Thin-film formation of Si clathrates on Si wafers

Ohashi, Fumitaka; Iwai, Yoshiki; Noguchi, Akihiro; Sugiyama, Tomoya; Hattori, Minoru; Ogura, Takuya; Himeno, Roto; Kume, Tetsuji; Ban, Takayuki; Nonomura, Shuichi

doi:10.1016/j.jpcs.2013.12.009

Cited by 17 publications

(29 citation statements)

References 30 publications

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“…So far, the techniques employed to grow (type I or type II) clathrate thin films are: (a) Pulsed laser deposition (PLD), (b) thermal decomposition of a thin film Zintl precursor phase and more recently, (c) melt spinning thick films of clathrate on a substrate. 22,[47][48][49][50] Of these, both the PLD and melt spinning techniques have been demonstrated only for type I clathrates. Both these techniques require clathrate powder for making the target (PLD) or the melt (melt spinning).…”

Section: Thin Film Synthesismentioning

confidence: 99%

“…Thermal decomposition of thin film Zintl precursors A few reports on synthesis of type II clathrates in thin film form exist. 22,48,49,53 In all cases, a thin film of Zintl precursor (NaSi) is formed by reacting Na metal with Si. The source of Si can be a Si wafer or a thin film of Si on a substrate and precursor synthesis can either be carried out under Ar or vacuum.…”

Section: Thin Film Synthesismentioning

confidence: 99%

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Group IV clathrates: synthesis, optoelectonic properties, and photovoltaic applications

et al. 2014

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Group IV clathrates are a unique class of guest/framework type compounds that are considered potential candidates for a wide range of applications (superconductors to semiconductors). To date, most of the research on group IV clathrates has focused heavily on thermoelectric applications. Recently, these materials have attracted attention as a result of their direct, wide band gaps for possible use in photovoltaic applications. Additionally, framework alloying has been shown to result in tunable band gaps. In this review, we discuss the current work and future opportunities concerning the synthesis and optical characterization of group IV clathrates for optoelectronics applications.

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Section: Thin Film Synthesismentioning

confidence: 99%

Section: Thin Film Synthesismentioning

confidence: 99%

Group IV clathrates: synthesis, optoelectonic properties, and photovoltaic applications

et al. 2014

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“…It was suggested that the underlying symmetries of the diamond silicon faces could lead to preferential growth of a silicon clathrate film of either the sI or sII polymorphs. 61,64 The preferential growth of sI or sII raises an interesting question about the role of lattice and domain matching, and the underlying symmetry of the crystal planes, on the formation of clathrate hydrates. Lattice matching refers to the one-to-one matching of lattice constants between substrate and film.…”

Section: Introductionmentioning

confidence: 99%

Structure of the Ice–Clathrate Interface

et al. 2015

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Clathrate hydrates are crystals in which water molecules form hydrogen-bonded cages that enclose small nonpolar molecules, such as methane. In the laboratory, clathrates are customarily synthesized from ice and gas guest under conditions for which homogeneous nucleation of hydrates is not possible. It is not known how ice assists in the nucleation of clathrate hydrates or how ice forms on clathrate hydrate in the case of self-preservation. There is no lattice matching between any plane of ice and clathrate hydrates; therefore, an interfacial transition layer has to form to connect the two crystals. Here, we use molecular dynamic simulations to study the structure of ice−clathrate interfaces produced by alignment and equilibration of the crystals, competitive growth of ice and clathrate from a common solution, nucleation of hydrate in the presence of a growing ice front, and nucleation of ice in the presence of clathrate hydrates. We find that the interfacial transition layer between ice and clathrate is always disordered and has a typical width of two to three water layers. Water in the interfacial transition layer has tetrahedral order lower than either ice or clathrate and higher than liquid water under the same thermodynamic conditions. The potential energy of the water in the interfacial transition layer is between those in liquid water and the crystals. Our results suggest that the disordered interfacial transition layer could assist in the heterogeneous nucleation of clathrates from ice and ice from clathrates by providing a lower surface free energy than the ice−liquid and clathrate−liquid interfaces.

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“…Therefore, we expected the epitaxial growth of the Si clathrate (111) plane on the Si (111) substrate. Concerning the NaSi film, which is a precursor of the Si clathrate, the epitaxial growth on the Si (111) surface was strongly suggested by previous works [14,15]. Furthermore, the type-I and -II Si clathrate thin films were selectively formed on the Si (100) and Si (111) substrates, respectively [15].…”

Section: Introductionmentioning

confidence: 87%

“…Recently, we have synthesized type-I and type-II Si clathrate thin films (Na 8 Si 46 and Na x Si 136 ) on single-crystalline Si substrates [14][15][16]. The Si clathrate films were obtained from a well-controlled thermal annealing of the NaSi films under vacuum.…”

Section: Introductionmentioning

confidence: 99%

Cross-sectional transmission electron microscope observation of Si clathrate thin films grown on Si (111) substrates

et al. 2017

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By means of high-resolution transmission electron microscopy (HR-TEM) observations, and energy dispersive X-ray analyses performed with a scanning TEM (STEM-EDX), we evaluated the residual Na contents and the induced crystal strains in type-II Si clathrate films grown on a Si substrate and treated with iodine for Na elimination. Cross-sectional TEM and STEM-EDX observations verified the formation of the type-II Si clathrate thin film on the Si substrate. The guest-free (without any Na inclusion) clathrate crystal was obtained by iodine (I 2) treatment for more than 3 cycles. The resulting films were polycrystalline. No buffer layer was observed at the boundary of the Si clathrate crystal film and the substrate, suggesting a chemical bonding between them. The crystalline strains defined here by the deviation of the d value were within 3.5%. These findings might allow us to fabricate epitaxial Si clathrate films on Si substrates.

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Thin-film formation of Si clathrates on Si wafers

Cited by 17 publications

References 30 publications

Group IV clathrates: synthesis, optoelectonic properties, and photovoltaic applications

Group IV clathrates: synthesis, optoelectonic properties, and photovoltaic applications

Structure of the Ice–Clathrate Interface

Cross-sectional transmission electron microscope observation of Si clathrate thin films grown on Si (111) substrates

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