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1
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Oxidation Studies of the Graphite Surface by Scanning Tunneling Microscopy and Photoelectron Spectroscopy

100%
Klusek Z., Phaner M., Krapf P., Porte L.
Acta Physica Polonica A
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1994
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vol. 86
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issue 6
947-954
EN
Scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy were used to study oxidation effects of nitric acid on highly oriented pyrolytic graphite surface. This treatment was performed at different temperatures and etching times with the aim of realizing local binding sites on the surface without creating deep defects. Then these three technics were found in good agreement to characterize the weakly oxidized surface. A wavy structure different from pure graphite at atomic scale was imaged by scanning tunneling microscopy. This modification was correlated to the presence of carboxylic groups on the surface revealed by X-ray photoelectron spectroscopy. Both spectroscopies of scanning tunneling and X-ray photoelectron demonstrated the vanishing of π bands characteristic from sp^{2} graphitic hybridization. This was attributed to dehybridization corresponding to new bondings of the graphite carbons in the carboxylic groups.
2
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Topographic and Energetic Heterogeneity Studies of Oxidized Graphite Surface by Scanning Tunneling Microscopy/Spectroscopy and Photoelectron Spectroscopy

100%
Klusek Z.
Acta Physica Polonica A
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1997
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vol. 91
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issue 3
569-582
EN
Scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy are used to study oxidation effects of nitric acid on a highly-oriented pyrolytic graphite surface. Various etching times at constant temperature are applied in order to create local binding sites on the surface without creating deep defects. A single and paired chains structure, different from pure graphite at atomic scale, is shown by scanning tunneling microscopy. This can be explained by the presence of oxygenate groups on the surface, revealed by X-ray photoelectron spectroscopy. Both scanning tunneling spectroscopy and X-ray photoelectron spectroscopy demonstrate the vanishing of π bands characteristic of sp^{2} graphite hybridization. This, in turn, can be explained by dehybridization related to new bondings of the graphite carbons in the oxygenate groups. An important result of area averaging spectroscopy is the observed energetic heterogeneity considered in terms of the changes of local electronic density of states of the oxidized surface.
3
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Nanostructuring and Hardness Investigations of Thin Films by Scanning Force Microscopy

100%
Nowicki M., Richter A., Ries R., Oszwałdowski M.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
437-441
EN
The scanning force microscope was used to scratch thin films and to write nanoscale pattern on surfaces as well as to perform nanoindentation for hardness measurements. Different thin film materials such as C_{60} films, diamond-like carbon, metals and semiconducting films have been investigated.
4
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Influence of Atomic and Electronic Structure of a Tip on Stm Images

100%
Jurczyszyn L., Mingo N., Flores F.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
307-315
EN
Theoretical studies of the influence of electronic and atomic structure of a tip on scanning tunneling microscopy images are presented. Results are discussed for the scanning of Al(001) and Al(001)+Xe surfaces performed within aluminum and nickel tips of a different geometry.
5
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Surface Investigation by Scanning Tunnelling Microscopy in Liquid Medium

100%
Phaner M., Robach Y., de Villeneuve C., Wojczuk S., Olejniczak W., Porte L.
Acta Physica Polonica A
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1993
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vol. 83
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issue 5
611-619
EN
Scanning tunneling microscopy in liquid environment has gained an increased interest in recent years. The specific features of the in situ observation of surface structures at the solid/liquid interface are first presented. Next, a high resolution imaging of high oriented pyrolytic graphite (HOPG) graphite surface shows the potentiality of our home-made microscope. The last study, performed on technological InP. substrates, illustrates the extensive applications of in situ imaging in the fields of semiconductor technology.
6
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Scanning Tunneling Spectra and Low Energy Ion Scattering Studies of the Verwey Transition in MBE Fe_3O_4 (100) Thin Film

