arXiv subjects

Nassar Doudin

Publications and source records attributed to Nassar Doudin.

4 recordsLinked to original sources

arXiv2026

Electric-field control of hydrogen bonding via interfacial charge at atomic resolution

Hydrogen-bond networks govern molecular structure and function across chemistry, biology and materials science, yet their deterministic control at the atomic scale remains a central challenge (1-9).Here, we directly visualize how an external electric field enables reversible control of a hydrogen-bond network in monolayer ice on graphite through interfacial charge redistribution. Low-temperature scanning tunnelling microscopy reveals a field-driven transition from a mobile, physisorbed, non-wetting water phase to an ordered hexagonal monolayer, enabling deterministic nucleation, growth and complete wetting on an otherwise inert surface. Systematic variation of the field induces continuous lattice strain coexisting with discrete conductance states, revealing coupled structural and electronic responses. Reversal of the field polarity drives collective dipolar inversion, enabling switching between symmetry-equivalent configurations without disrupting the lattice. Supported by first-principles theory and bias-dependent imaging, these effects arise from field-induced modification of the interfacial electronic structure rather than purely geometric or orientational effects. These results establish interfacial charge redistribution as a general mechanism for electrically programming hydrogen-bond networks, providing a route to control molecular organization, electronic properties and collective dipolar order at interfaces.

cond-mat.mtrl-sci↗

arXiv2022

Two-Dimensional Transition Metal Silicate Formed on Ru (0001) by Hydrogenation

Bottom-up synthesis of two-dimensional transition-metal silicates has been challenging due to strong overlayer-substrate interactions, which prevents the exfoliation of the overlayer. Here, using density functional theory calculations, we systematically investigate the hydrogenation of the overlayer as a way to decrease the substrate and overlayer interactions. Using the Fe$_2$Si$_2$O$_8\cdot$O/Ru(0001) structure as our starting point Wlodarczyk et. al. [1], we study hydrogenation levels up to Fe$_2$Si$_2$O$_9$H$_4\cdot$/Ru(0001). Structural and thermodynamical properties are studied at different hydrogenation levels to show under which conditions, the exfoliation can be feasible. Simulated core-level shifts show that Fe is primarily in 3+ state through the hydrogenation of Fe$_2$Si$_2$O$_8\cdot$O/Ru(0001). Simulated reflection adsorption infrared spectroscopy (RAIRS) yield distinctive shifts in vibrational properties with increasing hydrogenation which can guide experiments. [1] R. Wlodarczyk et al., "Atomic structure of an ultrathin Fe-silicate film grown on a metal: A monolayer of clay?", J. Am. Chem. Soc., 135, 19222, (2013).

cond-mat.mtrl-sci↗

arXiv2022

Scalable production of single 2D van der Waals layers through atomic layer deposition: Bilayer silica on metal foils and films

The self-limiting nature of atomic layer deposition (ALD) makes it an appealing option for growing single layers of two-dimensional van der Waals (2D-VDW) materials. In this paper it is demonstrated that a single layer of a 2D-VDW form of SiO2 can be grown by ALD on Au and Pd polycrystalline foils and epitaxial films. The silica was deposited by two cycles of bis (diethylamino) silane and oxygen plasma exposure at 525 K. Initial deposition produced a three-dimensionally disordered silica layer; however, subsequent annealing above 950 K drove a structural rearrangement resulting in 2D-VDW; this annealing could be performed at ambient pressure. Surface spectra recorded after annealing indicated that the two ALD cycles yielded close to the silica coverage obtained for 2D-VDW silica prepared by precision SiO deposition in ultra-high vacuum. Analysis of ALD-grown 2D-VDW silica on a Pd(111) film revealed the co-existence of amorphous and incommensurate crystalline 2D phases. In contrast, ALD growth on Au(111) films produced predominantly the amorphous phase while SiO deposition in UHV led to only the crystalline phase, suggesting that the choice of Si source can enable phase control.

cond-mat.mtrl-sci↗

arXiv2021

Magnetism and Piezoelectricity in Stable Transition Metal Silicate Monolayers

Two-dimensional van der Waals (2D vdW) materials that display ferromagnetism and piezoelectricity have received increased attention. Despite numerous 2D materials have so far been reported as ferromagnetic, developing an air stable and transferable vdW material that is multiferroic has been challenging. To address this problem, we report our work on layered transition metal silicates that are derivatives of kaolinites and lizardites with transition metal substituting on Al$^{3+}$ and Mg$^{2+}$ sites using ab-initio calculations. Using Density Functional Theory (DFT), we show that these compounds are stable under varying O$_2$ partial pressure and can be synthesized using a surface assisted method. We show that these materials have finite out-of-plane piezoelectric response thanks to the lack of inversion symmetry and also they can be tailored to be ferrimagnetic with a non-zero net moment.

cond-mat.mtrl-sci↗