Advanced Chemical Vapor Deposition Research Articles

Centimeter-level MoS2 films with controllable number of layers by face-to-face chemical vapor deposition strategy

Two-dimensional layered transition metal dichalcogenides (TMDCs) are highly promising in field-effect-transistors (EFTs), photodetectors, flexible devices, but the limitation of uncontrollable size and number of layers is a huge challenge for the development of these devices. Although some breakthroughs like wafer-level MoS2 have been achieved on specific substrates such as copper foil or sapphire using advanced chemical vapor deposition, electrical and optoelectronic testing requires the transfer of material from these substrates to SiO2/Si substrates. In this paper, we developed a face-to-face confined space CVD scheme for the preparation of centimeter-level MoS2 thin films on amorphous SiO2/Si substrate. In contrast to traditional confined-space CVD scheme where the MoO3 powder is often piled like a small hill in the small quartz boat, The MoO3 powder is evenly spread in the small quartz boat, facing directly up to the growing substrate with a “face-to-face” growth mode. Therefore, the nucleation centers are uniformly distributed on the growing substrate, finally resulting in a uniform and clean continuous film originating from the coalescence of numerous MoS2 domains grown up from these nucleation centers. The layer number can be well controlled by adjusting growing parameters like growing temperature, gas flow rate and growth time. Our facile but robust face-to-face growth strategy may be a great supplementary to the wafer-level growth of 2D TMDCs.

CVD Synthesis of 3D-Shaped 3D Graphene Using a 3D-Printed Nickel-PLGA Catalyst Precursor.

Earlier, various attempts to develop graphene structures using chemical and nonchemical routes were reported. Being efficient, scalable, and repeatable, 3D printing of graphene-based polymer inks and aerogels seems attractive; however, the produced structures highly rely on a binder or an ice support to stay intact. The presence of a binder or graphene oxide hinders the translation of the excellent graphene properties to the 3D structure. In this communication, we report our efforts to synthesize a 3D-shaped 3D graphene (3D2G) with good quality, desirable shape, and structure control by combining 3D printing with the atmospheric pressure chemical vapor deposition (CVD) process. Direct ink writing has been used in this work as a 3D-printing technique to print nickel powder–PLGA slurry into various shapes. The latter has been employed as a catalyst for graphene growth via CVD. Porous 3D2G with high purity was obtained after etching out the nickel substrate. The conducted micro CT and 2D Raman study of pristine 3D2G revealed important features of this new material. The interconnected porous nature of the obtained 3D2G combined with its good electrical conductivity (about 17 S/cm) and promising electrochemical properties invites applications for energy storage electrodes, where fast electron transfer and intimate contact with the active material and with the electrolyte are critically important. By changing the printing design, one can manipulate the electrical, electrochemical, and mechanical properties, including the structural porosity, without any requirement for additional doping or chemical postprocessing. The obtained binder-free 3D2G showed a very good thermal stability, tested by thermo-gravimetric analysis in air up to 500 °C. This work brings together two advanced manufacturing approaches, CVD and 3D printing, thus enabling the synthesis of high-quality, binder-free 3D2G structures with a tailored design that appeared to be suitable for multiple applications.

Universal Precise Growth of 2D Transition-Metal Dichalcogenides in Vertical Direction.

Two-dimensional transition-metal dichalcogenides (TMDs) have been one of the hottest focus of materials due to the most beneficial electronic and optoelectronic properties. Up to now, one of the big challenges is the synthesis of large-area layer-number-controlled single-crystal films. However, the poor understanding of the growth mechanism seriously hampers the progress of the scalable production of TMDs with precisely tunable thickness at an atomic scale. Here, the growth mechanisms in the vertical direction were systemically studied based on the density functional theory (DFT) calculation and an advanced chemical vapor deposition (CVD) growth. As a result, the U-type relation of the TMD layer number to the ratio of metal/chalcogenide is confirmed by the capability of ultrafine tuning of the experimental conditions in the CVD growth. In addition, high-quality uniform monolayer, bilayer, trilayer, and multilayer TMDs in a large area (8 cm2) were efficiently synthesized by applying this modified CVD. Although bilayer TMDs can be obtained at both high and low ratios of metal/chalcogenide based on the suggested mechanism, they demonstrate significantly different optical and electronic transport properties. The modified CVD strategy and the proposed mechanism should be helpful for synthesizing and large-area thickness-controlled TMDs and understanding their growth mechanism and could be used in integrated electronics and optoelectronics.