80%
Kim-Ngan N., Soszka W., Hietschold M.
Acta Physica Polonica A
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2001
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vol. 99
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issue 2
267-276
EN
The (100) surface of magnetite Fe_3O_4 thin film was studied by a UHV low-temperature scanning tunneling microscope and by an ion scattering spectroscopy. The tunneling spectra revealed a widening of the gap with decreasing temperature, which may be related to the metal-insulator phase transition in this material. A strong effect of this phase transition on ion scattering from such a surface was observed. The temperature dependence of the scattered ion yield, R^+(T), revealed two minima at around 100 K and at 125 K under Ne^+ bombardment with the primary energy up to 6 keV. The disappearance of the high-temperature minimum at a bombarding energy of 6.5 keV gave a further evidence for the ion velocity dependence of the character of the R^+(T) curve, which has been first observed for a MBE Fe_3O_4 (111) film surface.
7
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Manipulations with Atoms and Clusters

80%
Czajka R.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
813-828
EN
The investigation and fabrication of nanometer-scale structures becomes a reality due to the development of scanning tunneling microscopy and related techniques. The final goal, manipulations with the individual atoms and molecules, has been achieved. D.M. Eigler used the scanning tunneling microscope (working at low temperatures ca. 4 K) to position individual xenon atoms on a single-crystal nickel surface with atomic precision. Mesoscopic systems composed of metallic or non-metallic clusters are intensively studied because of their new and interesting properties, and perspectives of subsequent application in nanolithography in order to create various structures of a very high degree of miniaturization. In this review, (i) the potential of scanning probe microscopes for revealing subtle details of surfaces down to atomic resolution is presented, (ii) a variety of different atomic manipulations processes and other surface modifications are reviewed against the background of different, more or less universal approaches, and finally (iii) a few examples of cluster surface structures created and/or modified by means of scanning tunneling microscope are demonstrated.
8
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Photostriction of CdF_{2}:In Crystals

80%
Suchocki A., Raułuszkiewicz J., Langer J., Koziarska-Glinka B.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
1005-1008
EN
Lattice relaxation accompanying phototransformation of In bistable centers from the ground, deep state to the shallow state in CdF_{2} crystal has been measured with the use of scanning tunnelling microscope. It is shown that relatively small macroscopic changes of the crystal length in the order of 1.8×10^{-6} accompany the phototransformation of In ions. Lattice expansion upon the influence of population of shallow donor levels in CdF_{2} explains the observed small changes of lattice constant during the process.
9
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Scanning Tunneling Spectroscopy Sensitive to Layer Structure of BSCCO

80%
Aleszkiewicz M., Aleszkiewicz P., Raułuszkiewicz J.
Acta Physica Polonica A
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1997
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vol. 91
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issue 3
597-604
EN
Scanning tunneling microscopy images and scanning tunneling spectroscopy characteristics were measured at 4.2 K in liquid helium bath on the cleaved in air a-b surface of Bi_{2}Sr_{2}CaCu_{2}O_{8} (BSCCO-2212). Electronic densities of states and superconductivity parameters Δ and Γ evaluated from dI/dV characteristics depend on tip-sample distance s: with shortening of the distance s superconducting gap structure becomes more distinct, i.e. Δ increases and Γ decreases. We explain this phenomenon as a non-vacuum tunneling, where for longer s tunneling electrons reach only the surface contamination layer on non-metallic BiO top-surface layer, whereas for shorter s tunneling electrons penetrate also deeper lying CuO layers reflecting their superconducting properties. The dependence of Δ on s is evaluated. This result allows to understand better the non-vacuum scanning tunneling microscopy imaging: by adjusting properly the tip-sample distance one can select suitable local density of states contributing dominantly to the scanning tunneling microscopy images taken on BSCCO.
10
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Scanning Force Microscopy on Laser Ablated Silicon Nitride Films

