Materials with near‐zero temperature coefficient of resistivity (nz‐TCR) are critical for precision electronics operating across wide temperature ranges, yet achieving ultra‐stable resistivity remains a challenge. Here, a mixed nitride Ti─Si─N thin film system is demonstrated exhibiting exceptional nz‐TCR stability (0.05 ppm K −1 ) from 80 to 420 K, realized through atomic‐level control of electron scattering mechanisms. By tuning Si content in TiN (2–4 at%), a TCR transition from metallic (positive) to insulating (negative) behavior is induced, with optimal stability at Ti 0.98 Si 0.02 N. Atomic layer deposition enables precise synthesis, while structural, electronic, and thermal characterization, supported by density functional theory‐based calculations, reveal that nz‐TCR arises from a control of elastic mean free path and average diffusion length of electrons. The elastic mean free path (0.712 nm) approaches the lattice parameter (0.455 nm), and the average diffusion length (5.5 nm) aligns with the size of Si decorated grains (5.66 nm), thus leading to temperature invariant electronic transport. This work provides a generalizable design principle for ultra‐stable nz‐TCR resistors using composition control and grain‐boundary engineering.

This paper presents a large-scale ab initio simulation study of amorphous silicon hydride (a-Si1-xHx) with an emphasis on the structure and properties of the material across a range of hydrogen concentration by combining accelerated molecular dynamics (MD) simulations with first-principles density-functional calculations. The accelerated MD scheme relied on classical metadynamics, which enabled the development of 2500+ high-quality structural models of a-Si1-xHx, with system sizes ranging from 150 to 6000 atoms and hydrogen concentrations vary from 6 to 20 at. %. The resulting amorphous networks were found to be completely free from any coordination defects and that they all exhibited a pristine band-gap in their electronic spectrum. The microstructural properties of hydrogen distributions were examined with an emphasis on the presence of isolated and clustered environments of hydrogen atoms. The results were compared with experimental data obtained from X-ray diffraction, infrared spectroscopy and nuclear magnetic resonance studies.

As topological insulators (TIs) are becoming increasingly intriguing, the community is exploring transformative applications that require interfacing TIs with other materials such as ferromagnets or superconductors. Herein, we report on the manifestations of superconducting electrons carried by topological surface states (TSS) in Bi2Se3 films. As key signatures of TSS-carried Cooper pairs, we uncover the hysteresis of magnetoresistance (MR) and the switching behavior of anisotropic magnetoresistance (AMR). For in-plane fields perpendicular to the injected current, AMR shows negative switching (resistance drop) when the contacts become superconducting, which is consistent with a cooperative Zeeman effect enabled by the spin-momentum locking of TSS. The MR and AMR behaviors are robust, occurring reliably in multiple samples, from different sources, and with different defect concentrations. Our findings can guide novel developments in superconductor/TI quantum devices relying on supercurrent detection as well as lead to more refined transport signatures of Majorana zero-modes in the future.

Atomic Layer Deposition processed (ALD) titanium silicon nitride (TiSiN) thin film was investigated as a diffusion barrier. TiSiN successfully reduced the out-diffusion of boron from the poly-Si layer on the Si substrate by 10 times and fluorine into the substrate from the subsequent W deposition by 2 times. Si doping caused the TiSiN to be deposited in an amorphous phase even though TiN easily crystallizes to a columnar polycrystalline structure which could be a diffusion path. In addition, ultra-thin TiSiN films maintain continuity and conformality which can fulfill the requirements of a diffusion barrier and simplify the stack integration.

