Carbon Nanotube Modification Using BaF2 Vapor in Ultra-High Vacuum Environment

2003 ◽  
Vol 782 ◽  
Author(s):  
Francisco Santiago ◽  
Victor H. Gehman ◽  
Karen Long ◽  
Kevin A. Boulais
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Heat Exposure ◽  
Major Change ◽  
Ultra High Vacuum ◽  
Force Microscopy ◽  
Before And After ◽  
Potential Applications

ABSTRACTCarbon nanotubes have attracted significant attention in the scientific community due to their unique properties and potential applications. One of the most promising applications is a carbon-nanotube transistor. The motivation of this work is to find ways to connect carbon nanotubes directly to silicon using Ba as a chemical link. We studied chemical interactions between carbon nanotubes and BaF2 vapors using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Surfaces of silicon wafers were chemically modified to allow the epitaxial growth of BaF2 using molecular beam epitaxy (MBE). Samples containing 2D single crystal islands of BaF2 were covered with carbon nanotubes with an average coverage of 10 nanotubes per um2. The samples were transferred to an outgasing station inside the MBE system and heated to 900°C for two hours in a pressure of 10-9 mbar. XPS C1s data before and after heat show a major change in the nature of the carbon nanotube electronic states. In addition XPS shows formation of a Ba-C “carbide like” bond and no presence of fluorine. AFM images of the same region taken before and after heat exposure show remarkable changes in the surface morphology of the carbon-nanotube wall.

Fundamental study of the interaction of Ti atoms with spruce surfaces

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 523-527 ◽  
Author(s):  
Lothar Klarhöfer ◽  
Florian Voigts ◽  
Dominik Schwendt ◽  
Burkhard Roos ◽  
Wolfgang Viöl ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Strong Interactions ◽  
Titanium Oxide Film ◽  
Fundamental Study ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Metal Atoms

Abstract Metastable induced electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were applied to study the interaction of Ti metal atoms with spruce surfaces. Spruce surfaces were produced by planing splints from a spruce bar. Ti atoms were adsorbed from a metal evaporator under ultra-high vacuum conditions. The amount adsorbed corresponds to 10 monolayer equivalents. Strong interactions between the spruce surface and metals atoms occurred. Impinging Ti atoms were oxidized by the spruce surface. No Ti agglomeration or particle formation was observed. The surface was smoothed by the Ti applied and was completely covered by a titanium oxide film.

scholarly journals Microstructure and Optical Properties of E-Beam Evaporated Zinc Oxide Films—Effects of Decomposition and Surface Desorption

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3510
Author(s):  
Lukasz Skowronski ◽  
Arkadiusz Ciesielski ◽  
Aleksandra Olszewska ◽  
Robert Szczesny ◽  
Mieczyslaw Naparty ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Optical Properties ◽  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Oxide Films ◽  
Growth Direction ◽  
Ultra High Vacuum ◽  
X Ray ◽  
Force Microscopy ◽  
Zinc Oxide Films

Zinc oxide films have been fabricated by the electron beam physical vapour deposition (PVD) technique. The effect of substrate temperature during fabrication and annealing temperature (carried out in ultra high vacuum conditions) has been investigated by means of atomic force microscopy, scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. It was found that the layer deposited at room temperature is composed of Zn and ZnO crystallites with a number of orientations, whereas those grown at 100 and 200 ∘C consist of ZnO grains and exhibit privileged growth direction. Presented results clearly show the influence of ZnO decomposition and segregation of Zn atoms during evaporation and post-deposition annealing on microstructure and optical properties of zinc oxide films.

Temperature Induced Phase Transformation on the 4H-SiC(11-20) Surface

2006 ◽  
Vol 527-529 ◽  
pp. 673-676 ◽  
Author(s):  
W.Y. Lee ◽  
S. Soubatch ◽  
Ulrich Starke
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
X Ray ◽  
Force Microscopy ◽  
Low Energy Electron Diffraction ◽  
Atomic Force ◽  
Surface Phases ◽  
Low Energy Electron

The atomic structure of the 4H-SiC(11 2 0) surface including possible phase transformations via Si deposition and annealing has been investigated using low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The sample is initially prepared by hydrogen etching before loading into the ultra-high vacuum system. The sample is then out-gassed to remove oxygen from the surface. To explore the existence of ordered surface phases, Si is deposited on the sample at 850°C for 15 minutes followed by a series of sequential annealing steps. Throughout this process, the surface is monitored by LEED, AES and XPS. LEED shows that the surface continuously maintains a (1×1) periodicity. Yet, two unique and distinguishable (1×1) phases can be identified. The changes between these phases are clearly demonstrated by the LEED spot intensities. Simultaneously, the Auger and XPS data show a decrease in Si intensity.

Role of Oxygen in Growth of Carbon Nanotubes on SiC

2006 ◽  
Vol 527-529 ◽  
pp. 1575-1578 ◽  
Author(s):  
Wei Jie Lu ◽  
John Boeckl ◽  
W.C. Mitchel ◽  
J. Rigueur ◽  
W.E. Collins
Keyword(s):  
Carbon Nanotubes ◽  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Structural Defects ◽  
Oxygen Species ◽  
Oxygen Compound ◽  
X Ray ◽  
Multi Wall Carbon Nanotubes

Carbon nanotubes (CNTs) grown on SiC are metal-free, well-aligned, and with low structural defects. In this study, CNT formation on SiC is examined in high vacuum (10-5torr) and ultra-high vacuum (10-8torr). Multi-wall carbon nanotubes and graphitic structures are the main products on the SiC surface at 1400-1800°C in 10-5torr. Under ultra-high vacuum, the decomposition rate of SiC is much lower than in high vacuum, indicating that SiC is decomposed by oxidation reaction. Using X-ray photoelectron spectroscopy (XPS), the intensity of the O1s peak at 530.3 eV decreases with increasing take-off angle, indicating that this oxygen species exists on the walls of CNTs. The results show that oxygen with a low pressure not only oxidizes SiC, but also forms a highly thermally stable carbon-oxygen compound, and interacts with the CNTs at high temperatures.

