Organic molecules on diamond (001): a synchrotron Study

Ph.DDOCTOR OF PHILOSOPH

Enhanced surface transfer doping of diamond by V2O5 with improved thermal stability

Surface transfer doping of hydrogen-terminated diamond has been achieved utilising V2O5 as a surface electron accepting material. Contact between the oxide and diamondsurface promotes the transfer of electrons from the diamond into the V2O5 as revealed by the synchrotron-based high resolution photoemission spectroscopy. Electrical characterization by Hall measurement performed before and after V2O5 deposition shows an increase in hole carrier concentration in the diamond from 3.0 × 1012 to 1.8 × 1013 cm−2 at room temperature. High temperature Hall measurements performed up to 300 °C in atmosphere reveal greatly enhanced thermal stability of the hole channel produced using V2O5 in comparison with an air-induced surface conduction channel. Transfer doping of hydrogen-terminated diamond using high electron affinity oxides such as V2O5 is a promising approach for achieving thermally stable, high performance diamond based devices in comparison with air-induced surface transfer dopin

Substrate-mediated growth of oriented, vertically aligned MoS2 nanosheets on vicinal and on-axis SiC substrates

The layer- and morphology-dependent properties of two-dimensional molybdenum disulfide (MoS2) have established its relevance across broad applications in electronics, optoelectronics, sensing, and catalysis. Understanding how to manipulate the material growth to achieve the desired properties is the key to tailoring the material towards a specific application. In this work, we investigate the growth of vertically standing MoS2 nanosheets by chemical vapor deposition on vicinal and on-axis 4H-SiC (0001) substrates. In both cases the MoS2 flakes exhibit three preferred orientations, aligning with the substrate directions due to strain minimization of a MoO2 intermediate phase. Whereas MoS2 grown on vicinal SiC substrates exhibits strict near-vertical alignment, scanning electron microscopy and near-edge X-ray absorption fine structure (NEXAFS) measurements indicate a near-random vertical orientation when MoS2 is grown on on-axis SiC. Photoemission spectroscopy and NEXAFS measurements indicate the presence of defects and disordered edges which establish the suitability of the material for applications in sensing and catalysis

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Etching characteristics for tracks of carbon cluster ions in polycarbonate

A series of chemical etching experiments were carried out on polycarbonate foils irradiated by carbon cluster ions with an energy of 0.6 MeV/atom. The bulk etching rate was calculated from weight loss. The transversal etching rate was obtained by using linear fit to the pore diameters under a time sequence. It was found that the transversal etching rate depends on the rate of electronic energy deposition of projectiles. A distinctly irregular pore size distribution was found on the image of etched pores after C4+ irradiation and after one hour etching and explained as the contribution of dissociation of the carbon cluster

Quantitative femtosecond charge transfer dynamics at organic/electrode interfaces studied by core-hole clock spectroscopy

Organic semiconductor materials have important applications in organic electronics and other novel hybrid devices. In these devices, the transport of charge carriers across the interfaces between organic molecules and electrodes plays an important role in determining the device performance. Charge transfer dynamics at the organic/electrode interface usually occurs at the several femtoseconds timescale, and quantitative charge transfer dynamics data can been inferred using synchrotron‐based core‐hole clock (CHC) spectroscopy. In this research news, we have reviewed recent progress in the applications of CHC spectroscopy on the quantitative characterization of charge transfer dynamics at organic/electrode interfaces. By examining charge transfer dynamics at different types of interface, from weakly interacting van der Waals‐type interfaces to interfaces with strong covalent bonds, we discuss a few factors that have been found to affect the charge transfer dynamics. We also review the application of CHC spectroscopy to quantify through‐bonds and through‐space charge transport in organic molecules

Flexible sensors based on hybrid materials

With the rapid development of mobile Internet and intelligent devices, flexible electronic technology has attracted wide attention driven by the huge demand of the market. As one type of flexible electronic devices, flexible sensors have attracted great interest because of their promising prospects in artificial intelligence, medical health, and environmental protection. In recent years, flexible sensors with high sensitivity, selectivity, good deformability, reliable stability, and portability are urgently needed to meet the developments of artificial skin, human-computer interaction, point of care diagnostics and wearable electronic devices

Quantitative femtosecond charge transfer dynamics at organic/electrode interfaces studied by core-hole clock spectroscopy

This chapter reviews the recent progress in the application of core‐hole clock (CHC) spectroscopy on the quantitative characterization of charge transfer dynamics between organic molecules and electrodes. It presents important concepts and fundamental principles of the CHC technique. CHC is a powerful time‐resolved technique that allows for the study of charge transfer times in the femtosecond domain, and is widely applicable to various organic/electrode systems. The chapter discusses interfacial energy level alignment and its implication to probing charge transfer dynamics. It gives a simple account of experimental procedures for conducting CHC measurements at organic/electrode interfaces from sample preparation to spectral collection. The chapter also presents a number of examples employing the CHC technique to quantify charge transfer times at different types of interfaces including the organic/metal interface, organic/semiconductor interface, and self‐assembled monolayers (SAMs) ‐electrode interface

Synthesis and characterization of the regiorandom homopolymer of 3-alkyldithieno[3,2-b:2',3'-d]thiophene for thin-film transistors

A regiorandom homopolymer of 3-alkyldithieno[3,2-b:2[prime or minute],3[prime or minute]-d]thiophene (P3ADTT) has been prepared by oxidative polymerization using Iron(iii) Chloride and oxygen as oxidants. The physical and electrochemical properties of the homopolymer were investigated and compared with those of P3HT. Its application in organic field-effect transistors showed annealing-free hole mobility up to 0.048 cm2 V-1 s-1 at room temperature and a significant thermally stable mobility of 0.13 cm2 V-1 s-1 at 200 [degree]C with a current on/off ratio of greater than 105