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A process for growing gallium nitride (GaN) vertical p–i–n homojunctions on (111) silicon substrates using metalorganic chemical vapor deposition was developed, and a triple mesa etch technique was used to fabricate efficient betavoltaic energy converters. Monte Carlo simulation platform CASINO was used to model beta radiation penetration into GaN to aid device design. The resulting devices were tested under irradiation from a scanning electron microscope electron beam (e-beam) tuned to imitate the energies of the 63Ni beta emission spectrum. Based on current–voltage measurements taken under e-beam illumination, a maximum open-circuit voltage of ∼ 412 mV and a maximum short-circuit current density of ∼ 407 nA/cm2 were measured. A high fill factor of ∼ 0.77 and power conversion efficiency of ∼ 6.6 % were obtained. Additionally, the proposed triple mesa etch technique used to create these betavoltaics has the potential for further use in fabricating many types of electronic devices using a wide variety of material platforms. [ABSTRACT FROM AUTHOR]

The construction of heterojunctions has attracted considerable attention among the various strategies of water-splitting for hydrogen evolution due to their band structure advantages. In this research, we combined chemical vapor deposition and pulsed laser deposition to fabricate MoS2/g-C3N4 heterojunction films on indium-tin oxide glass substrates, and we studied the photoelectrochemical (PEC) performance. The x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and scanning electron microscope characterizations suggested the successful preparation of MoS2/g-C3N4 heterojunction films. In particular, the shifts of the peak positions in the XPS spectra indicated the formation of a strong interaction between the g-C3N4 and MoS2 films. After depositing MoS2 on the g-C3N4 film, the visible-light absorption was enhanced and broadened, the electrical conductivity improved, and the intensity of the photoluminescence peak decreased. As a result, the greater generation, faster transport, and lower recombination rate of electrons and holes caused the heterojunction films to show higher PEC performance. More importantly, the obtained MoS2/g-C3N4 film was confirmed to be an n–n type heterojunction and to have a typical type-II band structure, which could indeed suppress the recombination and promote the separation, transfer, and transport of photogenerated electron–holes. Finally, the obtained MoS2/g-C3N4 film successfully achieved the overall water-splitting and the H2 evolution rate when the visible-light radiation reached 252 µmol/h. [ABSTRACT FROM AUTHOR]

Al-doped ZnO (AZO) is a promising candidate as a transparent conducting electrode. However, the electrical properties of AZO deteriorate greatly after exposing it to excessive heat. This limits the applications of AZO in devices that experience a demanding operation environment. It has been shown that a ZnO cap layer with proper morphology is capable to dramatically improve the thermal stability of AZO. However, the detailed mechanism is not yet clear. A comparison study of the electrical properties of AZO with a ZnO cap layer prepared by magnetron sputtering (MS) at low substrate temperature (70 °C) and chemical vapor deposition (CVD) at high substrate temperature (600 °C) indicates that MS-prepared ZnO is much less effective in protecting AZO from an oxidizing environment under elevated temperature than the CVD-prepared ZnO. The morphology and crystal structures of two types of ZnO/AZO, investigated by a scanning electron microscope and x-ray diffraction, are relatively similar, whereas the atomic structures (e.g., defects) revealed by Raman spectroscopy are rather different. The results suggest that it is difficult to improve the thermal stability of electrical properties of AZO without a proper restructuring process and a ZnO cap layer that could sacrifice its own structural order. The discoveries offer a novel approach to improve the performance of other transparent conducting oxides. [ABSTRACT FROM AUTHOR]

High-angle annular dark-field (HAADF) imaging and electron energy loss spectroscopy (EELS) in a Cs-corrected scanning transmission electron microscope were utilized to analyze the interfacial atomic structure of InAs/GaSb superlattices (SLs) grown by metalorganic chemical vapor deposition (MOCVD) on InAs substrates. Despite high growth temperature, narrow interface (IF) widths of less than 2.5 monolayers (MLs) and 3.8 MLs were extracted from HAADF and EELS, respectively, indicating that the IF quality of MOCVD-grown InAs/GaSb SLs is comparable to those grown by molecular beam epitaxy. GaAs-type IFs are considered to account for the narrow IF width. In addition, GaSb-on-InAs IFs were found to be sharper and more strained than InAs-on-GaSb IFs, which is correlated with the special gas supply and switching sequence during MOCVD growth. The strain profile deduced from the HAADF image suggests that little Sb is incorporated into InAs sublayers and 7% In is incorporated into GaSb sublayers. [ABSTRACT FROM AUTHOR]