Fabrication of free-standing vertically aligned carbon nanotubes structures by pyrolysis of ferrocene in conditions of low to high local ‘carbon-to metal’ ratio

We report the observation of selective fabrication of carbon nano-onions (CNOs) and carbon nanotubes (CNTs) films in an advanced chemical vapour deposition (CVD) approach. Selective formation of these nanostructures is triggered by a residence-time induced variation of carbon to metal ratios in the atomic species of the pyrolyzed ferrocene vapour. The use of high sublimation temperatures is found to play a crucial role in reducing such residence time. Due to this effect, free standing vertically aligned CNTs films could be nucleated in the outer zone of the CVD reactor. The characteristics of these structures were investigated using multiple characterization techniques, namely: TEM, SEM, XRD, UV–vis and Raman spectroscopy.

Encapsulation of FePt and FePt3 alloys inside carbon-foam materials

We demonstrate an advanced chemical vapour deposition (CVD) approach in which the addition of Pt-containing hydrocarbons to ferrocene allows the nucleation of a novel carbon-foam material completely filled with elemental Fe and Pt crystal-phases. These phases are then found to alloy into tetragonal FePt and cubic FePt3 in specific annealing conditions. A dependence of the FePt nucleation on the Ar/H2 flow rate is reported. In addition, high pressure (5 GPa) experiments are found to favor the formation of a single FePt3 encapsulated phase together with the nucleation of C–O rich carbon layers in the foam surface.

The Next Level of Advanced Interface Research

With the first issue in 2018, Advanced Materials Interfaces is entering its 5th year as a journal publishing top-level research on interface technologies and effects – a good occasion to take a look back. Since its launch as an independent journal in 2014, Advanced Materials Interfaces has established its role as an outlet for high-quality research on surface and interface science. In this short time, it has already attracted many important, highly interdisciplinary contributions from recognized experts from all over the world. The number of submissions has been steadily increasing over the years and only in 2017 Advanced Materials Interfaces received already more than 1600 manuscripts and published almost 400 articles. We are very grateful to all authors and to our reviewers and Editorial Board Members who ensure that only the very best articles are finally selected for publication. The impact of the journal is also reflected in the first full Impact Factor of 4.279 (2017 Journal Citation Reports) confirming the influence and importance of the journal within the scientific community. A selection of top-cited articles in 2017 can be found in Table 1. Some articles have drawn additional attention via news and social media platforms, which is reflected by their high Altmetric score. A selection of articles that had an exceptionally broad impact in media in 2017 is shown in Table 2. One of the journal's highlights represent the Special Issue of the Max-Planck Institute of Colloids and Interfaces – Perspectives in Interface Research – which was guest edited by Helmuth Möhwald and the Special Issue on Advances in Chemical Vapor Deposition dedicated to Michael Hitchman and guest edited by Francis Maury et al. In 2018 Advanced Materials Interfaces continues presenting high-level publications to its readers. For example, the next special issues to be released this year will deal with “Interfacial Engineering of Perovskite Solar Cells” guest edited by E. Kymakis and “Self-Healing Materials” guest edited by N. De Belie et al. We are particularly happy to celebrate our 5th volume. On this occasion we are starting an Advanced Materials Interfaces Hall of Fame series of invited-only review articles from the top scientists in the field. These selected contributions will be published in the upcoming issues of this year. Please watch out for the first two reviews published in this issue by J. Werner et al. on “Perovskite/Silicon Tandem Solar Cells: Marriage of Convenience or True Love Story? – An Overview” and by Y. Qi et al. on” Recent Advances in Spiro-MeOTAD Hole Transport Material and Its Applications in Organic-Inorganic Halide Perovskite Solar Cells”. The articles will be marked to indicate that they are part of the series, and will be collected into a special virtual issue online, to be highlighted on our Advanced Science News service (www.advancedsciencenews.com). With the great development during the past years, new journals have joined the “Advanced” family, so you should not miss out on exploring those as well. Of particular note are Advanced Theory and Simulations, Advanced Quantum Technologies, and Advanced Therapeutics launched in 2017. We are confident that those journals will make a strong contribution to the scientific effort as well. And… there is more good news for 2018! Starting from January 2018 all journals of the Advanced Family as well as the Macro­molecular Journals will waive the cost for printing colour figures! We look forward to sharing much more exciting interface-related research with you this year and hope that you will enjoy reading the articles of the present issue. On behalf of the editorial team,

