The discovery of carbon nanotubes (CNTs) has sparked great interest in the scientific world because of their remarkable electrical and physical properties. Only a thorough understanding of these properties, however, will allow CNTs to be commercially viable. Essentially, CNTs are graphite-like surfaces of sp2 hybridized carbon atoms in the form of tubes. CNTs could range from single-walled carbon nanotubes (SWNTs), consisting of one cylindrical graphite sheet to multi-walled nanotubes (MWNTs) that have concentric sheets. Nanotubes can be synthesized using a number of techniques such as electric arc–discharge, laser ablation and catalytic chemical vapor deposition (CCVD). In this project the CCVD technique was used for the synthesis of CNTs because of it simplicity and availability. The source of carbon was not the conventional hydrocarbon gas, but was camphor, a botanical hydrocarbon that is a solid at room–temperature. Ferrocene was the catalyst, not only because it has been used before in the synthesis of nanotubes, but it appears to be one of the best catalysts during the CCVD synthesis of nanotubes. The presence of nitrogen gas is known to assist in the synthesis of CNTs that have a bamboo–like structure; hence the effect of carrier gases such as nitrogen, argon/hydrogen and argon on the quality of nanotubes synthesized was investigated. Initially, the optimal experimental method for the synthesis of CNTs was determined by varying the reaction path length, temperature, mixing the catalyst and carbon source together or keeping them separate and varying the %m/m of the catalyst to carbon source. It was found that either an increase in the reaction temperature or an increased path length resulted in an increase in the mass of product obtained, whereas mixing the catalyst and carbon source together as opposed to them being separated only caused a slight variation in the mass of product synthesized. The mass of product synthesized also increased as the catalyst concentration increased. The remainder of the project was aimed at investigating the role of different gases: nitrogen, argon and hydrogen (in argon) in the CCVD synthesis of CNTs. The resulting materials were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and laser Raman analysis. The results indicated that this method could be tailored to synthesize either carbon spheres or carbon nanotubes of specific diameters and quality. Finally, in an attempt to synthesize aligned carbon nanotubes, catalyst supports {characterized using Brunauer-Emmett-Teller analysis (BET)} namely; silica, alumina and magnesium oxide were used. Although this was not successful for the synthesis of aligned CNTs under the conditions used, alumina showed the most promise. / Mr. S. Durbach Dr. R. W. Krause

In this work, a systematic study relating the surface morphologies, electrical and structural properties of both doped and undoped InAs and InAsSb epitaxial films grown by metalorganic chemical vapour deposition (MOCVD) was undertaken. A comparative study using TBAs and AsH3 as the group V source in the growth of InAs revealed a considerable improvement, primarily in the electrical properties of InAs grown using TBAs with no significant difference in the surface morphology. InAs layers grown using TBAs, exhibited superior 77 K mobilities of up to 46 000 cm2/Vs, exceeding the best MOCVD data to date. The feasibility of tetraethyl tin (TESn) as an n-type dopant in InAs was to our knowledge investigated for the first time. The incorporation efficiency of this dopant was extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that the doping efficiency is temperature dependent and is not influenced by a variation of the V/III ratio or substrate orientation. Furthermore, Sn doping concentrations could be controlled over 2 orders of magnitude ranging between 2.7 x 1017 and 4.7 x 1019 cm-3 with 77 K mobilities ranging from 12 000 to 1300 cm2/Vs. The electrical properties of zinc doped InAs employing dimethyl zinc (DMZn) as the ptype dopant, were studied as a function of V/III ratio and substrate orientation. The effect of a variation of these parameters on the structural properties and surface morphology of InAs is also reported. The substrate orientation appears to have no influence on the Zn incorporation. An increase in Zn incorporation resulted in a deterioration of both the surface morphology and structural quality of the InAs layers. The incorporation efficiency of DMZn in InAsSb was studied as a function of growth temperature, V/III ratio and DMZn flow rate. A higher Zn incorporation was observed in InAsSb epitaxial layers grown at a lower temperature and V/III ratio as opposed to the layers grown at a higher temperature and V/III ratio. This study also revealed that the use of DMZn caused a dopant memory effect. A two-layer model proposed by Nedoluha and Koch (1952) was used to simulate the Hall measurements of Zn doped InAs and InAsSb in order to correct the shortcomings of conventional Hall measurements in determining the electrical properties exhibited by these materials.

Graphene, a layer of carbon atoms arranged in a honeycomb-type structure, has attracted enormous interest since it was first isolated in 2004. Chemical vapor deposition (CVD) is one of the most common techniques to produce graphene but questions remain on how best to standardize its growth. Different designs of reactors, numerous sub-types of CVD (plasma-enhanced, low pressure…), catalytic metal foils that vary in surface chemistry and texture… these are all variables that are abundantly scrutinized in the literature. Despite the scattering of procedures and observations, it is rare to find comparative studies of graphene growth. In this thesis, two thermal CVD reactors were explored to grow single–layer graphene (SLG) on a 50 μm copper foil. These set–ups were very different, one being a “showerhead” cold–wall type whereas the other one had a tubular hot-wall chamber. Their inner volume, gas flow limits, and heating rates were other differentiating factors. The work had three critical steps: pre–growth treatment of the metal foil, growth step and SLG transfer. All required absolute control to obtain high quality, uniform and cm2–scale SLG placed on a SiO2 substrate. Overall, and after standardizing the surface of the metal foil, it was possible to design a CVD recipe for the two reactors that differed only on the gas flow rates used. Thus, and contrary to an often-used argument in the literature, SLG growth recipes can be transferred amongst thermal CVD reactors.

