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1. Omega‐Gate Silicon Nanowire Geometric Diodes with Reconfigurable Self‐Switching Operation and THz Rectification

   https://doi.org/10.1002/aelm.202300466  

   White, Kelly_L; Rogelberg, Gordon_V; Custer, Jr., James_P; Cahoon, James_F (October 2023, Advanced Electronic Materials)

   Abstract Geometric diodes (GDs) represent a relatively unconventional class of diode that produces an asymmetric current response through carrier transport in an asymmetric geometry. Synthesized from the bottom up, Si nanowire‐based GDs are three‐dimensional, cylindrically symmetric nanoscale versions capable of room‐temperature rectification at GHz‐THz frequencies with near zero‐bias turn‐on voltages. Here, by fabricating three‐terminal n‐type Si nanowire GDs with axial contacts and an omega‐gate electrode, a distinct class of reconfigurable self‐switching geometric diodes (SSGDs) is reported. Single‐nanowire SSGD device measurements demonstrate a significant dependence of diode current and polarity on gate potential, where the diode polarity reverses at a gate potential of ≈−1 V under specific grounding conditions. Finite‐element modeling reproduces the experimental results and reveals that the gate potential—in combination with the morphology and dopant profile—produces an asymmetric potential along the nanowire axis that changes asymmetrically with axial bias, altering the effective conductive channel within the nanowire to yield diode behavior. The self‐switching effect is retained in two‐terminal SSGD devices, and modeling demonstrates that both three‐terminal and two‐terminal devices support rectification through THz frequencies. The results reveal a new mechanism of operation for nanowire‐based GDs and characterize a new type of self‐switching diode with reconfigurable polarity. 

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2. Selective phosphorus doping of polycrystalline silicon on glass using self-assembled monolayer doping (MLD) and flash anneal

   https://doi.org/https://doi.org/10.1016/j.matlet.2021.130780  

   Glenn Packard; Carolyn Spaulding; Alex Taylor; Karl Hirschman; Scott Williams, Santosh Kurinec (August 2021, Materials letters)

   Aldo R. Boccaccini (Ed.)

   We report doping of thin (~60 nm) amorphous silicon (a-Si) on glass substrate to form n + polycrystalline silicon on glass in selective regions using Monolayer doping (MLD) via Flash Lamp Annealing (FLA). The phosphorus monolayer was formed on the exposed regions of SiO2 patterned a-Si, through functionalization with chemically bound Diethyl vinylphosphonate (DVP) dopant molecules. The samples were capped with SiO2 and annealed using a single xenon flash pulse (5.0 J/cm2, 250 μs) to simultaneously crystallize a-Si, incorporate and activate phosphorus dopants. SIMS results show an average concentration of 8x1019 cm−3 in the 60 nm of thin silicon on glass. Electrical results show a resistivity of ~6.60x10−2 Ω.cm in doped regions. N-channel field effect transistor devices are successfully demonstrated using this MLD-FLA technique. 

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3. Advanced Materials - Epitaxial Growth of Large-Scale 2D CrTe2 Films on Amorphous Silicon Wafers With Low Thermal Budget

   https://doi.org/10.5281/zenodo.12958062  

   Jin, Wencan (July 2024, Zenodo)

   2D van der Waals (vdW) magnets open landmark horizons in the development of innovative spintronic device architectures. However, their fabrication with large scale poses challenges due to high synthesis temperatures (>500 °C) and difficulties in integrating them with standard complementary metal-oxide semiconductor (CMOS) technology on amorphous substrates such as silicon oxide (SiO2) and silicon nitride (SiNx). Here, a seeded growth technique for crystallizing CrTe2 films on amorphous SiNx/Si and SiO2/Si substrates with a low thermal budget is presented. This fabrication process optimizes large-scale, granular atomic layers on amorphous substrates, yielding a substantial coercivity of 11.5 kilo-oersted, attributed to weak intergranular exchange coupling. Field-driven Néel-type stripe domain dynamics explain the amplified coercivity. Moreover, the granular CrTe2 devices on Si wafers display significantly enhanced magnetoresistance, more than doubling that of single-crystalline counterparts. Current-assisted magnetization switching, enabled by a substantial spin–orbit torque with a large spin Hall angle (85) and spin Hall conductivity (1.02 ×  107 ℏ/2e  Ω⁻¹  m⁻¹), is also demonstrated. These observations underscore the proficiency in manipulating crystallinity within integrated 2D magnetic films on Si wafers, paving the way for large-scale batch manufacturing of practical magnetoelectronic and spintronic devices, heralding a new era of technological innovation. 

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4. Fano Resonance in Ion-Bombarded Au-SiO2 Nanocomposites: Analysis of Mode Coupling and Optical Properties

   https://doi.org/10.3390/coatings15050605  

   Guggilla, Padmaja; Palwai, Sharvare; Davis, Angela; Lassiter, Jonathan; Budak, Satilmis; Varner, Clyde (May 2025, Coatings)

   This study investigates the optical properties of ion-bombarded Au-SiO2 nanocomposites, focusing on the enhanced Fano resonance observed in these samples. The formation of nanocrystals and nanocavities due to ion bombardment leads to significant interactions between plasmonic and vibrational modes, resulting in pronounced Fano resonance in the strong coupling regime. The study aims to explain the closer spacing of modes, the elevated baseline absorbance, and the asymmetric lineshape observed in the ion-bombarded samples. A detailed analysis is provided, comparing these findings with other sample preparations, such as Au-coated SiO2 and 20 nm Au colloidal on SiO2. The implications of these results for understanding plasmonic behavior and their potential applications in nanophotonics are discussed. 

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5. CuTi as Potential Liner- and Barrier-Free Interconnect Conductor

   https://doi.org/10.1109/TED.2024.3373376  

   Zhang, Minghua; Gall, Daniel (May 2024, IEEE Transactions on Electron Devices)

   CuTi layers are co-sputter deposited on 20-nm-SiO2/Si(001) wafers at 350 ℃ to quantify their stability in direct contact with a dielectric and to explore the potential of CuTi as barrier- and liner-free interconnect metal. X-ray diffraction pole figures indicate a preferred 001 out-of-plane crystalline orientation and Rutherford backscattering confirms a stoichiometric composition. Vacuum annealing tests at 450 ℃ of CuTi layers indicate considerably higher thermal stability than for pure Cu layers, including negligible dewetting observed by scanning electron microscopy and negligible intermixing with the oxide substrate quantified by photoelectron spectroscopy. Four-point bend tests show a 25% higher interfacial toughness for CuTi/SiO2 than Cu/SiO2 interfaces. CuTi/SiO2 samples also exhibit a 300-times longer failure time than Cu/SiO2 during time-dependent dielectric breakdown tests using an externally applied 3 MV/cm electric field. The higher stability of CuTi in comparison to Cu is attributed to a higher cohesive energy in combination with an atomically thin self-limiting Ti oxide layer at the CuTi/SiO2 interface. 

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