Cluster-ion bombardment of thin films

1984 ◽  
Vol 42 ◽  
pp. 358-359
Author(s):  
M. C. Ledbetter ◽  
M. Matthew ◽  
R. J. Beuhler ◽  
L. Friedman
Keyword(s):  
High Vacuum ◽  
Carbon Films ◽  
Vacuum System ◽  
Sonic Nozzle ◽  
Thin Carbon ◽  
Weakly Ionized ◽  
Charged Clusters ◽  
Cluster Ion ◽  
Ion Impact ◽  
Singly Charged

Energetic cluster ion impact on solid surfaces can be used to deposit large quantities of kinetic energy in small assemblies of atoms in the surface. Extremely high transient pressures and increases in the density of surface atoms are produced by these impact processes. Significant alteration of surface structure is expected. We have investigated the effects of bombardment of thin carbon films with singly charged clusters of argon atoms and protonated water molecules accelerated to energies as high as 300 kV. Clusters were generated in weakly ionized plasmas produced by a corona discharge at atmospheric pressure in helium carrier gas. The singly charged seed ions in this discharge served as nuclei in the expanding gas mixture that was introduced into a high vacuum system through a super sonic nozzle and a differentially pumped skimmer.

Energetic Cluster Ion Impacts on Carbon and Gold/Carbon Films

1985 ◽  
Vol 43 ◽  
pp. 384-385
Author(s):  
M.C. Ledbetter ◽  
M.W. Matthew ◽  
R.J. Beuhler ◽  
L. Friedman
Keyword(s):  
Water Clusters ◽  
Carbon Films ◽  
Solid Surfaces ◽  
Cluster Ions ◽  
Water Molecules ◽  
Transmission Electron ◽  
Pure Carbon ◽  
Cluster Ion ◽  
Singly Charged ◽  
20 Nm

Mass analyzed beams of accelerated cluster ions have been used to study energy transfer processes on impact with solid surfaces. Singly-charged water molecule clusters containing between 20 and 150 water molecules and one proton have been accelerated to kinetic energies as high as 300 kV and collided with 10 nm films of carbon or carbon covered with 2 μg/cm2 evaporated gold. Alterations in the structure of these films have been studied by transmission electron microscopy.Carbon films bombarded with water clusters of 25 and 100 molecules accelerated to 300 kV are shown in Fig. 1. The use of 100 water molecules produced craters about 7-8 nm in diameter and even 50 molecules produced craters about 1.5-2 nm in diameter; however, 25 molecules failed to produce any detectable alterations in the film. The bombardment of a gold-covered film by similar clusters is shown in Fig. 2. In these cases, gold grains were removed to form voids about 10-20 nm in diameter, even by the clusters as small as 25 molecules, which produced no craters in pure carbon.

Heavy Atom Cluster Labeling of Biological Specimens

1985 ◽  
Vol 43 ◽  
pp. 718-719
Author(s):  
J.J. Lipka ◽  
J.F. Hainfeld ◽  
J.S. Wall
Keyword(s):  
Heavy Metal ◽  
Heavy Atom ◽  
Carbon Films ◽  
Cluster Labeling ◽  
Heavy Atoms ◽  
Glycoprotein Complex ◽  
Thin Carbon ◽  
Lysine Residues ◽  
Cluster Ion ◽  
Beam Dose

The Brookhaven STEM is capable of resolving single heavy atoms deposited on thin carbon films with a beam dose > 103 el Å-2 Single heavy atoms, therefore, are unsuitable as fiducial markers on unordered biological specimens because of the high beam dose required for direct visualization. Heavy metal-clusters or heavy metal-containing complexes have been resolved at much lower beam doses, as low as 30 el Å-2, and therefore may be useful as directly visible labels.The polyamine undecagold (11-Au) cluster ion, [(p-H2NCH2C6H4)3P]7 Au113+, has been used to covalently label the carbohydrate sites of the glycoprotein complex of human haptoglobin hemoglobin (Hp˙Hb) by a route which should be general for any glycoprotein with oxidizable carbohydrate residues. Proteins with reactive lysine residues have been covalently 11-Au labeled by the reactions noted in Scheme 1.

