Growth and transmission electron microscopy studies of nanomaterials 1 2

Chapter Introduction Chapter Introduction Nanotechnology is rapidly emerging as an important research field all over the world because of its potential for revolutionizing every aspects of modern day science Technological bottlenecks in the roadmap for semiconductor technology are creating increasingly more complex problems for scientists which call for a paradigm shift in the fundamental concepts and architecture of electronic devices and materials processing It is inevitable that nanotechnology will play a central role in this due to the new possibilities presented by dimensional materials, as well as the increasingly demanding manipulation and processing techniques required for the assembly and manufacture of these devices Dimensional nanomaterials present fundamentally different physical concepts to conventional bulk materials because of their unique density-of-states as well as vibrational and electronic confinements Confinement effects are attributed to the electronic and vibrational excitations with characteristic lengths comparable to the diameter of the crystallites As a result, substantial modifications of the density of states and electronic structure should be expected The challenge therefore is to create nanomaterials with a monodispersion in their sizes, and then to study the correlation in properties, size and structure However, the synthesis of nanomaterials with controlled dimensions, desired shapes, as well as oriented growth on a substrate, Chapter Introduction is technically non-trivial The growth of uniformly-sized dimensional nanomaterials requires careful control of catalyst size and dispersion matrix to prevent aggregation Ordered orientation of the nanomaterials on a substrate, or selective growth of the nanomaterials for making wire circuitry and devices, in a manner that is compatible with large scale industrial synthesis and conventional microelectronic processing methods, are technologically challenging problems A number of novel strategies have been developed to address these targets This thesis is motivated by the challenge of synthesizing semiconductor nanomaterials that may have potential applications in electronic devices Using chemical vapor deposition, a range of semiconductor nanomaterials has been successfully synthesized These include BN nanocapsules, ZnS nanowires, SiC nanocones and CuInS2 thin films The internal microstructure of these materials will be mainly studied using TEM and other characterization tools Other areas which will be discussed in this thesis include the relationship between the size of nanomaterials and the catalysts, the influence of growth conditions on the morphology and structure of final products, the growth mechanism of these nanomaterials, and the mechanism of morphology and phase transfer of these nanomaterials In the following section, a brief introduction to the science and technology of nanomaterials will be presented Following which, several characterization Chapter Introduction techniques will be discussed with particular emphasis on the application of TEM for the characterization of nanomaterials Finally a brief introduction to the following chapters will be presented “In the great future -we can arrange the atoms the way we want; the very atoms, all the way down!” Richard Feynman, 1959 1.1 Nanotechnology Nanotechnology can be broadly defined as the application of science to develop new materials and processes by manipulating molecules and atoms in the length scales of 1-100 nanometers In general, any technology related to features of nanometer scale: thin films, fine particles, chemical synthesis, advanced microlithography, and so forth can be classified as nanotechnology It is an interdisciplinary field which can impact the traditional disciplines of physics, chemistry and biology at the fundamental molecular and atomic level In terms of engineering, devices are constructed at the molecular scale and function at this scale However, nanotechnology is not simply a miniaturization in size, but an entire paradigm shift in physical concepts, system design and materials manufacturing