In Situ Electron Spectroscopic Identification of Carbon Species Deposited by Laser Ablation

1996 ◽  
Vol 436 ◽  
Author(s):  
E. C. Samano ◽  
Gerardo Soto ◽  
Arturo Gamietea ◽  
Leonel Cota
Keyword(s):  
Substrate Surface ◽  
Pyrolytic Graphite ◽  
Deposition Process ◽  
Carbon Films ◽  
Spectroscopic Techniques ◽  
Carbon Species ◽  
Thin Carbon ◽  
Spectroscopic Identification ◽  
Relationship Of

AbstractThin carbon films were grown on Si (111) substrates by ablating a graphite target utilizing an excimer pulsed laser in a UHV Riber © LDM-32 system. Two kinds of films were produced, a highly oriented pyrolytic graphite (HOPG) type and a diamond-like carbon (DLC) type. A relationship of the films microstructure with laser power density and substrate conditions was observed. The HOPG films were homogeneous but the DLC films were heterogeneous, as shown by micrographs. The thin films are monitored and analyzed in situ during the first stages of the deposition process. The monitoring was done by RHEED and the characterization by several surface spectroscopic techniques, AES, XPS and EELS. The formation of a SiC interface was observed for both films due to the reaction of the first carbon species with the substrate surface.

Chemical Properties of A-Si:H Interface Layers on Oxide-Covered and Hydrogen-Terminated Silicon

1996 ◽  
Vol 420 ◽  
Author(s):  
Jürgen Knobloch ◽  
Peter Hess
Keyword(s):  
Film Growth ◽  
Substrate Surface ◽  
Chemical Properties ◽  
Deposition Process ◽  
Native Oxide ◽  
Difference Spectra ◽  
Initial Stage ◽  
Laser Cvd ◽  
Interface Layers

AbstractHigh quality a-Si:H films were deposited by pulsed VUV (157nm) laser CVD, allowing digital control of the deposition process. Nucleation and growth on native oxide-covered Si (100) and on H-terminated Si (111) surfaces were studied in situ by FTIR transmission spectroscopy with sub-monolayer sensitivity. The film thickness was monitored simultaneously using a quartz crystal microbalance (QCM) with comparable resolution. The in situ spectra reveal that the nature of the substrate surface significantly influences the hydrogen bonding configuration in the interface region. In both cases the assumed cluster growth during the initial stage is characterized by a band around 2100cm−1, which is assigned to SiHX (x = 1 – 3) surface modes. This band broadens until the clusters coalesce and band saturation occurs. At this time a second band starts to grow at 2000cm−1, which is attributed to bulk SiH bonds. Difference spectra calculated for layers at different depths with definite thickness and the deconvolution of the broad feature observed during the very first stage of film growth indicate the existence of a hydrogen-rich layer at the substrate surface whose composition and thickness depend on the properties of the substrate surface.

scholarly journals Влияние энергии ионной стимуляции на удельное электросопротивление углеродных пленок, полученных методом импульсно-плазменного осаждения в атмосфере азота

2019 ◽  
Vol 61 (11) ◽  
pp. 2244
Author(s):  
И.А. Завидовский ◽  
O.A. Стрелецкий ◽  
О.Ю. Нищак ◽  
A.A. Хайдаров
Keyword(s):  
Electron Diffraction ◽  
Deposition Process ◽  
Carbon Films ◽  
Gas Mixture ◽  
Specific Resistivity ◽  
Energy Increase ◽  
Nitrogen Gas ◽  
Graphite Phase ◽  
Thin Carbon ◽  
Ion Assistance

In the paper, thin carbon films deposited by pulse-plasma ion-assisted sputtering of graphite in argon-nitrogen gas mixture are discussed. The EELS and electron diffraction showed the graphite phase enlargement with the ion assistance energy increase. Application of ion assistance during the deposition process made it possible to control the films specific resistivity, altering it from 10^5 to 10^2 Ohm⋅cm.

