DFT study of the adsorption and dissociation of 5-hydroxy-3-butanedithiol-1,4-naphthaquinone (Jug-C4-thiol) on Au(111) surface

Efficient Spin-Selective Electron Transport at Low Voltages of Thia-Bridged Triarylamine Hetero[4]helicenes Chemisorbed Monolayer

The Chirality Induced Spin Selectivity (CISS) effect describes the capability of chiral molecules to act as spin filters discriminating flowing electrons according to their spin state. Within molecular spintronics, efforts are focused on developing chiral-molecule-based technologies to control the injection and coherence of spin-polarized currents. Herein, for this purpose, we study spin selectivity properties of a monolayer of a thioalkyl derivative of a thia-bridged triarylamine hetero[4]helicene chemisorbed on a gold surface. A stacked device assembled by embedding a monolayer of these molecules between ferromagnetic and diamagnetic electrodes exhibits asymmetric magnetoresistance with inversion of the signal according to the handedness of molecules, in line with the presence of the CISS effect. In addition, magnetically conductive atomic force microscopy reveals efficient electron spin filtering even at unusually low potentials. Our results demonstrate that thia[4]heterohelicenes represent key candidates for the development of chiral spintronic devices.

Alkyl-Modified Gold Surfaces: Characterization of the Au-C Bond

The surface of gold can be modified with alkyl groups through a radical crossover reaction involving alkyliodides or bromides in the presence of a sterically hindered diazonium salt. In this paper, we characterize the Au-C(alkyl) bond by surface-enhanced Raman spectroscopy (SERS); the corresponding peak appears at 387 cm^-1 close to the value obtained by theoretical modeling. The Au-C(alkyl) bond energy is also calculated, it reaches -36.9 kcal mol^-1 similar to that of an Au-S-alkyl bond but also of an Au-C(aryl) bond. In agreement with the similar energies of Au-C(alkyl) and Au-S-(alkyl), we demonstrate experimentally that these groups can be exchanged on the surface of gold.

Effects of H2 and N2 treatment for B2H6 dosing process on TiN surfaces during atomic layer deposition: an ab initio study

For the development of the future ultrahigh-scale integrated memory devices, a uniform tungsten (W) gate deposition process with good conformal film is essential for improving the conductivity of the W gate, resulting in the enhancement of device performance. As the memory devices are further scaled down, uniform W deposition becomes more difficult because of the experimental limitations of the sub-nanometer scale deposition even with atomic layer deposition (ALD) W processes. Even though it is known that the B₂H₆ dosing process plays a key role in the deposition of the ALD W layer with low resistivity and in the removal of residual fluorine (F) atoms, the roles of H₂ and N₂ treatments used in the ALD W process have not yet been reported. To understand the detailed ALD W process, we have investigated the effects of H₂ and N₂ treatment on TiN surfaces for the B₂H₆ dosing process using first-principles density functional theory (DFT) calculations. In our DFT calculated results, H₂ treatment on the TiN surfaces causes the surfaces to become H-covered TiN surfaces, which results in lowering the reactivity of the B₂H₆ precursor since the overall reactions of the B₂H₆ on the H-covered TiN surfaces are energetically less favorable than the TiN surfaces. As a result, an effect of the H₂ treatment is to decrease the reactivity of the B₂H₆ molecule on the TiN surface. However, N₂ treatment on the Ti-terminated TiN (111) surface is more likely to make the TiN surface become an N-terminated TiN (111) surface, which results in making a lot of N-terminated TiN (111) surfaces, having a very reactive nature for B₂H₆ bond dissociation. As a result, the effect of N₂ treatment serves as a catalyst to decompose B₂H₆. From the deep understanding of the effect of H₂ and N₂ during the B₂H₆ dosing process, the use of proper gas treatment is required for the improvement of the W nucleation layers.

Our results showed the effects of H₂ and N₂ treatment on TiN surfaces, using density functional theory calculations. These imply that the understanding of gas treatment gives us insight into improving the W ALD process for future memory devices.