Roie Yerushalmi

As data storage demands increase, the need for highly dense memory solutions becomes crucial. Magnetic nanostructures offer a pathway to achieve dense memory devices, but standard magnetic memory bit sizes are limited to over 50 nm due to fundamental ferromagnetic properties. In this study, a 10 nm chiral magnetic memory device is introduced using a self‐assembly gold nano‐floret device. The device is composed of a SiGe nanowire with a selectively decorated gold metallic shell deposited at the nanowire tip. The tip with the thiol linkers functions as a weak ferromagnet particle that is stabilized by the chiral ligands. The nano‐floret functions as a high geometrical aspect ratio electrode measuring 30–60 nm in diameter and 1–10 microns in length. The mechanical contact of the Au with a counter Ti electrode forms a nanojunction that can be probed electrically, bridging the gap between the nanoscale and the microscale. In this junction, chiral molecules are adsorbed together with 10 nm super‐paramagnetic iron oxide nanoparticles (SPIONs) forming a magnetic memory device. The same device provides valuable insights into the chiral monolayer properties on selected metal surfaces demonstrating a new approach for characterizing the molecular tilt angle in monolayers of chiral molecules.

Atomic layer deposition of Al₂O₃ onto intrinsic Si and ultra-shallow p-type doping of Si after rapid thermal processing, respectively.

Hematite is a classical photoanode material for photoelectrochemical water splitting due to its stability, performance, and low cost. However, the effect of particle size is still a question due to the charge transfer to the electrodes. In this work, we addressed this subject by the fabrication of a photoelectrode with hematite nanoparticles embedded in close contact with the electrode substrate. The nanoparticles were synthesized by a solvothermal method and colloidal stabilization with charged hydroxide molecules, and we were able to further use them to prepare electrodes for water photo-oxidation. Hematite nanoparticles were embedded within electrospun tin-doped indium oxide nanofibers. The fibrous layer acted as a current collector scaffold for the nanoparticles, supporting the effective transport of charge carriers. This method allows better contact of the nanoparticles with the substrate, and also, the fibrous scaffold increases the optical density of the photoelectrode. Electrodes based on nanofibers with embedded nanoparticles display significantly enhanced photoelectrochemical performance compared to their flat nanoparticle-based layer counterparts. This nanofiber architecture increases the photocurrent density and photon-to-current internal conversion efficiency by factors of 2 and 10, respectively.

Spin electronics is delivering a much desired combination of properties such as high speed, low power, and high device densities for the next generation of memory devices. Utilizing chiral-induced spin selectivity (CISS) effect is a promising path toward efficient and simple spintronic devices. To be compatible with state-of-the-art integrated circuits manufacturing methodologies, vapor phase methodologies for deposition of spin filtering layers are needed. Here, we present vapor phase deposition of hybrid organic-inorganic thin films with embedded chirality. The deposition scheme relies on a combination of atomic and molecular layer deposition (A/MLD) utilizing enantiomeric pure alaninol molecular precursors combined with trimethyl aluminum (TMA) and water. The A/MLD deposition method deliver highly conformal thin films allowing the fabrication of several types of nanometric scale spintronic devices. The devices showed high spin polarization (close to 100%) for 5 nm thick spin filter layer deposited by A/MLD. The procedure is compatible with common device processing methodologies.