Mechanical Properties of Laser Processed Diamond-Like Carbon Films

1995 ◽  
Vol 397 ◽  
Author(s):  
Ashok Kumar ◽  
R. B. Inturi ◽  
Y. Vohra ◽  
U. Ekanayake ◽  
N. Shu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Chemical Properties ◽  
High Hardness ◽  
Deposition Process ◽  
Carbon Films ◽  
Diamond Like Carbon

ABSTRACTDiamond-like carbon (DLC) films have a unique combination of physical and chemical properties such as high hardness, optical transparency, low coefficient of friction and chemical inertness. A pulsed laser (248 nm) has been used to ablate a pyrolytic graphite target to deposit DLC films on Si (100) and 7059 Corning glass substrates. The deposition was carried out in high vacuum (≤ 10−6 Torr) at different temperatures ranging from room temperature to 400°C. The films were characterized by x-ray diffraction, scanning electron microscope, and Raman spectroscopie techniques. The mechanical properties (hardness and Young's modulus) of these films were characterized by nanoindentation. We have found that the films deposited at room temperature and 100°C show the characteristic features of DLC films and have the better hardness and modulus properties compared to the films fabricated at higher temperatures, which transform into amorphous carbon. Correlations of pulsed laser deposition process parameters with the properties of deposited DLC films will be discussed in this paper.

Laser Ablation Deposition of Diamond-Like Carbon Films

1992 ◽  
Vol 285 ◽  
Author(s):  
S. Leppävuori ◽  
J. Levoska ◽  
J. Vaara ◽  
O. Kusmartseva
Keyword(s):  
Laser Ablation ◽  
Laser Beam ◽  
Power Density ◽  
Pyrolytic Graphite ◽  
Deposition Process ◽  
Carbon Films ◽  
Fused Silica ◽  
Optical Measurements ◽  
Diamond Like Carbon ◽  
X Ray Diffraction

ABSTRACTDiamond-like carbon (DLC) thin films were prepared by laser ablation deposition. The deposition process was carried out in a vacuum chamber at a base pressure of about 10−5 mbar using the focused beam from either an Nd:YAG laser or an XeCl excimer laser and a pyrolytic graphite target. The peak power density of the laser beam was about 108 W/cm2, and 1010 W/cm2. respectively. The effect of varying power density of the laser beam also was examined. The films were deposited on fused silica and silicon single crystal substrates between room temperature and 600 °C with and without hydrogen addition. The properties of the films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman and Fourier transform infrared (FTIR) spectrometry, electrical conductivity and optical measurements. The best films were insulating (σ<10−6 Ω−1 cm−1), hard, partly transparent (optical gap 1.3 − 2.2 eV) and smooth without any particulates on the surface.

Parameter Optimization for the Arc-Adlc-Deposition Process

1994 ◽  
Vol 349 ◽  
Author(s):  
O. Knotek ◽  
F. Löffler ◽  
C. Barimani ◽  
J. Brand
Keyword(s):  
Film Growth ◽  
Deposition Process ◽  
High Energy ◽  
Carbon Films ◽  
Process Efficiency ◽  
Substrate Current ◽  
Thin Carbon ◽  
Mechanical Filter ◽  
Cathodic Arc Evaporation ◽  
Reactive Gases

ABSTRACTOne method used by the industry for the deposition of thin carbon films is the dc cathodic arcion plating process. The evaporation of a graphite cathode by a high energy arc beam results in the production of carbon atoms, ions and macroscopic graphitic fragments. All these particles influence the film growth, the structure and therefore the film properties. The incorporation of the macroscopic graphitic fragments can be avoided by the use of mechanical or magnetic filters in front of the cathode. These filters prevent the direct bombardment of the substrates with particles. This particle separation involves decreased substrate current densities and this means lower deposition temperature (< 200°C) and growth rates. With the addition of inert (argon) and reactive gases (nitrogen and methane) and the use of a bias voltage on the substrate economical deposition rates of 2-4 μm/h and good adhesion on various materials can be reached.This paper describes the production of amorphous hydrogen and hydrogen-free carbon films by a modified cathodic arc evaporation process using a simple mechanical filter for particle reduction. It shows the influence of some process parameters on the optimization of the process stability and process efficiency. Some characteristic properties of these coatings are shown by an example.