Ar Cluster Ion Bombardment Effects on Semiconductor Surfaces

2000 ◽  
Vol 647 ◽  
Author(s):  
Toshio Seki ◽  
Kazumichi Tsumura ◽  
Takaaki Aoki ◽  
Jiro Matsuo ◽  
Gikan H. Takaoka ◽  
...  
Keyword(s):  
Surface Modification ◽  
Variable Temperature ◽  
Ion Beam ◽  
High Vacuum ◽  
Ion Bombardment ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Cluster Ion ◽  
Ion Impact ◽  
The Impact

AbstractNew surface modification processes have been demonstrated using gas cluster ion irradiations because of their unique interaction between cluster ions and surface atoms. For example, high quality ITO films could be obtained by O2 cluster ion assisted deposition at room temperature. It is necessary to understand the role of cluster ion bombardment during film formation for the further developments of this technology. Variable Temperature Scanning Tunneling Microscope (VT-STM) in Ultra High Vacuum (UHV) allows us to study ion bombardment effects on surfaces and nucleation growth at various temperatures.The irradiation effects between Ar cluster ion and Xe monomer ion were compared. When a Si(111) surface with Ge deposited to a few Å was annealed to 400°C, it was observed that many islands of Ge were formed. The surface with the Ge islands was irradiated by these ions. In the STM image of cluster-irradiated surface, large craters with diameter of about 100 Å were observed, while only small traces with diameter of about 20 Å were observed in monomer-irradiated surface. The number of Ge atoms displaced by one Ar cluster ion impact was much larger than that by one Xe ion impact. This result indicates that Ar cluster ion impacts can enhance the physical modification of Ge islands. When the sample irradiated with Ar cluster was annealed at 600°C, the hole remained, but the outer rim of the crater disappeared and the surface structure was reconstructed at the site of the rim. The depth of damage region in the target became shallower with decrease of the impact energy. These results indicate that low damage and useful surface modification can be realized using the cluster ion beam.

Replication of Wet Objects and Cells

1974 ◽  
Vol 32 ◽  
pp. 102-103
Author(s):  
S. Basu ◽  
D. F. Parsons
Keyword(s):  
Water Vapor Pressure ◽  
High Vacuum ◽  
Polystyrene Latex ◽  
Vacuum System ◽  
Saturated Water Vapor ◽  
Replication Method ◽  
New Methods ◽  
Saturated Water ◽  
Water Vapors ◽  
Intermediate Chamber

We are approaching the invasiveness of cancer cells from the studies of their wet surface morphology which should distinguish them from their normal counterparts. In this report attempts have been made to provide physical basis and background work to a wet replication method with a differentially pumped hydration chamber (Fig. 1) (1,2), to apply this knowledge for obtaining replica of some specimens of known features (e.g. polystyrene latex) and finally to realize more specific problems and to improvize new methods and instrumentation for their rectification. In principle, the evaporant molecules penetrate through a pair of apertures (250, 350μ), through water vapors and is, then, deposited on the specimen. An intermediate chamber between the apertures is pumped independently of the high vacuum system. The size of the apertures is sufficiently small so that full saturated water vapor pressure is maintained near the specimen.

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

A Freeze Shadow Technique for the Preparation of Soft Paint Latexes for Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 314-315
Author(s):  
Earl R. Walter ◽  
Glen H. Bryant
Keyword(s):  
Sample Preparation ◽  
High Vacuum ◽  
Vacuum System ◽  
Latex Particles ◽  
New Methods ◽  
Diffusion Pump ◽  
Film Forming ◽  
Routine Basis ◽  
Distribution Studies ◽  
Preparation Techniques

With the development of soft, film forming latexes for use in paints and other coatings applications, it became desirable to develop new methods of sample preparation for latex particle size distribution studies with the electron microscope. Conventional latex sample preparation techniques were inadequate due to the pronounced tendency of these new soft latex particles to distort, flatten and fuse on the substrate when they dried. In order to avoid these complications and obtain electron micrographs of undistorted latex particles of soft resins, a freeze-dry, cold shadowing technique was developed. The method has now been used in our laboratory on a routine basis for several years.The cold shadowing is done in a specially constructed vacuum system, having a conventional mechanical fore pump and oil diffusion pump supplying vacuum. The system incorporates bellows type high vacuum valves to permit a prepump cycle and opening of the shadowing chamber without shutting down the oil diffusion pump. A baffeled sorption trap isolates the shadowing chamber from the pumps.

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.

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