Low temperature Carbon Nano-tubes (CNTs) growth technology is developed in this work with the insert of Al (Aluminum) between Ni (Nickel) and Ti (Titanium) as the reactant. The optimized Al thicknesses are also investigated. CNTs growth at the low temperature below 400 °C is the key factor for the back end of line compatible process integration. In this work, we grow the CNTs by thermal chemical vapor deposition process at 350 and 400 °C. The low ratio of peak ID/IG in Raman spectra and scanning electron microscope images proves the CNTs material quality. On the other hand, the high thermal conductivity (k) value of ∼50 W m − 1 K − 1 is also demonstrated. Both high material quality and k value on our low temperature grown CNTs show promising opportunities for the integration of semiconductor three dimensional packages and power-via related applications. [ABSTRACT FROM AUTHOR]

Investigation of the effect of crystal defects on nonpolar a-GaN films grown by metalorganic chemical vapor deposition on r-sapphire substrates is presented. Samples were grown at different temperatures and the same V/III ratio. High-temperature nucleation in combination with low-temperature GaN buffer layer growth was used to achieve a smooth morphology and "mirror" surface. The macrostructures of the defects were investigated using a scanning electron microscope. Defect concentration via dislocation type correlation was analyzed by diffractometry investigation. Structural quality was investigated via x-ray diffraction. The correlation between the densities of mixed threading dislocations and V-defects was determined. It was detected that the origin of V-defects on the a-plane and c-plane was the same despite having completely different geometries and structures. We also investigated the dependence of V-defect density on a-GaN film growth temperature at a constant hydrogen flow through a triethylgallium source, and we also investigated how the V/III ratio influenced the V-defect structure. Optimum growth parameters for defect concentration reduction were determined. [ABSTRACT FROM AUTHOR]

In this study, a femtosecond laser etching method is proposed to pattern an aluminum nitride (AlN) film, grown by metal-organic chemical vapor deposition on sapphire. Via control of typical pulse energies, the designed pattern was precisely written in the AlN film. The morphology of the patterned structures was characterized using a three-dimensional laser scanning confocal microscope and a scanning electron microscope; crystalline quality and film strain were analyzed using a Raman spectrometer and a transmission electron microscope. The results indicate that consistent morphologies were achieved with only slight changes to the crystalline quality. The tensile stress of the AlN film was released, and the film surface was slightly compressed after laser patterning. Thus, femtosecond etching has the potential to be an in situ patterning method during film growth. [ABSTRACT FROM AUTHOR]

Thermal conductivity measurements in commercially available, chemical vapor deposition-grown, heat-treated and non-heat-treated multiwalled carbon nanotubes (MWCNTs) are reported. The thermal conductivity of individual samples is measured using a suspended platinum wire as a thermal resistance probe in a 'T-type' configuration. Changes in third harmonic voltage are measured across the heated suspended platinum wire as a specimen is attached to the platinum wire's midpoint. An analytic model is used to correlate the reduction in the average temperature of the probe wire to the thermal resistance (and thermal conductivity) of the attached sample. Experiments are implemented inside a scanning electron microscope equipped with nanomanipulators for sample selection, and a gas injection system for platinum based electron beam-induced deposition to improve thermal contact resistances. The results indicate a nearly 5-fold increase in the average thermal conductivity of MWCNT samples annealed with a 20-h 3000 °C annealing heat treatment compared to the as-grown samples. However, specimen-specific morphological defects, such as kinking, Y-branches, etc., are found to negate, to a large degree, the advantage of the heat treatment process. The thermal contact resistance between the MWCNT and the electron beam-induced deposition contacts is estimated using an anisotropic diffusive mismatch model that includes the effect of fin resistance. Adjusting the thermal conductivity to include the effect of thermal contact resistance is found to increase the thermal conductivity by approximately 5%. Once adjusted for thermal contact resistance, the average thermal conductivity of the heat-treated MWCNT specimens is 228 W/m-K, with the highest measured thermal conductivity being 765 ± 150 W/m-K. The results highlight the importance of MWCNT quality in thermal management applications. [ABSTRACT FROM AUTHOR]

