1991 - 1995

Photon emission induced by the scanning tunneling microscope
R. Berndt, Scanning Microsc. 9, 687 (1995)
[BibTeX]
@article{RBE_SCMI95,
  author = {R. Berndt},
  title = {Photon emission induced by the scanning tunneling microscope},
  journal = {Scanning Microscopy},
  volume = {9},
  pages = {687--693},	
  year = {1995}
}
 
 
Apparent superstructures in scanning tunneling microscopy
J. Li, R. Berndt, W.-D. Schneider, Appl. Phys. Lett. 67, 921 (1995)

Abstract:
Apparent superstructures have been observed with scanning tunneling microscopy (STM) on well-ordered Ag(110) surfaces. These superstructures are due to the discrete sampling of the atomic corrugation in STM. Such sampling effects may explain superstructures observed previously with STM on graphite surfaces.

[BibTeX]
@article{JTL_APL95,
  author = {J. Li and R. Berndt and W.-D. Schneider},
  title = {Apparent superstructures in scanning tunneling microscopy},
  journal = {Appl. Phys. Lett.},
  volume = {67},
  pages = {921--923},	
  year = {1995},
  url = {http://link.aip.org/link/?APL/67/921},
  doi = {http://doi.org/10.1063/1.114695}
}
 
 
Scanning Probe Microscopies with Multiple Interactions
R. Berndt, in Photons and Local Probes, O.M. und R. Möller (Hrsg.) NATO ASI Series E 300, 209-214 (Kluwer, Dordrecht, 1995)

Abstract:
A low-temperature ultra-high vacuum scanning tunneling microscope (STM) is used to excite photon emission from Au(110) surfaces. In the detected photon intensity the (1x2) reconstruction of the Au surface is clearly resolved. This first observation of atomic resolution in STM-induced photon emission is interpreted in terms of local variations of the electromagnetic interaction of tip and sample occurring at constant tunneling current. Similar effects are expected to affect other scanning probe methods, in particular those involving photons. On this background molecularly resolved photon maps of C60 monolayers are discussed.

[BibTeX]
@inbook{RBE_NASI95,
  author = {R. Berndt},
  chapter = {Scanning Probe Microscopies with Multiple Interactions},
  title = {Photons and Local Probes},
  editor = {O. Marti und R. Möller},
  series = {NATO ASI Series E},
  volume = {300},
  pages = {209--214},
  publisher = {Kluwer, Dordrecht},	
  year = {1995},
  url = {http://dx.doi.org/10.1007/978-94-011-0423-4_17},
  doi = {http://doi.org/10.1007/978-94-011-0423-4},
  isbn = {978-94-011-0423-4}
}
 
 
Atomic resolution in photon emission induced by a scanning tunneling microscope
R. Berndt, R. Gaisch, W.-D. Schneider, J. Gimzewski, B. Reihl, R. Schlittler, M. Tschudy, Phys. Rev. Lett. 74, 102 (1995)

Abstract:
A low-temperature ultrahigh-vacuum scanning tunneling microscope (STM) is used to excite photon emission from Au(110) surfaces. In the detected photon intensity the (1 × 2) reconstruction of the Au surface is clearly resolved. This first observation of atomic resolution in STM-induced photon emission is interpreted in terms of local variations of the electromagnetic interaction of tip and sample occurring at constant tunneling current. Similar effects are expected to affect other scanning probe methods, in particular those involving photons.

[BibTeX]
@article{RBE_PRL95,
  author = {R. Berndt and R. Gaisch and W.-D. Schneider and J.K. Gimzewski and B. Reihl and R.R. Schlittler and M. Tschudy},
  title = {Atomic resolution in photon emission induced by a scanning tunneling microscope},
  journal = {Phys. Rev. Lett.},
  volume = {74},
  pages = {102--105},	
  year = {1995},
  url = {http://link.aps.org/abstract/PRL/v74/p102},
  doi = {http://doi.org/10.1103/PhysRevLett.74.102}
}
 
 
Photon emission from C_60 in a nanoscopic cavity
R. Berndt, J. Gimzewski, Proc. NATO Advanced Research Workshop: "Scanning probe microscopies and molecular materials", Schloß Ringberg, Tegernsee, 29.5.-3.6.1994, (Dokumentenserver der HU Berlin, 1994)

Abstract:
We discuss properties of C_60 in an STM tunnel junction probed by elastic and inelastic tunneling. In particular, the interaction of the molecule with the metallic nanoscopic cavity comprised of tip and sample is considered. Molecular resolution in photon emission from C_60 monolayers is interpreted in these terms, and we address the extent to which photon emission from C_60 reflects properties of the cavity and of the molecule itself. We propose that the properties Of C_60 in such an environment are further modified with respect to its adsorbed state on a surface.