Object Wave Determination by Single-Sideband Methods

1973 ◽  
Vol 31 ◽  
pp. 266-267
Author(s):  
Kenneth H. Downing ◽  
Benjamin M. Siegel
Keyword(s):  
Phase Shift ◽  
Carbon Films ◽  
Object Wave ◽  
Electron Wave ◽  
Phase Object ◽  
Heavy Atoms ◽  
Single Sideband ◽  
Thin Carbon ◽  
Additional Phase Shift ◽  
Additional Phase

Under the “weak phase object” approximation, the component of the electron wave scattered by an object is phase shifted by π/2 with respect to the unscattered component. This phase shift has been confirmed for thin carbon films by many experiments dealing with image contrast and the contrast transfer theory. There is also an additional phase shift which is a function of the atomic number of the scattering atom. This shift is negligible for light atoms such as carbon, but becomes significant for heavy atoms as used for stains for biological specimens. The light elements are imaged as phase objects, while those atoms scattering with a larger phase shift may be imaged as amplitude objects. There is a great deal of interest in determining the complete object wave, i.e., both the phase and amplitude components of the electron wave leaving the object.

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

Scanning Secondary Electron Microscopy of Myofibrils Using Transmission Techniques

1975 ◽  
Vol 33 ◽  
pp. 556-557
Author(s):  
M. K. Lamvik
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Carbon Films ◽  
Photographic Recording ◽  
Transmission Electron ◽  
Thin Carbon ◽  
The Common ◽  
Scanning Electron ◽  
Better Than ◽  
Cellular Organelles

When observing small objects such as cellular organelles by scanning electron microscopy, it is often valuable to use the techniques of transmission electron microscopy. The common practice of mounting and coating for SEM may not always be necessary. These possibilities are illustrated using vertebrate skeletal muscle myofibrils.Micrographs for this study were made using a Hitachi HFS-2 scanning electron microscope, with photographic recording usually done at 60 seconds per frame. The instrument was operated at 25 kV, with a specimen chamber vacuum usually better than 10-7 torr. Myofibrils were obtained from rabbit back muscle using the method of Zak et al. To show the component filaments of this contractile organelle, the myofibrils were partially disrupted by agitation in a relaxing medium. A brief centrifugation was done to clear the solution of most of the undisrupted myofibrils before a drop was placed on the grid. Standard 3 mm transmission electron microscope grids covered with thin carbon films were used in this study.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

Synthesis of sandwich type acyclic tetra-nuclear silver(I)-N-heterocyclic carbene complexes for wound healing applications

2020 ◽  
Vol 75 (9-10) ◽  
pp. 369-376
Author(s):  
Ayesha Riaz ◽  
Muhammad Adnan Iqbal ◽  
Haq Nawaz Bhatti ◽  
Muhammad Shahid
Keyword(s):  
Alkyl Halides ◽  
Wound Contraction ◽  
Spectroscopic Techniques ◽  
Open Chain ◽  
Standard Drug ◽  
Sandwich Type ◽  
Benzimidazolium Salts ◽  
Multistep Reaction

AbstractTwo meta-xylyl linked tetrakis-benzimidazolium salts (L1-L2) as multidentate ligands and two respective silver complexes (C1 and C2) were synthesized. A multistep reaction was done at room temperature, starting with simple benzimidazole and alkyl halides, going through precursors and salt formation by reflux and finally in situ deprotonation of tetrabenzimidazolium salts with Ag2O to yield respective tetra-nuclear Ag(I)-N-heterocyclic Carbene (NHC) complexes. Propyl and butyl groups were bonded at the terminal positions of tetra-azolium open chain salts. Characterization of compounds was done by analytical and spectroscopic techniques. On the basis of spectroscopic data, a chemical structure with open chains having four Ag(I) ions sandwiched between NHC layers was established. Potential of synthesized complexes (C1 & C2) for wound contraction was evaluated and compared with standard wound contraction gel. Percentage wound contraction of both complexes was found very close to that of standard drug used in parallel.

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