80%
Vrînceanu C., Flueraru C., Dinescu M., Vasile E.
Acta Physica Polonica A
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1997
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vol. 91
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issue 5
1009-1014
EN
The following paper presents a study on laser-ablated silicon nitride films, obtained by the laser reactive ablation method. The aim of this paper is to investigate silicon nitride film surfaces, first by scanning electron microscopy and then, at a better resolution and a greater magnification, by the scanning (atomic) force microscopy technique.
11
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Near Field Optical Microscopy and Spectroscopy with STM and AFM Probes

80%
Bergossi O., Bachelot R., Wioland H., Wurtz G., Laddada R., Adam P., Bijeon J., Royer P.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
393-398
EN
This article deals with a new generation of scanning near field optical microscopes (SNOM), called apertureless SNOM, based on metallic, semi-conductive or dielectric probes. The classification of the apertureless probe among the usual SNOM probes is discussed in the first part. Then, we present the different apertureless SNOM configurations that we develop, with various commercial AFM and home-made tungsten tips, and several illumination and collection modes. Finally, after a preliminary result in near field imaging, we propose a promising application of such microscopes dedicated to the near field fluorescence spectroscopy.
12
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STM/AFM Images and Tunneling Spectra of Nd_{2-x}Ce_{x}CuO_{4-y} Single Crystals

80%
Susła B., Sadowski W., Klimczuk T., Czajka R.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
209-214
EN
The results of the scanning tunneling microscopy and spectroscopy as well as atomic force microscopy measurements on the Nd_{2-x}Ce_{x}CuO_{4-y} single crystals in ambient conditions are reported. Using the scanning tunneling microscopy we were able to modify the Nd_{2-x}Ce_{x}CuO_{4-y} ab-plane in air under the conditions of sample bias voltage V_{t}=500 mV and set current I_{s}=0.3 nA. It is possible to prepare atomically flat and clean surfaces as well as to create new structures in a nanometer scale in these electron-doped materials. The similar processes were not observed during atomic force microscopy imaging.
13
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Resonant Tunneling Through Discrete Electronic Levels of a C_{60} Molecule in the Presence of Charging Effects

80%
Millo O., Levi Y., Porath D.
|
EN
We have conducted tunneling spectroscopy studies for isolated C_{60} molecules in the double barrier tunnel junction configuration. The tunneling current-voltage (I-V) and dI/dV vs. V spectra of these molecules exhibit rich structures resulting from both resonant tunneling through the discrete levels and single electron charging effects. In particular, we observe degeneracy lifting within the molecular orbitals, probably due to the Jahn-Teller effect and local electric fields. Theoretical fits, performed using the "orthodox" model for single-electron tunneling modified to account for the discrete level spectrum of C_{60}, agree well with our data.
14
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STM Studies of the Proximity Effect in Superconducting Wires with Artificial Pinning Centers

80%
Levi Y., Millo O., Rizzo N., Prober D., Motowidlo L.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
425-430
EN
Scanning tunneling microscopy and spectroscopy were applied to study the proximity effect with nanometer spatial resolution. The measurements were conducted on novel superconducting wires, which consist of an ordered array of submicron diameter normal metal filaments (Cu, Ni) embedded in a superconducting (NbTi) matrix. Spatially resolved information about the local density of states is obtained by taking I-V curves simultaneously with topographic images. Our data provide direct evidence on the interplay between the normal and superconducting constituents in the vicinity of the interface between them.
15
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Scanning Tunneling Microscopy/Spectroscopy Investigations of the Interference Effects Caused by the Circular Pits on the Thermally Oxidized graphite Surface

80%
Klusek Z., Kalinowski M., Olejniczak W., Kobierski P.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
415-420
EN
The thermal oxidation of the graphite leads to the removal of monoatomic carbon layers from the surface and formation of circular pits on the exposed plane. Near the pit edges the scanning tunneling spectroscopy measurements show a series of very narrow flat regions on the I/V characteristics. The observed I/V flat regions appear only when the characteristic is recorded very close to the pit edges. The appearance of tunneling current steps can be explained by the oscillating character of the local density of states near the pit edges. A simple quantum mechanical model in 2D based on boundary condition for an electron wave function is proposed.
16
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Mechanisms of Yellow and Red Photoluminescence in Wurtzite and Cubic GaN

