Ultrathin W-Al dual interlayer approach to depositing smooth and adherent nanocrystalline diamond films on stainless steel

Diamond Deposition on Iron and Steel Substrates: A Review

This article presents an overview of the research in chemical vapor deposition (CVD) diamond films on steel substrates. Since the steels are the most commonly used and cost-effective structural materials in modern industry, CVD coating diamond films on steel substrates are extremely important, combining the unique surface properties of diamond with the superior toughness and strength of the core steel substrates, and will open up many new applications in the industry. However, CVD diamond deposition on steel substrates continues to be a persistent problem. We go through the most relevant results of the last two and a half decades, including recent advances in our group. This review discusses the essential reason of the thick catalytic graphite interlayer formed on steel substrates before diamond deposition. The high carbon diffusion in iron would induce severe internal carburization, and then voluminous graphite precipitated from the substrate. In order to hinder the catalytic graphite formation, various methods have been applied for the adherent diamond film deposition, such as pre-imposed various interlayers or multi-interlayers, special controls of the deposition process, the approaches of substrate alloying and so on. We found that adherent diamond films can be directly deposited on Al alloying steel substrates, and then the role of Al alloying element was examined. That is a thin dense amorphous alumina sublayer in situ formed on the alloying substrate, which played a critical role in preventing the formation of graphite phase and consequently enhancing diamond growth and adhesion. The mechanism of Al alloying suggests that the way used to improve hot corrosion resistance is also applicable. Then, some of the hot corrosion resistance methods, such as aluminizing, siliconizing, and so on, which have been used by some researchers examining CVD diamond films on steel substrates, are reviewed. Another way is to prepare diamond-like carbon (DLC) films on steel substrates at low temperature, and then the precipitated graphite from the internal carburization can be effectively avoided. In addition, based on some new findings, the understanding of the diamond nucleation and metastable growth is discussed.

Catalytic CVD synthesis of boron nitride and carbon nanomaterials - synergies between experiment and theory

Low-dimensional carbon and boron nitride nanomaterials - hexagonal boron nitride, graphene, boron nitride nanotubes and carbon nanotubes - remain at the forefront of advanced materials research. Catalytic chemical vapour deposition has become an invaluable technique for reliably and cost-effectively synthesising these materials. In this review, we will emphasise how a synergy between experimental and theoretical methods has enhanced the understanding and optimisation of this synthetic technique. This review examines recent advances in the application of CVD to synthesising boron nitride and carbon nanomaterials and highlights where, in many cases, molecular simulations and quantum chemistry have provided key insights complementary to experimental investigation. This synergy is particularly prominent in the field of carbon nanotube and graphene CVD synthesis, and we propose here it will be the key to future advances in optimisation of CVD synthesis of boron nitride nanomaterials, boron nitride - carbon composite materials, and other nanomaterials generally.

High-performance flexible electron field emitters fabricated from doped crystalline Si pillar films on polymer substrates

A high-performance flexible Si film-based field emission prototype device using H₂ plasma treated B-doped crystalline Si pillar nanostructure as cathode on polymer substrate is proposed.

The effects of Ti carbonization on the nucleation and oriented growth of diamond films on cemented carbide

To better understand the influence of carbonization of the Ti interlayer on diamond nucleation and growth, a series of Ti/diamond composite films were deposited on cemented carbide (WC:Co) substrates using a two-step deposition technique. The microstructural properties of the composite films were then characterized by scanning electron microscopy, X-ray diffractometry, and Raman spectroscopy, and their tribological properties were evaluated using a ball-on-disc tester and a metalloscope. The results showed that differences in carbonization for five Ti interlayers of different thicknesses led to variations in the preferred orientations of the TiC layers and in the subsequent nucleation and oriented growth of diamond. This suggests that Ti carbonization significantly influences the nucleation and growth of diamond and subsequently causes variations in the tribological properties of the produced diamond films.

Novel aspect in grain size control of nanocrystalline diamond film for thin film waveguide mode resonance sensor application

Nanocrystalline diamond (NCD) thin film growth was systematically investigated for application for the thin film waveguide mode resonance sensor. The NCD thin film was grown on the Si wafer or on the SiO2-coated sapphire substrate using the hot filament chemical vapor deposition (HFCVD). The structural/optical properties of the samples were characterized by the high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), near edge X-ray absorption fine structure (NEXAFS), X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. The waveguide modes of the NCD layer were studied by prism coupler technique using laser (wavelength: 632.8 nm) with varying incident angle. A novel aspect was disclosed in the grain size dependence on the growth temperature at the relatively low methane concentration in the precursor gas, which was important for optical property: the grain size increased with decreasing growth temperature, which was contrary to the conventional knowledge prevailing in the microcrystalline diamond (MCD) domain. We have provided discussions to reconcile such observation. An optical waveguide mode resonance was demonstrated in the visible region using the microstructure-controlled transparent NCD thin film waveguide, which provided a strong potential for the waveguide mode resonance sensor applications.

Engineering the interface characteristics of ultrananocrystalline diamond films grown on Au-coated Si substrates

Enhanced electron field emission (EFE) properties have been observed for ultrananocrystalline diamond (UNCD) films grown on Au-coated Si (UNCD/Au-Si) substrates. The EFE properties of UNCD/Au-Si could be turned on at a low field of 8.9 V/μm, attaining EFE current density of 4.5 mA/cm(2) at an applied field of 10.5 V/μm, which is superior to that of UNCD films grown on Si (UNCD/Si) substrates with the same chemical vapor deposition process. Moreover, a significant difference in current-voltage curves from scanning tunneling spectroscopic measurements at the grain and the grain boundary has been observed. From the variation of normalized conductance (dI/dV)/(I/V) versus V, bandgap of UNCD/Au-Si is measured to be 2.8 eV at the grain and nearly metallic at the grain boundary. Current imaging tunneling spectroscopy measurements show that the grain boundaries have higher electron field emission capacity than the grains. The diffusion of Au into the interface layer that results in the induction of graphite and converts the metal-to-Si interface from Schottky to Ohmic contact is believed to be the authentic factors, resulting in marvelous EFE properties of UNCD/Au-Si.