uv Studies of Tetrahedral Bonding in Diamondlike Amorphous Carbon

1997 ◽  
Vol 78 (25) ◽  
pp. 4869-4872 ◽  
Author(s):  
V. I. Merkulov ◽  
J. S. Lannin ◽  
C. H. Munro ◽  
S. A. Asher ◽  
V. S. Veerasamy ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Tetrahedral Bonding

Quantitative Studies of Tetrahedral Bonding in Amorphous Carbon Films Using Ultraviolet Raman Spectroscopy

1997 ◽  
Vol 498 ◽  
Author(s):  
K. W. R. Gilkes ◽  
S. Prawer ◽  
J. Robertson ◽  
H. S. Sands
Keyword(s):  
Raman Spectroscopy ◽  
Amorphous Carbon ◽  
Random Network ◽  
Carbon Films ◽  
Strongly Correlated ◽  
Amorphous Carbon Films ◽  
Quantitative Studies ◽  
Tetrahedral Bonding ◽  
Two Peaks ◽  
Non Destructive

ABSTRACTThe bonding in a series of unhydrogenated amorphous carbon films has been analysed quantitatively using Raman spectroscopy with ultraviolet excitation. The Raman spectra exhibit two broad Raman peaks at 1650 cm−1 and 1100 cm−1, due to sp2 and sp3 vibrational modes respectively. The former is a resonance feature associated with a large proportion of paired sp2 sites, while the latter is a weighted vibrational density-of-states for the distorted random network of sp3 sites. The position and relative intensity of the two peaks are shown to be strongly correlated with the percentage of sp3 sites in the films, providing a reliable measure of sp3 bonding which is both quantitative and non-destructive.

RAMAN SCATTERING STUDIES ON THE STRUCTURAL PROPERTIES OF PULSED LASER DEPOSITED AMORPHOUS CARBON NITRIDE THIN FILMS

2005 ◽  
Vol 19 (23) ◽  
pp. 3527-3545 ◽  
Author(s):  
M. RUSOP ◽  
T. SOGA ◽  
T. JIMBO
Keyword(s):  
Thin Films ◽  
Raman Scattering ◽  
Amorphous Carbon ◽  
Carbon Nitride ◽  
Structural Parameters ◽  
Pulsed Laser ◽  
Carbon Films ◽  
Amorphous Carbon Nitride ◽  
N Incorporation ◽  
Tetrahedral Bonding

Raman scattering analysis revealed that the structure of carbon films prepared by pulsed laser deposition (PLD) at room temperature is predominantly amorphous and the structure of amorphous carbon nitride ( a-CN x) thin films can be changed with varying substrate temperatures (ST) from 20°C to 500°C. The deposited a-CN x films are composed of C – N , C ≡ N and C – O bonded materials and the C – N and C ≡ N bonds are increased with ST. We have found that no other obvious peaks can be distinguished in the range 900–2300 cm-1 in which several peaks always appear in a-CN x films. The spectra were deconvoluted into Raman D and G peaks and the structural parameters are determined. The upward shifts of the Raman G peak towards 1592 cm-1 shows the evidence of a progressive formation of crystallites in a-CN x films upon increase of ST. While the upward shifts of the Raman D peak towards 1397 cm-1 have been related to the decrease of bond-angle disorder and sp3 tetrahedral bonding in its structure. Raman FWHM and I D /I G also indicate that N incorporation with increase of ST caused an increase in the number and/or size of graphitic domains in the a-CN x films.

Structure and Electronic Properties of Diamond-Like Amorphous Carbon

1994 ◽  
Vol 349 ◽  
Author(s):  
C. Z. Wang ◽  
K. M. Ho
Keyword(s):  
Electronic Properties ◽  
Amorphous Carbon ◽  
Ion Beam ◽  
Tight Binding ◽  
Carbon Films ◽  
Structural And Electronic Properties ◽  
Carbon Networks ◽  
Tetrahedral Bonding ◽  
Dynamics Method ◽  
Beam Deposition

ABSTRACTAmorphous carbon networks generated by quenching high-density liquid from hightemperature using a tight-binding molecular dynamics method are found to be dominated by tetrahedral bonding sites. The overall structural and electronic properties of these networks resemble those observed in experimental diamond-like amorphous carbon films produced by the mass-selected ion beam deposition technique. Our study shows that bonding and antibonding of π states associated with pairs and quartets of threefold “defected-atoms” embedded in the fourfold matrix yield a band gap of about 2 eV.

The Resolution and Contrast in Biological Sections Determined by Inelastic and Elastic Scattering

1973 ◽  
Vol 31 ◽  
pp. 224-225
Author(s):  
D. L. Misell
Keyword(s):  
Electron Microscopy ◽  
Adverse Effect ◽  
Elastic Scattering ◽  
Inelastic Scattering ◽  
Amorphous Carbon ◽  
Polymeric Materials ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Quantitative Estimates ◽  
Elastic Ratio

In the electron microscopy of biological sections the adverse effect of chromatic aberration on image resolution is well known. In this paper calculations are presented for the inelastic and elastic image intensities using a wave-optical formulation. Quantitative estimates of the deterioration in image resolution as a result of chromatic aberration are presented as an alternative to geometric calculations. The predominance of inelastic scattering in the unstained biological and polymeric materials is shown by the inelastic to elastic ratio, I/E, within an objective aperture of 0.005 rad for amorphous carbon of a thickness, t=50nm, typical of biological sections; E=200keV, I/E=16.