As the generation of memory devices evolve, the successful fabrication of high aspect ratio (HAR) features becomes more and more challenging. Apart from the traditional patterning, deposition and etch related issues, conformal film deposition onto these HAR structures becomes a critical parameter in determining the overall device yields. It is well established now that compared to conventional deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), atomic layer deposition (ALD) offers a pathway to highest conformality and step-coverage. On the other hand, film conformality, especially roughness property has trade-off relationship to step-coverage property. High-pressure process is appropriate to obtain high step-coverage performance in short ALD cycle time process, but roughness value becomes worse due to higher chance of crystalline film growth at high-pressure process condition. High roughness causes local variations in step-coverage and poses problems for deposition of subsequent layers and device performance. In the present study, we report that it is possible to obtain conformal and smooth TiN film by using low/high pressure two-step growth, initially low-pressure TiN growth, and secondly high-pressure TiN growth on the non-pattern and HAR pattern wafers. Eugenus’s versatile 300mm mini-batch system and HAR structures with approximately 120:1 (Dimension of bottom opening, and total height are approximately 17nm and 2μm, respectively) were used in this research, respectively. TiCl4 and NH3 were used as the precursors for TiN film deposition and grown TiN films were analyzed by using ellipsometry, atomic force microscopy (AFM) and transmission electron microscopy (TEM) to study the film properties and step-coverages. In addition, reactor-scale computational fluid dynamics (CFD) simulations were performed and correlated to on-wafer experimental results and utilized as a predictive tool. It was found that TiN film grown at low-pressure condition was more conformal and smoother than that grown at high-pressure condition, although step coverage value grown at low-pressure condition was worse than that grown at high-pressure condition. By optimizing low/high pressure two-step TiN growth condition, it was achieved that not only better roughness than that of pure high-pressure TiN, but also, better step coverage value than that of pure low-pressure TiN as well as than that of pure high-pressure TiN (Figure 1). Figure 1

Atomic layer deposition (ALD) is used to systematically vary the composition of TiSixN films by modulating the ratio of Ti and Si precursors with NH3 as a coreactant. The as-synthesized films have varying atomic (at.) % Si (0 ≤ x ≤ 24.2) to provide both metallic (i.e., TiN) and insulating (i.e., Si3N4) behavior. The competing material properties reduce the temperature coefficient of resistivity (TCR) of the film, thereby generating a regime where electrical conductance is independent of temperature. The TiSixN (Si = 3.4 at. %) film with 139.6 nm thickness exhibits a near-zero TCR of −23 ppm K−1, between 298 and 398 K, and a resistivity of 348.1 μΩ cm. Materials characterization using x-ray reflectometry, x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy, in conjunction with van der Pauw measurement and spectroscopic ellipsometry, are conducted to characterize film properties. Correlating structural, electrical, and optical properties provides insights into the electronic interactions of TiN with Si3N4, synthesized as an ALD nanocomposite thin film.

Free standing silica thin films with perpendicular ordered nanopores were obtained by electro-assisted self-assembly and subsequent detachment from PEDOT:PSS coated indium tin oxide (ITO) substrates.

Systematic optimization of molecular beam epitaxy growth parameters enabled high quality heteroepitaxy of In2Se3 on Si(111) surfaces. Surfaces of the best epilayers were characterized by atomically flat terraces that extended laterally for several hundred nanometers. These terraces were separated by single quintuple layer high steps. These In2Se3 films were suitable for subsequent high quality epitaxy of Bi2Se3. The quality of the In2Se3/Bi2Se3 interface was confirmed using atomic resolution transmission electron microscopy.

Using the Au-seeded vapor-liquid-solid technique, epitaxial single-crystal Si nanowires (NWs) can be grown laterally along Si(111) substrates that have been miscut toward [112¯]. The ratio of lateral-to-vertical NWs increases as the miscut angle increases and as disilane pressure and substrate temperature decrease. By exploiting these trends, conditions can be identified whereby all of the deposited Au seeds form lateral NWs. Growth is guided along the nanofaceted substrate via a mechanism that involves pinning of the trijunction at the liquid/solid interface of the growing nanowire.

Graphene oxide holds promise as a carbon-based nanomaterial that can be produced inexpensively in large quantities. However, its structural and electrical properties remain far from those of the graphene sheets obtained by mechanical exfoliation or by chemical vapor deposition—unless efficient reduction methods that preserve the integrity of the parent carbon-network structure are found. Here, the authors use molecular dynamics and density functional theory calculations to show that the oxygen from the main functional groups present on graphene oxide sheets is removed by the reducing action of carbon monoxide; the energy barriers for reduction by CO are very small and easily overcome at low temperatures. Infrared and Raman spectroscopy experiments confirm the reduction in CO atmosphere and also reveal a strong tendency for CO to heal vacancies in the carbon network. Our results show that reduced graphene oxide with superior properties can be obtained through reduction in CO atmosphere.