[BibTeX]
@inproceedings{RBE_NARW94,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Photon emission from C_60  in a nanoscopic cavity},
  booktitle = {Proc. NATO Advanced Research Workshop: "Scanning probe microscopies and molecular materials"},
  publisher = {Dokumentenserver der HU Berlin},
  address = {Schloß Ringberg, Tegernsee},
  period = {29.5.-3.6.1994},	
  year = {1994},
  url = {http://dochost.rz.hu-berlin.de/conferences/conf1/conference-liste.html}
}
 
 
Internal structure of C_60 on Au(110) as observed by low-temperature scanning tunneling microscopy
R. Gaisch, R. Berndt, W.-D. Schneider, J. Gimzewski, B. Reihl, R. Schlittler, M. Tschudy, J. Vac. Sci. Technol. B 12, 2153 (1994)

Abstract:
Scanning tunneling microscopy (STM) studies of C_60 molecules on a Au(110) single crystal surface have been performed in ultrahigh vacuum and at low temperatures (5 and 50 K). Submonolayer, monolayer, and bilayer coverages of C_60 have been sublimated onto reconstructed Au(110) 1 × 2 surfaces. STM images reveal ordered C_60 overlayers which are commensurate with the atomic geometry of the substrate. Moreover, we have observed intramolecular patterns within single C_60 molecules in unordered and ordered arrays of C_60 in the first as well as in the second adsorption layer which may be associated with different orientations of the fullerenes on the highly corrugated gold substrate.

[BibTeX]
@article{ROG_JVSTB94,
  author = {R. Gaisch and R. Berndt and W.-D. Schneider and J.K. Gimzewski and B. Reihl and R.R. Schlittler and M. Tschudy},
  title = {Internal structure of C_60  on Au(110) as observed by low-temperature scanning tunneling microscopy},
  journal = {J. Vac. Sci. Technol. B},
  volume = {12},
  pages = {2153--2155},	
  year = {1994},
  url = {http://link.aip.org/link/?JVB/12/2153},
  doi = {http://doi.org/10.1116/1.587729}
}
 
 
Bias-dependent STM images of oxygen-induced structures on Ti(0001) facets
R. Berndt, J. Gimzewski, R. Schlittler, Surf. Sci. 310, 85 (1994)

Abstract:
Titanium films grown on Si(111) surfaces in ultra-high vacuum were investigated using scanning tunneling microscopy (STM). STM images of adsorbate structures induced by oxygen adsorption on Ti(0001) facets are observed to change from protrusions to depressions depending on the applied bias voltage. Using electron spectroscopic data we interpret our results in terms of local, oxygen-induced modifications of the density of states.

[BibTeX]
@article{RBE_SSI94_2,
  author = {R. Berndt and J.K. Gimzewski and R.R. Schlittler},
  title = {Bias-dependent STM images of oxygen-induced structures on Ti(0001) facets},
  journal = {Surf. Sci.},
  volume = {310},
  pages = {85--88},	
  year = {1994},
  url = {http://dx.doi.org/10.1016/0039-6028(94)91373-0},
  doi = {http://doi.org/10.1016/0039-6028(94)91373-0}
}
 
 
Low-temperature scanning tunneling microscopy
B. Reihl, J. Gimzewski, R. Schlittler, M. Tschudy R. Berndt, R. Gaisch, W.-D. Schneider, Physica B 197, 64 (1994)

Abstract:
The novel technique of low-temperature scanning tunneling microscopy is used to study conventional and high-T_c superconductors (spatial identification and distribution of the superconducting gap, vortex movement, etc.), but also custom-designed materials which are unstable at room temperature, e.g. xenon layers and size-selected clusters, or species whose rotational or vibrational movements have to be frozen in to achieve atomic resolution. We present the specific design and advantages of our low-temperature ultra-high vacuum scanning tunneling microscope along with recent results on the internal structure of buck fullerene molecules and their photon emitting properties.

[BibTeX]
@article{BRL_PCB94,
  author = {B. Reihl and J.K. Gimzewski and R.R. Schlittler and M. Tschudy and R. Berndt and R. Gaisch and W.-D. Schneider},
  title = {Low-temperature scanning tunneling microscopy},
  journal = {Physica B},
  volume = {197},
  pages = {64--71},	
  year = {1994},
  url = {http://dx.doi.org/10.1016/0921-4526(94)90199-6},
  doi = {http://doi.org/10.1016/0921-4526(94)90199-6}
}
 
 
Sub-nanometer lateral resolution in photon emission from C_60 molecules on Au(110)
R. Berndt, R. Gaisch, W.-D. Schneider, J. Gimzewski, B. Reihl, R. Schlittler, M. Tschudy, Surf. Sci. 307-309, 1033 (1994)

Abstract:
We have used a scanning tunneling microscope (STM) as a local electron source to excite photon emission from ordered monolayers of C_60 molecules on Au (110) surfaces. In maps of the STM stimulated photon emission the C_60 molecules have been spatially resolved. The photon emission is most intense when the tip is centered above a molecule. The diameter of the emission spot is approximately 4 The results demonstrate the highest spatial resolution of light emission to date using a scanning probe technique.

[BibTeX]
@article{RBE_SSI94,
  author = {R. Berndt and R. Gaisch and W.-D. Schneider and J.K. Gimzewski and B. Reihl and R.R. Schlittler and M. Tschudy},
  title = {Sub-nanometer lateral resolution in photon emission from C_60  molecules on Au(110)},
  journal = {Surf. Sci.},
  volume = {307-309},
  pages = {1033--1037},	
  year = {1994},
  url = {http://dx.doi.org/10.1016/0039-6028(94)91535-0},
  doi = {http://doi.org/10.1016/0039-6028(94)91535-0}
}
 
 
Photon emission from nanostructures in a STM
R. Berndt, J. Gimzewski, R. Schlittler, Nanostruct. Mater. 3, 345 (1993)

Abstract:
Using an STM we have created and investigated individual small particles with apparent lateral dimensions between 10 Å and 250 Å on metal single-crystal surfaces and metallic films. These particles are clearly observed in simultaneous measurements of STM topographs and emissions of photons from the tunneling gap. The particles give rise to order-of-magnitude variations in photon intensity with subnanometer lateral resolution. We interpret the observed photon emission characteristics in term of ineleastic tunneling excitation of tip-induced, localised plasmon modes.

