Acceleration of metal-atom diffusion in electric field at metal/insulator interfaces: First-principles study

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The penetration and diffusion of metal atoms in self-assembled monolayers (SAMs) and pentacene solids were studied by first-principles calculations. It was shown in the case of SAM that metal atoms easily penetrate and diffuse in solids, reflecting the weak interaction between metal atoms and molecules. Even when diffusing metal atoms produce a cluster, such a cluster can easily diffuse in solids. In the case of pentacene, on the other hand, since the interaction between metal atoms and molecules is attractive and strong, metal atoms actively enter into solids and are tightly bonded to molecules. We found that Au atoms prefer to produce a cluster at the molecule edge and such a cluster is difficult to move, while Al atoms are scatteringly distributed and last the diffusion owing to the repulsive interaction between Al atoms. We showed that the difference in metal-atom behavior comes from the difference in electronic structure between SAM and pentacene, which are, respectively, σand π-orbital molecular systems.

“…40) Other calculation details can also be seen in our previous papers. [18][19][20][41][42][43] 3. Results and discussions…”

Section: Calculation Model and Methodsmentioning

confidence: 99%

Section: Effects Of Interaction Between Metal Atoms On Penetration An...mentioning

confidence: 98%

Metal-atom penetration and diffusion in organic solids: difference between σ- and π- orbital molecular systems

Watanabe

Nakayama

2019

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“…This is because superlattice geometry with the same two interfaces can avoid the unintentional electric field caused by electron transfer between two slab surfaces. 13,14) The superlattice is made of the alternative stacking of 9-11 monolayer TiN, 1-3 ILs and 25 monolayer Ge. The calculated lattice constants of bulk Ge and TiN are 5.64 and 4.26 Å, respectively, which well reproduces the observed values of 5.658 and 4.238 Å.…”

Section: Model and Methods Of Calculationmentioning

confidence: 99%

Origin of Fermi-level depinning at TiN/Ge(001) interfaces: first-principles study

Nishimoto¹,

Nakayama²

2019

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The origin of Fermi-level (FL) depinning at TiN/Ge interfaces was studied using first-principles calculation. It was shown that FL pinning occurs at abrupt clean interfaces, while depinning occurs at interfaces with N-rich interface layers such as TiN 2 and Ge 3 N 4 , which is in good agreement with the experiments. By analyzing electronic structures, we found that the termination of interface Ge atoms by N atoms, i.e. the production of interface N-Ge bonds, is the key to realize FL depinning at TiN/Ge interfaces. The effects of missing N-Ge interface bonds were also discussed.

“…[9][10][11] On the other hand, such penetration property in electric fields is used to produce metal nanowires in insulators, which connect two electrodes and thus are promising for resistive memory applications. [12][13][14] In our previous works, 15,16) we studied the diffusion of metal atoms around metal/SiO 2 interfaces in electric fields by the first-principles calculation and clarified that the metalatom penetration is markedly accelerated by the applied electric field. In particular, we showed that the potential barrier for penetration decreases almost linearly with increasing the electric field for metal atoms like Ag, Au, Al, and Pt, and such behavior is explained by considering the penetration depth of metal-induced gap state (MIGS) 1,17,18) and assuming the constant ionization charges of metal atoms during the diffusion.…”

Section: Introductionmentioning

confidence: 98%

Effect of electron transfer on metal-atom penetration into SiO₂ in electric field: first-principles study

Nagasawa¹,

Oikawa²,

Nakayama³

2021

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The penetration behavior of Ta, Nb, V, and Ti atoms into SiO2 substrate in the electric field are studied by the first-principles calculation, using the metal/SiO2 models. We found that the ionization charges of these atoms are extended over surrounding Si and O atoms and change with increasing the electric field reflecting the electron transfer from metal atoms to metal electrodes. These features are quite different from those of Ag, Au, Al, and Pt atoms discussed in our previous works [Y. Asayama et al., Mater. Sci. Semicond. Process. 70, 78 (2017); R. Nagasawa et al., Jpn. J. Appl. Phys. 57, 04FB05 (2018)]. It is shown that the variation of potential barrier for the penetration with increasing the electric field is approximately explained by considering these features and using the condenser-type model.