Invited; P-channel metal oxide thin film transistors for flexible CMOS logic: Challenges and opportunities

The ‘unique selling point’ of thin film transistors (TFTs) compared with MOSFETs is that the former do not require the substrate to be a semiconducting material. It is for this reason that TFTs are required for active matrix display backplanes. However, the development of the ‘Internet of Things’ (IoT) presents a new opportunity for TFTs as it becomes possible to build complex logic or memory circuits on flexible substrates that can be more easily incorporated into products such as clothing or packaging without the form factor restrictions that rigid semiconducting substrates impose. There have been recent reports of the successful fabrication of basic microprocessors comprising TFTs on plastic substrates instead of MOSFETs [1]. Please click Download on the upper right corner to see the full abstract

Novel Protocol for Generating Physiologic Immunogenic Dendritic Cells

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Development of combinatorial pulsed laser deposition for expedited device optimization in CdTe/CdS thin-film solar cells

A combinatorial pulsed laser deposition system was developed by integrating a computer controlled scanning sample stage in order to rapidly screen processing conditions relevant to CdTe/CdS thin-film solar cells. Using this system, the thickness of the CdTe absorber layer is varied across a single sample from 1.5 μm to 0.75 μm. The effects of thickness on CdTe grain morphology, crystal orientation, and cell efficiency were investigated with respect to different postprocessing conditions. It is shown that the thinner CdTe layer of 0.75 μm obtained the best power conversion efficiency up to 5.3%. The results of this work shows the importance that CdTe grain size/morphology relative to CdTe thickness has on device performance and quantitatively exhibits what those values should be to obtain efficient thin-film CdTe/CdS solar cells fabricated with pulsed laser deposition. Further development of this combinatorial approach could enable high-throughput exploration and optimization of CdTe/CdS solar cells.Peer Reviewe

Role of ALD Al2O3 Surface Passivation on the Performance of p-Type Cu2O Thin Film Transistors

High-performance p- type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu2O semiconductor channel grown by atomic layer deposition (ALD). The TFT switching characteristics were improved by applying a thin ALD Al2O3 passivation layer on the Cu2O channel, followed by vacuum annealing at 300 degrees C. Detailed characterization by transmission electron microscopy-energy dispersive X-ray analysis and X-ray photoelectron spectroscopy shows that the surface of Cu2O is reduced following Al2O3 deposition and indicates the formation of a 1-2 nm thick CuAlO2 interfacial layer. This, together with field-effect passivation caused by the high negative fixed charge of the ALD Al2O3, leads to an improvement in the TFT performance by reducing the density of deep trap states as well as by reducing the accumulation of electrons in the semiconducting layer in the device off-state.Peer reviewe

The prevalence of mild cognitive impairment in diverse geographical and ethnocultural regions: The COSMIC Collaboration

Background Changes in criteria and differences in populations studied and methodology have produced a wide range of prevalence estimates for mild cognitive impairment (MCI). Methods Uniform criteria were applied to harmonized data from 11 studies from USA, Europe, Asia and Australia, and MCI prevalence estimates determined using three separate definitions of cognitive impairment. Results The published range of MCI prevalence estimates was 5.0%-36.7%. This was reduced with all cognitive impairment definitions: performance in the bottom 6.681% (3.2%-10.8%); Clinical Dementia Rating of 0.5 (1.8%-14.9%); Mini-Mental State Examination score of 24-27 (2.1%-20.7%). Prevalences using the first definition were 5.9% overall, and increased with age (P < .001) but were unaffected by sex or the main races/ethnicities investigated (Whites and Chinese). Not completing high school increased the likelihood of MCI (P = .01). Conclusion Applying uniform criteria to harmonized data greatly reduced the variation in MCI prevalence internationally

Melanoma Models for the Next Generation of Therapies

There is a lack of appropriate melanoma models that can be used to evaluate the efficacy of novel therapeutic modalities. Here, we discuss the current state of the art of melanoma models including genetically engineered mouse, patient-derived xenograft, zebrafish, and ex&nbsp;vivo and in&nbsp;vitro models. We also identify five major challenges that can be addressed using such models, including metastasis and tumor dormancy, drug resistance, the melanoma immune response, and the impact of aging and environmental exposures on melanoma progression and drug resistance. Additionally, we discuss the opportunity for building models for rare subtypes of melanomas, which represent an unmet critical need. Finally, we identify key recommendations for melanoma models that may improve accuracy of preclinical testing and predict efficacy in clinical trials, to help usher in the next generation of melanoma therapies