[BibTeX]
@article{RBE_NMA93,
  author = {R. Berndt and J.K. Gimzewski and R.R. Schlittler},
  title = {Photon emission from nanostructures in a STM},
  journal = {Nanostructured Materials},
  volume = {3},
  pages = {345--348},	
  year = {1993},
  url = {http://dx.doi.org/10.1016/0965-9773(93)90097-U},
  doi = {http://doi.org/10.1016/0965-9773(93)90097-U}
}
 
 
Photon emission from adsorbed C_60 molecules with sub-nanometer lateral resolution
R. Berndt, R. Gaisch, J. Gimzewski, B. Reihl, R. Schlittler, W.-D. Schneider, M. Tschudy, Appl. Phys. A 57, 513 (1993)

Abstract:
We present the first experimental demonstration of spatially resolved photon emission of individual molecules on a surface. A scanning tunneling microscope (STM) was used as a local electron source to excite photon emission from hexagonal arrays of C_60 molecules on Au(110) surfaces. Specifically, we show that in maps of photon emission intensities, C_60 fullerenes appear as arrays of individual light emitters 4 Å in diameter and separated by 10 Comparison with simultaneously recorded STM images reveals, that most intense emission is detected when the STM tip is centered above a molecule. The results demonstrate the highest spatial resolution of light emission to date using a scanning probe technique.

[BibTeX]
@article{RBE_APA93,
  author = {R. Berndt and R. Gaisch and J.K. Gimzewski and B. Reihl and R.R. Schlittler and W.-D. Schneider and M. Tschudy},
  title = {Photon emission from adsorbed C_60  molecules with sub-nanometer lateral resolution},
  journal = {Appl. Phys. A},
  volume = {57},
  pages = {513--516},	
  year = {1993},
  url = {http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/BF00331750},
  doi = {http://doi.org/10.1007/BF00331750}
}
 
 
Electromagnetic interaction of metallic objects in nanometer proximity
R. Berndt, J. Gimzewski, P. Johansson, Phys. Rev. Lett. 71, 3493 (1993)

Abstract:
The chemical and proximity dependence of electromagnetic interactions of various metallic bodies at nanometer separations is probed through photon emission from a scanning tunneling microscope. The role of local dielectric properties is determined and the strength of the electromagnetic coupling in the cavity between tip and sample is investigated. The experimental results compare well with model calculations and show the relative role of the dielectric functions of both electrodes as well as the influence of proximity.

[BibTeX]
@article{RBE_PRL93,
  author = {R. Berndt and J.K. Gimzewski and P. Johansson},
  title = {Electromagnetic interaction of metallic objects in nanometer proximity},
  journal = {Phys. Rev. Lett.},
  volume = {71},
  pages = {3493--3497},	
  year = {1993},
  url = {http://link.aps.org/abstract/PRL/v71/p3493},
  doi = {http://doi.org/10.1103/PhysRevLett.71.3493}
}
 
 
Photon emission at molecular resolution induced by a scanning tunneling microscope
R. Berndt, R. Gaisch, J. Gimzewski, B. Reihl, R. Schlittler, W.-D. Schneider, M. Tschudy, Science 262, 1425 (1993)

Abstract:
The tip-surface region of a scanning tunneling microscope (STM) emits light when the energy of the tunneling electrons is sufficient to excite luminescent processes. These processes provide access to dynamic aspects of the local electronic structure which are not directly amenable to conventional STM experiments. From monolayer films of buck fullerenes on Gold(110) surfaces intense emission is observed when the STM tip is placed above an individual molecule. The diameter of this emission spot associated with buck is approximately 4 Å. These results demonstrate the highest spatial resolution of light emission to date using a scanning probe technique.

[BibTeX]
@article{RBE_SCI93,
  author = {R. Berndt and R. Gaisch and J.K. Gimzewski and B. Reihl and R.R. Schlittler and W.-D. Schneider and M. Tschudy},
  title = {Photon emission at molecular resolution induced by a scanning tunneling microscope},
  journal = {Science},
  volume = {262},
  pages = {1425--1427},	
  year = {1993},
  url = {http://dx.doi.org/10.1126/science.262.5138.1425},
  doi = {http://doi.org/10.1126/science.262.5138.1425}
}
 
 
Photon emission in sannning tunneling microscopy: interpretation of photon maps of metallic systems
R. Berndt, J. Gimzewski, Phys. Rev. B 48, 4746 (1993)

Abstract:
We analyze maps of the integral photon intensity emitted from the tunneling gap of a scanning tunneling microscope obtained simultaneously with topography from a variety of metal films and single crystal surfaces in UHV. The effects of adsorbates and structures created with the scanning tunneling microscope on their local photon emission properties are investigated to explore the potential of the technique for chemical mapping. It is proposed that contrasts in photon maps on a scale of some tens of nanometers are attributable to local variations in the field strength of tip-induced plasmon modes which are determined by the surface geometry of the junction and its dielectric properties. On a (sub)nanometer scale, a second contrast mechanism is observed to occur, consistent with geometry-induced variations in the matrix element for inelastic tunneling. A comparison of electron spectroscopic data with bias-dependent photon maps indicates that contrasts on a subnanometer scale are further mediated by local modifications of the density of final states positioned one quantum of energy (h nu) below the bottom of the elastic tunneling channel with respect to the Fermi level. These three mechanisms provide a framework for the interpretation of photon maps obtained on metallic systems.

