka et al., Phys. Rev. B 50, 7567 ͑1994͔͒. Our molecular dynamics calculations show that melting of bulk-like ␣-Sn starts at ϳ380°C and is complete at ϳ530°C according to the Lindemann criterion. Since we still observe the solid state at 450°C for the confined ␣-like Sn films, considerable superheating is observed for this system. The stability of the ultrathin confined ␣-like Sn layers arises from electronic interactions with the surrounding Si layers, as evidenced by the Mössbauer chemical shift.

NMR studies of metallic tin confined within porous matrices

“…Note that melting of isolated and supported tin particles was also consistent with theoretical predictions for a small spherical particle, [21][22][23]25 while pronounced superheating was observed for ␣-tin thin films in Sn/ Si multilayer structures. 9 As was found also for other metallic and nonmetallic liquids in confined geometry, the freezing phase transition in tin embedded in opal was shifted to lower temperatures compared to the melting with pronounced thermal hysteresis, which is generally believed to be related to nucleation processes ͑see, for instance, Refs. 21 and 26͒.…”

Interfacial melting mechanism of nanocrystals determined by interfacial energy and interfacial stress

“…The experimental results show that when nanocrystals are embedded in a rigid matrix to form a coherent interface (CI), an obvious superheating phenomenon can be observed at D o 20 nm. [1][2][3][4][5][6][7][8][9] However, when the nanocrystals construct an incoherent interface (II) with the matrix, a depression of T m (D) occurs. [10][11][12][13] Although T m (D) of nanostructured materials (NS) was found to drop with the decrease of D, it was weaker than that of nanoparticles (NPs).…”

Melting behavior and superheating capacity of REBa2Cu3Oy films with nano‐layer buffered structures

“…The superheating phenomena can be achieved by suppressing heterogeneous nucleation of melt at defect sites. The scientists explore this fascinating phenomenon in various structures, which opened up new horizons on this field . Nowadays, deep investigation on the superheating mechanism, searching novel structures possessing the high superheating capability, and realizing its practical application attract great attention in the scientific world .…”