A systematic study of tin-catalyzed vapor-liquid-solid (VLS) growth of silicon nanowires by plasma enhanced chemical vapor deposition at temperatures ranging from 300 to 400 degrees C is presented. Wire structure, morphology, and growth rate are - characterized as a function of process variables; The:nanowires are observed to have a crystalline core with a. polycrystalline shell due to simultaneous VLS axial growth and vapor-solid radial. growth Axial and radial growth rates are controllable through hydrogen dilution of the plasma which affects the concentration Of silane radicals in the plasma. In addition, wire length is observed to saturate with increasing, growth time Post growth chemical analysis suggests this is due to etching and disappearance of tin Seeds in the hydrogen plasma which occur in parallel with wire growth. This opens up the possibility of a unique in situ approach to fabricating metal-free nanowire arrays for device applications.

A systematic hybrid density functional theoretical study of three different types of single walled SiGe nanotubes in armchair (n, n) and zigzag (n, 0) (3 <= n <= 11) configurations is presented. The nanotubes have been represented by finite clusters with the dangling bonds saturated by hydrogen atoms. All structures have been both geometry and spin optimized without any symmetry constraints. Stability trend differs among armchair and zigzag nanotubes for the three different types. However, all SiGe nanotubes are semiconducting in nature, with a wide spectrum of band gaps. (C) 2008 Elsevier B. V. All rights reserved.

First principles calculations have been performed to study the electronic and geometric structures of zigzag and chiral silicon nanotubes and compared with the properties of armchair silicon nanotubes. The finite cluster approach with dangling bonds saturated with hydrogen atoms has been used. The theoretical formalism used is the hybrid density functional theory incorporating Hartree-Fock (HF) exchange with the density functional theory (DFT) exchange-correlation functional. In particular, we have used Becke's three parameter with the exchange-correlation functionals of Lee, Yang, and Parr (B3LYP) hybrid functional and the Los Alamos pseudopotential with the associated basis set LANL2DZ as implemented in the Gaussian 03 suite of programs. For silicon, the 1s, 2s, and 2p electrons have been represented by core potentials and the remaining electrons as valence states. A detailed comparison of the structures and stabilities of the nanotubes has been performed and the dependence of the electronic band gaps on the respective tube diameters has been investigated. We have also compared our results with other results published in the literature. Si-Si bond length alternation in SiNTs is more pronounced in SiNTs than that in CNTs, indicating a strong tendency for bond delocalization in Si nanotubes. Also as the number of Si atoms and tube diameter increases, the binding energy per atom for armchair nanotubes approaches saturation value. The band gaps of all the different nanotubes that we have studied vary from 0.129 eV (chiral 6, 2) to 1.159 eV (chiral 6, 3). We infer that some chiral SiNTs can possibly indicate metallic behavior. The Mulliken charge analysis shows that zigzag structures has predominantly ionic bonding while armchair and some of the chiral structures are covalently bonded.

Ab initio calculations within the framework of hybrid density functional theory and the finite cluster approximation have been performed for the electronic and geometric structures of three different types of armchair germanium carbide nanotube, from (3, 3) to (11, 11). Full geometry and spin optimizations with unrestricted symmetry have been performed. Physically pertinent quantities of interest such as the cohesive energies, band gaps, radial buckling, density of states, dipole moments, and Mulliken charge distributions have been investigated in detail for all nanotubes. For type I nanotubes, the largest cohesive energy obtained is 4.092 eV/atom, whereas for type II and type III nanotubes, the values are 3.987 eV/atom and 3.968 eV/atom, respectively. For optimized type I nanotubes, Ge atoms moved toward the tube axis and C atoms moved in the opposite direction after relaxation, opposite to the trends observed in types II and III. The band gaps for type I nanotubes are larger than the bulk 3C-GeC gap, varying between 2.666 and 3.016 eV, while type II and type III nanotubes have significantly lower band gaps, with all nanotubes being semiconducting in nature. Mulliken charge analysis indicates primarily ionic behavior for type I GeC nanotubes and a mixed ionic with covalent behavior for the other two types. None of the tubes appear to be magnetic. Applications in the field of nano-optoelectronic devices, molecular electronics, and band gap engineering are envisioned for GeC nanotubes.