Carbon nanotubes (CNTs) have great potential in many applications due to their unique structure and properties. However, there are still many unsolved problems hampering their real applications. This thesis focuses on three important issues limiting their applications, namely: (1) direct growth of CNTs without additional catalyst, (2) secondary growth of carbon nanotubes on primary CNT bed without using extra catalyst, (3) and CNT alignment mechanisms during the growth.<p> The CNTs used in this thesis were prepared by hot filament chemical vapor deposition (CVD) reactor and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Raman spectroscopy. Field electron emission (FEE) properties of the CNTs were also tested.<p> Oxidation-reduction method was adopted in direct growth of CNTs on Inconel 600 plates and proved effective. The effect of oxidation temperature on the growth of CNTs was studied. It was found that the oxidation temperature had an influence on CNT height uniformity and FEE properties: the higher the treatment temperature, the more uniform the resultant CNTs, and the better the FEE properties of the resultant CNTs. The contribution of different oxides formed at different temperatures were investigated to explain the effect of oxidation temperature on the CNT height uniformity.<p> Secondary CNTs were grown on primary ones by simply changing the carbon concentration. No additional catalyst was used during the whole deposition process. It was found that synthesizing primary CNTs at extremely low carbon concentration is key factor for the secondary growth without additional catalyst. The CNT sample grown with secondary nanotubes exhibited improved field emission properties.<p> The effect of bias voltage on growth of vertically aligned carbon nanotubes was investigated. The CNTs grown at -500V shows the best alignment. At the early growth stage, simultaneous growth of randomly oriented and aligned carbon nanotubes was observed. This was consistent with the alignment mechanism involving stress that imposed on catalyst particles on tube tips. Through the observation of CNT growth on the scratched substrates, catalyst particle size was found as another determining factor in the alignment of CNTs. Big catalyst particles promoted aligned growth of CNTs.

The focus of this thesis is the study of the field electron emission (FEE) of diamond and related films synthesized by plasma enhanced chemical vapor deposition. The diamond and related films with different morphologies and compositions were prepared in a microwave plasma-enhanced chemical vapor deposition (CVD) reactor and a hot filament CVD reactor. Various analytical techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy were employed to characterize the surface morphology and chemical composition.<p>The influence of surface morphology on the field electron emission property of diamond films was studied. The emission current of well-oriented microcrystalline diamond films is relatively small compared to that of randomly oriented microcrystalline diamond films. Meanwhile, the nanocrystalline diamond film has demonstrated a larger emission current than microcrystalline diamond films. The nanocone structure significantly improves the electron emission current of diamond films due to its strong field enhancement effect.<p>The sp2 phase concentration also has significant influence on the field electron emission property of diamond films. For the diamond films synthesized by gas mixture of hydrogen and methane, their field electron emission properties were enhanced with the increase of methane concentration. The field electron emission enhancement was attributed to the increase of sp2 phase concentration, which increases the electrical conductivity of diamond films. For the diamond films synthesized through graphite etching, the growth rate and nucleation density of diamond films increase significantly with decreasing hydrogen flow rate. The field electron emission properties of the diamond films were also enhanced with the decrease of hydrogen flow rate. The field electron emission enhancement can be also attributed to the increase of the sp2 phase concentration. <p>In addition, the deviation of the experimental Fowler-Nordheim (F-N) plot from a straight line was observed for graphitic nanocone films. The deviation can be mainly attributed to the nonuniform field enhancement factor of the graphitic nanocones. In low macroscopic electric field regions, electrons are emitted mainly from nanocone or nanocones with the largest field enhancement factor, which corresponds to the smallest slope magnitude. With the increase of electric field, nanocones with small field enhancement factors also contribute to the emission current, which results in a reduced average field enhancement factor and therefore a large slope magnitude.

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Multi-scale modeling of chemical vapor deposition (CVD) is a very broad topic because a large number of physical processes affect the quality and speed of film deposition. These processes have different length scales associated with them creating the need for a multi-scale model. The three main scales of importance to the modeling of CVD are the reactor scale, the feature scale, and the atomic scale. The reactor scale ranges from meters to millimeters and is called the reactor scale because it corresponds with the scale of the reactor geometry. The micrometer scale is labeled as the feature scale in this study because this is the scale related to the feature geometries. However, this is also the scale at which grain boundaries and surface quality can be discussed. The final scale of importance to the CVD process is the atomic scale. The focus of this study is on the reactor and feature scales with special focus on the coupling between these two scales. Currently there are two main methods of coupling between the reactor and feature scales. The first method is mainly applied when a modified line of sight feature scale model is used, with coupling occurring through a mass balance performed at the wafer surface. The second method is only applicable to Monte Carlo based feature scale models. Coupling in this second method is accomplished through a mass balance performed at a plane offset from the surface. During this study a means of using an offset plane to couple a continuum based reactor/meso scale model to a modified line of sight feature scale model was developed. This new model is then applied to several test cases and compared with the surface coupling method. In order to facilitate coupling at an offset plane a new feature scale model called the Ballistic Transport with Local Sticking Factors (BTLSF) was developed. The BTLSF model uses a source plane instead of a hemispherical source to calculate the initial deposition flux arriving from the source volume. The advantage of using a source plane is that it can be made to be the same plane as the coupling plane. The presence of only one interface between the feature and reactor/meso scales simplifies coupling. Modifications were also made to the surface coupling method to allow it to model non-uniform patterned features. Comparison of the two coupling methods showed that they produced similar results with a maximum of 4.6% percent difference in their effective growth rate maps. However, the shapes of individual effective reactivity functions produced by the offset coupling method are more realistic, without the step functions present in the effective reactivity functions of the surface coupling method. Also the cell size of the continuum based component of the multi-scale model was shown to be limited when the surface coupling method was used. Thanks to the work done in this study researchers using a modified line of sight feature scale model now have a choice of using either a surface or an offset coupling method to link their reactor/meso and feature scales. Furthermore, the comparative study of these two methods in this thesis highlights the differences between the two methods allowing their selection to be an informed decision.