Oxides with well-controlled optical and electrical properties are key for numerous advances in nanotechnology, including energy, catalysis, sensors, and device applications. In this study we introduce layer-by-layer deposition of silicon–titanium layered oxide (Si–Ti LO) thin films using combined MLD-ALD methodology (M/ALD). The Si–Ti LO film deposition is achieved by acid–base catalysis establishing an overall catalytic tandem M/ALD super cycle (CT-M/ALD). The catalytic nature of the process allows relatively fast deposition cycles under mild conditions compared with the typical cycle time and conditions required for ALD processes with silane precursors. The Si–Ti LO thin films exhibit tuneable refractive index and electrical conductivities. The refractive index is set by the stoichiometry of Si- to Ti-oxide phases simply by selecting the MLD to ALD proportion in the CT-M/ALD super cycle, with low and high refractive index, respectively. Thermal treatment of Si–Ti LO thin films resulted in conductive thin films with both graphitic and Magnéli oxide phases. Enhanced conductivity and reduced onset temperature for Magnéli phase formation were obtained owing to the unique Si–Ti layer structure and stoichiometry attained by the CT-M/ALD process and facilitated by breaking of Si–C bonds and Red–Ox reactions between the Si sub-oxide and TiO₂ phases leading to the conductive Magnéli phase. Hence, the embedded amine silane functions not only for catalysing Si–Ti LO deposition but also to further promote subsequent transformations during thermal processing. This work demonstrates the concept of embedding a meta-stable organic motif by the MLD step to facilitate transformation of an oxide phase by taking advantage of precise layer-by-layer deposition of alternating phases enabled by M/ALD.

The detection of enantiopurity for small sample quantities is crucial, particularly in the pharmaceutical industry; however, existing methodologies rely on specific chiral recognition elements, or complex optical systems, limiting its utility. A nanoscale chirality sensor, for continuously monitoring molecular chirality using an electric circuit readout, is presented. This device design represents an alternative real-time scalable approach for chiral recognition of small quantity samples (less than 10³ adsorbed molecules). The active device component relies on a gold nanofloret hybrid structure, i.e., a high aspect ratio semiconductor–metal hybrid nanosystem in which a SiGe nanowire tip is selectively decorated with a gold metallic cap. The tip mechanically touches a counter electrode to generate a nanojunction, and upon exposure to molecules, a metal–molecule–metal junction is formed. Adsorption of chiral molecules at the gold tip induces chirality in the localized plasmonic resonance at the electrode–tip junction and manifests in an enantiospecific current response.

Real‐time and label‐free recognition of molecules is highly desired in numerous fields; however, most existing detection schemes require specific functionalization of the device suited for the molecule to be detected and is often complicated by nonselective adsorption. Current detection methodologies that deliver detailed molecular‐level information typically require elaborate analytical instrumentation to overcome these limitations, rendering those costly, not scalable, and nonportable techniques. Herein, a detection scheme is presented that rely on measurement of the tunneling currents through molecules under ambient conditions by employing a robust, scalable, portable, and water‐compatible device. High aspect ratio semiconductor–metal hybrid nanosystems, which feature a metal tip (Au) that functions as a nanoelectrode, are utilized to create self‐formed nanojunctions. Analyte molecules intercalate between the nanoscopic gold tip and a counter electrode, resulting in distinctive tunneling currents. Characteristic dI/dV fingerprint traces, unique to the density of states of the molecular species embedded in the liquid medium, are detectable. Resetting is demonstrated by desorption of adsorbed molecules by applying a reset voltage bias. This study paves the way toward low‐cost, on‐site, and real‐time information‐rich molecular detectors.

Doping methodologies using monolayers offer controlled, ex situ doping of nanowires (NWs), and 3D device architectures using molecular monolayers as dopant sources with uniform, self‐limiting characteristics. Comparing doping levels and uniformity for boron‐containing monolayers using different methodologies demonstrates the effects of oxide capping on doping performances following rapid thermal anneal (RTA). Strikingly, for noncovalent monolayers of phenylboronic acid (PBA), highest doping levels are obtained with minimal thermal budget without applying oxide capping. Monolayer damage and entrapment of molecular fragments in the oxide capping layer account for the lower performance caused by thermal damage to the PBA monolayer, which results in transformation of the monolayer source to a thin solid source layer. The impact of the oxide capping procedure is demonstrated by a series of experiments. Details of monolayer fragmentation processes and its impact on doping uniformity at the nanoscale are addressed for two types of surface chemistries by applying Kelvin probe force microscopy (KPFM). These results point at the importance of molecular decomposition processes for monolayer‐based doping methodologies, both during preanneal capping step and during rapid thermal processing step. These are important guidelines to be considered for future developments of appropriate surface chemistry used in monolayer doping applications.