Observation of Atom Rows in Thorium Pyromellitate Using a Field Emission STEM

1977 ◽  
Vol 35 ◽  
pp. 80-81
Author(s):  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Field Emission ◽  
Amorphous Carbon ◽  
Carbon Film ◽  
Dark Field Image ◽  
Dark Field ◽  
Amorphous Carbon Film ◽  
Atomic Size ◽  
Wide Range ◽  
A Chain

It is interesting to observe polymers at atomic size resolution. Some works have been reported for thorium pyromellitate by using a STEM (1), or a CTEM (2,3). The results showed that this polymer forms a chain in which thorium atoms are arranged. However, the distance between adjacent thorium atoms varies over a wide range (0.4-1.3nm) according to the different authors.The present authors have also observed thorium pyromellitate specimens by means of a field emission STEM, described in reference 4. The specimen was prepared by placing a drop of thorium pyromellitate in 10-3 CH3OH solution onto an amorphous carbon film about 2nm thick. The dark field image is shown in Fig. 1A. Thorium atoms are clearly observed as regular atom rows having a spacing of 0.85nm. This lattice gradually deteriorated by successive observations. The image changed to granular structures, as shown in Fig. 1B, which was taken after four scanning frames.

Electron-diffraction studies of amorphous carbon thin films

1993 ◽  
Vol 51 ◽  
pp. 1100-1101
Author(s):  
David A. Muller
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Amorphous Carbon ◽  
Glassy Carbon ◽  
Spherical Structure ◽  
Local Ordering ◽  
Carbon Arc ◽  
Similar Appearance ◽  
Carbon Thin Films ◽  
Large Spherical

The sp2 rich amorphous carbons have a wide variety of microstructures ranging from flat sheetlike structures such as glassy carbon to highly curved materials having similar local ordering to the fullerenes. These differences are most apparent in the region of the graphite (0002) reflection of the energy filtered diffracted intensity obtained from these materials (Fig. 1). All these materials consist mainly of threefold coordinated atoms. This accounts for their similar appearance above 0.8 Å-1. The fullerene curves (b,c) show a string of peaks at distance scales corresponding to the packing of the large spherical and oblate molecules. The beam damaged C60 (c) shows an evolution to the sp2 amorphous carbons as the spherical structure is destroyed although the (220) reflection in fee fcc at 0.2 Å-1 does not disappear completely. This 0.2 Å-1 peak is present in the 1960 data of Kakinoki et. al. who grew films in a carbon arc under conditions similar to those needed to form fullerene rich soots.

Scanning Tunneling Microscopy of Amorphous Carbon Films

1990 ◽  
Vol 48 (1) ◽  
pp. 318-319
Author(s):  
Mircea Fotino ◽  
D.C. Parks
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Amorphous Carbon ◽  
Carbon Films ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Amorphous Carbon Films ◽  
Image Optimization ◽  
Step Procedure ◽  
Stm Images

In the last few years scanning tunneling microscopy (STM) has made it possible and easily accessible to visualize surfaces of conducting specimens at the atomic scale. Such performance allows the detailed characterization of surface morphology in an increasing spectrum of applications in a wide variety of fields. Because the basic imaging process in STM differs fundamentally from its equivalent in other well-established microscopies, good understanding of the imaging mechanism in STM enables one to grasp the correct information content in STM images. It thus appears appropriate to explore by STM the structure of amorphous carbon films because they are used in many applications, in particular in the investigation of delicate biological specimens that may be altered through the preparation procedures.All STM images in the present study were obtained with the commercial instrument Nanoscope II (Digital Instruments, Inc., Santa Barbara, California). Since the importance of the scanning tip for image optimization and artifact reduction cannot be sufficiently emphasized, as stressed by early analyses of STM image formation, great attention has been directed toward adopting the most satisfactory tip geometry. The tips used here consisted either of mechanically sheared Pt/Ir wire (90:10, 0.010" diameter) or of etched W wire (0.030" diameter). The latter were eventually preferred after a two-step procedure for etching in NaOH was found to produce routinely tips with one or more short whiskers that are essentially rigid, uniform and sharp (Fig. 1) . Under these circumstances, atomic-resolution images of cleaved highly-ordered pyro-lytic graphite (HOPG) were reproducibly and readily attained as a standard criterion for easily recognizable and satisfactory performance (Fig. 2).

Assessment of Amorphous Carbon Coating for Artificial Joints Application

2005 ◽  
Vol 48 (2) ◽  
pp. 190-198 ◽  
Author(s):  
O. O. Ajayi ◽  
B. Shi ◽  
M. J. Soppet ◽  
A. Erdemir ◽  
H. Liang ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Carbon Coating ◽  
Artificial Joints
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