Study of Au/n- ZnSe contact by ballistic electron emission microscopy

Ballistic Electron Emission Microscopy (BEEM) has been used to characterise the Au/n-ZnSe contact. A mean statistical BEEM threshold of 1.63eV is in good agreement with literature. Metal - Insulator- Semiconductor (MIS) structures are invoked to explain the Schottky barrier height dispersion and the observed shift of BEEM thresholds to higher values.Ballistic Electron Emission Microscopy (BEEM) has been used to characterise the Au/n-ZnSe contact. A mean statistical BEEM threshold of 1.63eV is in good agreement with literature. Metal - Insulator- Semiconductor (MIS) structures are invoked to explain the Schottky barrier height dispersion and the observed shift of BEEM thresholds to higher values

u/n-Si(100) contact homogeneity studied by direct and reverse ballistic electron emission microscopy and spectroscopy

The Au/n-Si(100) contact has been studied using reverse ballistic electron emission microscopy and spectroscopy. Two types of localised collector currents have been observed; one, positive corresponding to electron injection into Si, and the other, negative, associated with hole injection into the semiconductor. The comparative trial of BEEM and reverse BEEM images from the same area shows this difference to be linked to the interface structure. Effects of surface roughness on the observed contrasts are also discussed.The Au/n-Si(100) contact has been studied using reverse ballistic electron emission microscopy and spectroscopy. Two types of localised collector currents have been observed; one, positive corresponding to electron injection into Si, and the other, negative, associated with hole injection into the semiconductor. The comparative trial of BEEM and reverse BEEM images from the same area shows this difference to be linked to the interface structure. Effects of surface roughness on the observed contrasts are also discussed

Electron Wave Function in Armchair Graphene Nanoribbons

By using analytical solution of a tight-binding model for armchair nanoribbons, it is confirmed that the solution represents the standing wave formed by intervalley scattering and that pseudospin is invariant under the scattering. The phase space of armchair nanoribbon which includes a single Dirac singularity is specified. By examining the effects of boundary perturbations on the wave function, we suggest that the existance of a strong boundary potential is inconsistent with the observation in a recent scanning tunneling microscopy. Some of the possible electron-density superstructure patterns near a step armchair edge located on top of graphite are presented. It is demonstrated that a selection rule for the G band in Raman spectroscopy can be most easily reproduced with the analytical solution.Comment: 7 pages, 4 figure

Ballistic electron emission microscopy of the Au-Si (100) interface

In this paper, experiments performed on Au-Si (100) junctions by Ballistic Electron Emission Microscopy (BEEM), a method for studying the metal -semiconductor interface, are presented. BEEM spectra show a characteristic threshold that yields the Schottky barrier height at the interface. The average barrier height is found to be lower than the usual values of Au-Si contacts. BEEM images result from the spatial variations of the current in the semiconductor and present unusual local contrasts. These phenomena are analysed in terms of interface quality

Study of the Electron Mean Free Path by Ballistic Electron Emission Microscopy

Ballistic Electron Emission Microscopy allows buried interfaces to be characterized with a subnanometer resolution. Additionnally, the electron mean free path in a thin metal layer can thus be investigated with a good level of accuracy. This paper presents the latest results in this field for an Au/n-Si Schottky diode. A discussion is also proposed to link these results with the still controversial interpretations of BEEM contrasts.La microscopie par émission d'électrons balistiques permet la caractérisation d'interfaces enfouies, avec une résolution inférieure au nanomètre. De plus, le libre parcours moyen des électrons dans une fine couche métallique peut être étudié avec une excellente précision. Cet article présente les derniers résultats dans ce domaine, pour des diodes Schottky Au/n-Si. Une discussion est également proposée pour relier ces résultats aux interprétations, toujours très controversées, des contrastes fournis par les images BEEM

Spectroscopy of Light Emission from a Scanning Tunneling Microscope in Air

Light emission has been detected at the tip-sample junction of a Scanning Tunneling Microscope (S.T.M.) in air on noble metallic surfaces. A spectroscopic study of emitted photons for Au-Au and PtIr-Au tunneling junctions is presented. The general aspect of the spectra depends on the materials used in the junctions; a study of the spectra as a function of tunneling current and surface bias voltage reveals similar and reproducible characteristics.Une émission de lumière a été détectée au niveau de la jonction pointe-surface d'un microscope à effet tunnel dans l'air sur des surfaces de métaux nobles. Une étude spectroscopique des photons émis par des jonctions tunnel Au-Au et PtIr-Au est présentée. L'aspect général des spectres dépend des matériaux utilisés ; une étude en fonction du courant tunnel et de la tension de polarisation de la jonction révéle des caractéristiques similaires et reproductibles

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Photon emission from STM of granular gold in UHV: comparison with air and study of spectra shifting with tip position

This paper presents an experimental study using photon emission derived from scanning tunnelling microscopy (STM) of a granular gold surface in Ultra High Vacuum (UHV). The aim is to make a comparison with previous results obtained in air or in UHV. The photon emission spectrum also evidences a significant energy shift as the tip moves on a surface grain. This shift is attributed to the local geometry of the junction and to peculiar crystallographic properties of the surface

Photon emission by scanning tunneling microscopy in air

A photon emission experiment has been done by Scanning Tunneling Microscopy in air. The emitted photons from a gold surface are collected in order to print side by side the STM topography and the corresponding photoemission mapping. Significant correlations can be observed between both images. The emission spectra are also collected while scanning the surface, thus yielding simultaneously a third piece of information. The results are markedly different from those obtained in ultra high vacuum.Une expérience d'émission de photons par microscopie à effet tunnel a été effectuée dans l'air. Les photons émis par une surface d'or sont collectés de manière à obtenir côte à côte une topographie STM et la cartographie photonique correspondante. Des correlations évidentes sont observées entre les deux images. Des spectres d'émission sont collectés simultanément en balayant la surface, donnant un troisième type d'information sur la surface. Les résultats sont un peu différents de ceux obtenus dans l'ultra vide