Quantum Confinement and Thickness-Dependent Electron Transport in Solution-Processed In₂O₃ Transistors

The dependence of charge carrier mobility on semiconductor channel thickness in field-effect transistors is a universal phenomenon that has been studied extensively for various families of materials. Surprisingly, analogous studies involving metal oxide semiconductors are relatively scarce. Here, spray-deposited In_{2}O_{3} layers are employed as the model semiconductor system to study the impact of layer thickness on quantum confinement and electron transport along the transistor channel. The results reveal an exponential increase of the in-plane electron mobility (µe) with increasing In2O3 thickness up to ≈10 nm, beyond which it plateaus at a maximum value of ≈35 cm^{2} V^{−1} s^{−1}. Optical spectroscopy measurements performed on In_{2}O_{3} layers reveal the emergence of quantum confinement for thickness <10 nm, which coincides with the thickness that µe starts deteriorating. By combining two- and four-probe field-effect mobility measurements with high-resolution atomic force microscopy, it is shown that the reduction in µe is attributed primarily to surface scattering. The study provides important guidelines for the design of next generation metal oxide thin-film transistors

Hidden negative linear compressibility in lithium L-tartrate†

Development of artificial muscles, next-generation pressure sensors and precision optics relies on advances in materials with anomalous mechanical properties. Negative linear compressibility, NLC, is one such rare, counterintuitive phenomenon, in which a material expands along one axis under hydrostatic pressure. Both classical and recent NLC materials face a pay-off between the active pressure range and magnitude of NLC, and in the vast majority of cases the NLC effect decreases with pressure. By decoupling the mechanical behaviour of building units for the first time in a winerack framework containing two different strut types, we show that lithium L-tartrate exhibits NLC with a maximum value, Kmax = -21 TPa^-1, and an overall NLC capacity, χNLC = 5.1 %, that are comparable to the most exceptional materials to date. Furthermore, the contributions from molecular strut compression and angle opening interplay to give rise to so-called “hidden” negative linear compressibility, in which NLC is absent at ambient pressure, switched on at 2 GPa and sustained up to the limit of our experiment, 5.5 GPa. Analysis of the changes in crystal structure using variable-pressure synchrotron X-ray diffraction reveals new chemical and geometrical design rules to assist the discovery of other materials with exciting hidden anomalous mechanical properties

Temperature stability of thin film refractory plasmonic materials

Materials such as W, TiN, and SrRuO3 (SRO) have been suggested as promising alternatives to Au and Ag in plasmonic applications owing to their stability at high operational temperatures. However, investigation of the reproducibility of the optical properties after thermal cycling between room and elevated temperatures is so far lacking. Here, thin films of W, Mo, Ti, TiN, TiON, Ag, Au, SrRuO3 and SrNbO3 are investigated to assess their viability for robust refractory plasmonic applications. These results are further compared to the performance of SrMoO3 reported in literature. Films ranging in thickness from 50 to 105 nm are deposited on MgO, SrTiO3 and Si substrates by e-beam evaporation, RF magnetron sputtering and pulsed laser deposition, prior to characterisation by means of AFM, XRD, spectroscopic ellipsometry, and DC resistivity. Measurements are conducted before and after annealing in air at temperatures ranging from 300 to 1000° C for one hour, to establish the maximum cycling temperature and potential longevity at elevated temperatures for each material. It is found that SrRuO3 retains metallic behaviour after annealing at 800° C, while SrNbO3 undergoes a phase transition resulting in a loss of metallic behaviour after annealing at 400° C. Importantly, the optical properties of TiN and TiON are degraded as a result of oxidation and show a loss of metallic behaviour after annealing at 500° C, while the same is not observed in Au until annealing at 600° C. Nevertheless, both TiN and TiON may be better suited than Au or SRO for high temperature applications operating under vacuum conditions

Efficacy of pulsed-dye laser for viral warts--an internal audit.

Pulsed-dye laser (PDL) surgery is a recognized treatment of viral warts. Initial studies in 1993 by Tan et al achieved a 72% cure rate for 39 patients after a mean of 1.68 treatments. Since then, conflicting response rates ranging from 47-95% have been reported. The records of 44 patients, who attended the Laser Unit at St. James's Hospital between January 1999 to June 2000, were reviewed. Follow-up was conducted by telephone interview or questionnaire. Twenty-eight (64%) patients identified for the study responded. The average number of treatments was 4 (range 1-12) and mean treatment intervals were 4.9 weeks (3-10). Our results showed 64% complete clearance of all the areas treated, and 46% complete clearance of the 13 areas identified as recalcitrant. Rates for complete clearance varied with anatomic site: 73% for the face, 68% for the hands, and 40% for feet. Seventy-eight percent (7/9) of periungal warts completely cleared, and 70% (7/10) mosaic warts cleared. Twenty-five percent of the patients complained of severe pain during treatment. Post-operative complications were few, and rarely affected the patients' lifestyle. The recurrence of warts, in weeks to months following the last treatment, was reported by 36% of the patients. Seventy-nine percent of patients were satisfied with the treatment they were given. PDL may be useful in treatment of refractory warts in selected patient populations. The study identified a need to address pain control in a significant number of patients

Effect of processing temperature on film properties of ZnO prepared by the aqueous method and related organic photovoltaics and LEDs

Here the influence of processing temperature on the properties of zinc oxide (ZnO) thin films fabricated using a carbon-free solution process is investigated. Our results show that the film processing temperature influences a wide range of structural and electro-optical properties. Films processed at 100 °C are shown to be formed of coalesced ZnO nanoparticles, whose dimensions increase with the processing temperature, accompanied by an increase in electron mobility. ZnO films processed at different temperatures were incorporated as electron transport layers (ETLs) in organic photovoltaic devices with PCDTBT:PC71BM as the active layer. We find that the ETLs processed at low temperature (100–200 °C) exhibit good device performance compared with those prepared at elevated temperatures, an effect we attribute to shifts in the work function and electrical conductivity. Interestingly a similar trend is observed when our ZnO is used as an electron injection layer in organic light emitting diodes, where the EILs processed at >200 °C show higher turn-on voltages and lower efficiencies than those annealed in the 100–200 °C range

Digital pulse shaping to mitigate linear crosstalk in Nyquist-spaced 16QAM WDM transmission systems

We demonstrate that a 128-tap RRC filter with 1% rolloff factor is sufficient to limit linear crosstalk induced OSNR penalty to <1dB in a Nyquist-spaced DP-16QAM WDM transmission system with a net ISD of 6.66b/s/Hz. © 2014 Engineers Australia

Nyquist-WDM-based system performance evaluation

We describe an experimental evaluation of a Nyquist-WDM-based transmission system. Nine 10.7 GHz-spaced WDM channels were generated, carrying polarisation-division-multiplexed QPSK with digital Nyquist pulse shaping at 10 Gbaud. Back-to-back characterisation and long-haul transmission tests using a recirculating fibre loop are described, and a comparison of experimental performance with that predicted by theory, based on the Gaussian-noise model of nonlinear propagation, is carried out. © 2013 IEEE