Topographical changes induced by high dose carbon-bombardment of graphite

1993 ◽  
Vol 8 (10) ◽  
pp. 2587-2599 ◽  
Author(s):  
B.K. Annis ◽  
D.F. Pedraza ◽  
S.P. Withrow
Keyword(s):  
Dose Rate ◽  
Pyrolytic Graphite ◽  
Surface Region ◽  
Scanning Tunneling ◽  
High Dose ◽  
Near Surface ◽  
Optical Scanning ◽  
Atomic Force ◽  
First Time ◽  
High Shearing

Highly oriented pyrolytic graphite has been implanted at room temperature with 165 keV C+-ions at doses from 6 × 1017 to 3 × 1019 ions/m2. Implantation-induced topographical changes of differing size scales were studied by optical, scanning electron, scanning tunneling, and atomic force microscopies. Defects with atomic resolution are seen for the lower dose implants. The formation of a vacancy line is revealed for the first time. At the higher doses a dendrite-like system of deep surface cracks is observed. This cracking develops as a result of the large basal plane contraction produced by irradiation which generates high shearing stresses between the implanted, damaged surface layer and the underlying material. Two independent systems of ridges have been characterized. One appears to follow a crystallographic direction while the other appears as a dense, intricate, generally curvilinear network with short ramifications. Additional experiments in which both the ion energy and dose rate have been varied indicate that ridge evolution progresses with increased energy and fluence, but is independent of dose rate. It is suggested that the ridge networks may form as a result of C transport by diffusion from the heavily damaged near-surface region or of a tectonic-plate-like motion or both. The geometric features of the ridge networks are related to the subsurface radiation damage as well.

Formation of Au-nanocrystals in TiO2 and SrTiO3 by ion implantation in restricted volumes

2003 ◽  
Vol 792 ◽  
Author(s):  
R. Fromknecht ◽  
G. Linker ◽  
K. Sun ◽  
S. Zhu ◽  
L.M. Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Ion Implantation ◽  
Dose Rate ◽  
Size Distribution ◽  
Average Particle Size ◽  
Surface Region ◽  
High Dose ◽  
Average Particle ◽  
Tem Analysis ◽  
Near Surface

ABSTRACTAu-ions were implanted at RT conventionally and through a mask into TiO2- and SrTiO3-single crystals with doses in the range from 1×1015Au+/cm2 to 1×1017Au+/cm2, and dose rates of ∼1011ions/sec and ∼3×1013ions/sec, at an energy of 260keV; some samples subsequently were annealed at temperatures up to 1100K. The Au-atoms precipitated to nanocrystals during implantation with an average particle size of 1.5nm. HRTEM investigations revealed that the Au-nanocrystals, embedded in amorphous TiO2-regions, have a broad size distribution varying from large sizes in the near surface region to smaller sizes at larger depths. In the annealing process a coarsening and a reorientation of the Au-nanocrystals is observed. At 1000K the particle size of the textured Au-implant was evaluated to be ∼6nm. Implantation with a high dose rate performed through a metal mask with holes of 120μm diameter and without annealing resulted in an almost equidistant arrangement of the Au-nanocrystals with a narrow size distribution of 2–6nm in TiO2 and 3–5nm in SrTiO3 in the near surface region. Au-ion implantation through an e-beam resist mask (50nm × 50nm holes), with doses ranging from 1×1015Au+/cm2 to 4×1015Au+/cm2 at the low dose rate and annealed at 1000K, lead to a periodic structure of the Au-nanocrystals. The nanocrystal size, evaluated from TEM analysis, in the as-implanted state was ∼5nm and after annealing at 1000K sizes of several nanometers to several tens of nanometers were observed.