[BibTeX]
@article{RBE_PRB93,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Photon emission in sannning tunneling microscopy: interpretation of photon maps of metallic systems},
  journal = {Phys. Rev. B},
  volume = {48},
  pages = {4746--4754},	
  year = {1993},
  note = {reprinted in SPIE Milestone Series 107, 376 (1995)},
  url = {http://link.aps.org/abstract/PRB/v48/p4746},
  doi = {http://doi.org/10.1103/PhysRevB.48.4746}
}
 
reprinted in SPIE Milestone Series 107, 376 (1995)
 
Internal structure of C_60 fullerene molecules as revealed by low temperature scanning tunneling microscopy
R. Gaisch, R. Berndt, J. Gimzewski, B. Reihl, R. Schlittler, W.-D. Schneider, M. Tschudy, Appl. Phys. A 57, 207 (1993)

Abstract:
We have performed Scanning Tunneling Microscopy (STM) in ultra-high vacuum at low temperatures (5 and 50K) of unordered and ordered C_60 layers adsorbed on a Au(110) surface. STM topographs of the frozen C_60 molecules reveal four symmetric patterns within single molecules, which may be associated with different orientations of the fullerenes on a highly corrugated gold substrate.

[BibTeX]
@article{ROG_APA93,
  author = {R. Gaisch and R. Berndt and J.K. Gimzewski and B. Reihl and R.R. Schlittler and W.-D. Schneider and M. Tschudy},
  title = {Internal structure of C_60  fullerene molecules as revealed by low temperature scanning tunneling microscopy},
  journal = {Appl. Phys. A},
  volume = {57},
  pages = {207--208},	
  year = {1993},
  url = {http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/BF00331447},
  doi = {http://doi.org/10.1007/BF00331447}
}
 
 
Characterization and application of nanoscale artifacts in scanning tunneling microscopy
R. Berndt, J. Gimzewski, in Atomic and Nanoscale modification of materials, P. Avouris (Hrsg.) NATO ASI Series E 239, 327-335 (Kluwer, Dordrecht, 1993)

Abstract:
We describe various experiments in which nanostructures fabricated with the tip of a scanning tunneling microscope are utilized as tools. These artifacts serve as geometric and electronic reference structures and as model systems for photon emission experiments to probe local electromagnetic fields and inelastic tunneling processes. We apply bias-dependent imaging and photon emission from the STM to deduce chemical information on nanostructures and the STM tip.

[BibTeX]
@inbook{RBE_NASI93,
  author = {R. Berndt and J.K. Gimzewski},
  chapter = {Characterization and application of nanoscale artifacts in scanning tunneling microscopy},
  title = {Atomic and Nanoscale modification of materials},
  editor = {Ph. Avouris},
  series = {NATO ASI Series E},
  volume = {239},
  pages = {327--335},
  publisher = {Kluwer, Dordrecht},	
  year = {1993},
  url = {http://dx.doi.org/10.1007/978-94-011-2024-1_29},
  doi = {http://doi.org/10.1007/978-94-011-2024-1},
  isbn = {978-94-011-2024-1}
}
 
 
Photon emission from small particles in a STM
R. Berndt, J. Gimzewski, Z. Phys. D 26 S, 87 (1993)

Abstract:
Various experiments in which we fabricate nanostructures and then utilize them for local experiments are described. In the examples presented structures are used as atomic markers to observe temporal changes on Au(110)(1×2) surfaces, as electronic markers on oxidized Ti (0001) facets, and as a local probe for electromagnetic field enhancement and inelastic tunneling on a variety of metal and adsorbate systems. Local optical/uv analysis of structures on Cu(111) surfaces is found to be related to the fabrication technique. We illustrate that the combination of fabrication and manipulation, together with the ability to experiment using a range of physical phenomena on the local scale, can provide a significant contribution to scanning probe microscopies and the development of nanoscale science. In particular the importance of and prospects for obtaining local chemical information are addressed.

[BibTeX]
@article{RBE_ZPD93,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Photon emission from small particles in a STM},
  journal = {Z. Phys. D},
  volume = {26 S},
  pages = {87--88},	
  year = {1993},
  url = {http://dx.doi.org/10.1007/BF01425626},
  doi = {http://doi.org/10.1007/BF01425626}
}
 
 
Photon emission from transition metal surfaces in scanning tunneling microscopy
R. Berndt, J. Gimzewski, Int. J. Mod. Phys. B 7, 516 (1993)

Abstract:
Light emission from noble metal surfaces excited by a scanning tunneling microscope has been interpreted as arising from in elastic tunneling excitation of tip-induced plasmon modes. We have extended this work to study the adsorption of oxygen on Ti and have observed the formation of structures with subnanometer lateral dimensions which give rise to clear contrasts in STM topographs and photon intensity maps. The experimental results strongly indicate that these contrasts are due to oxygen-induced variations of the local density of states.