Ferromagnetically filled carbon nano-onions: the key role of sulfur in dimensional, structural and electric control.

A key challenge in the fabrication of ferromagnetically filled carbon nano-onions (CNOs) is the control of their thickness, dimensions and electric properties. Up to now literature works have mainly focused on the encapsulation of different types of ferromagnetic materials including α-Fe, Fe3C, Co, FeCo, FePd3 and others within CNOs. However, no report has yet shown a suitable method for controlling both the number of shells, diameter and electric properties of the produced CNOs. Here, we demonstrate an advanced chemical vapour deposition approach in which the use of small quantities of sulfur during the pyrolysis of ferrocene allows for the control of (i) the diameter of the CNOs, (ii) the number of shells and (iii) the electric properties. We demonstrate the morphological, structural, electric and magnetic properties of these new types of CNOs by using SEM, XRD, TEM, HRTEM, EIS and VSM techniques.

In Recognition of Professor Hitchman: Advances in Chemical Vapor Deposition

Chemical vapor deposition (CVD) processes had been around for nearly 100 years before they began to attract interest from materials scientists and electronics engineers in the 60s and 70s, as a result of the rapidly growing microelectronics industry. The successful development of this complicated technology required a deep physicochemical understanding of deposition processes and reaction mechanisms. This resulted in a large number of scientists from different disciplines studying the basics of CVD.

Tuning high magnetizations in foam-like carbon-based films completely filled with α-Fe

We report an advanced chemical vapour deposition approach which yields not previously observed carbon-based foam-like films completely filled with a single phase of α-Fe. These films are found in the region of the chemical vapour deposition reactor where the temperature is relatively low (650–770 °C) and exhibit a high saturation magnetization as high as 200–220 emu/g at room temperature when small concentrations of Cl-radicals are added to the pyrolysing CVD system by mixing 0.15 ml of dichlorobenzene to ferrocene. Instead when the only ferrocene is used a lower saturation magnetization of 140–145 emu/g is found due to an amorphous arrangement of the Fe-phase in some parts of the foam. Also we show that for much higher concentration of Cl radicals (0.65 ml of dichlorobenzene mixed to ferrocene) a dramatic decrease of the quantity of crystalline α-Fe is found together with the formation of amorphous Fe and FexOx phases.

Time as the Fourth Dimension: Opening up New Possibilities in Chemical Vapor Deposition

Thin films of inorganic materials are essential to several technologies we take for granted in our everyday lives. They form the basis of touch screens in smart phones and the electronic components in computers. Dating back more than a century, chemical vapor deposition (CVD) is one of the most common methods to form these films. In CVD, the atoms needed for the thin film are typically supplied by a continuous flow of gaseous precursor molecules and incorporated into the film by gas phase and surface chemical reactions. The continuous demand for more precise thin film fabrication on more complex shapes at lower temperatures sets a demand for more advanced CVD methods. The development of better designed precursor molecules is one important path to evolve CVD; the other path is to evolve the way in which we do CVD. In this perspective I will describe how using time as a fourth dimension in CVD can enable fabrication of new thin film materials and material structures at lower temperatures and on more complex...

