Structure of the {001} talc surface as seen by atomic force microscopy: Comparison with X-ray and electron diffraction results

In this study the surface structure of a centimetre sized crystal of talc from the Trimouns deposit (Ariège, France) was imaged by atomic force microscopy. The direct image shows detailed characteristics of clay tetrahedral surfaces. The unit-cell dimensions obtained 30 using atomic force microscopy (aor = 5.47±0.28 and bor = 9.48±0.28 Å) are found to be slightly higher, with an increased uncertainty, than those obtained using X-ray diffraction (aor = 5.288±0.007 and bor = 9.159±0.010 Å) and selected-area electron diffraction (aor = 5.32±0.03 and bor = 9.22±0.05 Å). Talc has a quasi-ideal surface, clean of strong 34 structural distortion as compared to most of other clay minerals and unlikely surface 35 relaxation. The observation on the obtained image of apparent cell dimension enlargement is 36 then more likely attributed to instrumental artefacts, also responsible for scattered values of unit-cell parameters rather than related to any surface structural features

Impact of He and H relative depth distributions on the result of sequential He+ and H+ ion implantation and annealing in silicon

International audienceSequential He++H+ ion implantation, being more effective than the sole implantation of H+ or He+, is used by many to transfer thin layers of silicon onto different substrates. However, due to the poor understanding of the basic mechanisms involved in such a process, the implantation parameters to be used for the efficient delamination of a superficial layer are still subject to debate. In this work, by using various experimental techniques, we have studied the influence of the He and H relative depth-distributions imposed by the ion energies onto the result of the sequential implantation and annealing of the same fluence of He and H ions. Analyzing the characteristics of the blister populations observed after annealing and deducing the composition of the gas they contain from FEM simulations, we show that the trapping efficiency of He atoms in platelets and blisters during annealing depends on the behavior of the vacancies generated by the two implants within the H-rich region before and after annealing. Maximum efficiency of the sequential ion implantation is obtained when the H-rich region is able to trap all implanted He ions, while the vacancies it generated are not available to favor the formation of V-rich complexes after implantation then He-filled nano-bubbles after annealing. A technological option is to implant He+ ions first at such an energy that the damage it generates is located on the deeper side of the H profile

Electrical behavior of the Au/MoS2 interface studied by light emission induced by scanning tunneling microscopy

cited By 12International audienceLight emitted in the tunneling junction of a scanning tunneling microscope has been used to establish the electrical characteristics of nanojunctions made of Au islands deposited on flat MoS2 surfaces. It is shown that these characteristics are those of rectifying contacts when the gold islands are isolated and that they evolve toward those of ohmic contacts when the island density increases. It is observed that the rectifying behavior also evolves over time as on infinite metal/semiconductor contacts. Using the STM tip, single gold islands can be manipulated on the MoS2 surface so that their electrical behavior can be changed depending on their position with regard to the other islands

Effect of multiple tips on light emission induced by STM from gold nanostructures

cited By 6International audienceLight emission induced by scanning tunneling microscope on gold islands grown on MoS2 surfaces has been investigated. Surface geometry and roughness show that different apexes of the same tip can modify the energy of photons emitted in the tunneling junction. Comparisons of topography and photon map are used to locate islands imaged twice and to represent approximately the tip shape used. Light emission spectroscopy on the same island with two apexes of the multiple tip reveals variations of emission properties according to the apex used, showing the importance of tip geometry in the emission process induced by tip induced plasmon modes

Reply to "comment on 'tip-to-surface distance variations vs voltage in scannine tunneline microscopy'"

cited By 0International audienceThe comments of Ley-Koo reveal first a true notational mistake in the ξ parameter. However, the numerical results are not significantly modified. Second, a theoretical inconsistency about nonconfocal hyperboloids is pointed out. We find that the use of nonconfocal hyperboloids as an approximation is necessary to analytically solve the problem

Light emission from spectral analysis of Au/MoS2 nanocontacts stimulated by scanning tunneling microscopy

cited By 19International audienceDue to a Volmer-Weber growth mode, the deposition of ultrathin gold films on molybdenite substrates leads to the formation of three-dimensional gold islands. The light emission detected on these islands has been attributed to a radiative decay of localized plasmons excited by inelastic tunneling electrons. This emission exhibits puzzling properties compared to what is usually observed on thicker gold films. Spectral analysis of emitted light enables current-voltage characteristics of the Au/MoS2 interface to be determined at a nanometer scale

Tip-to-surface distance variations vs voltage in scanning tunneling microscopy

cited By 19International audienceThis paper presents an experimental and theoretical study of distance vs voltage characteristics of Au/Au tunnel junctions in air and UHV. Qualitative and quantitative results are compared with the classical models of Tersoff and Hamann and Simmons. To fit experimental conditions, the Simmons model has been extended in three dimensions using a hyperboloidal tip. However, a large discrepancy between theoretical and experimental quantitative results has been found in air because of barrier height lowering due to electrode contamination. An experimental rescaling factor is used in the modified Simmons model to fit any (Formula presented) curve with high accuracy. These results are mainly interpreted in terms of gold surface elastic deformations. © 1999 The American Physical Society

Imaging using tip-surface distance variations vs. voltage in scanning tunneling microscopy

cited By 0International audienceThis paper presents a novel imaging technique related to scanning tunneling microscopy. It is based on the representation of distance-voltage characteristic amplitudes at each point in the scanned area. On polycrystalline gold surfaces, contrasts are found to be a function of crystallographic orientations. Moreover, this technique allows atomic resolution on graphite surfaces. In this case, elastic deformation at the atomic scale has to be considered to account for the contrasts observed

A hybrid instrument combining electronic and photonic tunnelling for surface analysis

cited By 0International audienceA PSTM working in the collection mode and based on an STM probe-sample regulation scheme has been developed. This original hybrid instrument for surface analysis uses apertureless metal-coated chemically etched optical fibres. The use of an electronic tunnelling-based feedback loop significantly reduces tip-sample distance and leads to the collection of a high level near-field optical (NFO) signal. A simple amplified photodiode is thus used to perform optical signal acquisition and to draw electromagnetic field maps of sample surfaces. Experimental results on nanostructured gold surfaces are presented

Reply to "comment on 'tip-to-surface distance variations vs voltage in scannine tunneline microscopy'"

cited By 0International audienceThe comments of Ley-Koo reveal first a true notational mistake in the ξ parameter. However, the numerical results are not significantly modified. Second, a theoretical inconsistency about nonconfocal hyperboloids is pointed out. We find that the use of nonconfocal hyperboloids as an approximation is necessary to analytically solve the problem