The effect of substrate pretreatments such as ultrasonication or scratching by diamond powder on the microstructure and field emission characteristics of diamond grown over silicon and macroporous (anodized) silicon substrates was investigated. These films were grown in a hot filament chemical vapor deposition (CVD) system. Scanning electron microscope (SEM) studies revealed that ultrasonic pretreatment of the substrates increases nucleation density of CVD diamond by two orders of magnitude. Atomic force microscopy and energy dispersive x-ray analysis of the substrates showed that seeding is responsible for the enhanced nucleation density of diamond. SEM study showed that diamond powder scratching of porous silicon leads to uniform coverage of the substrate by the CVD diamond. Cross-sectional SEM showed growth of diamond inside the pores only after pretreating porous silicon with diamond powder. Raman spectroscopy of all the samples showed a scattering peak corresponding to diamond. Discontinuous diamond films also exhibited Raman bands corresponding to nanocrystalline diamond, diamondlike carbon, graphite, and silicon carbide. The presence of these phases of carbon was further confirmed by high resolution transmission electron microscopy studies. Field emission studies revealed that discontinuous diamond films grown on porous silicon (after diamond powder ultrasonic pretreatment) had the lowest threshold field (5.4 V/μm). [ABSTRACT FROM AUTHOR]

Metal-organic chemical vapor deposition has been used for selective epitaxy of GaN pyramids ranging in size from over 1 μm to 500 nm in length at the base. Pyramids are terminated by {1101} crystal facets. The optical properties of the pyramids are investigated by cathodoluminescence (CL) in a scanning electron microscope. CL spectrum imaging reveals the pyramid apices to emit light at ∼363.4 nm corresponding to the emission wavelength of relaxed GaN. As the CL excitation is moved away from the apex a systematic redshift is observed. The redshift is ∼4 nm for pyramids with 3 μm base dimension and ∼2 nm for the 500 nm pyramids. The shift is attributed to diffusion of silicon and oxygen into the GaN pyramids due to SiO2 mask decomposition with negligible contribution from stress. The observations are backed by finite element simulations of diffusion and stress. [ABSTRACT FROM AUTHOR]

The electrical conduction behavior of undoped ultrananocrystalline diamond (UNCD) and its dependence on deposition temperature and chemical structure are presented. UNCD films were grown using a microwave plasma-enhanced chemical vapor deposition technique at deposition temperatures of 400 °C and 800 °C. The chemical structure of the UNCD films is characterized with several tools including: Elastic recoil detection analysis, Fourier transform infrared spectroscopy, electron energy loss spectroscopy, Raman spectroscopy, and environmental scanning electron microscope. The results show a higher content of sp2-bonded carbon for the 800 °C deposition samples (∼65%) in comparison with the 400 °C samples (∼38%). In both kinds of films, the hydrocarbon bonds have the saturated sp3 structures, while there is lower hydrogen content in the 800 °C samples (∼8%) than in the 400 °C samples (∼10%). For conduction properties, experiments are conducted using a probe station and conductive-atomic force microscopy. Experimental data show that the samples deposited at 800 °C are several orders of magnitude more conductive than the 400 °C samples. The conduction occurs primarily along the grain boundary for both types of samples. The conductivity of both types of films also shows field dependent nonlinear behavior. Both the Poole–Frenkel models and single and overlapping Coulombic potential models show that the conduction is directly correlated with the sp2 bond carbon density, and the role of the hydrocarbon bonds in the conduction path is formed by the network of the sp2 bonded carbon. [ABSTRACT FROM AUTHOR]

