Embedded Binary Eutectic Alloy Nanostructures: A New Class of Phase Change Materials

Abstract

Phase change materials are essential to a number of technologies ranging from optical data storage to energy storage and transport applications. This widespread interest has given rise to a substantial effort to develop bulk phase change materials well suited for desired applications. Here, we suggest a novel and complementary approach, the use of binary eutectic alloy nanoparticles embedded within a matrix. Using GeSn nanoparticles embedded in silica as an example, we establish that the presence of a nanoparticle/matrix interface enables one to stabilize both nanobicrystal and homogeneous alloy morphologies. Further, the kinetics of switching between the two morphologies can be tuned simply by altering the composition.

Modeling pulsed-laser melting of embedded semiconductor nanoparticles

“…Phase change materials are studied widely for high-density data storage applications; a current system of interest is semiconductor or semiconductor-metal alloy nanoparticles confined in a transparent matrix [1]. Phase change applications require a method of reliably switching the material from one phase to the other.…”

Interfacial free energies determined from binary embedded alloy nanocluster geometry

“…Confinement within a matrix offers the opportunity of changing interfacial free energies (e.g., through choice of nanostructure and matrix materials) and can result in a number of interesting geometries and properties. [3][4][5][6][7][8][9] For example, implantation of Ge and Sn within the same SiO 2 matrix, followed by annealing, leads to the formation of binary eutectic alloy nanostructures (BEANs). At equilibrium, these BEANs assume a bilobed form wherein one lobe consists of crystalline Ge (presumably with some small amount of Sn), and the other lobe crystalline Sn (perhaps with some Ge).…”

“…At equilibrium, these BEANs assume a bilobed form wherein one lobe consists of crystalline Ge (presumably with some small amount of Sn), and the other lobe crystalline Sn (perhaps with some Ge). 6 Predicting the thermophysical properties of these nanostructure requires knowledge of the relevant interfacial free energies. For elemental and simple compound nanocrystals, interfacial energies are often obtained through study of the melting transition.…”

“…6. GeAu BEANs are produced by implanting Ge into Au-doped silica films fabricated by co-sputtering Au and Si under a 90% Ar-10% O atmosphere onto Si(111) substrates.…”

“…The Ge:Sn ratio in this region varies roughly between 2:1 and 4:1 (as measured by Rutherford Backscattering), and the integrated total dose is 3:1. 6 Thus, we determine the composition of the GeSn bilobes to lie at 25 at. % Sn.…”