80%
Godlewski M., Suski T., Grzegory I., Porowski S., Langer R., Barski A., Bergman J., Monemar B., Goldys E., Phillips M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
326-330
EN
The origin of two "deep" photoluminescence (PL) emissions observed in wurtzite (yellow PL) and cubic (red PL) GaN is discussed. PL and time-resolved PL studies confirm donor-acceptor pair character of the yellow band in wurtzite GaN and point to participation of shallow donors in this emission. A similar PL mechanism is proposed for the red emission of cubic GaN. We further show a puzzling property of both yellow and red PLs. Both yellow and red emissions show spatial homogeneity and are only weakly dependent on surface morphology.
17
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STM Observations of Ferromagnetic Clusters

80%
Wawro A., Kasuya A.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
443-448
EN
Co, Fe and Ni clusters of nanometer size, deposited on silicon and graphite (highly oriented pyrolytic graphite), were observed by a scanning tunneling microscope. Deposition as well as the scanning tunneling microscope measurements were carried out in an ultrahigh vacuum system at room temperature. Detailed analysis of Co cluster height was done with the scanning tunneling microscope equipped with a ferromagnetic tip in the magnetic field up to 70 Oe. It is found that bigger clusters (few nanometers in height) exhibit a dependence of their apparent height on applied magnetic field. We propose that such behaviour originates from the ferromagnetic ordering of cluster and associate this effect to spin polarized tunneling.
18
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Morphology and Optical Properties of Laser-Assisted Chemical Vapour Deposited GaN

80%
Goldys E., Godlewski M., Tansley T.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
331-335
EN
Properties of GaN epilayers grown by laser-assisted chemical vapour deposition are discussed. Good crystallinity and surface morphology of the films is demonstrated. Micro-Raman spectra are explained by scattering by small, randomly oriented cubic phase units present in the GaN film.
19
Content available remote

Scanning Tunneling Microscopy of Ordered Organic Monolayer Films on Si(001)

80%
Hamers R., Hovis J., Liu H.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
289-295
EN
Scanning tunneling microscopy and optical spectroscopy techniques have been utilized to investigate the formation of ordered organic monolayer films on the (001) face of silicon. Cyclopentene and 1,5-cyclooctadiene both produce monolayer films that are ordered translationally and rotationally. The rotational orientations of the molecules arise from the directional interaction of the π orbitals of the starting alkene with the π orbital of the dimers comprising the reconstructed Si(001) surface, with the Si(001) surface acting as a template for determining the directionality of molecules in the subsequent organic film. Using single-domain Si(001) samples, it is shown that the molecular films also exhibit anisotropy in optical properties when measured on centimeter length scales.
20
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Spatially Resolved Chemistry on Bimetallic Surfaces

80%
Behm R.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
259-272
EN
The local chemical properties of bimetallic surfaces, which are often drastically different from those of each of the components, will be discussed. Using CO adsorption as a probe molecule it will be shown for two model systems, Au/Pd(111) and Pt/Ru(0001), that their chemical properties depend decisively on the local surface structure and that the correct interpretation of area integrating spectroscopic and kinetic data obtained from such surfaces requires detailed knowledge of their (defect) structure and of the distribution of the different components in the surface layer. It will further be shown that information on the local chemical properties of specific structural elements such as monolayer islands and monolayer island edges, and specific surface ensembles can be gained by applying high resolution scanning tunneling microscopy imaging and area integrating spectroscopic techniques in combination to bimetallic surfaces whose morphology and composition is varied in a systematic and controlled way. Based on experimental results adsorption on a monolayer A / substrate B system is suggested as a model for gaining information on the modifications in chemical properties of AB alloy surfaces due to metal-metal interactions.
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