[BibTeX]
@article{RBE_IJPB93,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Photon emission from transition metal surfaces in scanning tunneling microscopy},
  journal = {Int. J. Mod. Phys. B},
  volume = {7},
  pages = {516--519},	
  year = {1993},
  url = {http://dx.doi.org/10.1142/S0217979293001086},
  doi = {http://doi.org/10.1142/S0217979293001086}
}
 
 
Optical Spectroscopy and Microscopy Using Scanning Tunneling Microscopy
J. Gimzewski, R. Berndt, R. Schlittler, A. McKinnon, M. Welland, T. Wong, P. Dumas, M. Gu, C. Syrykh, F. Salvan, A. Hallimaoui, in Near Field Optics, D.P. und D. Courjon (Hrsg.) NATO ASI Series E 242, 333-340 (Kluwer, Dordrecht, 1993)

Abstract:
Light, emission arising from an electron making a transition between two energy levels provides one of the most important sources of information on the electronic structure of matter. In optical microscopy and spectroscopy, the spatial resolution achievable is generally limited by the wavelength of the photons involved. Two approaches developed to overcome this limitation are near-field optic probes to spatially confine the electromagnetic fields used and the use of sub-nm sized electron excitation probes. The latter approach, developed by us using the STM, has similarities and differences with the former approach which forms the main part of the present workshop. We discuss the technique with examples of optical spectroscopy and, comparisons of topography and photon maps for metal, semiconductor and adsorbate systems.

[BibTeX]
@inbook{GIM_NASI93_2,
  author = {J.K. Gimzewski and R. Berndt and R.R. Schlittler and A.W. McKinnon and M.E. Welland and T.M.H. Wong and Ph. Dumas and M. Gu and C. Syrykh and F. Salvan and A. Hallimaoui},
  chapter = {Optical Spectroscopy and Microscopy Using Scanning Tunneling Microscopy},
  title = {Near Field Optics},
  editor = {D.W. Pohl und D. Courjon},
  series = {NATO ASI Series E},
  volume = {242},
  pages = {333--340},
  publisher = {Kluwer, Dordrecht},	
  year = {1993},
  url = {http://dx.doi.org/10.1007/978-94-011-1978-8_38},
  doi = {http://doi.org/10.1007/978-94-011-1978-8},
  isbn = {978-94-011-1978-8}
}
 
 
Local experiments using nanofabricated structures in scanning tunneling microscopy
J. Gimzewski, R. Berndt, R. Schlittler, in Nanosources and Manipulation of Atoms under High Fields and Temperatures: Applications, V. Binh, N. Garcia and K. Dransfeld (Hrsg.) NATO ASI Series E 235, 219-228 (Kluwer, Dordrecht, 1993)

Abstract:
Various experiments in which we fabricate nanostructures and then utilize them for local experiments are described. In the examples presented structures are used as atomic markers to observe temporal changes on Au(110)(1×2) surfaces, as electronic markers on oxidized Ti (0001) facets, and as a local probe for electromagnetic field enhancement and inelastic tunneling on a variety of metal and adsorbate systems. Local optical/uv analysis of structures on Cu(111) surfaces is found to be related to the fabrication technique. We illustrate that the combination of fabrication and manipulation, together with the ability to experiment using a range of physical phenomena on the local scale, can provide a significant contribution to scanning probe microscopies and the development of nanoscale science. In particular the importance of and prospects for obtaining local chemical information are addressed.

[BibTeX]
@inbook{GIM_NASI93,
  author = {J.K. Gimzewski and R. Berndt and R.R. Schlittler},
  chapter = {Local experiments using nanofabricated structures in scanning tunneling microscopy},
  title = {Nanosources and Manipulation of Atoms under High Fields and Temperatures: Applications},
  editor = {V.T. Binh and N. Garcia and K. Dransfeld},
  series = {NATO ASI Series E},
  volume = {235},
  pages = {219--228},
  publisher = {Kluwer, Dordrecht},	
  year = {1993},
  url = {http://dx.doi.org/10.1007/978-94-011-1729-6_19},
  doi = {http://doi.org/10.1007/978-94-011-1729-6},
  isbn = {978-94-011-1729-6}
}
 
 
Isochromat spectroscopy of photons emitted from metal surfaces in STM
R. Berndt, J. Gimzewski, Ann. Phys. 505, Issue 2, 133 (1993)

Abstract:
The pronounced variation of the intensity of photons emitted from the tunneling gap of an STM with respect to the applied bias voltage V_t is studied experimentally using simultaneous measurements of tunneling characteristics and photon emission. We show that the structure in isochromat photon spectra are determined by the following: bias-dependent changes in tunneling characteristics, density of initial and final states, and modifications of tip-induced plasmon modes. It is demonstrated that isochromat spectra provide a conclusive test for the inelastic tunneling mechanism. Coupling between tunneling electrons and tip-induced plasmon modes which gives rise to the intense photon emission observed is discussed within this model.

[BibTeX]
@article{RBE_ANP93,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Isochromat spectroscopy of photons emitted from metal surfaces in STM},
  journal = {Ann. Phys.},
  volume = {505, Issue 2},
  pages = {133--140},	
  year = {1993},
  url = {http://www3.interscience.wiley.com/cgi-bin/abstract/112480530/ABSTRACT},
  doi = {http://doi.org/10.1002/andp.19935050205}
}
 
 
Aspects of photon emission from metallic surfaces in scanning tunneling microscopy
R. Berndt, J. Gimzewski, Physica Status Solidi A: Applications and Material Science 131, 31 (1992)
[BibTeX]
@article{RBE_PSSA92,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Aspects of photon emission from metallic surfaces in scanning tunneling microscopy},
  journal = {Physica Status Solidi A: Applications and Material Science},
  volume = {131},
  pages = {31},	
  year = {1992},
  url = {http://dx.doi.org/10.1002/pssa.2211310107},
  doi = {http://doi.org/10.1002/pssa.2211310107}
}
 
 
Injection luminescence from CdS (1120) studied with STM
R. Berndt, J. Gimzewski, Phys. Rev. B 45, 14095 (1992)

Abstract:
We have used a scanning tunneling microscope tip as source for both electrons and holes to study injection luminescence from CdS (1120) surfaces cleaved in UHV. Band gap radiation and emission from radiative deep levels are resolved in optical spectra. Isochromat spectra of photon intensity as a function of negative tip voltage exhibit discrete steps which are discussed in terms of pair creation thresholds. For positive polarities hole creation in the valence band results in continuous increase in luminescence with a threshold of ≈ 2.5 V. Spatial maps of the resulting integrated light intensity acquired simultaneously with the conventional topographic image reveal image contrasts on the subnanometer scale which are attributed to defects such as dislocations or radiative deep levels.

