1,721,233 research outputs found
A novel low temperature fabrication approach of multichannel zinc oxide nanowire field effect transistors for biosensing applications
No full textSensing of
bacteria, viruses and biomolecules is increasingly important for environmental
monitoring and healthcare applications. Electronic devices as transducer
elements, that are scaled down to nanometre dimensions offer a sensitive
electrical detection of bioanalytes. In this work, nanowire field effect
transistors (NWFET) made from zinc oxide (ZnO) offer high sensitivity and low
thermal budget fabrication compared to silicon nanowire sensors.
The novelty of this work is a new low temperature top-down
fabrication process, which makes it possible to define ZnO NWFET arrays with
different numbers of nanowires simultaneously and systematically compare their
electrical performance. The main feature of this process is a developed bilayer
photoresist pattern with a retrograde profile, which enables the modification
of the nanowire in width, length, height and the number of transistor channels.
The approach is compatible with low cost manufacture without electron beam
lithography and benefits from process temperatures below 150ºC. Process
reliability has been investigated by scanning electron microscopy (SEM),
transmission electron microscopy (TEM), x-ray diffraction (XRD) and atomic
force microscopy (AFM). The nanowires exhibit a cross section dimension of 30.9
nm height and 257.4 nm width and varying lengths from 5 µm to 45 µm and show a
very smooth top surface with a root mean squared (rms) roughness of only 1.2
nm. Electrical measurements demonstrate enhancement mode transistors, which
show a scalable correlation between the number of nanowires and the electrical
characteristics. Thereby, devices with 100 nanowires exhibit the best
performance with a high field effect mobility of 11.0 cm2/Vs, on/off current ratio of 4 × 107 and subthreshold swing of 660 mV/dec.
The fabricated multichannel ZnO NWFET have been investigated
for their potential bio-sensing capabilities. The ZnO NWFET passivated with Al2O3 is able to
operate 16 hours continuously in phosphate buffered saline (PBS) solution with
a very small current drift of 1.3 % per hour. It was found, that an Al2O3 passivation
layer of 30 nm gives the best electrical performance of the ZnO NWFETs. Hereby,
the ZnO NWFET shows a very good recovery behaviour up to 81.8 % of its original
signal output current. The output current of the ZnO NWFET shifts to different
ionic strengths in aqueous solutions and changes during exposure with 10x, 100x
and 1000x diluted PBS of up to 23.7%. Investigations on the sensing
capabilities on proteins show that the ZnO NWFET responds at a very low drain
voltage of 5 mV to varying charges within liquid solutions containing lysozyme
and bovines serum albumin (BSA). An output current signal change between these
two proteins of 295.5 % was measured, indicating a very good sensitivity of the
ZnO nanowire channel to the presence of surrounding charges.
After evidence was provided that the fabricated ZnO NWFET are
capable for bio-sensing experiments, a mask design was developed, which allows
to package the ZnO NWFET with gold wire bonding onto a polychlorinated biphenyl
(PCB) board to enable statistical bio-sensing experiments. Hereby individual
ZnO NWFETs can be addressed and measured by flushing laser cut poly(methyl
methacrylate) (PMMA) micro fluidic channels with analytes solutions.</p
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
Dataset supporting the publication "Vertical Integration of KTN on SOI Wafer"
No full textThis dataset contains all the FIB-SEM images, experimental and simulation data used to generate the figures included in the main text of the publication "Vertical Integration of KTN on SOI Wafer" in Optics Express (2024) https://doi.org/10.1364/OE.525582
This dataset contain three main folders:
The first folder (experiment) contains all experimental data obtained from passive characterisation of the structures.
The second folder (simulation) contains simulation EME file and the final sweep results.
The third folder (images) contains the microscopic and FIB-SEM images.
The files are presented in excel files, JPG files for images and lsf, and lms files for simulations.
The data is accessible via CC BY license.</span
Impact of bias stress and endurance switching on electrical characteristics of polycrystalline ZnO-TFTs with Al2O3 gate dielectric
No full textThis study experimentally investigates electrical characteristics and degradation phenomena in polycrystalline zinc oxide thin-film transistors (ZnO-TFTs). ZnO-TFTs with Al2O3 gate dielectric, Al-doped ZnO (AZO) source–drain contacts, and AZO gate electrode are fabricated using remote plasma-enhanced atomic layer deposition at a maximum process temperature of 190 °C. We employ positive bias stress (PBS), negative bias stress (NBS), and endurance cycling measurements to evaluate the ZnO-TFT performance and examine carrier dynamics at the channel-dielectric interface and at grain boundaries in the polycrystalline channel. DC transfer measurements yield a threshold voltage of −5.95 V, a field-effect mobility of 53.5 cm2/(Vbold dots), a subthreshold swing of 136 mV dec−1, and an on-/off-current ratio above 109. PBS and NBS measurements, analysed using stretched-exponential fitting, reveal the dynamics of carrier trapping and de-trapping between the channel layer and the gate insulator. Carrier de-trapping time is 88 s under NBS at −15 V, compared to 1856 s trapping time under PBS at +15 V. Endurance tests across 109 cycles assess switching characteristics and temporal changes in ZnO-TFTs, focusing on threshold voltage and field-effect mobility. The threshold voltage shift observed during endurance cycling is similar to that of NBS due to the contrast in carrier trapping/de-trapping time. A measured mobility hysteresis of 19% between the forward and reverse measurement directions suggests grain boundary effects mediated by the applied gate bias. These findings underscore the electrical resilience of polycrystalline ZnO-TFTs and the aptitude for 3D heterogeneous integration applications
Vertical Integration of KTN on SOI wafer
No full textOptical modulators play an important role in communication systems, and silicon has been a focal point in this field thanks to its compatibility with CMOS fabrication. However, silicon’s lack of inherent electro-optic behavior makes it suboptimal for modulation purposes. Conversely, potassium tantalate niobate (KTN) materials boast an improved electro-optic coefficient, presenting a path for improving modulation efficiency. However, limited research exists on KTN materials due to the difficulties associated with their fabrication. Here, a fabrication methodology is described for wafer-scale vertical integration of KTN material onto silicon-on-insulator (SOI) wafers. The resulting devices exhibit a propagation loss of 3.3 dBmm1 and a transition loss within the range of 0.46 to 0.76 dB, which are in agreement with simulations. This method tackles the fabrication challenges and showcases the potential of utilising KTN as the integration material on silicon platform for future optical modulators
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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