1,720,959 research outputs found
Tunable Plasmonic Quantum Light Source with Silver Nanoclusters on a Silver Surface
No full text2020 The Korean Physical Society Scanning tunneling luminescence (STL) can be used to investigate the optical properties of nanostructures with high spatial resolution beyond the diffraction limit of light. To get appropriate STL spectra, one needs to modify the tip repeatedly. However, such irreversible tip modification often leads to very unstable tips. Here, by using a scanning tunneling microscope (STM) tip, we demonstrate that STL spectra are tunable via silver nanocluster arrays fabricated directly on a silver surface. The silver nanoclusters are created by transferring silver atoms from the silver tip to the silver surface under STM. We found that the STL spectra were enhanced (suppressed) at higher (lower) energy on the clusters and that they showed opposite behaviors between the nanoclusters. Without relying on the irreversible tip shape modification, our findings indicate that we can tune the STL spectra simply by moving the STM tip over the nanoclusters. Our method can be used to provide a tunable light source for systematic nano-optical experiments and for nanoscale optical devices11sciekc
Influence of the Tip Shape on Scanning Tunneling Luminescence Spectra: Implications for Nanomaterial Characterization
No full textScanning tunneling luminescence (STL) provides a unique opportunity to determine the optical properties of nanostructures beyond the diffraction limit. However, the relationship between the STL spectra and nanoscale tip shapes remains poorly understood because of the uncertainty regarding the nanoscale tip geometry. Here, we provide direct experimental evidence supporting a relationship between the tip shapes and resulting STL spectra. We find that asymmetric nanoscale tips generated dissimilar STL spectra in different directions by simultaneously collecting STL spectra in two opposing directions. Our experiment provides an efficient way to tune the STL spectra, which can be used to characterize the optical properties of nanomaterials.11Nsciescopu
Unusual Diffusion Behavior of Copper-Hexadecafluoro-Phthalocyanine Molecules on Au(111)
No full text© 2020, The Korean Physical Society. The unusual bias-voltage dependence of copper-hexadecafluoro-phthalocyanine (F16CuPc) molecules on Au(111) was investigated by using scanning tunneling microscopy/spectroscopy (STM/STS) at low temperatures. Depending on the bias polarity, the molecules seem to cover the whole surface of Au(111) at positive bias voltages while they are apparently invisible in STM images at negative bias voltages. Here, we experimentally demonstrate that the molecular diffusivity on Au(111) varies according to the applied electric field induced between the STM tip and the Au(111) surface rather than the intrinsic molecule-substrate interaction. Such results are corroborated by STS measurements indicating that attraction/repulsion of a molecule indeed occurs under an STM tip at positive/negative bias voltages during sweeps of the bias voltage. In addition, we found that the diffusive molecules are immobilized at a temperature of 8 K at both positive and negative bias voltages due to a lack of thermal energy for diffusion11sciekc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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