This technology is expected to allow the construction of very compact and high performance computing devices or molecular sensors High hopes have been pinned Chapter Introduction on nanotechnology to provide the impetus for breakthroughs needed in many areas which has reached conventional technological limits 1.2 Nanomaterials Table 1.1 Examples of dimensional nanomaterials Dimension Existing type Examples (b) (a) Quantum 2-D wells super-thin films (a) InAsP/InGaP multi-quantum wells (Campi R etc, J Crys Growth) [2]; (b) wurtzite ZnS single-crystal nanosheets (Yu SH etc, Adv Mate.) [3] nanowires 1-D nanorods nanotubes nanocones (a) Au nanotubes (Sun Y, Nano Lett.) [4]; (b) Well aligned ZnO nanowires (Huang, M etc Science) [5] (a) (b) 0-D (the sizes of the materials are nm in length ) Quantum dots (a)InGaAs/GaAs quantum dots (Ozasa K etc, Ultramicroscopy) [6]; (b) Ag nanocubes (Xia etc, Science)[7] Chapter Introduction The enabling of nanotechnology requires the use of nanomaterials, which refer to materials wherein at least one dimensional size is on nanometer scale (1-100 nm) According to the geometric dimensionality, nanomaterials can be categorized into three groups: Two dimensional (2-D), one dimensional (1-D) and zero dimensional (0-D) nanostructured materials Table 1.1 lists current examples of dimensional nanomaterials and their usage in technologies Nanomaterials have unique optical, electronic and catalytic properties, which often depend strongly on their size and are very different from the corresponding bulk materials For example, the bandgap of CdS quantum dot can be tuned between 2.5 to eV, while the irradiative rate for the lowest allowed optical excitations ranges from several nanoseconds down to tens of picoseconds when its size decreases to nanometer scale [1] If the size of the crystal is small enough, quantum confinement due to discrete electron charge or energy levels can be observed macroscopically Quantum confinement means that electrons are trapped in a small area, like particles in a box model The nanomaterials show continuous energies and momentum in free directions, and confinement restricted in (2D nanomaterials), (1D nanomaterials) and (0D nanomaterials) directions The energy separations of the confined states and their numbers depend on the materials property, the length scale and potential offsets Figure 1.1 illustrates the simple relationship between density of states and Chapter Introduction confinement dimensions The accurate treatments of confinement require high-order calculations to account for the band structures However, most investigations of quantum confinement now focus on its optical effects, which is similar to the tunable optical excitations of CdS nanodots mentioned above Bulk DOS 2D Energy 1D 0D Figure 1.1 Density of states characterized by the confinement dimension The interests in nanomaterials are sometimes motivated and sustained by the availability of powerful electron microscope for studying these materials It is only when materials are observed under these microscopes that the possibilities of generating nanosized particles in chemical reactions can be verified The greatly improved resolution and sensitivity of modern microscopes provides the opportunity for the “discovery” of carbon nanotubes by Prof Ijima [8] When Richard Feynman Chapter Introduction gave his classic talk in 1959, the highest attainable resolution of transmission electron microscopy (TEM) was only nm The resolution of current state-of-art TEM has improved to 0.19 nm (the size of an average atom) when carbon nanotubes were discovered in 1991 The invention of other new instruments also promotes research on nanomaterials In the early 1980’s, the scanning tunneling microscope (STM) was invented at IBM-Zurich in Switzerland This was the first instrument that was able to “see” atoms in conductive and semiconductor materials A few years later, the Atomic Force Microscope (AFM) was invented, expanding the types of materials that could be investigated to insulating materials Currently, a large number of techniques, such as Scanning Electron Microcopy (SEM), small-angle X-ray Diffraction (SAXRD), scanning