Abstract:Density functional/molecular dynamics simulations have been performed to determine structural and other properties of amorphous Ag/Ge/S and Ge/S alloys. In the former, the calculations have been combined with experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure). Ag/Ge/As alloys have high ionic conductivity and are among the most promising candidates for future memristor technology. We find excellent agreement between the experimental results and large-scale (500 atoms) si… Show more
“…2) in the present work may be related to the metallic component observed in the samples of Souchier et al before switching. Correspondingly, the Type-II regions in the present work may be related to the component of nonmetallic bonding detected by Souchier et al [39], and could correspond to the a-Ag-Ge-S matrix containing more of units such as Ge-AgS 3 and Ge-GeS 3 [40]. By analogy with the work of Souchier et al, a possible origin of the Type-I and Type-II regions is non-uniformity in the supply of Ag.…”
and the pattern of Ag enrichment originates from the columnar-porous structure of the as-deposited film that is to some extent preserved in the electrolyte after photodoping. Type-II regions have lower Ag content, are typically 10-20 nm across, and appear to conform to the usual description of the photoreaction products of the opticallyinduced dissolution and diffusion of silver in a thin-film chalcogenide. The microstructure, with two types of region and aligned nanocolumns, is present in the electrolyte after photodoping without any applied bias, and is important for understanding switching mechanisms, and writing and erasing cycles, in programmable-metallization-cell memory.
“…2) in the present work may be related to the metallic component observed in the samples of Souchier et al before switching. Correspondingly, the Type-II regions in the present work may be related to the component of nonmetallic bonding detected by Souchier et al [39], and could correspond to the a-Ag-Ge-S matrix containing more of units such as Ge-AgS 3 and Ge-GeS 3 [40]. By analogy with the work of Souchier et al, a possible origin of the Type-I and Type-II regions is non-uniformity in the supply of Ag.…”
and the pattern of Ag enrichment originates from the columnar-porous structure of the as-deposited film that is to some extent preserved in the electrolyte after photodoping. Type-II regions have lower Ag content, are typically 10-20 nm across, and appear to conform to the usual description of the photoreaction products of the opticallyinduced dissolution and diffusion of silver in a thin-film chalcogenide. The microstructure, with two types of region and aligned nanocolumns, is present in the electrolyte after photodoping without any applied bias, and is important for understanding switching mechanisms, and writing and erasing cycles, in programmable-metallization-cell memory.
“…The use of pyMolDyn is described in detail in the online documentation (see links above). To illustrate its usage, we take the attached input file AgGeS‐BOX.xyz, which shows a result of a 500‐atom simulation of an amorphous alloy of Ag, Ge, and S (Ag 100 Ge 168 S 232 ) in a cubic box of size 21.799 Å . The first three lines of the input are then: 500CUB 21.799AG −7.738 ……”
“…The result is also consistent with the X‐ray diffraction profile of Ge 3–2 x Ag 2 x S 3 ( x = 0.6–1.0) glasses, [ 23 ] the distinct scattering function of (Ag 2 S) x (GeS 2 ) 1– x ( x = 0.3, 0.4, 0.5) glasses obtained from neutron diffraction, [ 24 ] and the X‐ray and neutron structure factors of Ag 20 (Ge 0.42 S 0.58 ) 80 glasses. [ 25 ] In every case, a large peak is observed around Q = 2.0 Å −1 . These results indicate that a new network structure is constructed involving Ag atoms by silver photodiffusion.…”
Section: Resultsmentioning
confidence: 97%
“…[ 28–30 ] Actually, the structural study of Ag x (Ge 0.42 S 0.58 ) 100– x glasses demonstrated that the cavity volume of x = 0 is much greater than that of x = 20. [ 25 ] The voids in the Ge–S network can be filled with Ag ions in the process of silver photodiffusion.…”
Silver photodiffusion into amorphous chalcogenides is the photoinduced phenomenon, in which mobile Ag ions are injected into semiconductor films, and is applicable to nonvolatile memory devices. To understand the role of light illumination in the silver diffusion into a chalcogenide layer, the excitation light energy dependence of silver photodiffusion in Ag/a‐Ge20S80/Si substrate stacks is investigated by neutron reflectivity, X‐ray reflectivity, and X‐ray diffraction. The measurements reveal that there is an energy threshold to induce silver photodiffusion, which corresponds to the optical gap of amorphous Ge20S80. The excitation of the lone‐pair electrons to the antibonding states by the light illumination with greater energy than the optical gap leads to the bond breaking, and the Ge–S network structure is reorganized involving Ag ions.
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