Scanning Tunneling Microscopy and Atomic Force Microscopy Investigation of Organic Tetracyanoquinodimethane Thin Films

1997 ◽  
Vol 12 (8) ◽  
pp. 1942-1945 ◽  
Author(s):  
H. J. Gao ◽  
H. X. Zhang ◽  
Z. Q. Xue ◽  
S. J. Pang
Keyword(s):  
Thin Films ◽  
Atomic Force Microscopy ◽  
Scanning Tunneling Microscopy ◽  
Pyrolytic Graphite ◽  
Film Surface ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microscopy Investigation

Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) investigation of tetracyanoquinodimethane (TCNQ) and the related C60-TCNQ thin films is presented. Periodic molecular chains of the TCNQ on highly oriented pyrolytic graphite (HOPG) substrates were imaged, which demonstrated that the crystalline (001) plane was parallel to the substrate. For the C60-TCNQ thin films, we found that there were grains on the film surface. STM images within the grain revealed that the well-ordered rows and terraces, and the parallel rows in different grains were generally not in the same orientation. Moreover, the grain boundary was also observed. In addition, AFM was employed to modify the organic TCNQ film surface for the application of this type of materials to information recording and storage at the nanometer scale. The nanometer holes were successfully created on the TCNQ thin film by the AFM.

Scanned probe microscopy in biology

1993 ◽  
Vol 51 ◽  
pp. 508-509
Author(s):  
Knute A. Fisher
Keyword(s):  
Pyrolytic Graphite ◽  
Piezoelectric Transducers ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Whole Cells ◽  
Flat Surfaces ◽  
The Past ◽  
Atomic Force ◽  
Scanned Probe Microscopy ◽  
And Control

Numerous scanned probe microscopes (SPM) have been developed over the past decade. Most are based on the precise positioning of sample and probe using piezoelectric transducers, and some have the capability of imaging flat surfaces with atomic resolution. The first atomic resolution SPM applied to biological samples was the scanning tunneling microscope (STM). The atomic force microscope (AFM) was subsequently developed and over the past few years has become the instrument of choice for biological applications.Early investigators applied the STM to examinations of organic and biological systems ranging from small molecules to nucleic acids, globular and fibrillar proteins, and larger structures such as viruses, membranes, and even whole cells. Much of this work was done during the mid-80s using electricallyconductive highly-oriented pyrolytic graphite (HOPG) as a substrate. Images were often difficult to obtain and control experiments were lacking. Unfortunately, when careful experiments were undertaken, they revealed that HOPG itself was capable of generating images previously thought to be biological.

COMPARATIVE STUDY OF THIOL FILMS ON C(0001) AND Au(111) SURFACES BY SCANNING PROBE MICROSCOPY

1997 ◽  
Vol 04 (04) ◽  
pp. 637-649 ◽  
Author(s):  
F. TERÁN ARCE ◽  
M. E. VELA ◽  
R. C. SALVAREZZA ◽  
A. J. ARVIA
Keyword(s):  
Pyrolytic Graphite ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Electrochemical Characteristics ◽  
Tunneling Microscopy ◽  
Test Reaction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Electron Transfer Processes ◽  
Substrate Nature

The structures resulting from 1-dodecanethiol, 1-butanethiol and 1,9-nonanedithiol films produced on highly oriented pyrolytic graphite (HOPG) and gold(111) have been comparatively studied by scanning probe microscopies. Molecular resolution images resulting from atomic force microscopy (AFM) and scanning tunneling microscopy (STM) of different thiol films show the formation of arrays of molecules parallel to the HOPG surface. The electrochemical response of the ferro-ferricyanide reaction was used to test the characteristics of electron transfer processes in thiol-covered HOPG as compared to the bare substrate. The decrease in the heterogeneous rate constant for the test reaction appears to be directly related to the degree of film thickness uniformity. For comparison, films with the same kind of thiols were produced on Au(111). Although the electrochemical characteristics of these films appear to be the same irrespective of the substrate nature, the structure of the films on Au(111) is different from that produced on HOPG.