We report on the roles of hydrogen dilution on the microstructural and optoelectronic properties of boron-doped nanocrystalline silicon thin films grown by plasma-enhanced chemical vapor deposition on glass substrates, through x-ray diffraction, scanning electron microscope, Raman scattering, optical transmission, temperature-dependent dark conductivity, and elastic recoil detection analysis (ERDA) measurements. The grain size, crystallinity, absorption coefficient, refractive index, and conductivity are found to decrease basically with increasing hydrogen dilution ratio ΔH. The Tauc’s optical band gap is found to increase with ΔH due to the quantum size effect. By the aid of hydrogen ion bombardment effect [J. Appl. Phys. 93, 1262 (2003)] as well as the hydrogen-induced annealing effect, the clear increase of hydrogen content with ΔH and the different hydrogen distribution from ERDA help us to elucidate the correlation of hydrogen dilution with the crystallinity and grain size. The argument has been further supported by a simple absorption model and the yielded refractive index and absorption coefficient. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the effects of laser cutting on the structure of a chemical vapor deposited film by using cathodoluminescence in the scanning electron microscope. Discussion on diamond films grown from the chemical vapor deposited phase; Use of excimer lasers; Effects of laser irradiation on diamonds.

Presents a study that examined the growth of a diamond from a mixture of carbon-oxygen and carbon-hydrogen without gas phase hyperdilution of hydrogen. Use of laser excited chemical vapor deposition; Information on several techniques in synthesizing diamonds; Scanning electron microscope micrographs of the substrate surface before and after growth in a mixture with laser excitation.

As far as we know, all the single nanowire (NW) metal-semiconductor field-effect transistors (MESFETs) reported are based on n-type NWs. We report MESFETs based on p-type Zn3P2 single NWs in this paper. The p-type Zn3P2 single NW MESFETs operate in the enhancement mode (E-mode). The source-drain current decreases with gate bias (VG) increasing, confirming the p-type conductance of the Zn3P2 NWs. Typically, the p-type Zn3P2 single NW MESFET has an on/off current ratio of 103, a threshold gate voltage of -0.4 V, and a maximum transconductance of 110 nS. [ABSTRACT FROM AUTHOR]

Examines the growth of cubic and hexagonal gallium nitride (GaN) films on gallium arsenide substrates by plasma-assisted low-pressure metalorganic chemical vapor deposition. Use of triethylgallium and nitrogen radicals; Temperature dependence of the GaN growth rates; Application of a scanning electron microscope.

Presents a study which fabricated gallium arsenide (GaAs) micro tip for scanning tunneling microscope by selective metalorganic chemical vapor deposition. Description of the fabrication method used; Overview of a scanning electron microscope (SEM) photograph of the GaAS selective epitaxial layers; Description of the SEM photograph of the apex of the GaAS selective epitaxial layer treated by (NH[sub4])[sub2]S[subx] solution; Observation of the highly oriented pyrolytic graphite surfaces.

Presents a study which used cathodoluminescence (CL) in the scanning electron microscope to study the upper surface and cross-sectional samples of chemical vapor deposited diamond films. Concentration of dislocation related radiative centers; Details of the experimental method used in the study; Description of the total CL image of the lateral surface of the sample.

Tuning of the Fermi level is investigated in graphene channels using two in-plane gates with significantly different-sized isolating gaps. While the n-type tuning was achievable in both schemes, the wide-gap device had an enhanced minimum drain current and less prominent current modulation than the narrow-gap device. In addition, further p-type tuning was not observed in the wide-gap device at negative gate biases. These phenomena indicated that both devices had distinct field-strength dependences and Fermi level tuning effects, which may be critical for the practical design of devices. [ABSTRACT FROM AUTHOR]

The flower-like SnO2 particles are synthesized through a simple hydrothermal process. The microstructure, morphology and the infrared emissivity property of the as-prepared products are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and infrared spectroradio meter (ISM) respectively. The results show that the as-prepared SnO2 products are all indexed to tetragonal cassiterite phase of SnO2. The different molarity ratios of the OH- concentration to Sn4+ concentration ([OH-]:[Sn4+]) and the polyacrylamide (PAM) lead to the different morphological structures of SnO2, which indicates that both the [OH-]:[Sn4+] and the PAM play an important role in the morphological evolution respectively. The infrared emissivities of the as-prepared SnO2 products are discussed. [ABSTRACT FROM AUTHOR]