Fabrication of High-Density Carbon-Nanotube Coatings on Microstructured Substrates

2000 ◽  
Vol 621 ◽  
Author(s):  
Zheng Chen ◽  
Yonhua Tzeng ◽  
Chao Liu
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Active Surface ◽  
Deposition Process ◽  
Ultra High Vacuum ◽  
Active Surface Area ◽  
Field Emission Properties ◽  
Ni Substrate

ABSTRACTFabrication and characterization of carbon nanotubes deposited on microstructured Ni substrate are presented. The highly active surface-area of the microstructured Ni substrate provides highdensity nucleation sites for carbon nanotubes. Coated fine Ni powder also serves as a catalyst for the nanotube growth. Hydrocarbon mixtures were used as the carbon source for the chemical vapor deposition process. Carbon nanotubes deposited on the microstructured Ni substrate were examined by SEM. An ultra high vacuum chamber was used to characterize the field emission properties of carbon nanotube coatings.

Investigation of Graphene Growth on 4H-SiC

2009 ◽  
Vol 615-617 ◽  
pp. 223-226 ◽  
Author(s):  
A. Castaing ◽  
Owen J. Guy ◽  
Michal Lodzinski ◽  
S.P. Wilks
Keyword(s):  
Photoelectron Spectroscopy ◽  
Graphene Layer ◽  
Bulk Material ◽  
High Vacuum ◽  
Epitaxial Graphene ◽  
Ultra High Vacuum ◽  
Graphene Growth ◽  
Graphene Layers ◽  
Force Microscopy ◽  
Wide Range

This paper reports the investigation of epitaxial graphene growth on 4H-SiC substrates. Growth has been performed under ultra high vacuum (UHV) conditions at temperatures ranging from 1150 to 1250°C, and the formation of the graphene layer has been monitored using X-ray photoelectron spectroscopy (XPS). A gradient of 100°C in temperature was introduced across the sample in order to grow a wide range of thicknesses along the sample. Atomic force microscopy (AFM) of the surface shows that the epitaxial graphene layer follows the topography of the bulk material and introduces very little surface roughness. This paper also reports the electrical characterisation of the graphene layers.

Growth of Carbon Nanotubes on Copper Substrates Using a Nickel Thin Film Catalyst

2009 ◽  
Vol 1204 ◽  
Author(s):  
Gowtam Atthipalli ◽  
Prashant Kumta ◽  
Wei Wang ◽  
Rigved Epur ◽  
Prashanth H Jampani ◽  
...  
Keyword(s):  
Thin Film ◽  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Nickel Catalyst ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Ultra High Vacuum ◽  
Thin Film Catalyst ◽  
Carbon Nanotube Growth ◽  
Nanotube Growth

AbstractCarbon nanotubes with their attractive properties, one-dimensional character, and their large aspect ratio are ideal candidates for a variety of applications including energy storage, sensing, nanoelectronics, among others. We have studied the growth of carbon nanotubes on copper substrates using a nickel thin film as a catalyst. The catalyst was sputtered in a chamber having a base pressure in the ultra-high-vacuum regime. By adjusting the sputtering parameters, the effects of the morphology and the thickness of the nickel catalyst on the growth of carbon nanotubes have also been investigated. Multiple hydrocarbon sources as carbon feedstock (methane, acetylene and xylene) and corresponding catalyst precursors and varying temperature conditions were used during the Chemical Vapor Deposition (CVD) process to understand and best determine the ideal conditions for carbon nanotube growth on copper. Correlation between the thickness of the thin film nickel catalyst and the carbon nanotube diameter is also presented in the study. Characterization techniques used to study the morphology of the CNTs grown on copper include SEM, TEM and HRTEM, Raman Spectroscopy

Structure and morphology of Clean and Magnesium - Dosed Sapphire Surfaces

1993 ◽  
Vol 317 ◽  
Author(s):  
Yan Yu ◽  
R.J. Lad
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Force Microscopy ◽  
Structure And Morphology ◽  
Diffraction Patterns ◽  
Abrupt Interface ◽  
Initial Deposition

ABSTRACTThe structure and morphology of r-axis (1012) and c-axis (0001) sapphire (a-Al2O3) surfaces were studied with Low Energy and Reflection High Energy Electron Diffraction (LEED and RHEED) and Atomic Force Microscopy (AFM). Following heat treatments at 1000°C in 5×10-7 torr O2, both surfaces exhibited (1×1) diffraction patterns. Regular step-terrace structure was observed on the (1012) surface with the AFM, but no step structure was visible on the (0001) surface. The initial growth of magnesium overlayers dosed onto the (1012) surface at 25°C in ultra-high vacuum was monitored with RHEED and the chemical interactions at the Mg / Al2O3 interface were characterized with X-ray Photoelectron Spectroscopy (XPS). During the initial deposition, very little interaction between mg and the Al2O3 substrate occurs and a very abrupt interface is formed. At larger mg doses, a textured polycrystalline mg overlayer is produced. Annealing the mg film above 300°C causes some oxidation of mg at the Mg / Al2O3 interface, but most of the mg desorbs from the surface.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

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