auger spectroscopy and Photoluminescence (PL) have been applied to help scientists to obtain more detailed information about nanomaterials 1.3 The applications of TEM on the study of nanomaterials Among all the characterization instruments, TEM is one of the most powerful tools used routinely and has played the most important role in characterizing nanostructures Its ability for providing information on the internal microstructure of nanomaterials at resolution down to atomic level surpasses that of most other instruments One example is the determination of composition of Chapter Introduction quantum dots The spatial resolution of XPS, STM and PL can not determine the compositional variations within the dot but TEM allows the determination of several levels of information: from the elemental mapping of the dot, to the study of the epitaxial interface between the dot and substrate, to the determination of the crystalline quality of the dot [9, 10] TEM can be operated in various modes for the characterization of the structural and electronic properties of materials (table 1.2) Due to a large number of literatures and publications in this area, focus will be placed on the TEM techniques that are used in this thesis and some recent novel applications used in nanotechnology Table 1.2 TEM techniques used in nanotechnology Techniques Imaging Diffraction pattern EDX EELS Holographic mapping Information provided Morphology, shape and internal structure 1.3.1 Internal crystal structure 1.3.1 Chemical and electronic structure 1.3.2 Chemical and electronic structure; elemental distribution and phase mapping electric and magnetic fields Observing dynamic phase transformation process and surface reactions in-situ TEM Chapter 1.3.2 1.3.3 1.3.4.1 Observing the growth process of nanomaterials 1.3.4.2 Nanomeasurement of physical properties 1.3.4.3 Chapter Introduction 1.3.1 Crystal structure of nanomaterials The most important application of TEM is used for the characterization of the internal nanostructure of materials, a good example is the study of the structure of carbon nanotube In High Resolution TEM images, the parallel fringes (0002) shown in figure 1.2 are the profile view of tube walls that is tangent to the electron beam The uniform spacing between the parallel fringes that corresponds to the tube walls is 0.34 nm, which indicates the structures are seamless and have a tubular structure [8] Figure 1.2 HRTEM images of multi-walled carbon nanotubes (Iijima S Nature 354, 56, 1991) Combined with diffraction patterns, TEM can provide direct imaging of the surface structures, chirality of nanotubes, and the distribution of atoms in one sheet layer Figure 1.3 shows a HRTEM image of a WS2 coated multi-walled carbon Chapter Introduction nanotubes [11] The WS2 coating, verified by EDX, shows a fringe which is darker than the layers of carbon surrounding the carbon nanotube Figure 1.3 HRTEM image of a WS2 partly coated MWCN (arrows indicate amorphous WO3) (Whitby RLD etc, Chem Phys Lett 2002, 359, 121) Figure 1.4a shows the diffraction pattern derived from the image in figure 1.3 The (0002) carbon plane is observed as a streak extending across the center of the image (arrow A, Figure 1.4b) and some faint ( 10 ) carbon spots (black dashed line, Figure 1.4b) are visible outside the ring of WS2 spots The horizontal spots spacing (arrow B) is ca 0.21 nm, corresponding to an armchair edge of (10 ) Additionally, two sets of diffraction spots arising from front and rear regions appear in hexagonal arrays, which match the diffraction pattern of the hexagonal WS2 structure The two hexagonal arrays are rotated away from each other by ca 17° and are inclined at ca 8.5° to the CNT axis In other words, the WS2 coating is an 8.5° helical tube The hexagonal pattern, clearly seen between two walls, corresponds to the extension of the WS2 single sheet coating on the back of the CNT, as shown in 10 Chapter Experiment Evaporator Gun Gas injection Gas thermal cracker Deposition source Specimen stage Column CCD camera Figure 2.4 Schematic view of MERLION system The specimen may be heated, and/or treated by gas reaction in the pre-treating chamber (PTC) before