Multi-scale modeling of chemical vapor deposition (CVD) is a very broad topic because a large number of physical processes affect the quality and speed of film deposition. These processes have different length scales associated with them creating the need for a multi-scale model. The three main scales of importance to the modeling of CVD are the reactor scale, the feature scale, and the atomic scale. The reactor scale ranges from meters to millimeters and is called the reactor scale because it corresponds with the scale of the reactor geometry. The micrometer scale is labeled as the feature scale in this study because this is the scale related to the feature geometries. However, this is also the scale at which grain boundaries and surface quality can be discussed. The final scale of importance to the CVD process is the atomic scale. The focus of this study is on the reactor and feature scales with special focus on the coupling between these two scales. Currently there are two main methods of coupling between the reactor and feature scales. The first method is mainly applied when a modified line of sight feature scale model is used, with coupling occurring through a mass balance performed at the wafer surface. The second method is only applicable to Monte Carlo based feature scale models. Coupling in this second method is accomplished through a mass balance performed at a plane offset from the surface. During this study a means of using an offset plane to couple a continuum based reactor/meso scale model to a modified line of sight feature scale model was developed. This new model is then applied to several test cases and compared with the surface coupling method. In order to facilitate coupling at an offset plane a new feature scale model called the Ballistic Transport with Local Sticking Factors (BTLSF) was developed. The BTLSF model uses a source plane instead of a hemispherical source to calculate the initial deposition flux arriving from the source volume. The advantage of using a source plane is that it can be made to be the same plane as the coupling plane. The presence of only one interface between the feature and reactor/meso scales simplifies coupling. Modifications were also made to the surface coupling method to allow it to model non-uniform patterned features. Comparison of the two coupling methods showed that they produced similar results with a maximum of 4.6% percent difference in their effective growth rate maps. However, the shapes of individual effective reactivity functions produced by the offset coupling method are more realistic, without the step functions present in the effective reactivity functions of the surface coupling method. Also the cell size of the continuum based component of the multi-scale model was shown to be limited when the surface coupling method was used. Thanks to the work done in this study researchers using a modified line of sight feature scale model now have a choice of using either a surface or an offset coupling method to link their reactor/meso and feature scales. Furthermore, the comparative study of these two methods in this thesis highlights the differences between the two methods allowing their selection to be an informed decision.

The focus of this thesis is the study of the field electron emission (FEE) of diamond and related films synthesized by plasma enhanced chemical vapor deposition. The diamond and related films with different morphologies and compositions were prepared in a microwave plasma-enhanced chemical vapor deposition (CVD) reactor and a hot filament CVD reactor. Various analytical techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy were employed to characterize the surface morphology and chemical composition.<p>The influence of surface morphology on the field electron emission property of diamond films was studied. The emission current of well-oriented microcrystalline diamond films is relatively small compared to that of randomly oriented microcrystalline diamond films. Meanwhile, the nanocrystalline diamond film has demonstrated a larger emission current than microcrystalline diamond films. The nanocone structure significantly improves the electron emission current of diamond films due to its strong field enhancement effect.<p>The sp2 phase concentration also has significant influence on the field electron emission property of diamond films. For the diamond films synthesized by gas mixture of hydrogen and methane, their field electron emission properties were enhanced with the increase of methane concentration. The field electron emission enhancement was attributed to the increase of sp2 phase concentration, which increases the electrical conductivity of diamond films. For the diamond films synthesized through graphite etching, the growth rate and nucleation density of diamond films increase significantly with decreasing hydrogen flow rate. The field electron emission properties of the diamond films were also enhanced with the decrease of hydrogen flow rate. The field electron emission enhancement can be also attributed to the increase of the sp2 phase concentration. <p>In addition, the deviation of the experimental Fowler-Nordheim (F-N) plot from a straight line was observed for graphitic nanocone films. The deviation can be mainly attributed to the nonuniform field enhancement factor of the graphitic nanocones. In low macroscopic electric field regions, electrons are emitted mainly from nanocone or nanocones with the largest field enhancement factor, which corresponds to the smallest slope magnitude. With the increase of electric field, nanocones with small field enhancement factors also contribute to the emission current, which results in a reduced average field enhancement factor and therefore a large slope magnitude.

