Surface Functionalized Titanium Nitride Electrode for CMOS Compatible Bioelectronic Devices.

Titanium nitride (TiN) films were tested for their suitability as upper electrodes in metal–oxide–semiconductor (MOS) capacitors and Schottky diodes and as metal gate electrodes in fin field effect transistor devices. TiOxNy formation on TiN surfaces was confirmed by x-ray photoelectron spectroscopy and appears to be associated with exposure of the metal electrodes to ambient air. In order to avoid the formation of TiOxNy and TiO2, a layer of aluminum (Al) was deposited in situ after the TiN deposition. TiN work function was calculated for the devices to study how dipole variation at the interface TiN/SiO2 influences TiN work function. TiOxNy and TiO2 formation at the film surface was found to affect the dipole variations at the TiN/SiO2 interface increasing the dipole influence on MOS structure. Furthermore, the estimated values TiN work function are suitable for complementary metal–oxide–semiconductor (CMOS) technology. Finally, this work had shown that Al/TiN structure can be used in CMOS technology, especially on n-type metal–oxide–semiconductor field effect transistor devices.

Ongoing advancements in the design and fabrication of semiconductor devices have prompted the exploration of chemical approaches for the metallization of titanium nitride (TiN), a uniquely conductive ceramic material, as alternatives to conventional, high-cost, physical-based deposition techniques. Although direct electrolytic deposition of thin metallic films onto TiN surfaces remains industrially impractical, electroless metallization using an amine-terminated seed layer presents a promising solution. In this study, a copolymer of 4-nitrophenyl and 4-vinylpyridine (a PVP-like film) is successfully electrografted onto the TiN surface via diazonium chemistry. The interaction between the resulting amine-terminated PVP-like seed layer and a PdCl2/HCl activator is throughout investigated to provide insight into the autocatalytic mechanism underlying the electroless nickel plating process. This process facilitates the formation of a compact, continuous nickel–boron (Ni–B) thin film. The electrolessly deposited Ni–B layer serves as a robust base for subsequent electrolytic copper deposition, enabling the effective filling of serpentine structures in silicon microdevices. Thus, this work introduces a fully aqueous metallization approach suitable for microelectromechanical systems (MEMS). More importantly, covalent bonding of the electrografted polymer, as confirmed by X-ray photoelectron spectroscopy (XPS), is discussed to elucidate the strong adhesion properties of the PVP-like/Ni–B/Cu multilayer stack on the TiN surface.

The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxy-nitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were ∼1.5 and ∼1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260 ± 70 ng/cm(2).

ABSTRACTAbility to control key characteristics of electrodeposited polymers plays a vital role for their applications. In this work the results on tailoring the thickness of electronically insulating poly(phenylene oxide) (PPO) type polymer films have been showed. Pinhole‐free PPO films with variable thickness in the range of 10–50 nm were grown by controlling the potential applied during the electrochemical polymerization on the surface of titanium nitride (TiN) substrates. The insulating properties of the PPO film were confirmed by testing its permeability to redox species by cyclic voltammetry. Thermal stability of the PPO films with different thicknesses was investigated by in‐situ spectroscopic ellipsometry up to 400 °C in various environments. This insight is important for the optimization of the PPO anneal conditions in order to remove the residual solvent and potentially improve the polymer chains stacking. Our results provide the basis for electrodeposition of PPO films with variable thickness for diverse applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44533.

Adsorption and desorption kinetics of tetrakis(dimethylamino)titanium and dimethylamine on TiN surfaces

Surface chemistry and film growth during TiN atomic layer deposition using TDMAT and NH 3

Lithium sulfide (Li2 S) is a promising cathode material with high capacity, which can be paired with nonlithium metal anodes such as silicon or tin so that the safety issues caused by the Li anode can be effectively avoided. However, the Li2 S full cell suffers from rapid capacity degradation due to the dissolution of intermediate polysulfides. Herein, a Li2 S/Si full cell is designed with a Li2 S cathode incorporated by titanium nitride (TiN) polysulfide immobilizer within parallel hollow carbon (PHC). This full cell delivers a high initial reversible capacity of 702 mAh gLi2S -1 (1007 mAh gsulfur -1 ) at 0.5 C rate and excellent cyclability with only 0.4% capacity fade per cycle over 200 cycles. The long cycle stability is ascribed to the strong polysulfide anchor effect of TiN and highly efficient electron/ion transport within the interconnected web-like architecture of PHC. Theoretical calculations, self-discharge measurements, and anode stability experiments further confirm the strong adsorption of polysulfides on the TiN surface. The present work demonstrates that the flexible Li2 S cathode and paired Si anode can be used to achieve highly efficient Li-S full cells.

The physical and electrical properties as well as thermal stability of reactively sputtered titanium nitride (TiN) film serving as a diffusion barrier was studied for silver (Ag) metallization. The thermal stability of Ag/TiN metallizations on Si with 12-nm-thick TiN barriers, as-deposited and after annealing at 300-650°C in N2/H2 for 30 min, was investigated with sheet resistance measurement, X-ray diffraction, focused ion beam-scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. According to electrical measurement no change of sheet resistance was found after annealing at 600°C, but an abrupt rise appeared at 650°C annealing. There are two causes by which the Ag/TiN/Si structure became degraded. One is agglomeration of the silver layer, and the other is oxidation and diffusion which are also associated problems during thermal annealing.

