Halogen Based Surface Chemistries for Graphene Synthesis

2010 ◽  
Vol 1259 ◽  
Author(s):  
Srikanth Raghavan ◽  
Timothy C. Nelson ◽  
Tobias Denig ◽  
C D Stinespring
Keyword(s):  
Electron Transfer ◽  
Photoelectron Spectroscopy ◽  
Surface Layers ◽  
Near Surface ◽  
X Ray ◽  
Inductively Coupled ◽  
Graphene Synthesis ◽  
P Type ◽  
Surface Chemistries ◽  
Second Peak

AbstractHalogen based (CF4 and Cl2) inductively coupled reactive ion etching (ICP-RIE) has been used to selectively etch silicon from 6H-SiC to produce a controlled number of carbon layers. After annealing at temperatures in the range of 550 °C to 1100 °C to reconstruct the near surface layers, x-ray photoelectron spectroscopy has been used to characterize the composition of the films. For the Cl2 based ICP-RIE, two carbon species are observed. One is due to carbon bound as SiC in the substrate and a second which can be attributed to graphene. In the case of CF4 based etching the situation is similar except the second peak is most closely aligned with p-type graphene. This is most likely due to electron transfer from the graphene to the trace levels of fluorine remaining on the surface after annealing.

An ESCA and SEM Study of Changes in the Surface Composition and Morphology of Low-Calcium Coal Fly Ash as a Function of Aqueous Leaching

1986 ◽  
Vol 86 ◽  
Author(s):  
Myra M. Soroczak ◽  
H. C. Eaton ◽  
M. E. Tittlebaum
Keyword(s):  
Fly Ash ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Coal Fly Ash ◽  
Near Surface ◽  
X Ray ◽  
Sem Study ◽  
Before And After ◽  
New Material ◽  
Surface Chemistries

ABSTRACTThe reactivity of coal fly ash is dependent on the chemical composition of the surface. As reactions occur the ash particle size decreases and new material is available for reaction. This means that the near-surface chemistry can also be important. In the present study the surface chemistries of three ashes are determined by x-ray photoelectron spectroscopy both before and after exposure to a hydrating/leaching environment. Scanning electron microscopy is used to reveal ash morphology. The concentration of sulfur, found at the ash surfaces as a sulfate, and sodium decreased after leaching while the amount of iron and aluminum increased. Other elements, including calcium, increased and decreased with leaching depending on which ash was analyzed. Changes which occurred in the ash morphology after the removal of leachable elements are discussed.

Gold nanoclusters reductively deposited on porous silicon: morphology and electronic structures

1998 ◽  
Vol 76 (11) ◽  
pp. 1707-1716 ◽  
Author(s):  
I Coulthard ◽  
S Degen ◽  
Y -J Zhu ◽  
T K Sham
Keyword(s):  
Gold Nanoparticles ◽  
Porous Silicon ◽  
Photoelectron Spectroscopy ◽  
Gold Nanoclusters ◽  
Gold Complex ◽  
X Ray Diffraction ◽  
Complex Ions ◽  
X Ray ◽  
Preparation Conditions ◽  
P Type

Utilizing porous silicon as a reducing agent and a substrate, gold complex ions [AuCl4]- were reduced from aqueous solution to produce nanoparticles of gold upon the surface of porous silicon. Scanning electron microscopy (SEM) was utilized to study the morphology of the porous silicon layers and the deposits of gold nanoparticles. It is found that preparation conditions have a profound effect on the morphology of the deposits, especially on porous silicon prepared from a p-type wafer. The gold nanoparticles, varying from micrometric aggregates of clusters of the order of 10 nm, to a distribution of nearly spherical clusters of the order of 10 nm, to strings of ~10 nm were observed and compared to bulk gold metal using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). These techniques confirm and complement the SEM findings. The potential for this reductive deposition technique is noted.Key words: gold nanostructures, reductive deposition, porous silicon, morphology, X-ray spectroscopy.

Surface Characterization of W/Ni/Al2O3 Catalysts

1997 ◽  
Vol 497 ◽  
Author(s):  
M. H. Jordão ◽  
J. M. Assaf ◽  
P. A. P. Nascente
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Surface Characterization ◽  
Nickel Content ◽  
Stable Phase ◽  
Preparation Methods ◽  
X Ray ◽  
Inductively Coupled ◽  
Temperature Programmed ◽  
Two Phases

