Microwave Plasma Jet Chemical Vapor Research Articles

Extraordinary Field Emission of Diamond Film Developed on a Graphite Substrate by Microwave Plasma Jet Chemical Vapor Deposition

This work reports both numerical and experimental studies of the reconditioning of a microwave plasma jet chemical vapor deposition (MPJCVD) system for the growth of diamond film. A three-dimensional plasma fluid model is constructed for investigating and conditioning the MPJCVD system and optimizing its operating conditions. The methodology solves electromagnetic wave and plasma dynamics self-consistently using an adaptive finite element method as implemented in COMSOL Multiphysics. The whole system has been modeled under varying parameters, including the reactor geometry, microwave power, and working gas pressure. Using an operating condition identical to the optimized simulation results, the MPJCVD system successfully fabricates a diamond-thin film on a graphite substrate. The SEM image reveals the presence of a diamond film uniformly distributed with particles of a size of ~1 μm. The field emission from the diamond film grown from our homemade MPJCVD system on the graphite substrate presents extraordinary properties, i.e., extremely high current density and relatively low turn-on voltage. The turn-on electric field observed could be as low as ~4 V/μm. This developed model provides valuable physical insights into the MPJCVD system, which guided performance improvements. The work may find applications in surface hardening and provide a better cold cathode for field electron emission.

Sensors made of carbon ceramic composite materials

Carbon nanotubes (CNTs) were deposited on barium titanate (BaTiO3) substrates using the microwave plasma jet chemical vapor deposition (MPJCVD) system. Accelerometer sensors were then made of both as-obtained carbon ceramic (CNTs/BaTiO3) composite materials and barium titanate (BaTiO3). The variations of the output voltages under various accelerating amplitudes were examined on two kinds of sensors at vibrating frequencies of 200Hz, 500Hz, 800Hz, and 2000Hz, respectively. It is found that the output voltages and the sensitivity of CNTs/BaTiO3 sensors were higher than those of BaTiO3 sensors at each vibrating frequency.

Synthesis and Characterization of Porous ZnO-CNT Nanocomposites Prepared by Microwave Plasma Jet Chemical Vapor Deposition System

In the present study, we fabricated the CNT-porous ZnO composite by Microwave Plasma Jet Chemical Vapor Deposition (MPJCVD) System. The morphology and characteristics of the CNT-porous ZnO were examined by SEM, EDS and Raman spectrometer. Finally, a few carbon content was found to exist within the CNT-porous ZnO nanocomposite.

Field emission characteristics study for ZnO–CNTs composites by the microwave plasma jet chemical vapor deposition system

The field emission (FE) properties of the carbon nanotubes (CNTs) grown on zinc oxide (ZnO) films have been reported in the present study. The ZnO films were first spun on a Si substrate by a spin coater, and then the grown CNTs were grown on the surface of the ZnO films by the microwave plasma jet chemical vapor deposition (MPJCVD) system. The experimental results showed that ZnO–CNT composite exhibited superior FE performance compared to that of CNTs and ZnO nanowires. The turn-on field of an emission device constructed with the ZnO–CNT composite was 0.31Vμm−1, which was lower than that of the common CNTs and ZnO nanowires/nanorods. As the results of field emission tests, the CNTs on ZnO films could be a useful material in the emission applications.

A study of growth and surface performance analysis of nanographites grown using microwave plasma jet chemical vapor deposition system

Nanographites were grown using a microwave plasma jet chemical vapor deposition (MPJCVD) system. The E-H tuner of the MPJCVD was controlled by a personal computer. Monitoring of plasma jet was done through an optical emission spectroscopy and a charge coupled detector camera. High frequency structure simulator software was used to calculate electrical fields around specimens at different positions of the E-H tuner of the MPJCVD. Nanographites, composed of sp2 hybrid orbital, were grown at a microwave power of 800 W. The carbon bonds, both C–C and C=C bonds, of as-grown nanographites were measured to have characteristic peaks at 1309 and 1595 cm−1 using Raman spectroscopy. The mean size of the nanostructured graphite was nearly 50 nm under scanning electron microscopy observation. The measurement of contact angle on such graphite films was made by laying drops of deionized (DI) water, 0.03 and 0.09 M sodium chloride (NaCl) and was found to be 153°, 147°, and 136°, respectively. An electro-wetting test was also performed on the graphite films by adding electrical voltage through the CA measurement. It was found that contact angles of electro-wetting test for graphite films become 110° and 37° for DI water and NaCl solution, respectively.