The role of Br in the selective synthesis of thin-walled carbon-nanotubes with micrometre-length Fe3C-filling, Fe3C tip-filled carbon nanotubes or empty carbon nanotubes by pyrolysis of ferrocene and (6-bromohexyl)ferrocene mixtures

We report an advanced chemical vapour deposition method which allows the synthesis-selection of thin walled carbon nanotubes filled with Fe3C, Fe3C tip-filled nanotubes or of empty nanotubes by addition of (6-bromohexyl)ferrocene to ferrocene.

Enhanced saturation magnetization in buckypaper-films of thin walled carbon nanostructures filled with Fe3C, FeCo, FeNi, CoNi, Co and Ni crystals: the key role of Cl.

We report an advanced chemical vapour deposition approach which allows the direct in situ synthesis of cm-length ultrathin buckypapers comprising carbon nanostructures filled with Fe3C, FeCo, FeNi, CoNi, Co and Ni by sublimation and pyrolysis of single or combined metallocenes with very low quantities of dichlorobenzene. As a result, extremely high saturation magnetizations of 117 emu g(-1), 90 emu g(-1) and 80 emu g(-1) are obtained for the specific cases of Fe3C, FeCo and FeNi, respectively, while variable saturation magnetizations of 70 emu g(-1), 58 emu g(-1) and 6.7 emu g(-1) are obtained for Co, CoNi and Ni respectively.

Computational investigation of surface reactivity of functionalized silicon surfaces in deposition processes

Recent advances in chemical vapor deposition and atomic layer deposition coupled with the ever-increasing demand for better control over the interface formation driven by practical applications require understanding and controlling chemical reactions, leading to the deposition of metal-based films onto semiconductor substrates at a truly atomic level. Computational investigation of possible surface-mediated reactions of metalorganic precursors used to deposit thin films used in practical applications allows for an efficient screening of the parameters needed to optimize the process of interface formation. Here, we will use a simple frontier orbital analysis coupled with cluster calculations to explore the surface reactions of functionalized silicon surfaces with test metalorganic precursor molecules. Two molecular precursors are investigated. Trimethylaluminum allows us to investigate the contribution of relatively simple C–Al and C–H dissociation processes in determining the mechanism of surface reaction with a silicon surface either terminated with hydrogen or modified with several nitrogen- or oxygen-containing functional groups. Following similar processes with tetrakis(dimethylamido)titanium provides an opportunity to expand the type of processes investigated and to decouple electronic and steric factors determining surface reactivity.

Hardide™: advanced nano-structured CVD coating

Hardide™ is a family of new low-temperature Chemical Vapour Deposition (CVD) Tungsten/Tungsten Carbide coatings. Coating consists of Tungsten Carbide nano-particles dispersed in metal Tungsten matrix, that give the material enhanced hardness of between 1100 Hv and 1800 Hv, and abrasion resistance up to 12 times better than Hard Chrome. Nano-structured materials show unique toughness, crack and impact-resistance. The coating is resistant to acids and aggressive media, can be produced on steel, including stainless steel and some tool steels, with coating thickness varied from 5 microns to 100 microns. Gas-phase CVD process allows coating internal surfaces and items of complex shape like dies, moulds, pump cylinders. Homogeneous pore-free structure facilitates finishing by honing, polishing, mirror finish can be achieved with suitable substrate. Use of Hardide with cutting tools for paper and plastics makes them self-sharpening. Application of Hardide increases life of tools and critical components and reduces down-time.

Reduction of PFC emissions to the environment through advances in CVD and etch processes

One the most focused environmental health and safety (EHS) goals for the semiconductor industry has been to reduce perfluorocompound (PFC) emissions because of their high global warming potentials and long residence times in the atmosphere. During the last decade, significant achievements have been reached in attaining this goal. Chemical vapor deposition (CVD) chamber cleaning and plasma etch are two processes that use PFCs in which studies have been conducted to reduce emissions. Two successful strategies for reducing PFC emissions and enhancing process performance are described.