No description available.

No description available.

The nucleation and successful growth of copper (Cu) thin films on diffusion barrier/adhesion promoter substrates during metal-organic chemical vapor deposition (MOCVD) are strongly dependent on the initial Cu precursor-substrate chemistry and surface conditions such as organic contamination and oxidation. This research focuses on the interactions of bis(1,1,1,5,5,5-hexafluoroacetylacetonato)copper(II), [Cu(hfac)2], with polycrystalline tantalum (Ta) and polycrystalline as well as epitaxial titanium nitride (TiN) substrates during Cu MOCVD, under ultra-high vacuum (UHV) conditions and low substrate temperatures (T < 500 K). The results obtained from X-ray photoelectron spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Temperature Programmed Desorption (TPD) measurements indicate substantial differences in the chemical reaction pathways of metallic Cu formation from Cu(hfac)2 on TiN versus Ta surfaces.

by Poon Chun Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 110-112). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.2 / ABSTRACT --- p.3 / TABLE OF CONTENTS --- p.5 / LIST OF FIGURES --- p.8 / LIST OF TABLES --- p.13 / Chapter CHAPTER 1 --- INTRODUCTION --- p.14 / Chapter 1.1 --- Overview --- p.14 / Chapter 1.2 --- Ferromagnetism --- p.15 / Chapter 1.3 --- Ferromagnetic granular thin film --- p.16 / Chapter 1.4 --- Ferromagnetism-magnetization --- p.17 / Chapter 1.5 --- Ferromagnetism - magnetization of a polycrystalline --- p.18 / Chapter 1.6 --- Soft and hard magnetic materials --- p.21 / Chapter 1.7 --- Preparation methods --- p.22 / Chapter 1.8 --- This thesis --- p.24 / Chapter CHAPTER 2 --- SAMPLE PREPARATION AND EXPERIMENTAL METHODS --- p.25 / Chapter 2.1 --- Sample preparation --- p.25 / Chapter 2.1.1 --- The pulsed filtered cathodic arc co-deposition system --- p.25 / Chapter 2.1.2 --- Details of sample preparation --- p.27 / Chapter 2.1.3 --- Improvement of the target holder --- p.30 / Chapter 2.2 --- Rutherford backscattering spectrometry (RBS) --- p.30 / Chapter 2.3 --- X-ray diffraction (XRD) --- p.32 / Chapter 2.3.1 --- Diffraction technique --- p.32 / Chapter 2.3.2 --- Scherrer's formula --- p.35 / Chapter 2.4 --- Raman spectroscopy --- p.35 / Chapter 2.5 --- Transmission electron microscopy (TEM) --- p.36 / Chapter 3.5.1 --- The technique of transmission electron microscopy (TEM) --- p.36 / Chapter 3.5.2 --- Transmission electron microscopy (TEM) sample preparation --- p.37 / Chapter 2.6 --- X-ray photoelectron spectroscopy (XPS) --- p.41 / Chapter 2.6.1 --- The principle of XPS --- p.41 / Chapter 2.6.2 --- Qualitative analysis of XPS (chemical shift) --- p.43 / Chapter 2.7 --- Scanning probe microscopy (SPM) --- p.43 / Chapter 2.7.1 --- The principle of atomic force microscopy (AFM) --- p.43 / Chapter 2.7.2 --- Tapping mode atomic force microscopy --- p.44 / Chapter 2.7.3 --- Magnetic force microscopy (MFM) --- p.46 / Chapter 2.8 --- Vibrating sample magnetometer (VSM) --- p.47 / Chapter 2.8.1 --- The principle of VSM operation --- p.47 / Chapter 2.8.2 --- Useful of the pick up coils --- p.49 / Chapter 2.8.3 --- M-H Loop --- p.50 / Chapter 2.9 --- Four-contacts technique --- p.51 / Chapter CHAPTER 3 --- CHARACTERIZATION OF CO-DEPOSITED CO-C SAMPLES --- p.53 / Chapter 3.1 --- Introduction --- p.53 / Chapter 3.2 --- Results and discussion --- p.54 / Chapter 3.2.1 --- NRBS measurements --- p.54 / Chapter 3.2.2 --- X-ray diffraction --- p.57 / Chapter 3.2.3 --- Raman spectroscopy --- p.59 / Chapter 3.2.4 --- AFM and MFM measurements --- p.64 / Chapter 3.2.4.1 --- AFM result --- p.64 / Chapter 3.2.4.2 --- MFM result --- p.68 / Chapter 3.2.5 --- Vibrating sample magnetometer (VSM) measurements --- p.73 / Chapter 3.3 --- Summary --- p.78 / Chapter CHAPTER 4 --- CHARACTERIZATION OF CO-DEPOSITED FE-C SAMPLES --- p.79 / Chapter 4.1 --- Introduction --- p.79 / Chapter 4.2 --- Results and discussion --- p.80 / Chapter 4.2.1 --- NRBS measurement --- p.80 / Chapter 4.2.2 --- X-ray diffraction --- p.81 / Chapter 4.2.3 --- x-ray photoelectron spectroscopy (XPS) --- p.84 / Chapter 4.2.4 --- AFM results --- p.87 / Chapter 4.2.5 --- MFM results --- p.91 / Chapter 4.2.6 --- Vibrating sample magnetometer (VSM) measurements --- p.95 / Chapter 4.2.7 --- Resistivity --- p.99 / Chapter 4.2.8 --- Transmission electron microscopy (TEM) --- p.100 / Chapter 4.3 --- Application potential --- p.101 / Chapter 4.4 --- Summary --- p.104 / Chapter CHAPTER 5 --- CONCLUSION --- p.106 / Chapter 5.1 --- Main results of this work --- p.106 / Chapter 5.2 --- Future work --- p.108 / REFERENCE --- p.110 / PUBLICATIONS --- p.112 / APPENDIX --- p.113

