Pressure-induced semiconductor-metal transitions in amorphous Si and Ge

Shimomura, Osamu; Minomura, Shigeru; Sakai, Norisuke; Asaumi, Katsuyuki; Tamura, Kouichi; Fukushima, Junichi; Endo, Hidenori

doi:10.1080/14786437408213238

Cited by 166 publications

(65 citation statements)

References 10 publications

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“…Shimomura et al 39 have observed at room temperature a structural transition to a metallic phase at 10 GPa in a-Si and at 6 GPa in a-Ge, as shown in Fig. 19.…”

Section: Free Energy Catastrophementioning

confidence: 94%

“…Several runs were attempted at and beyond 6.0 GPa, but none resulted in interpretable TRR traces 28 . Shimomura et al 39 reported a semiconductor-to-metal structural transition at ~6 GPa in vacuum-evaporated a-Ge at room temperature, and we suspect this phase transition eliminated the TRR traces in the runs at highest pressure. Figure 6 is a plot of the temperature dependence of v in our ambient pressure results (anneals in the DAC without argon loading) along with the original data of Csepregi et al 2 .…”

Section: Pressure-enhanced Speg Of Gementioning

confidence: 99%

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Pressure-enhanced crystallization kinetics of amorphous Si and Ge: Implications for point-defect mechanisms

Lü

Nygren

Aziz

1991

Journal of Applied Physics

151

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The effects of hydrostatic pressure on the solid-phase epitaxial growth (SPEG) rate v of intrinsic Ge(100) and undoped and doped Si(100) into their respective self-implanted amorphous phases are reported. Samples were annealed in a high-temperature, high-pressure diamond anvil cell. Cryogenically loaded fluid Ar, used as the pressure transmission medium, ensured a clean and hydrostatic environment. v was determined by in situ time-resolved visible (for Si) or infrared (for Ge) interferometry. v increased exponentially with pressure, characterized by a negative activation volume of −0.46Ω in Ge, where Ω is the atomic volume, and −0.28Ω in Si. The activation volume in Si is independent of both dopant concentration and dopant type. Structural relaxation of the amorphous phases has no significant effect on v. These and other results are inconsistent with all bulk point-defect mechanisms, but consistent with all interface point-defect mechanisms, proposed to date. A kinetic analysis of the Spaepen–Turnbull interfacial dangling bond mechanism is presented, assuming thermal generation of dangling bonds at ledges along the interface, independent migration of the dangling bonds along the ledges to reconstruct the network from the amorphous to the crystalline structure, and unimolecular annihilation kinetics at dangling bond ‘‘traps.’’ The model yields v = 2 sin(θ)vsnr exp[(ΔSf + ΔSm)/k] exp− [(ΔHf + ΔHm)/kT], where ΔSf and ΔHf are the standard entropy and enthalpy of formation of a pair of dangling bonds, ΔSm and ΔHm are the entropy and enthalpy of motion of a dangling bond at the interface, vs is the speed of sound, θ is the misorientation from {111}, and nr is the net number of hops made by a dangling bond before it is annihilated. It accounts semiquantitatively for the measured prefactor, orientation dependence, activation energy, and activation volume of v, and the pressure of a ‘‘free-energy catastrophe’’ beyond which the exponential pressure enhancement of SPEG cannot continue uninterrupted due to a vanishing barrier to dangling bond migration. The enhancement of v by doping can be accounted for by an increased number of charged dangling bonds, with no change in the number of neutrals, at the interface. Quantitative models for the doping dependence of v are critically reviewed. At low concentrations the data can be accounted for by either the fractional ionization or the generalized Fermi-level-shifting models; methods to further test these models are enumerated. Ion irradiation may affect v by altering the populatio

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“…Shimomura et al 39 have observed at room temperature a structural transition to a metallic phase at 10 GPa in a-Si and at 6 GPa in a-Ge, as shown in Fig. 19.…”

Section: Free Energy Catastrophementioning

confidence: 94%

Section: Pressure-enhanced Speg Of Gementioning

confidence: 99%

Pressure-enhanced crystallization kinetics of amorphous Si and Ge: Implications for point-defect mechanisms

Lü

Nygren

Aziz

1991

Journal of Applied Physics

151

View full text Add to dashboard Cite

show abstract

“…11,15 Subsequently, Si-II phase is frequently cited as a transition state for the CAT of Si. However, a-Si was also reported to exhibit sharp resistance change under pressure, 20 and discontinuous load-depth curves may be caused by processes other than phase transformation, for example, massive dislocation nucleation and motion and so on. 10 As such, in the absence of direct evidence, the necessity of the Si-II phase during the CAT process is uncertain, and has in fact been challenged by several research groups.…”

Section: Introductionmentioning

confidence: 99%

In situ TEM study of deformation-induced crystalline-to-amorphous transition in silicon

et al. 2016

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The mechanism responsible for deformation-induced crystalline-to-amorphous transition (CAT) in silicon is still under considerable debate, owing to the absence of direct experimental evidence. Here we have devised a novel core/shell configuration to impose confinement on the sample to circumvent early cracking during uniaxial compression of submicron-sized Si pillars. This has enabled large plastic deformation and in situ monitoring of the CAT process inside a transmission electron microscope. We demonstrate that diamond cubic Si transforms into amorphous silicon through slip-mediated generation and storage of stacking faults (SFs), without involving any intermediate crystalline phases. By employing density functional theory simulations, we find that energetically unfavorable single-layer SFs create very strong antibonding interactions, which trigger the subsequent structural rearrangements. Our findings thus resolve the interrelationship between plastic deformation and amorphization in silicon, and shed light on the mechanism underlying deformation-induced CAT in general.

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“…At higher pressures Si undergoes a phase transition from semiconducting diamondlike fcc to conductive tetragonal ␤ Sn and then to an insulating bcc phase upon release of pressure. Shimomura et al 10 observed a sharp change in the crystalline structure of Si at 15 GPa, while subsequent studies placed the transition at slightly lower pressure: 10-13 GPa. To illustrate the experimental conditions under which these two mechanisms can operate, the local pressure as a function of tip size and applied load are related to limits for increased current due to band gap effects and for a local phase transformation.…”

mentioning

confidence: 99%