1,720,971 research outputs found
Characterization of the electric transport properties of black phosphorous back-gated field-effect transistors
Full text linkWe use thin layers of exfoliated black phosphorus to realize back-gated field-effect transistors in which the Si/SiO2 substrate is exploited as gate electrode. To prevent the detrimental effect of the air exposure the devices are protected by Poly(methyl methacrylate).
We report the observation of an improved contact resistance at the interface between the layered material and the metal contact by electrical conditioning. We also demonstrate the existence of a hysteresis in the transfer characteristics that improves by increasing the gate voltage sweep
range. Finally, we prove the suitability of such transistors as memory devices
Gated BP/MoS2 Heterostructure with Temperature Enhanced Photocurrent
No full textTwo-dimensional van der Waals heterostructures offer versatile platforms for multifunctional optoelectronic devices. In this work, we study the electrical transport and the photoresponse in BP/MoS2 heterostructures made of multi-layer black phosphorus (BP) exfoliated over CVD-grown monolayer molybdenum disulfide (MoS2) with Cr contacts. The heterostructures show good rectification and a dominant n-type behavior under a back-gate voltage. The exposure to light reveals a high photoresponse with photocurrent enhanced by the rising temperature. The BP/MoS2 devices can be operated over a wide range of temperatures, either below or above room temperature.
An energy band model that considers a type II BP/MoS2 heterojunction between two back-to-back Schottky junctions, at the Cr/BP and Cr/MoS2 interfaces, is proposed to explain the
experimental results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Manipulation of the electrical and memory properties of MoS2 field-effect transistors by highly charged ion irradiation
No full textField-effect transistors based on molybdenum disulfide (MoS2) exhibit a hysteresis in their transfer characteristics, which can be utilized to realize 2D memory devices. This hysteresis has been attributed to charge trapping due to adsorbates, or defects either in the MoS_2 lattice or in the underlying substrate. We fabricated MoS2 field-effect transistors on SiO2/Si substrates, irradiated these devices with Xe30+ ions at a kinetic energy of 180 keV to deliberately introduce defects and studied the resulting changes of their electrical and hysteretic properties. We find clear influences of the irradiation: While the charge carrier mobility decreases linearly with increasing ion fluence (up to only 20 % of its initial value) the conductivity actually increases again after an initial drop of around two orders of magnitude. We also find a significantly reduced n-doping (1012 cm-2) and a well-developed hysteresis after the irradiation. The hysteresis height increases with increasing ion fluence and enables us to characterize the irradiated MoS2 field-effect transistor as a memory device with remarkably longer relaxation times (≈ minutes) compared to previous works
BP/MoS2 Van Der Waals Heterojunctions for Self‐Powered Photoconduction
No full text2D materials can be combined without the need for lattice matching, leading to various van der Waals heterostructures with novel functionalities. Herein, it focuses on a vertical heterostructure made of thin black phosphorus (BP) over monolayer molybdenum disulfide (MoS2) that is characterized using a four-probe configuration. The device exhibits contact resistance negligible compared to the resistance of the BP/MoS2 channel, rectifying current-voltage (IV) characteristics, dominant n-type conduction resulting from type II band alignment and field effect mobility ≈1 cm2 V−1 s−1 limited by MoS2. An energy barrier at the BP/MoS2 interface of 68 meV is estimated using IV measurements at different temperatures. Additionally, the BP/MoS2 device exhibits fast photoresponse, conductance depending linearly on the incident light power, and photovoltaic effect, suggesting its suitability for self-powered photodetection. The spectral response is nearly constant in the 450 − 600 nm range and declines for wavelengths above 600 nm, that is for light energies below the energy bandgap of MoS2. Both the short circuit current Isc and the open circuit voltage Voc show a dependence on the incident power and wavelength, with maximum values Isc ≈ 0.12 nA and Voc ≈ 75 mV under 126 μW incident white light power. These findings highlight the potential of BP/MoS2 heterojunctions for optoelectronic applications
Pressure-Dependent Current Transport in vertical BP/MoS2 heterostructures
No full textvan der Waals heterostructures between two-dimensional (2D) materials offer versatile platforms for innovative electrical device architectures and applications. Black phosphorus (BP) and molybdenum disulfide (MoS2) emerge as promising candidates for heterostructures, owing to their exceptional electronic properties and gate-tunable capabilities. In this work, we study the electrical properties of a vertical BP/MoS2 heterostructure fabricated onto a SiO2/Si substrate in a back-gate configuration. We focus on the effect of air pressure, from atmospheric pressure to 10−4 mbar, and show that best electrical performances are enabled at the lower pressure. The heterostructure exhibits gate-tunable rectifying current-voltage characteristics, with a rectification ratio close to 103. The rectifying characteristics present a kink in the forward region revealing different conduction mechanisms, namely drift-diffusion and band-to-band tunneling. Furthermore, when used as a transistor, the device s..
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