Hong Liang = 用化学气相淀积方法生长氮化物纳米材料 / 洪亮. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Hong Liang = Yong hua xue qi xiang dian ji fang fa sheng chang dan hua wu na mi cai liao / Hong Liang. / Acknowledgements --- p.ii / Abstract --- p.iii / Contents --- p.v / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Motivation --- p.2 / Chapter 1.2.1 --- A1N and AlGaN nanowires --- p.2 / Chapter 1.2.2 --- CVD --- p.3 / Chapter 1.3 --- Our work --- p.3 / Chapter Chapter 2 --- Experiment --- p.7 / Chapter 2.1 --- CVD system --- p.7 / Chapter 2.2 --- Sources and Substrates --- p.7 / Chapter 2.3 --- Growth of A1N nanowires --- p.8 / Chapter 2.4 --- Growth of AlGaN nanowires --- p.9 / Chapter Chapter 3 --- Characterization --- p.11 / Chapter 3.1 --- Scanning Electron Microscopy --- p.11 / Chapter 3.1.1 --- Topographic images by secondary electrons --- p.11 / Chapter 3.1.2 --- Elemental Analysis by Energy Dispersive X-ray --- p.12 / Chapter 3.2 --- Transmission Electron Microscopy --- p.12 / Chapter 3.3 --- X-Ray Diffraction --- p.14 / Chapter 3.4 --- Micro-Raman --- p.15 / Chapter Chapter 4 --- Results and Discussion --- p.18 / Chapter 4.1 --- A1N nano-structures --- p.18 / Chapter 4.1.1 --- A1N nano-leaves grown on silicon substrates --- p.18 / Chapter 4.1.2 --- A1N nanowires grown on silicon substrates --- p.19 / Chapter 4.1.3 --- SiNx nanowires grown on silicon substrates --- p.22 / Chapter 4.1.4 --- A1N nanowires grown on sapphire substrates --- p.26 / Chapter 4.1.5 --- Comparison with the results of other research groups --- p.31 / Chapter 4.2 --- AlGaN nano-structures --- p.33 / Chapter 4.2.1 --- AlGaN nanowires grown on silicon substrates --- p.33 / Chapter 4.2.2 --- Temperature dependence --- p.38 / Chapter 4.2.3 --- The influence of the mass ratio (Ga/Al) in the precursor metal sources --- p.43 / Chapter 4.2.4 --- Substrate effect --- p.46 / Chapter Chapter 5 --- Suggestion of the growth mechanism --- p.51 / Chapter 5.1 --- Growth mechanisms: an introduction --- p.51 / Chapter 5.2 --- The growth mechanisms for our produced samples --- p.57 / Chapter 5.2.1 --- Growth mechanism for A1N nanowires --- p.58 / Chapter 5.2.2 --- Growth mechanism for AlGaN nanowires --- p.61 / Chapter 5.2.3 --- Substrate effect --- p.65 / Chapter Chapter 6 --- Conclusions --- p.71 / Appendix --- p.73

Thesis (M.Ch.E.)--University of Delaware, 2007. / Principal faculty advisor: Brian G. Willis, Dept. of Chemical Engineering. Includes bibliographical references.

This study employed a commercial code to simulate a chemical vapor deposition process in a rectangular chamber for deposition of a silicon dioxide layer on a rectangular substrate. We focus on the deposition rate on the substrate surface. We discuss the effects of the Reynolds number, the distance from inlet to substrate, the size of inlet region, the temperature of the inlet region, and the temperature of substrate. The results show that as the temperature increase, the deposition rate on the substrate grows highly. This effect will decrease if the temperature is above the specific range. Besides, it is easily deposited unequally on the edge and corner region of the substrate. However, the central region on the substrate is still uniform. We could get bigger uniform area to adjust the proper conditions.