The Influence of Implantation Conditions and Target Orientation in High Dose Implantation of Al+ into Si

1983 ◽  
Vol 27 ◽  
Author(s):  
F. Nam-Avar ◽  
J. I. Budnick ◽  
A. Fasihuddin ◽  
H. C. Hayden ◽  
D. A. Pease ◽  
...  
Keyword(s):  
Dose Rate ◽  
Surface Composition ◽  
High Vacuum ◽  
High Dose Rate ◽  
Ultra High Vacuum ◽  
High Dose ◽  
Polycrystalline Structure ◽  
Rutherford Back Scattering ◽  
Near Surface ◽  
Projected Range

ABSTRACTWe report the preliminary results of a study to determine the dependence of the near surface composition and structure on total dose, dose rate, vacuum condition and substrate orientation for Al implantation into Si (111) and Si (100) with doses up to 2 × 10l8 ions/cm2. Our studies include the results of Rutherford Back Scattering (RBS), Auger Electron Spectroscopy (AES) and x-ray diffraction measurements on samples implanted with a 100 keV energy in a diffusion pumped vacuum (DPV) system (10−6 Torr) with and without a LN2 trap and in an ultra high vacuum (UHV) system (2–4) x 10−8 Torr.Results of high dose rate (50 μA/cm2 ) implantation into Si (111) in an untrapped DPV system indicate that Al segregates with a preferred (111) orientation. For a dose of 1 × 1018 ions/cm2 the surface is Al-rich to a depth of 2500Å while for lower doses the surface is silicon-rich. A carbon build-yp occurred for samples prepared by low dose rate (5 μA/cm2 ) implantation. However, no Al segregation could be observed for doses of less than 1018 ions/cm2 . A similar behavior has been observed for Si (100) except that Al segregation occurs with a polycrystalline structure. Moreover, the segregated Al is present at depths greater than the projected range.When implantation was carried out in a DPV system with a LN2 trap, no carbon peaks could be observed by RBS regardless of the dose rate. For these conditions, as well as for the implantation of Al in an UHV system, we find Al segregation with a polycrystalline structure independent of the dose rates and target orientations we used. Al is observed at a depth greater by a factor of two than the expected value from the Rpcalculations. The Al depth penetration increases with the dose of implantation.

The Effects of Kcn Etching on Cu-Rich Epitaxial CuInSe2 Thin Films

1996 ◽  
Vol 426 ◽  
Author(s):  
P. Fons ◽  
S. Nikl ◽  
A. Yamada ◽  
M. Nishitanp ◽  
T. Wada ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Region ◽  
Etching Time ◽  
Cation Sublattice ◽  
Epitaxial Thin Films ◽  
Near Surface ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Integrated Intensity

AbstractA series of Cu-rich CuInSe2 epitaxial thin films were grown by molecular beam epitaxy on GaAs(001) substrates from elemental sources at a growth temperature of 450 °C. All samples were grown with an excess of Cu. Electron microprobe analysis (EPMA) indicated a Cu/ In ratio of about 2.1–2.6 in the as-grown films. Additionally, the Se/ (In+Cu) ratio was observed to be ∼0.95 indicating that the films were slightly Se poor. These Cu-rich samples were etched in a KCN solution for periods ranging from 30 seconds to 3 minutes. EPMA measurements indicated that the bulk Cu/ In ratio was reduced to ∼0.92 in all films regardless of etching time. Atomic force microscopy (AFM) was used to characterize the topology of each sample before and after etching. These measurements indicated that the precipitates present on the as-grown films were removed and large nearly isotropic holes were etched into the sample to a depth of over 1000 Å even for etching times as short as 30 seconds. The samples were also evaluated both before and after etching using a Phillips MRD diffractometer with parallel beam optics and a 18,000 watt Cu rotating anode X-ray source in the chalcopyrite [001], [101], and [112] directions. A peak was observed at ∼15 degrees in the [001] scan after etching consistant with the presence of the ordered vacancy compound, CuIn3Se5. Additionally the integrated intensity ratios of the chalcopyrite (202) reflection to the chalcopyrite (101) reflection ∝(fCu-fIn)2 along the [101] direction indicated the presence of a near-surface region containing cation sublattice disorder that was subsequently removed by the etching process.