We investigate a seed layer-free growth of HfO2 on commercially available chemical vapor deposited (CVD) graphene from various suppliers. It is revealed that the samples of monolayer graphene transferred from Cu to SiO2/Si substrates have different coverage with bi- and multi-layer graphene islands. We find that the distribution and number of such islands impact the nucleation and growth of HfO2 by CVD. In particular, we show that the edges and surface of densely distributed bi-layer graphene islands provide good nucleation sites for conformal CVD HfO2 layers. Dielectric constant of 16 is extracted from measurements on graphene-HfO2-TiN capacitors. [ABSTRACT FROM AUTHOR]

Threading dislocations, stacking faults, and associated partial dislocations significantly degrade the optical and electrical properties of materials such as non-polar III-nitride semiconductor thin films. Stacking faults are generally difficult to detect and quantify with existing characterization techniques. We demonstrate the use of electron channeling contrast imaging in the scanning electron microscope to non-destructively reveal basal plane stacking faults terminated by partial dislocations in m-plane GaN and InGaN/GaN multiple quantum well structures grown on γ-LiAlO2 by metal organic vapor phase epitaxy. [ABSTRACT FROM AUTHOR]

Electron beam induced deposition (EBID) has been investigated by many researchers for a number of applications requiring maskless deposition of material. Here, a scanning electron microscope is used to perform EBID of cobalt (Co) nanoparticles, which are then used as the catalyst for selected-area growth of carbon nanotubes (CNTs). Co nanoparticles were deposited using cobalt tricarbonyl nitrosyl as the precursor. They are oxygen plasma ashed to remove residual carbon from the deposition process prior to the growth of CNTs using a chemical vapor deposition (CVD) process. Co deposits made using different doses were found to have different catalytic properties. At sufficiently low doses, the deposits were insufficient to catalyze any CNT growth. At higher doses, single-walled CNT (SWCNT) growth was observed. Still higher doses produced deposits that catalyzed multiwalled CNT growth as well as some SWCNT growth. These differences in catalytic behavior are believed to result from nanoparticle size variations between and within the deposits. As a result, by using EBID deposited catalyst, it is possible to not only control where CNTs grow but also the kind of CNTs (SW or MW) grown during a single CVD run. [ABSTRACT FROM AUTHOR]

Films of ZnO have been grown on R-plane sapphire substrates by atmospheric-pressure chemical vapor deposition (AP-CVD) using Zn powder and H2O as source materials. Variation in growth rate as a function of substrate temperature can be divided into three regions: re-evaporation region, mass transport controlled region, and surface controlled region. Scanning electron microscope observations revealed that the surface morphology of the film is dependent not only on substrate temperature but also on Zn source and H2O source temperatures. X-ray diffraction patterns of most of the films showed a dominant (110) peak, indicating highly A-axis oriented growth. A single crystalline A-plane ZnO film without mixed domain was successfully grown by optimizing the growth condition. Visible region photoluminescence changed from orange-red emission to blue-green emission systematically by adjusting Zn source and H2O source temperatures. This result suggests the possibility of defect control in our AP-CVD system. For the films grown at TS=700 °C in the mass transport controlled region, resistivity decreased from 0.45 to 0.007 Ω cm as TH2O rised from 54 to 75 °C. [ABSTRACT FROM AUTHOR]

The authors have measured the field emission properties of freestanding bare and Au-coated Ni nanowires randomly distributed on thin metallic substrates. The nanowires of uniform length and diameter were grown in the etched ion-tracked pores of polycarbonate membranes by electrochemical deposition. While bare Ni samples yielded only 1.6×104 emitters/cm2 at 10 V/μm, Au coating of the Ni nanowires improved the emission site density to 1.4×105/cm2 at 5 V/μm and about 1.6×106 emitters/cm2 at 18 V/μm. Average field enhancement factors β of 331 for bare Ni and 302 for Au-coated Ni nanowires correspond well to their cylindrical shape in the scanning electron microscope images. Stable Fowler-Nordheim-like emission was obtained on average up to currents of about 0.4 and 8 μA for bare and Au-coated Ni nanowires, respectively. Locally measured I-V curves, maximum current Imax, and derived β values hint for the clustering of nanowires. [ABSTRACT FROM AUTHOR]