loading into the microscope if necessary A special specimen holder allows the sample to be heated to up to 1200 ˚C in the polepiece of the electron microscope whilst deposition is taking place and with the electron beam irradiating the region of the sample of interest The post column imaging filter attached to MERLION was used for all the energy filtered work presented here 2.1.4 Sample preparation Si pieces (6 mm × mm) were cut from a silicon wafer and hand-ground from 300 µm to 230 µm Then the substrates were dimpled uniaxially to 20 µm at the centre, followed by chemical etching to perforation in a solution of HF : 41 Chapter Experiment HNO3 : H2O =1:3:1 to make the etched edge of the hole thin enough to allow the electron to pass through The nanoparticles were then cast onto the substrates by evaporation from an ethanol suspension in an ultrasonic bath Only those particles sitting at the edge of the hole can be seen under electron beam The process is illustrated in figure 2.5 The electric current was directly passed through the Si substrate and the temperature was calibrated using a pyrometer Back Front Back Front Si (6 mm × mm) Hand grind 300μm Dimple Etching 230μm Back Front Side view Particles Figure 2.5 Schematic of the sample preparation procedure 2.1.5 Routine TEM For routine TEM analysis, the nanowires and films were mechanically removed from the substrate and ultrasonically dispersed in ethanol before being dispersed onto a 200-mesh holy carbon coated copper grid The samples were observed using a Philips CM300 microscope (field emission gun) equipped with 42 Chapter Experiment an EDX detector and operated at an accelerating voltage of 300 KV The resolution of the CM300 is 0.17 nm 2.2 Chemical vapor deposition (CVD) of CuIn(Ga)S(Se)2 films In this experiment, CuInS2, CuGaS2 and CuInSe2 thin films were grown from s single source precursor using a chemical vapor deposition process 2.2.1 Chemical vapor deposition (CVD) CVD is a synthesis process in which the chemical volatile precursors are transformed into gaseous molecules and react near or on a heated substrate to form a solid deposit This gas-solid reaction at the surface of a substrate is the heterogeneous reaction CVD is considered one of the great complex and versatile process of reactions Gas Phase Reaction Desorption of Precursor Transport to Surface Adsorption of Film Precursor Desorption of Volatile Reaction Products Step Growth Surface Diffusion Nucleation and Island Growth Figure 2.6 Schematic of transport and reaction process in CVD 43 Chapter Experiment The basic physiochemical process of CVD in general is shown schematically in figure 2.6 This may be summarized as follows [5]: 1) Mass transportation of the precursor or the decomposed vapors to the deposition zone 2) Adsorption of the vapors on the substrate 3) Surface diffusion of the precursors 4) Decomposition of precursor molecules on surface and incorporation into solid films 5) Recombination of molecular byproducts and desorption into gas phase 6) Mass transportation of the by-products out of the reactor 2.2.2 Synthesis of single source precursor The single source precursors used in the experiment were all synthesized by Dr TC Deivaraj and Ms Keqin (under supervision of A/P JJ Vittal) 2.2.2.1 Synthesis of (Et3NH)[In(SC{O}Ph)4] [1] Two derivatives of anionic homoleptic thiocarboxylate complexes, namely [Et3NH][M(SC{O}Ph)4]·H2O (M ~ In3+ (1), Ga3+ (2)) have been prepared as shown by the equations given below MX3 + PhC{O}SNa → “[M(SC{O}Ph)3]” “[M(SC{O}Ph)3]” + [Et3NH]+[ SC{O}Ph]- → [Et3NH]+[M(SC{O}Ph)4] 44 Chapter Experiment A creamy white precipitate was formed when InCl3 (0.20 g, 0.90 mmol) reacted with NaSC{O}Ph, which was formed in situ by reacting NaOH (0.11 g, 2.70 mmol) and PhC{O}SH (319 µL, 2.70 mmol) in 30 mL of water The solution was stirred for about 30 and then [Et3NH]+[ SC{O}Ph]- in CH2Cl2 (15 mL) (prepared by reacting 106 µL of PhC{O}SH and 126 µL of NEt3) was added The yellow CH2Cl2 layer was separated and layered with petroleum ether to get cream colored crystalline precipitate The compound was filtered, washed with cold MeOH and Et2O and dried under vacuum Yield 0.62 g (89%) 