Coating of Ti-6Al-4V alloy substrates with TiN/Ti multi-layered films by magnetron sputtering in Ar gas atmosphere was examined, aiming at the application of the alloy to artificial heart valves, in order to improve not only the adhesion between the deposited film and the alloy but also the surface smoothness of titanium nitride coatings and thereby to improve the blood compatibility as well as the biocompatibility of the alloy coated with the titanium nitride film. The effects of the thickness of the TiN (titanium nitride) layer on the surface morphology of the film were investigated, in order to develop TiN coatings with higher blood compatibility. The multi-layered films were deposited by sputtering in sequence pure titanium and titanium nitride targets. The thickness of titanium nitride layer was varied from 300 nm to 800 nm, while that of pure titanium was constantly 200 nm. Under visual observation, the obtained multi-layered films looked yellow gold and appeared to be uniform and adhesive, while TiN monolithic films deposited directly onto the alloy substrate under the same sputtering conditions peeled off partly. Therefore it was found that the multi-layered thin films were more adhesive to the alloy than the monolithic films. According to AFM (Atomic Force Microscope) images for both of the films, the surface morphology of each TiN layer observed under the scope of nanometer-scaled area was rough with pits and bumps, while that under the scope of micrometer-scaled area was smooth without such pits and bumps. Furthermore based on the AFM, the surface roughness measured under the area of nanometer scale was found to increase with the increase of the thickness of the TiN layer in the multi-layered film, although that measured under the area of micrometer scale was assumed to be independent of the thickness of the TiN layer.

Reactive magnetron sputtering technique was used to gain titanium nitride (TiN) films on W18Cr4V high-speed steel and GCr15 bearing steel substrates at low temperature. The Surface chemical composition of the films was analyzed using energy dispersive X-ray spectroscopy (EDXS) and the surface morphology was examined using atomic force microscopy (AFM). Moreover, a series of experiments have been conducted to study the relationship between interfacial bonding strength and some major technological parameters, that is, substrate surface roughness, negative bias voltage, intermediate transition layer, substrate hardness, and ion etching before deposition. The experimental results have indicated that the TiN film with typical ratio of chemical metric can be deposited on substrates using reactive magnetron sputtering technique below 140°C. The AFM image has showed that the TiN film using magnetron sputtering technique was composed of densely distributed nano-grains with uniform structure. Its surface was flat and smooth. The indentation testing results have showed that the increase of surface roughness and substrate hardness improves the bonding strength of TiN / substrate significantly. Furthermore, the bonding strength of TiN / substrate can also be improved through the following methods: (1) choosing a proper intermediate transition layer; (2) adopting ion etching before deposition and (3) increasing negative bias voltage before deposition.

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XPS study for reactively sputtered titanium nitride thin films deposited under different substrate bias

In this study, type I collagen was fixed onto plasma-sprayed porous titanium coatings by either adsorptive immobilization or covalent immobilization. Surface characterization by scanning electron microscopy (SEM), diffuse reflectance Fourier transform infrared spectroscopy (DR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the biochemical modification of the titanium coatings. The immobilizing effects of type I collagen, including variations in the amount and stability of collagen, were investigated using Sirius red staining. A greater amount of collagen was found on the covalently immobilized titanium coating, and higher stability was achieved relative to the absorptive immobilization surface. Human mesenchymal stem cells (hMSCs) were used to evaluate the cytocompatibility of the modified titanium coatings. Type I collagen immobilized on titanium coating led to enhance cell-material interactions and improved hMSC functions, such as attachment, proliferation, and differentiation. Interestingly, covalently immobilized collagen on titanium coating showed a greater capability to regulate the osteogenic activity of hMSCs than did absorbed collagen, which was explained in terms of the increased amount and higher stability of the covalently linked collagen. The type I collagen covalently immobilized titanium coatings with improved biological function may exhibit better osteointegration in clinical application.

This study investigates ultrathin titanium nitride (TiN) films in terms of their crystallographic structure, surface chemistry, sheet resistance and mechanical durability. These TiN ultrathin films were created by Atomic Layer Deposition (ALD) using TiCl4 and NH3 as precursors. The process consisted of 100, 200, 300 and 400 deposition cycles yielding ultrathin films 4.7, 9.4, 14.1 and 18.8 nm in thickness, respectively. Different planar substrates were employed, namely Si wafers, soda lime glasses and Ti foil. Based on image analyses, the deposition rate of 0.047 nm per cycle for ALD TiN (at 400 °C) was determined. A sheet resistance of 287 Ω/□ was achieved for the 18.8 nm film. X-ray diffraction (XRD) analysis confirmed the formation of cubic TiN with increasing crystallinity and texture with increased thickness. Sputter depth profiling in tandem with X-ray photoelectron spectroscopy (XPS) distinguished the uppermost oxidized surface from the stoichiometric TiN core in the films. Scratch tests demonstrated an enhanced adhesion and scratch resistance with ALD TiN films, aligned with the observed microstructural improvements. The comprehensive correlation between the film thickness, and their chemical composition, crystalline structure and mechanical performance highlights the vital role of ALD parameters in preparing TiN thin films for advanced technological applications.

Friction and wear of TiN-4140 steel couples in methanol