Deposition of nanocrystalline diamond and titanium oxide coatings onto pyrolytic carbon using CVD and sol–gel techniques

In this paper, we report the deposition of freestanding nanocrystalline diamond (NCD) films and dense nanocrystalline titanium oxide (nc-TiO 2) coatings onto pyrolytic carbon (PyC) using advanced chemical vapour deposition (CVD) and sol–gel techniques, respectively. The micro-structural properties, such as surface morphology and crystallinity, of PyC, NCD and nc-TiO 2 were characterised using XRD, Raman spectroscopy and SEM analysis. Freestanding NCD films were prepared using our newly introduced time-modulated CVD (TMCVD) process. Furthermore, conventional sol–gel technique was used to uniformly coat PyC with dense nc-TiO 2 coatings. The as-grown nc-TiO 2 coatings were found to display smooth surface profiles and the average crystallite size was in the range approximately 30–50 nm.

Relaxation and photoluminscence of different post-processed Si/Si 1− xGe x quantum well structures grown by CVD

We have used high resolution X-ray diffraction photoluminescence (PL) and secondary ion mass spectrometry to study the structural and optical properties of different Si/Si 1− x Ge x quantum well (QW) structures grown using an advanced chemical vapor deposition (CVD) reactor. To understand the stability of the QW designs, and correlate the structural as well as the optical properties with the interlayer diffusion of these structures, we have subjected the different QWs to post-processing temperatures ranging from 600°C to 1000°C for 1 h each. The investigated samples include single, symmetric and different asymmetric double QW structures. The main finding of this study is that post-growth thermal stability of this CVD grown QW is different from MBE grown samples. In addition, the design of the QW being single or double QW structure is clearly observed to affect the interlayer diffusion and hence, stability.

Role of rapid photothermal processing in environmentally conscious semiconductor manufacturing

Compliance with the increasingly stringent environmental laws will force the phasing out of conventional methods for the manufacture of all semiconductor devices. Development of processes with the highest possible material and energy efficiencies is the heart of the present ecological preservation efforts. Besides other benefits, rapid isothermal processing (RIP) also uses less energy than furnace processing. Further increase of material and energy efficiencies is possible by using rapid photothermal processing. Central to this method is the use of quantum photoeffects in conventional RIP systems. This approach can be consolidated with advanced chemical vapor deposition methods that further lower the wastages leading to systems that can give significant improvements over those presently used. Key experimental results and possible future directions are presented.

Rapid synthesis of Y-Ba-Cu-O tape on metal substrate by chemical vapor deposition technique

Abstract An advanced chemical vapor deposition (CVD) system has been developed for rapid formation of a superconducting oxide tape on long metal substrates. In this system, a mixed fine powder of source materials was slowly fed to a vaporizer with a carrier gas by a fine powder feeder, and the source gas from the vaporizer was continuously introduced to the reactor with oxygen gas. This system has a long substrate conveying equipment. By this system, using Hastelloy C-276 tapes with YSZ buffer as substrates, 1 meter long superconducting Y-Ba-Cu-O (YBCO) tapes could be obtained. These tapes had a critical temperature (Tc) with zero resistivity above 77.3 K and the best part of the tape had a Tc at 84 K and a critical current density (Jc) of 330 A/cm2 (77.3 K, 0 T).

On diamond windows for high power synchrotron X-ray beams

Recent advances in chemical vapor deposition (CVD) technology have made available thin, free-standing polycrystalline diamond foils that can be used as the window material on high heat load synchrotron X-ray beamlines. Diamond windows have many advantages that stem from the exceptionally attractive thermal, structural, and physical properties of diamond. Numerical simulations indicate that diamond windows can offer an attractive and at times the only alternative to beryllium windows for use on the third generation X-ray synchrotron radiation beamlines. Utilization, design, and fabrication aspects of diamond windows for high heat load X-ray beamlines are discussed, and analytical and numerical results are presented to provide a basis for the design and testing of such windows.