[BibTeX]
@article{RBE_PRB92,
  author = {R. Berndt and J.K. Gimzewski},
  title = {Injection luminescence from CdS (1120) studied with STM},
  journal = {Phys. Rev. B},
  volume = {45},
  pages = {14095--14099},	
  year = {1992},
  url = {http://link.aps.org/abstract/PRB/v45/p14095},
  doi = {http://doi.org/10.1103/PhysRevB.45.14095}
}
 
 
Observation of local photoemission using a scanning tunneling microscope
J. Gimzewski, R. Berndt, R. Schlittler, Ultramicroscopy 42--44, 366 (1992)

Abstract:
We report photoelectron emission characteristics from cesiated gold (110) surfaces illuminated by photons using the tip of a scanning tunneling microscope as a local probe. An analysis of tip current as a function of applied bias permits determination of the maximum kinetic energy of impinging photoelectrons whose value is in good agreement with an independent analysis based on macroscopic measurements of the surface workfunction. Based on our preliminary results, possible schemes for the fabrication of local probe photoelectron analysers for use with synchrotron or laser illumination are developed. Additional physical considerations suggest that liquid environmnts should in particular introduce a useful exponential dependence of the elastic photoemission signal intensity on tip-surface separation.

[BibTeX]
@article{GIM_UMI92,
  author = {J.K. Gimzewski and R. Berndt and R.R. Schlittler},
  title = {Observation of local photoemission using a scanning tunneling microscope},
  journal = {Ultramicroscopy},
  volume = {42--44},
  pages = {366--370},	
  year = {1992},
  url = {http://dx.doi.org/10.1016/0304-3991(92)90294-T},
  doi = {http://doi.org/10.1016/0304-3991(92)90294-T}
}
 
 
Tunneling characteristics at atomic resolution on close-packed metal surfaces
R. Berndt, J. Gimzewski, R. Schlittler, Ultramicroscopy 42--44, 528 (1992)

Abstract:
We have observed atomic resolution in constant current topography along close packed directions on Cu(111), Au(110) (1×2) and Ag(111) surfaces in UHV. Novel experimental information obtained from tunneling I-V and I-s characteristics observed under "atomic resolution" conditions is presented. Our results are discussed in the light of current theoretical models. We suggest that foreign material in the tip apex plays an important role in the imaging mechanism.

[BibTeX]
@article{RBE_UMI92_2,
  author = {R. Berndt and J.K. Gimzewski and R.R. Schlittler},
  title = {Tunneling characteristics at atomic resolution on close-packed metal surfaces},
  journal = {Ultramicroscopy},
  volume = {42--44},
  pages = {528--532},	
  year = {1992},
  url = {http://dx.doi.org/10.1016/0304-3991(92)90318-E},
  doi = {http://doi.org/10.1016/0304-3991(92)90318-E}
}
 
 
Enhanced photon emission from the STM: a general property of metal surfaces
R. Berndt, J. Gimzewski, R. Schlittler, Ultramicroscopy 42--44, 355 (1992)

Abstract:
Light emission observed from noble metal surfaces in an STM has been interpreted as arising from inelastic tunneling excitation of radiative tip-induced plasmon modes. We discuss recent extensions of this work to clean and oxygen-covered transition metal surfaces. Photon intensities observed in the tunnel mode permit mapping and spectroscopic investigation of sub-nanometer areas of the surfaces of Cu, Fe, and Ti. Our results corroborate the theory developed for noble metals. Contrasts in photon maps on an atomic scale caused by adsorbates are discussed.

[BibTeX]
@article{RBE_UMI92,
  author = {R. Berndt and J.K. Gimzewski and R.R. Schlittler},
  title = {Enhanced photon emission from the STM: a general property of metal surfaces},
  journal = {Ultramicroscopy},
  volume = {42--44},
  pages = {355--359},	
  year = {1992},
  url = {http://dx.doi.org/10.1016/0304-3991(92)90292-R},
  doi = {http://doi.org/10.1016/0304-3991(92)90292-R}
}
 
 
Computer algebra approach to surface lattice dynamics
R. Berndt, A. Lock, C. Wöll, Surf. Sci. 276, 213 (1992)

Abstract:
Lattice dynamical calculations for surfaces with large unit cells, e.g. adsorbate overlayers or stepped surfaces, are hampered by the complexity of the dynamical matrix for these systems. We demonstrate the use of computer algebra to calculate analytical expressions for the elements of the dynamical matrix for a force constant model. Extensions to other interaction models such as the shell model or the bond charge model are feasible.