scholarly journals Electron transfer between anatase TiO2 and an O2 molecule directly observed by atomic force microscopy

2017 ◽  
Vol 114 (13) ◽  
pp. E2556-E2562 ◽  
Author(s):  
Martin Setvin ◽  
Jan Hulva ◽  
Gareth S. Parkinson ◽  
Michael Schmid ◽  
Ulrike Diebold
Keyword(s):  
Atomic Force Microscopy ◽  
Electron Transfer ◽  
Photoelectron Spectroscopy ◽  
Uv Light ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Near Surface ◽  
Force Microscopy ◽  
Atomic Force

Activation of molecular oxygen is a key step in converting fuels into energy, but there is precious little experimental insight into how the process proceeds at the atomic scale. Here, we show that a combined atomic force microscopy/scanning tunneling microscopy (AFM/STM) experiment can both distinguish neutral O2 molecules in the triplet state from negatively charged (O2)− radicals and charge and discharge the molecules at will. By measuring the chemical forces above the different species adsorbed on an anatase TiO2 surface, we show that the tip-generated (O2)− radicals are identical to those created when (i) an O2 molecule accepts an electron from a near-surface dopant or (ii) when a photo-generated electron is transferred following irradiation of the anatase sample with UV light. Kelvin probe spectroscopy measurements indicate that electron transfer between the TiO2 and the adsorbed molecules is governed by competition between electron affinity of the physisorbed (triplet) O2 and band bending induced by the (O2)− radicals. Temperature–programmed desorption and X-ray photoelectron spectroscopy data provide information about thermal stability of the species, and confirm the chemical identification inferred from AFM/STM.

Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy

2014 ◽  
Vol 95 ◽  
pp. 299-301 ◽  
Author(s):  
E.S. Moura ◽  
C.A. Zeituni ◽  
R.K. Sakuraba ◽  
V.D. Gonçalves ◽  
J.C. Cruz ◽  
...  
Keyword(s):  
Dose Rate ◽  
Absorbed Dose ◽  
High Dose Rate ◽  
High Dose ◽  
Near Surface ◽  
Iridium 192

Ordering of a Functional Molecules on a Flat Surface as Evidenced by Scanning Probe Microscopies: The Case of a Di-Alkyl Amino Group

1998 ◽  
Vol 4 (S2) ◽  
pp. 304-305
Author(s):  
Christopher Gorman ◽  
Igor Touzov ◽  
Russell Miller
Keyword(s):  
Flat Surface ◽  
Pyrolytic Graphite ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Distinctive Features ◽  
Atomic Force ◽  
Highly Ordered Pyrolytic Graphite ◽  
Organic Functional Groups ◽  
Packing Arrangement

Our group is interested in exploring how functional molecules (e.g. those composed of organic functional groups that do not necessarily lend themselves to an ordered 2D packing arrangement) can form well-ordered adlayers with functional properties. To this end. we have studied the formation of self assembled structures of 5-(N,N-didecyl-amino)-2.4- pentadienal (DAPDA, Figure 1) deposited on a highly ordered pyrolytic graphite (HOPG) surface. This molecule has two distinctive features that should dramatically affect its ordering on a surface. Neither of these have been systematically explored in ordered adlayers. First, the extended conjugation of the molecule gives it a large in-plane dipole moment as well as a high polarizability. Second, it contains two hydrocarbon tails, only one of which can lie coplanar with the conjugated moiety. Both molecularly resolved monolayer and bilayer structures were found using a combination of scanning tunneling microscopy and tapping mode atomic force microscopies.

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