Conventional Chemical Vapor Deposition Reactor Research Articles

Low-temperature synthesis of vertically aligned graphene through microwave-assisted chemical vapour deposition

The intrinsic properties of vertically aligned graphene (VG), such as a high ratio of exposed active edge sites compared to inert basal sites, non-stacking morphology and large surface-to-volume ratio make it applicable to numerous advanced technologies such as sensors, flexible electronics and fuel cells. Plasma-enhanced chemical vapour deposition has emerged as a promising technique to synthesise graphene at lower temperatures than a conventional chemical vapour deposition (CVD) process, providing a better control over the deposition parameters to tailor graphene properties.This study presents a cost effective, scalable, single step synthesis of a high quality VG at low temperatures. The samples were synthesised in a microwave (MW) assisted CVD reactor, which allowed for the decomposition of CH4 and H2 gas mixtures in Ar as a carrier gas, and VG growth directly onto Si wafer substrates without any additional heat applied to the substrate. Deposition conditions, such as MW power, gas ratio, and substrate-to-plasma separation were optimized to tailor the morphology, growth rate and electrochemical performance of the VG. The physiochemical analysis revealed that the fabricated VG consisted of high quality vertically aligned sp2 graphene, whilst a cyclic voltammetry analysis confirmed that the structures are electrochemically active and demonstrate a typical characteristics of quasi-reversible processes.

Synthesis and purification of bimetallic catalysed carbon nanotubes in a horizontal CVD reactor

Carbon nanotubes (CNTs) were synthesised by a conventional chemical vapour deposition (CVD) method using acetylene as carbon source and a bimetallic catalyst of Fe–Co supported on a CaCO3 support. The CNTs were characterised by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), energy dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA). The TEM images show clustered CNTs and reveal the outer and inner diameters of these nanomaterials. The XRD analysis shows the characteristic broad peak of graphitised carbon; the RS indicates that these materials have a high degree of crystallinity while the TGA shows the high thermal stability of the materials. EDS analysis also indicates that the purification method employed was able to remove the impurities in the CNT samples.

Development of a spatially controllable chemical vapor deposition reactor with combinatorial processing capabilities

Most conventional chemical vapor deposition (CVD) systems do not have the spatial actuation and sensing capabilities necessary to control deposition uniformity or to intentionally induce nonuniform deposition patterns for single-wafer combinatorial CVD experiments. In an effort to address these limitations, a novel CVD reactor system has been developed that can explicitly control the spatial profile of gas-phase chemical composition across the wafer surface. This paper discusses the construction of a prototype reactor system featuring a three-zone, segmented showerhead design. Experiments are performed to assess the ability of this reactor system to deposit tungsten films by the hydrogen reduction process; segment-to-segment process recipes are controlled to deposit spatially nonuniform W films. The capabilities of this reactor system for materials discovery research are discussed.

Simulation‐based design and experimental evaluation of a spatially controllable CVD reactor

AbstractMost conventional chemical vapor deposition (CVD) systems do not have the spatial actuation and sensing capabilities necessary to control deposition uniformity, or to intentionally induce nonuniform deposition patterns for single‐wafer combinatorial CVD experiments. In an effort to address these limitations, a novel CVD reactor system has been developed that can explicitly control the spatial profile of gas‐phase chemical composition across the wafer surface. This paper discusses the simulation‐based design of a prototype reactor system and the results of preliminary experiments performed to evaluate the performance of the prototype in depositing tungsten films. Initial experimental results demonstrate that it is possible to produce spatially patterned wafers using a CVD process by controlling gas‐phase reactant composition, opening the door to a new class of flexible and highly controllable CVD reactor designs. © 2005 American Institute of Chemical Engineers AIChE J, 51:572–584, 2005

Deposition of polycrystalline diamond films using conventional and time-modulated CVD processes

Thin polycrystalline diamond films have been deposited using both conventional chemical vapour deposition (CVD) and time-modulated CVD (TMCVD) processes. Films deposited using conventional CVD methods were found to be rough and exhibited columnar growth characteristics. The average crystallite size and the surface roughness of the as-grown films increased with film thickness. It was found that with increasing methane concentration the overall nucleation density increased. However, increasing the methane concentration deteriorated the quality of the films, in terms of diamond carbon phase purity, as evident from the Raman spectra. The TMCVD process involved pulsing methane gas initially at higher concentration, into the CVD reactor during the nucleation stage of the diamond CVD process followed by the extended growth duration at a lower methane concentration. The TMCVD process produced films that displayed smoother surfaces. In addition, the films were grown at higher growth rates compared to the conventional CVD films. A preliminary model explaining the mechanism of the TMCVD process is presented.

Bias assisted etching of diamond in a conventional chemical vapor deposition reactor

A novel technique for selectively etching diamond films is presented. This letter describes a technique by which diamond may be etched in a conventional plasma assisted chemical vapor deposition (CVD) reactor at rates comparable to those reported for both electron cyclotron resonance and reactive ion etching techniques. This technique involves negatively biasing the diamond film, while it is immersed in a mostly hydrogen containing plasma. Negative dc bias assisted etching of CVD diamond films is performed in both microwave and dc plasma reactors over a wide range of temperatures and pressures. Speculation on the etching mechanisms is also included.

Low-temperature heteroepitaxy of Ge on Si by GeH4 gas low-pressure chemical vapor deposition

The crystalline quality of Ge grown epitaxially on Si can be improved by using GeH4/H2 gas low-pressure chemical vapor deposition at a low temperature of 410 °C and surface-cleaning processing with a purified-H2 flow prior to GeH4 introduction into a CVD reactor. H2 flow processing is carried out at growth temperature. The dislocation density of a 1.3-μm thick Ge film is nearly 2×108 cm−2, which is as low as that of molecular-beam epitaxy (MBE)-grown Ge films. Stacking faults commonly generated in the CVD-grown Ge films at temperatures higher than 700 °C are not observed. The 700 °C heat treatment of the Ge film reduces dislocation density to 2×107 cm−2 and causes no interface reaction between Ge and Si. This technique is superior to conventional chemical vapor deposition (CVD) techniques for Ge epitaxial growth.

Phosphorus Incorporation during Silicon Epitaxial Growth in a CVD Reactor

The phosphorus incorporation process during the deposition of silicon epitaxial films in a conventional chemical vapor deposition (CVD) system has been investigated. This was carried out by studying the steady‐state and the transient behaviors of a epitaxial system. The behavior of the system was also compared to that of the system. These dopant incorporation processes behave differently in that one is controlled by thermodynamics (phosphorus) and the other by kinetics (arsenic). An epitaxial doping model was used to explain these differences and to simulate the behavior of the epitaxial system. The model was capable of simulating epitaxial dopant profiles corresponding to various time‐varying phosphine gas flows in two different CVD systems.