[BibTeX]
@article{RBE_SSI92_2,
  author = {R. Berndt and A. Lock and Ch. Wöll},
  title = {Computer algebra approach to surface lattice dynamics},
  journal = {Surf. Sci.},
  volume = {276},
  pages = {213--225},	
  year = {1992},
  url = {http://dx.doi.org/10.1016/0039-6028(92)90710-N},
  doi = {http://doi.org/10.1016/0039-6028(92)90710-N}
}
 
 
The role of proximity plasmon modes on noble metal surfaces in scanning tunneling microscopy
R. Berndt, J. Gimzewski, Surf. Sci. 269-270, 556 (1992)

Abstract:
Light emission from Cu(111) and Au(110) surfaces in the scanning tunneling microscope has been characterised. Fluorescence spectra are interpreted as arising from inelastic tunneling excitation of radiative tip-induced plasmon modes. Maps of integral photon intensity measured simultaneously with topography are used to visualise the localised nature of these modes.

[BibTeX]
@article{RBE_SSI92,
  author = {R. Berndt and J.K. Gimzewski},
  title = {The role of proximity plasmon modes on noble metal surfaces in scanning tunneling microscopy},
  journal = {Surf. Sci.},
  volume = {269-270},
  pages = {556--559},	
  year = {1992},
  url = {http://dx.doi.org/10.1016/0039-6028(92)91308-X},
  doi = {http://doi.org/10.1016/0039-6028(92)91308-X}
}
 
 
Scanning-tunneling-microscope study of antiphase domain boundaries, dislocations and local mass transport on Au(110) surfaces
J. Gimzewski, R. Berndt, R. Schlittler, Phys. Rev. B 45, 6844 (1992)

Abstract:
We have used a scanning tunneling microscope to investigate surface defects and atomic motion occurring on Au(110)(1 × 2) reconstructed surfaces at room temperature over a period of time of several hours. Evaluation of time lapse topographies shows that distinct changes occur at step structures and domain walls. These features can be classified into basic building blocks to model surface disorder and from the relative changes occurring at each element a local description of mass transport is obtained. Local transport via kinks occurring along atomic rows of the superstructure in 11-bar0 is observed to dominate. Finally, unique atomic structures introduced by bulk dislocations are presented and the subsequent influence on the creation of new phase boundaries and distortions in the surface superstructure are discussed.

[BibTeX]
@article{GIM_PRB92,
  author = {J.K. Gimzewski and R. Berndt and R.R. Schlittler},
  title = {Scanning-tunneling-microscope study of antiphase domain boundaries, dislocations and local mass transport on Au(110) surfaces},
  journal = {Phys. Rev. B},
  volume = {45},
  pages = {6844--6857},	
  year = {1992},
  url = {http://link.aps.org/abstract/PRB/v45/p6844},
  doi = {http://doi.org/10.1103/PhysRevB.45.6844}
}
 
 
Photon emission processes in STM
R. Berndt, J. Gimzewski, R. Schlittler, in Scanned Probe Microscopies, K. Wickramasinghe (Hrsg.) AIP Conference Series 231, 328-336 (American Institute of Physics, New York, 1992)

Abstract:
We discuss recent progress in the investigation of photon emission processes occurring in the tip-surface region of the STM. Through the use of selected examples recorded on metals and semiconductors some interesting aspects of this area of research are presented. In particular, radiative plasmon modes on metals specific to the STM geometry and their excitation by inelastic tunneling are compared to luminescence processes in semiconductors. The ability to fabricate nanostructures on Cu and investigate their photon emission characteristics with atomic resolution is included to give a feeling for the frontier aspect of this research.

[BibTeX]
@inbook{RBE_AIP92,
  author = {R. Berndt and J.K. Gimzewski and R.R. Schlittler},
  chapter = {Photon emission processes in STM},
  title = {Scanned Probe Microscopies},
  editor = {K. Wickramasinghe},
  series = {AIP Conference Series},
  volume = {231},
  pages = {328--336},
  publisher = {American Institute of Physics, New York},	
  year = {1992}
}
 
 
Inelastic tunneling excitation of tip-induced plasmon modes on noble-metal surfaces
R. Berndt, J. Gimzewski, P. Johansson, Phys. Rev. Lett. 67, 3796 (1991)

Abstract:
Light emission characteristics from the tunnel gap of a scanning tunneling microscope are used to elucidate the interaction of tunneling electrons with tip-induced plasmon modes on Ag, Au, and Cu surfaces. Enhanced redshifted spectra are observed in the tunneling regime. Model calculations of optical spectra in this range agree well with the experimental data. Isochromat spectra are used to demonstrate that the principal excitation process occurs via inelastic tunneling.

[BibTeX]
@article{RBE_PRL91,
  author = {R. Berndt and J.K. Gimzewski and P. Johansson},
  title = {Inelastic tunneling excitation of tip-induced plasmon modes on noble-metal surfaces},
  journal = {Phys. Rev. Lett.},
  volume = {67},
  pages = {3796--3799},	
  year = {1991},
  url = {http://link.aps.org/abstract/PRL/v67/p3796},
  doi = {http://doi.org/10.1103/PhysRevLett.67.3796}
}
 
 
Application of computer algebra to surface lattice dynamics
R. Berndt, A. Lock, G. Witte, C. Wöll, Proc. Int'l Symposion on Symbolic and Algebraic Computation, Bonn, 15.-17.7.1991, S. Watt (Hrsg.) pp. 433-437 (ACM Press, New York, 1991)
[BibTeX]
@inproceedings{RBE_ISSAC91,
  author = {R. Berndt and A. Lock and G. Witte and Ch. Wöll},
  title = {Application of computer algebra to surface lattice dynamics},
  booktitle = {Proc. Int'l Symposion on Symbolic and Algebraic Computation},
  editor = {S.M. Watt},
  pages = {433--437},
  publisher = {ACM Press, New York},
  address = {Bonn},
  period = {15.-17.7.1991},	
  year = {1991}
}
 