The strain dependence of conductance of monolayer graphene has been studied experimentally here. The results illustrate the notable transitions: the slight increase, the dramatic decrease, and the sudden dropping of the conductance by gradually increasing the uniaxial strain. The graphene conductance behaves reversibly by tuning of the elastic tensile strain up to 4.5%, while it fails to recover after the plastic deformation at 5%. The change in conductance due to strain is surprisingly high, which indicates the potential applications in electromechanical devices. [ABSTRACT FROM AUTHOR]

Positioning of charged nanoparticles with the help of charge patterns in an insulator substrate is a known method. However, the creation of charge patterns with a scanning electron microscope for this is relatively new. Here a scanning electron microscope is used for the creation of localized charge patterns in an insulator, while a glowing wire generator is used as the nanoparticle source. The deposited palladium nanoparticles are used as catalysts for the localized growth of carbon nanotubes in a chemical vapor deposition oven. The authors show first the results on local carbon nanotube growth using this procedure. [ABSTRACT FROM AUTHOR]

We have demonstrated electrostatic switching in vertically oriented carbon nanofibers synthesized on refractory metallic nitride substrates, where pull-in voltages Vpi ranged from 10 to 40 V. A nanoprobe was used as the actuating electrode inside a scanning-electron microscope and van der Waals interactions at these length scales appeared significant, suggesting such structures are promising for nonvolatile memory applications. A finite element model was also developed to determine a theoretical Vpi and results were compared to experiment. Nanomanipulation tests also revealed tubes synthesized directly on Si by dc plasma-enhanced chemical-vapor deposition with ammonia and acetylene were electrically unsuitable for dc nanoelectromechanical switching applications. [ABSTRACT FROM AUTHOR]

A rapid yet simple methodology to synthesize carbon nanotubes (CNTs) in a room temperature environment has been demonstrated using an inductive heating system. Substrates of either heavily doped silicon or nickel-coated, lightly doped silicon have been used to synthesize CNTs using Fe as the catalyst. Aligned carbon nanotubes with growth rates as high as 200 μm/min have been achieved in less than 1 min. Transmission electron micrographs illustrated average diameters of 8 and 6.8 nm for CNTs grown under average temperatures of 760 and 910 °C, respectively. This system allows the synthesis of CNTs that is easy to set up, fast, clean, and inexpensive. [ABSTRACT FROM AUTHOR]

The surface morphology of screen-printed carbon nanotube films was modified by using the poly-dimethylsiloxane (PDMS) elastomer. The entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. In addition, the cathode film morphology of top-gated triode structures can be treated by using the proposed surface treatment technique, which is a low-cost process. [ABSTRACT FROM AUTHOR]

We prepared W–Ga–C composite contacts on W–Ga–C composite nanowires by focused-ion-beam-induced chemical vapor deposition using a dual-beam scanning electron microscope/focused-ion-beam system. The current-voltage (I-V) characteristics of wires were found to change from nonlinear to linear with increasing wire thickness. For wires with small dimensions, which result in strong nonlinear I-V behavior at room temperature, pairs of contacts were fabricated along the wire under different ion energies and scanning modes. Nonlinear and asymmetric rectifying I-V characteristics were observed. The results suggest that nanoscaled W–Ga–C nanowires may behave similarly to semiconductors and that the contact characteristics may be modified using different deposition conditions. Furthermore, ohmiclike junctions could be formed through the use of specific deposition conditions for the contact pads and nanowires. [ABSTRACT FROM AUTHOR]

Oriented crystallization of GaSb on patterned, oxidized Si substrates was achieved by metalorganic chemical vapor deposition. The Si substrate was formed by patterning an array of inverted square pyramids having {111} sidewall facets, using lithography and anisotropic etching in KOH. The orientation and structure of GaSb crystals, at various stages of the growth, were examined by scanning electron microscopy and x-ray diffraction. X-ray diffraction pole figure analysis shows that {111} planes of GaSb are predominantly parallel to the {111} planes of the inverted pyramids. Extra (111) spots observed in the x-ray diffraction pole figure are interpreted in terms of multiple twinning of GaSb. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2–30 walls with an inner diameter of 3–8 nm. Raman spectrum analysis shows G-band at 1580 cm−1 and D-band at 1340 cm−1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources. [ABSTRACT FROM AUTHOR]