ABSTRACTCatalysts containing tungsten and nickel oxides are important in hydrodesulfurization (HDS), hydrogénation (HY), and steam reforming of hydrocarbons. A series of W/Ni/Al2O3 catalysts was prepared by two different methods: (1) coprecipitation of nickel and aluminium hydroxicarbonate from their nitrates, followed by calcination and impregnation of tungsten; (2) precipitation of boehmite from aluminium nitrate, followed by impregnations of nickel, firstly, and tungsten. The nickel content was kept constant, while the amount of tungsten varied from 2.5 to 15.5 wt-%. The resulting oxides were characterized by inductively coupled plasma spectroscopy (ICP), atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). ICP and AAS were used to determine the W, Ni, and Al concentrations. XRD detected two phases: NiO and NiAl2O4 (no phase containing metallic tungsten was detected). Increasing the amount of W, the quantity of NiAl2O4 rose, the quantity of NiO decreased, and the particle size of NiO enlarged. The TPR profiles presented three peaks: one at about 1000 °C, associated to a very stable phase; for the samples prepared by coprecipitation, the other two peaks corresponded to “free NiO” and a nonstoichiometric aluminate. For the samples prepared by impregnation, those peaks corresponded to NiO and NiAl2O4. XPS identified Al2O3, NiAl2O4, and Al2(WO4)3 for both preparation methods. Increasing the amount of tungsten in the impregnated samples, NiWO4 was also observed.

Effect of Cleaning Chemistries on Cobalt: Surface Chemistries and Electrical Characterization

2018 ◽  
Vol 282 ◽  
pp. 263-267
Author(s):  
Quoc Toan Le ◽  
Els Kesters ◽  
Yuya Akanishi ◽  
Marleen H. van der Veen ◽  
Atsushi Mizutani ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Spectroscopic Ellipsometry ◽  
Photoelectron Spectroscopy ◽  
Good Yield ◽  
Electrical Characterization ◽  
Cobalt Hydroxide ◽  
Dissolved Oxygen Concentration ◽  
X Ray ◽  
Xps Characterization ◽  
Surface Chemistries

The etching characteristics of ECD cobalt in different cleaning solutions were characterized using four-point probe, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. 0.05% HF solution with saturated dissolved oxygen concentration was found to result in a substantial etch of ECD cobalt (~5 nm/min). In contrast, cleaning in the SC1 1:4:100 mixture and the formulated mixture led to a significantly lower etch amount, which could be explained by the formation of a passivation layer at the surface. XPS characterization indicated the formation of a cobalt hydroxide at the surface. The electrical evaluation of the DD structure carried out after cleaning using the formulated chemical mixture and subsequent metallization showed good yield for the 22 nm Kelvin vias, testifying an efficient cleaning of the Co surface at the via bottom.

p-Type dopant incorporation and surface charge properties of catalyst-free GaN nanowires revealed by micro-Raman scattering and X-ray photoelectron spectroscopy

Nanoscale ◽  
2014 ◽  
Vol 6 (17) ◽  
pp. 9970-9976 ◽  
Author(s):  
Q. Wang ◽  
X. Liu ◽  
M. G. Kibria ◽  
S. Zhao ◽  
H. P. T. Nguyen ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Surface Charge ◽  
Photoelectron Spectroscopy ◽  
X Ray ◽  
Gan Nanowires ◽  
Catalyst Free ◽  
Dopant Incorporation ◽  
P Type

p-Type dopant (magnesium) incorporation and surface charge properties of catalyst-free GaN nanowires are revealed by micro-Raman scattering and X-ray photoelectron spectroscopy.

Revealing the mechanism of the early stages of Ni–W RABiTS oxidation

2010 ◽  
Vol 25 (12) ◽  
pp. 2362-2370 ◽  
Author(s):  
Andrey V. Blednov ◽  
Oleg Yu. Gorbenko ◽  
Dmitriy P. Rodionov ◽  
Andrey R. Kaul
Keyword(s):  
Internal Oxidation ◽  
Photoelectron Spectroscopy ◽  
Oxidation Mechanism ◽  
Surface Oxidation ◽  
Surface Region ◽  
Near Surface ◽  
Precise Position ◽  
X Ray ◽  
Early Stages ◽  
Phase And Chemical Composition

The early stages of surface oxidation of biaxially textured Ni–W tapes were studied using thermodynamic calculations along with experimental tape oxidation at low P(O2). Tape phase and chemical composition, surface morphology, and roughness were examined using x-ray diffraction (XRD), energy-dispersive x-ray analysis (EDX), secondary ion mass spectroscopy (SIMS), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For a Ni0.95W0.05 alloy tape, the precise position of the tape oxidation line in P(O2)–T coordinates was established. This line includes a break at T ≈ 650 °C that originates from the change of the W oxidation mechanism from internal oxidation to oxidation on a free surface accompanied by segregation of the alloy components in the tape near-surface region. The surface roughness of a polished tape increased drastically during internal oxidation of W; further tape oxidation did not affect the integral roughness parameters, but introduced numerous small (˜;100 nm) features on the tape surface comprising NiO precipitates.

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