2.2.2.2 Synthesis of [Et3NH][Ga(SC{O}Ph)4]·H2O [2] PhCOSH (138 µL, 1.17 mmol) in MeOH (10 mL) was allowed to react with NaOMe (prepared in situ by reacting Na (0.03 g, 1.17 mmol) in 10 mL of MeOH) to get NaSC{O}Ph A solution of Ga(NO3)3·H2O (0.10 g, 0.39 mmol) in 10 mL of MeOH was added The yellow solution was stirred for 15 and the solvents were removed under a flow of dry nitrogen [Et3NH]+[PhC{O}S]- in 20 mL of CH2Cl2 was added and the resulting solution was stirred for 30 The insoluble NaNO3 was then filtered and the filtrate was layered with 30 mL of petroleum ether and left over night at ˚C The white precipitate thus formed was washed with MeOH (5 mL) and Et2O and dried under vacuum Yield 0.22 g (78%) 45 Chapter Experiment 2.2.2.3 Synthesis of In(SPh)3 [3] The In(XPh)3 (X=S(3), Se(4)) single precursor was synthesized by the following reaction: In (s) + 3/2 PhX-XPh (s) In(XPh)3 (s) Indium metal powder (0.26 g, 2.26 mmol) was refluxed and stirred at a temperature of 130 ˚C with diphenyl disulfide (0.26 g, 3.25 mmol) in 50 mL of toluene for hrs The resulting white solid in a yellow solution was cooled to room temperature overnight The white precipitate was collected by filtration, rinsed with n-pentane and dried in vacuum Yield 0.83 g (86 %) 2.2.2.4 Synthesis of In(SePh)3 [4] Indium metal powder (0.49 g, 4.27 mmol) was vigorously refluxed and stirred with diphenyl diselenide (2.00 g, 6.40 mmol) in 40 mL of toluene for hrs The orange solution slowly turned yellow as the reaction proceeded The mixture was filtered hot to remove the unreacted Indium metal particles The yellow filtrate was cooled to room temperature where a yellow precipitate deposited The precipitate was collected, rinsed with n-pentane and dried in vacuum Yield 1.79 g (72 %) 46 Chapter Experiment 2.2.3 Deposition of CuIn(Ga)S(Se)2 thin films The CVD system employed for the growth of CuIn(Ga)S(Se)2 thin films consists of a stainless steel chamber equipped with a turbo-molecular pump Figure 2.7 below illustrates the schematic CVD chamber set up for the thin film deposition Connect to rotary pump thermocouple Thermocouple Turbomolecular pump Valve Cold cathode pressure gauge electrode Electrode Substrate substrate Shutter shutter View port Knudsen cell Knudsen cell View port Figure 2.7 Schematic setup of the CVD system The vacuum pressure was monitored by a cold cathode gauge The films were grown on a commercial Cu coated silicon wafer with a Cu thickness of 120 nm The Cu films were RF magnetron sputtered on the Si wafer Prior to growth, the Cu/Si substrates were cut into 1.0 × 2.5 cm pieces, rinsed in absolute ethanol, dried under N2 gas flow and mounted onto the substrate holder CVD was carried 47 Chapter Experiment out by thermally evaporating the inorganic precursor from a boron nitride cup that was installed at a distance of cm below the substrate under a dynamic vacuum of 1×10-5 torr The substrate was resistively heated by controlling the current flow to it while the precursor cup was thermally heated to a different temperature using a Re-Vap 900 Watt Power Supply for different precursors depending on the volatility and melting point of the precursors The substrate temperature was measured using a thermocouple directly inserted in-between the sample and the heating plate The reaction time was maintained at about 15 minutes 2.3 Growth and oxidation of ZnS nanowires 2.3.1 Preparation of the Au/Si (100) substrates A Si(100) wafer was cut into cm × cm pieces using a diamond scriber Then the surface of the Si(100) wafer was ultrasonically cleaned in acetone to remove impurities and dried in flowing nitrogen before sputtering Au The Au/Si(100) substrates were prepared using an Edwards Auto 306 electron beam evaporator which can deposit ultra pure films of materials that are difficult to deposit by thermal evaporation, such as dielectrics and highmelting-point metals The high degree of controllability of electron beam sources enables materials to be evaporated at a constant rate The system is also fitted with a quartz crystal deposition monitor to provide fully automatic film thickness control The base pressure of the system can reach 10-6 to 10-7 torr Au