 
Photon emission scanning tunneling microscope
R. Berndt, J. Gimzewski, R. Schlittler, J. Vac. Sci. Technol. B 9, 573 (1991)

Abstract:
The analysis of photons emitted from the tip-surface region of an STM has produced new information on local dissipative processes in tunneling. A key objective to extend our work to a general spectroscopic and microscopic method is to collect and detect photons as efficiently as possible and here we describe our experimental arrangements, one of which incorporates an ellipsoidal mirror and the other a lens system to collect the photons. The systems operate in UHV and have in situ sample and tip transfer facilities. Examples of a variety of photon spectroscopy modes including photon spectra, isochromat spectra, angular distributions, and photon mapping are presented.

[BibTeX]
@article{RBE_JVSTB91,
  author = {R. Berndt and J.K. Gimzewski and R.R. Schlittler},
  title = {Photon emission scanning tunneling microscope},
  journal = {J. Vac. Sci. Technol. B},
  volume = {9},
  pages = {573--577},	
  year = {1991},
  url = {http://link.aip.org/link/?JVB/9/573},
  doi = {http://doi.org/10.1116/1.585571}
}
 
 
Observation of the temporal evolution of the (1 × 2) reconstructed Au(110) surface using scanning tunneling microscopy
J. Gimzewski, R. Berndt, R. Schlittler, J. Vac. Sci. Technol. B 9, 897 (1991)

Abstract:
We present scanning tunneling microscopy (STM) observations of the Au(110) (1 × 2) reconstructed surface under ultrahigh vacuum conditions at room temperature. Selected pictures from sequences of STM images taken over several hours are discussed using basic building blocks consisting of steps and domain walls. The temporal evolution of surface structures is clearly observed. Our results unravel the important influence of domain boundaries on the kinetics of the surface in stabilizing energetically unfavorable geometries, such as steps along the [001] direction or steps exposing (331) minifacets.

[BibTeX]
@article{GIM_JVSTB91,
  author = {J.K. Gimzewski and R. Berndt and R.R. Schlittler},
  title = {Observation of the temporal evolution of the (1 × 2) reconstructed Au(110) surface using scanning tunneling microscopy},
  journal = {J. Vac. Sci. Technol. B},
  volume = {9},
  pages = {897--898},	
  year = {1991},
  url = {http://link.aip.org/link/?JVB/9/897},
  doi = {http://doi.org/10.1116/1.585491}
}
 
 
Observation of mass transport on Au(110)-(1x2) reconstructed surfaces using scanning tunneling microscopy
J. Gimzewski, R. Berndt, R. Schlittler, Surf. Sci. 247, 327 (1991)

Abstract:
Observations of the temporal evolution of antiphase boundaries on Au(110)-(1 × 2) surfaces using scanning tunneling microscopy (STM) are discussed. Our results support the suggestion that mass transport via kink sites is important for the nucleation and growth of the (1 × 2) phase. Cross-channel motion of atoms in the [001] direction is also observed, but less frequently, resulting in the collapse of domain wall structures. We propose that atomic rows of the superstructure-forming antiphase domain walls perpendicular to the [110] direction move in a concerted fashion.

[BibTeX]
@article{GIM_SSI91,
  author = {J.K. Gimzewski and R. Berndt and R.R. Schlittler},
  title = {Observation of mass transport on Au(110)-(1x2) reconstructed surfaces using scanning tunneling microscopy},
  journal = {Surf. Sci.},
  volume = {247},
  pages = {327--332},	
  year = {1991},
  url = {http://dx.doi.org/10.1016/0039-6028(91)90143-G},
  doi = {http://doi.org/10.1016/0039-6028(91)90143-G}
}
 
 
Surface dynamics of oxygen-covered Ni(100)
R. Berndt, J. Toennies, C. Wöll, Surf. Sci. 244, 305 (1991)

Abstract:
Ordered overlayers of oxygen atoms on Ni(100) have been investigated by inelastic scattering of He atoms. For the O-p(2 × 2) overlayer and the O-c(2 × 2) overlayer the surface-phonon dispersion curves of the Rayleigh mode have been determined for both high symmetry directions. Along the [100] azimuth of the c(2 × 2) overlayer a large gap of 3 meV between the two branches of the Rayleigh mode at the zone-boundary has been observed; this gives evidence for a very strong repulsive O---O interaction in the rather densely packed O-c(2 × 2) phase. Additionally, a flat phonon mode at about 10 meV has been observed for both high-symmetry directions of the O-c(2 × 2) phase, which was not resolved in earlier EELS measurements. Lattice-dynamical calculations were performed to interpret this behaviour and suggest that the flat mode corresponds to localized vibrations at defects within the O-c(2 × 2) overlayer.

[BibTeX]
@article{RBE_SSI91,
  author = {R. Berndt and J.P. Toennies and Ch. Wöll},
  title = {Surface dynamics of oxygen-covered Ni(100)},
  journal = {Surf. Sci.},
  volume = {244},
  pages = {305--320},	
  year = {1991},
  url = {http://dx.doi.org/doi:10.1016/0039-6028(91)90503-K},
  doi = {http://doi.org/10.1016/0039-6028(91)90503-K}
}