Chemical Vapor Deposition最新文献

A modified fluidized bed reactor is developed to homogenously coat micrometer-sized particles with reactive polymer films using CVD. This technique is found to be rapid (∼30 min per batch) and scalable (up to 1 g particles), and can create homogenous coatings on microparticles down to 10 μm in diameter. By tuning critical variables, such as working pressure and the carrier gas flow rate, full coverage of a reactive polymer film can be realized. Janus particles are synthesized and can be visualized via fluorescence microscopy.

This article presents an approach for modeling the vaporization of droplets of solvent and precursor mixture under vacuum in the pulsed-pressure (pp) CVD process. The pulsed, direct liquid injection apparatus with ultrasonic atomizer is demonstrated as a controllable and reliable alternative to the bubbler and carrier gas system. The numerical modeling solves mass, heat, and momentum continuity equations on liquid droplets, and is intended to evaluate the relative roles of the physical chemistry properties and reactor parameters in the fast vaporization of droplets. The sensitivity analysis proposed here shows that the vaporization time into the pulsed-liquid CVD system is mainly dependent on the heating available in the flash evaporation zone, then on the thermodynamic properties of the liquid solution.

Thin films of Y₂O₃ are deposited on Si(100) and Al₂O₃ (0001) substrates via metal-organic (MO)CVD for the first time using two closely related yttrium tris-amidinate compounds as precursors in the presence of oxygen in the temperature range 400–700 °C. The structural, morphological, and compositional features of the films are investigated in detail. At deposition temperatures of 500 °C and higher both the precursors yield polycrystalline Y₂O₃ thin films in the cubic phase. The compositional analysis revealed the formation of nearly stoichiometric Y₂O₃. The optical band gaps are estimated using UV-Vis spectroscopy. Preliminary electrical measurements are performed in the form of a metal oxide semiconductor (MOS) structure of Al/Y₂O₃/p-Si/Ag. Leakage currents and dielectric constants are also determined.

Carbon nanotube (CNT)-based electrochemical biosensors are used to determine the concentration of analytes by measuring mass, heat, or oxygen. CNTs, as an immobilizing platform of biomaterials, play an important role in enhancing the electron transfer mechanism of a biosensor. The large surface area and optimum aspect ratio (length to thickness) of CNTs maximize the amount of immobilized biomaterials on the surface. In this study, various aspect ratios of CNTs are reported, based on the alteration of growth mechanisms using CVD. The growth-dependent and -independent parameters of the CNT arrays are studied as functions of the synthesis method.

Remarkable developments and successes are witnessed in the fabrication and implementation of optical sensors based on localized surface plasmon resonance (LSPR) for the investigation of chemical and biological material quantities. We report on the reproducible fabrication of chemically stable surface immobilized AuNPs grown via organometallic chemical vapor deposition (OMCVD) on a polymer substrate, namely polystyrene (PS). Oxygen plasma-treated and UV ozone-treated PS samples depict enhanced amounts of polar -OH groups allowing for nucleation and growth of AuNPs. The optimum plasma treatment conditions, the largest shifts in the LSPR curves, and the bulk sensitivity of the OMCVD-grown AuNPs are discussed.

Amorphous hydrogenated silicon oxycarbide (a-SiCO:H) thin films are produced by remote microwave hydrogen plasma CVD using 1,1,3,3-tetramethyldisiloxane precursor. The effect of substrate temperature (T_S) on the chemical structure and some properties of resulting a-SiCO:H films is reported. The examination performed by infrared spectroscopy revealed that the increase in T_S involves the elimination of organic moieties from the film and its transformation from polymer-like to ceramic-like high-crosslink-density material. Due to their small surface roughness, high density, and good optical transparency, the a-SiCO:H films seem to be useful coatings for optical and electronic devices.

Fe₂O₃ nanostructures are fabricated on Si(100) and SiO₂ by plasma enhanced (PE)CVD from a Fe^III β-diketonate precursor. Depositions are carried out in Ar-O₂ plasmas, devoting particular attention to the influence of growth temperature (from 60 to 400 °C) on material chemico-physical properties. Remarkably, high purity, single-phase α-Fe₂O₃ nanostructures are obtained at temperatures as low as 60 °C. Furthermore, the deposit nano-organization can be tuned from <110>-oriented 2D nanoblade arrays to denser nanocolumns upon increasing the deposition temperature. A possible growth model is proposed to account for the observed structural/morphological features and light absorption properties of the target materials.

The ‘self-limiting’ character of graphene growth on the surface of metals such as Ni and Cu makes CVD the natural choice for growing large-area and continuous graphene films. Beyond graphene, absence of the self-limiting property results in a challenge to achieving large-area, high-quality two-dimensional (2D) crystals by CVD. Recent studies of structural, optical, and electrical properties of MoS₂-based atomic layers grown by CVD are reviewed, concluding that thermal vapor deposition will outperform thermal vapor sulfurization in producing the required materials. Whether gaseous sources will replace the now dominant solid sources in direct deposition methods is an open issue. The latest progression in various CVD techniques used in MoS₂ growth and their resultant products are discussed and compared.

Mesoporous nanostructures of tin(IV) oxide microballs are synthesized, using a single source precursor [Sn (OAc)(dmae)]₂ (where OAc = Acetato and dmae = dimethylaminoethanolato). The as-prepared microballs are characterized using X-ray diffraction, field emission scanning electron microscopy (FESEM), Fourier transform infrared and UV-vis spectroscopy, X-ray photoelectron spectroscopy and impedance spectroscopy. The focused ion beam (FIB) images of the exterior and interior surfaces of the microballs disclosed the presence of porous structures with mesopore of sizes ranging from 56-66 nm and 8.0 to 160 nm, respectively. The microballs exhibit high BET and Langmuir surface areas of 136 and 191.6 m² g⁻¹, respectively, and show capacities >600 mAhg⁻¹ over 60 cycles, as compared with unmodified tin oxide-based nanomaterials which show capacity < 500 mAh g⁻¹ after 50 cycles.