films with 48 Chapter Experiment thicknesses of 10 nm were deposited on Si substrate in this machine 2.3.2 Growth of ZnS nanowires ZnS nanowires were grown in the same chamber illustrated in figure 2.10 Supported Au nanoclusters were prepared by thermal annealing of Au film onto a Si(100) wafer ZnS nanowires were grown by thermally evaporating g of commercial ZnS powder (99.9%, Strem chemicals) under a dynamic vacuum of 1×10-5 torr The powder was evaporated from a high temperature Knudsen cell operated at 1000 ˚C, onto the Au/Si substrate, with the substrate temperature maintained at 700 ˚C The growth time was maintained between to 40 minutes 2.3.3 Oxidation of ZnS nanowires to ZnO Atomic oxidation of the ZnS nanowires was performed in an ultra-high vacuum system equipped with a remote discharge, 13.56 MHz radio-frequency oxygen atom beam source (Oxford Applied Research) The irradiation of the sample by the atomic O beam occurred at a background pressure of 1×10-4 torr and the RF power was set at 300 W The substrate temperature was maintained at 500 and 700 ˚C, respectively The treatment time was around 20 49 Chapter Experiment 2.3.4 in-situ TEM study of ZnS oxidation The in-situ TEM study was carried out in the MERLION system described in section 2.1.3 Conductive glue Back Front Si 300μm Hand grind Dimple Mount 230μm Figure 2.8 Schematic of the procedure of sample preparation Figure 2.8 shows the sample mounting process The ZnS nanowires were ultrasonically cleaned in absolute ethanol and then dispersed on the 200-mesh holy carbon coated copper grid Si pieces with a thickness of 230 µm were dimpled to perforation forming a small hole of ~0.7 mm square The copper grid was then mounted over the hole in the center of the silicon piece using CeramaBond 569-T adhesive, a special thermally conductive ceramic glue, with the center of the grid aligned over the hole of the silicon piece 2.4 Microwave plasma enhanced chemical vapor deposition (MW-PECVD) Plasma is one of the four states of matter It is a gas of charged particles (generally electrons and various ions) which interact with both externally applied electromagnetic fields and with fields they themselves generate Plasma can be 50 Chapter Experiment produced from a gas if enough energy is added to cause the electrically neutral atoms of the gas to split into positively and negatively charged atoms and electrons The precursor species injected into the plasma jet (nitrogen – hydrogen mixture) are broken into active radicals so that they can be used for film deposition applications where such energy is required to decompose the source Precursor N2/H2 Figure 2.9 Schematic setup of microwave plasma enhanced CVD The plasma-assisted deposition technique is a very popular method for growing materials Plasma systems afford the growth of uniform films over large substrate areas with the possibility of industrial scale up using more powerful reactors The schematic setup of the 2.45 GHz ASTex 5200 MW-PECVD system is 51 Chapter Experiment illustrated in figure 2.9 The system is evacuated by a mechanical rotary pump The sample is placed on the graphite substrate plate and heated by RF-induction heating below Hydrogen is introduced to initiate the plasma discharge, and then nitrogen and other gases are admitted to start the deposition 2.5 Raman measurement Raman spectroscopy has been used as an effective means of identifying the chemical composition of substances and analyzing molecular structures Micro-Raman measurements were performed using 514.5 nm line of radiation from an argon ion laser The scattered light was dispersed through a JY-T64000 triple monochromator system attached to a liquid nitrogen-cooled CCD detector The accuracy of Raman measurements was 0.2 cm-1 with a lateral resolution of µm at different temperatures (77–493 K) 2.6 X-ray diffraction (XRD) The X-ray diffraction of the films was obtained using a D5005 Bruker X-ray diffractometer at room temperature Cu Kα radiation of wavelength 1.5408 Å was used to record the XRD patterns in the range of 10˚ to 80˚ of 2θ The accelerating voltage and current were 40 kV and 40 mA respectively The XRD patterns were matched with the