Improvement on the synthesis technique of ultrananocrystalline diamond films by using microwave plasma jet chemical vapor deposition

In this paper, a particular class of smooth ultrananocrystalline diamond (UNCD) films synthesized by home-made microwave plasma jet chemical vapor deposition system (MPJCVD) with gas chemistry of Ar–1%CH 4–10%H 2 is presented. This synthesis by MPJCVD yields UNCD films identical to those UNCD films fabricated with Ar/CH 4 chemistry by MPCVD, but using relatively low Ar introduction, low pressure, and low power due to the focused microwave plasma jet enhanced the dissociation of react gases to form energetic species during the deposition. The transition from microcrystalline to ultrananocrystalline diamond films grown from Ar/Ar+H 2 0% to 90% plasmas using MPJCVD has been systematically studied. The results of this study showed that the grain size, surface roughness, and sp 3 bonding carbon concentration in the films decreased with the increase in Ar concentration. The reason is due to the great increase in renucleation during the films growth. The TEM images clearly exhibited the grain size of the films (Ar/Ar+H 2: 90%) in the range of 3–8 nm. The near-edge X-ray absorption fine structure spectrum also exhibited the clear bonding characteristics of diamond. Moreover, the plasma precarbonization was employed by MPJCVD prior to UNCD films synthesis in order to markedly enhance the smoothness of UNCD films. The UNCD film was synthesized via unique MPJCVD-enhanced nucleation and growth, which produced films with high growth rate (315 nm/h), smooth surfaces (∼11.7 nm rms), and extremely fine-grained (3–8 nm) distribution in the whole film.

Fabrication of nanogranular diamond films by MPJCVD system

Nanogranular diamond films have been prepared by microwave plasma jet chemical vapor deposition system (MPJCVD) with argon-rich (Ar/H2:90%) plasma. In this work, the plasma pre-carbonization (P.P.) pre-treatment was employed to obtain uniform and smooth (13.3nm rms) diamond films with high nucleation density. The diamond films were fabricated in various Ar/H2 concentrations from 0% to 100% and fixed at CH4 concentration of 1%. It can be clearly observed that the grain size of diamond films changed from micrometer to nanometer scale and down to 5nm at the concentration of 90% Ar/H2. The reason is due to the rise of C2 dimer in the plasma, which could be proved from the analysis of OES analysis.

Formation of ultrananocrystalline diamond films with nitrogen addition

Nitrogen-doped ultrananocrystalline diamond (UNCD) films have been prepared by the microwave plasma jet chemical vapor deposition system (MPJCVD) using a gas mixture of Ar-1%CH 4-10%H 2 and addition of 0.5–7% nitrogen. This growth process by MPJCVD with 10% hydrogen addition that yields UNCD films compared with those UNCD films produced by MPCVD with a high Ar/CH 4 ratio due to the focused microwave plasma jet greatly enhanced the enough dissociation of react gases and formed C 2 species with an energetic state at lower argon concentration. The surface morphologies were changed drastically from continuous to rough granular surface with increasing the nitrogen content due to the great rise of CN species in the plasma. The width of grain boundaries composed of sp 2-bonded carbon increased with increasing nitrogen content in the films. Moreover, the seldom defects in the UNCD films induced by the addition of nitrogen in the plasma were identified and investigated by using a scanning transmission electron microscope (STEM). The highest nitrogen-doped benefit with a N/C atomic ratio of 3.25% in UNCD films was reached by addition of only 3% N 2 in plasma (Ar-1%CH 4-10%H 2-3%N 2), showing the MPJCVD can greatly reduce the used amount of nitrogen in the synthesis of nitrogen-doped UNCD films.

An Investigation of Chemical Species and Electrical Property of Nitrogen-Doped Nanocrystalline Diamond Films Grown by Microwave Plasma Jet Chemical Vapor Deposition

This study investigated chemical species in the plasma while synthesizing nitrogen-doped nanocrystalline diamond (NCD) films using microwave plasma jet chemical vapor deposition (MPJCVD) system. The investigation is done by using in-situ plasma optical emission spectroscopy (OES). The electrical resistivity of the nitrogen-doped NCD films increases by 6 orders of magnitude (up to 6.7×10-4 Ω cm) with increasing nitrogen content. This approach also helps us in further understanding of the plasma species during depositing NCD films and also the electronic structure of grown conductive diamond phase through analysis of as-doped nitrogen contents.

Study on Site-Selective Growth of Carbon Nanotubes and Diamond Films With Barrier Layers

Microwave plasma jet chemical vapor deposition is used to grow array types of carbon nanotubes and diamond films on silicon substrates. In this study, we report a patterned growth of carbon nanotubes and diamond films using the barrier layer method, wherein the selective areas vary from 20×20 μm2 to 30×80 μm2. The field-emission measurement shows that the turn-on electric field for patterned carbon nanotubes and diamond films are 1.1 V/μm and 5 V/μm, respectively. Therefore, this method of site-selective growth of carbon nanotubes and diamond films can be applied to the production of field emitters.

Effect of CH/C<SUB>2</SUB> Species Density on Surface Morphology of Diamond Film Grown by Microwave Plasma Jet Chemical Vapor Deposition

The present research employs in-situ plasma Optical Emission Spectroscopy (OES) to explore the effect of microwave plasma jet chemical vapor deposition (MPJCVD) on activating CH4 þ H2 plasma environment and synthesizing diamond film. Surface morphology and main orientation of lattice plane of the diamond synthesized under different processing parameters are also examined. Since species such as CH, H2,