Carbon nanotubes (CNTs) have great potential in many applications due to their unique structure and properties. However, there are still many unsolved problems hampering their real applications. This thesis focuses on three important issues limiting their applications, namely: (1) direct growth of CNTs without additional catalyst, (2) secondary growth of carbon nanotubes on primary CNT bed without using extra catalyst, (3) and CNT alignment mechanisms during the growth.<p> The CNTs used in this thesis were prepared by hot filament chemical vapor deposition (CVD) reactor and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Raman spectroscopy. Field electron emission (FEE) properties of the CNTs were also tested.<p> Oxidation-reduction method was adopted in direct growth of CNTs on Inconel 600 plates and proved effective. The effect of oxidation temperature on the growth of CNTs was studied. It was found that the oxidation temperature had an influence on CNT height uniformity and FEE properties: the higher the treatment temperature, the more uniform the resultant CNTs, and the better the FEE properties of the resultant CNTs. The contribution of different oxides formed at different temperatures were investigated to explain the effect of oxidation temperature on the CNT height uniformity.<p> Secondary CNTs were grown on primary ones by simply changing the carbon concentration. No additional catalyst was used during the whole deposition process. It was found that synthesizing primary CNTs at extremely low carbon concentration is key factor for the secondary growth without additional catalyst. The CNT sample grown with secondary nanotubes exhibited improved field emission properties.<p> The effect of bias voltage on growth of vertically aligned carbon nanotubes was investigated. The CNTs grown at -500V shows the best alignment. At the early growth stage, simultaneous growth of randomly oriented and aligned carbon nanotubes was observed. This was consistent with the alignment mechanism involving stress that imposed on catalyst particles on tube tips. Through the observation of CNT growth on the scratched substrates, catalyst particle size was found as another determining factor in the alignment of CNTs. Big catalyst particles promoted aligned growth of CNTs.

Laser Chemical Vapor Deposition (LCVD) is a process by which reagent gases are thermally activated to react by means of a laser focused on a substrate. The reaction produces a ceramic or metallic deposit. This investigation focuses on the use of LCVD as a method for producing laminated composites, specifically carbon/silicon carbide laminates. The laminates that were produced were examined using scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) to determine composition. Deposit geometrical characteristics such as laminate thickness and volcano depth as well as deposit morphology were also determined using SEM. Another subset of experiments was performed for the purpose of simultaneously depositing carbon and silicon carbide, ie., codeposition.

As the minimum feature size in complementary metal-oxide-semiconductor (CMOS) devices shrinks, the leakage current through the gate insulator (silicon oxide) will increase sufficiently to impair device operation. A high dielectric constant (k) insulator is needed as a replacement for silicon oxide in order to reduce this leakage. Hafnium-based materials are among the more promising candidates for the gate insulator, however, it is hampered by material quality and thus has been slow to be introduced into high volume integrated circuit production. Hafnium oxynitride films are deposited by Metalorganic Chemical Vapor Deposition (MOCVD) and downstream microwave Plasma Enhanced Chemical Vapor Deposition (PECVD) employing different oxidants including O2, N2O, O2 plasma, N2O plasma, N2O/N2 plasma, and O2/He plasma in the current research. The effects of oxidants on deposition kinetics, morphology, composition, bonding structure, electrical properties and thermal stability of the resultant films each are investigated. The possible chemical/physical causes of these observations are developed and some mechanisms are proposed to explain the experimental results. Oxygen radicals, which are known of present in oxidizing environments are determined to play an essential role in defining both structures and the resultant electronic properties of deposited hafnium oxynitride films. This systematic investigation of oxidant effects on CVD grown hafnium oxide/oxynitride layers, in the absence of post-deposition annealing, provides new understanding to this area with potential importance to the integrated circuit industry.

This research has discussed the graphene growth mechanism and the achievement, the main purpose is to try the best method to grow graphene which is large size, uniform, and continue. The main issue is about growth and characterizations in full text which is separated by thermal annealing 6-H SiC(001) and chemical vapor deposition on the copper foil to grow graphenen. For instances, to adjust the growth parameters and the growth methods to get graphene and to control the quality, to analysis the number of layers, to research the characterizations during growth process, and to find the better transfer method are all the important focus in this paper. The morphology of samples is studied by SEM, AFM, STM, OM and so on, further the thickness of graphene layers can be observed by AFM and STM. Due to the limit of instruments, the thickness of graphene layer (~0.35 nm) and the thickness of 6-H SiC(001) steps (~1.5 nm) are not easy to observe actually. Raman spectroscopy is the main analysis tool I have employed, it is the fast way to calculate the number of layers (G, 2D band). In addition, Raman scattering is able to know the information of electronic structure variation (2D band), to investigate the stress which is caused by substrate and to estimate the quality of graphene (D, G band). Finally, I take chemical vapor deposition to grow graphenen on the copper foil. Sample is successfully transferred onto SiO2, and the number of graphene layers is estimated to be about two and the structure is AA stacking from these data. The data also shows the graphene is large size, uniform, and continue.