Joint Committee on Powder Diffraction Standards database (JCPDS) to determine their phase and lattice constant 52 Chapter Experiment 2.7 Scanning electron microscope - energy dispersive X-ray (SEM-EDX) The SEM images were obtained from a Joel-JSM 6700F scanning electron microscope equipped with Oxford EDX digital controller using an accelerating voltage of kV In order to take high magnification SEM images, a thin layer of gold or carbon film with a thickness of ~10 nm was thermally evaporated on the nonconductive films (such as SiO2, ZnS) to eliminate charging 2.8 Rutherford back scattering (RBS) RBS is a method to characterize the thickness and elemental concentrations of surface layers It involves measuring the number and energy of ions in a beam which backscatter after colliding with atoms in the near-surface region of a sample The acquired spectrum of the backscattered particles can be used to characterize the surface RBS measurements were carried out using MeV protons at 77 K from the Synchrotron accelerator at the Research Center for Nuclear Microscopy, NUS 2.9 X-ray photoelectron spectroscopy (XPS) XPS analysis was carried out using a spectrometer with a monochromatic Al K x-ray source (1486.6eV) on an ESCALAB 220IXL All binding energies were referenced to graphitic carbon The quantification studies were based on the determination of the peak area with the corresponding sensitivity factors 53 Chapter Experiment Gaussian peak deconvolution methods were employed to fit some peaks 2.10 Photoluminescence (PL) Features of the PL emission spectrum can be used to identify surface, interface, and impurity levels and to gauge alloy disorder and interface roughness PL is the spontaneous emission of light from a material under optical excitation [6, 7] It is a noncontact, nondestructive method of probing the electronic structure of materials Specifically, photo-excitation causes electrons within the material to move to the LUMO level When these electrons return to the HOMO level, the excess energy is released and may include the emission of light (a radiative process) or may not (a nonradiative process, phonon) The energy of the emitted light is related to the difference in energy levels between the LUMO and HOMO level The quantum yield of the light emission is related to the relative contribution of the radiative process The PL measurements were performed at room temperature using Accent Rapid Photoluminescence Mapping 2000 system using the 325 nm He-Cd laser line as an excitation source at 11 mW 2.11 Cathodoluminescence (CL) The type of CL emission is more or less the same as that of PL [7], the difference lies in the excitation source being electrons instead of photons The CL 54 Chapter Experiment measurements were carried out at 150 K at the Research Center for Nuclear Microscopy Reference: [1] Wang, Z.L Characterization of nanophase materials, Wiley-Vch, Welheim, 2000 [2] Wang Z.L J Phys Chem B 2000, 104, 1153 [3] Williams, D.B.; Carter, C.B Transmission Electron Microscopy, Plenum press, New York, 1996 [4] Brydson, R Electron energy loss spectroscopy, Bios Scientific Publishers Limited, UK, 2001 [5] Jones C.; Brien, P.O CVD of compound semiconductors: precursor synthesis, development and applications, Weinheim, 1997 [6] Gfroerer, T.H Photoluminescence in analysis of surfaces and interfaces, Encyclopedia of Analytical Chemistry, R.A Meyers (Ed.), 2000 [7] Vij D.R.; Singh, N Luminescence and related properties of II-IV semiconductors, Nova Science Publishers, Commack, NY, 1998 55 ... (nm) (? ?1) W/T υx1 υy1 υy1/ υx1 Ex Ey 55 33 1. 7 23 2 373 1. 6 46.6±0.6 50 .1? ?0.6 4.73 28 19 1. 5 396 576 1. 4 44.3? ?1. 3 45.5? ?2. 9 4.07 31 20 1. 6 6 62 958 1. 4 56.3±0.9 64.6? ?2. 3 8.90 44 39 1. 1 21 0 2 31 1 .1 37.9±0.6... 20 01, 4 92, 25 5 [11 ] Whitby R.L.D.; Hsu, W.K.; Boothroyd, C.B.; Kroto, H.W.; Walton, D.R.M Chem Phys Lett 20 02, 359, 12 1 33 Chapter Introduction [ 12 ] Wang, Z.L J Phys Chem B 20 00, 10 4, 11 53 [13 ]... process and surface reactions in-situ TEM Chapter 1. 3 .2 1. 3.3 1. 3.4 .1 Observing the growth process of nanomaterials 1. 3.4 .2 Nanomeasurement of physical properties 1. 3.4.3 Chapter Introduction 1. 3.1