Reducing Off-State Current in P-Type Metal Oxide Thin Film Transistors

The Internet of Things (IoT) is a system in which common objects in our lives are able to broadcast and communicate information as nodes in a large network of information. This diverse application system is a growing interest for many industries. Large Area Electronics (LAE) is required to effectively produce the mass quantity of small, low-profile devices that will be embedded in these objects. Due to the scale and irregularity of the form factor, the need for flexible thin-film electronics arises. Metal-oxide materials are a prime candidate. They can be fabricated cheaply, in large areas, using the current electronics infrastructure. Some devices are already being produced in industry; however, they typically rely on an NMOS device architecture, which is inferior to CMOS. While NMOS is a type of digital circuit design which utilises only n-type semiconductors, CMOS utilises complementary n-type and p-type transistors to enable low-power and stability. P-type metal-oxide semiconductors have performed poorly in transistor devices and have prevented metal-oxide electronics from using CMOS. A suitable p-type transistor, to complement current n-type technology, is needed in order to implement CMOS and improve flexible metal-oxide electronics enough to be viable for the IoT or other flexible electronics applications. In this work, metal oxide Cu2O Thin Film Transistors (TFTs) are fabricated using High Target Utilisation Sputtering (HiTUS). In previous work, it was shown that the high off-current associated with Cu2O TFTs may be attributed to an atypical minority-carrier electron current leakage in the off-state. This gives a focus for device improvement. Most research in this area has focused on material improvements and inventions to attempt to create high performance devices. After all, this was the method through which n-type metal oxides first thrived, with IGZO being the prime example. However, this work aims to instead alter the device design to work with the present material limitations. An Electron Blocking Layer (EBL) is proposed and implemented for the first time on metal oxide TFTs. Further, good-quality c-Si/Cu2O PN junctions are also fabricated and used to efficiently trial EBL materials. NiO and MoO3 EBL materials are shown to moderately improve the on-off ratio by 141 % from 5.1 to 12.3, while CuI and WO3 show no improvement. It was concluded that the minority carrier accumulation was not the dominant source of off-current leakage for devices in this work. In a further effort to identify the more dominant source of the off-current, defect passivation was investigated. A minimum of 5 nm of Al2O3, when applied as a passivation layer to the back channel of annealed Cu2O TFTs, was shown to greatly improve the on/off ratio by 150000 %, three orders of magnitude, from 11 to 1.7×104. Finally, a new TFT design is proposed, in light of the results from this work, that incorporates SnO and a graded Tantalum EBL.Churchill College Gulbenkian Yuval Cambridge Studentship Pragmatic Semiconductor Limite

Foraging Ecology of Nesting Green, Olive Ridley, and Leatherback Turtles from Northwest Costa Rica

Understanding what sea turtles are feeding on and where they are feeding is key to understand their overall biology and will aid in understanding what type of management actions are necessary in order to conserve and protect these endangered species. Here I set out to (1) examine the population-level isotopic profiles of three sea turtle species in the Eastern Tropical Pacific; (2) determine differences in their foraging strategies; (3) attempt to gain insights about their pre-nesting origins; and (4) determine whether body size would influence the isotopic values of an individual turtle. Stable isotope analysis (δ13C and δ15N values) was conducted on tissue samples from 52 sea turtles nesting on Playa Cabuyal, Costa Rica; 28 Pacific green (Chelonia mydas), 20 olive ridley (Lepidochelys olivacea), and 4 leatherback (Dermochelys coriacea). Nine satellite transmitters were also deployed on a separate population of post-nesting Pacific green turtles from Playa Cabuyal. Based on isotopic profiles, green turtles in the Eastern Tropical Pacific were found to be feeding at a higher trophic level when compared to green turtles in other regions and this was supported by their increased δ15N values (16 ± 0.8 ‰). Rather than shifting to herbivory as adults, green turtles foraging in the eastern Pacific are potentially remaining omnivorous. Tracking data further confirmed that green turtles are coastal migrators and are probably inhabiting areas with high δ15N values within this region. Olive ridley turtles are exhibiting similar behavior to olive ridley turtles elsewhere due to minimal variance in their isotopic profiles (δ13C = -15.1 ± 0.7 ‰, δ15N =14.2 ± 0.8 ‰) and their known nomadic behavior. Although a small sample size, leatherback turtles showed a shift in their foraging habitats suggesting they are also feeding inshore in addition to their pelagic behavior due to their increased δ13C values (-15.5 ± 0.4 ‰). Further, as body size increased in olive ridley’s, the δ15N values significantly decreased suggesting that larger turtles prefer deeper pelagic waters with less enriched N isotope concentrations. However, in order to rule out possible external factors influencing this relationship, knowing where the turtle is originating from is crucial. This project provides data for developing isoscapes in the Eastern Tropical Pacific to aid in understanding the spatial distribution of sea turtles and their foraging grounds and the impact that foraging area may have on overall biology of these species. This information can be used to prioritize high use foraging habitats and determine the most effective management practices for protecting these species and the prey and habitat on which they rely

Prediction of return to productivity three months following hospitalisation for trauma

Bibliography: pages 126-167.1. Traumatic brain injury and mild traumatic brain injury -- 2. Litigation in TBI and mTBI -- 3. Occupation and mTBI -- 4. Return to work following mild TBI: a systematic review -- 5. Overview, aims and hypotheses of the current study -- 6. Methods -- 7. Results -- 8. Discussion.Objective: The aim of the current study was to identify variables that could accurately predict return to full productivity three months post mild traumatic brain injury (mTBI). Return to productivity was defined as a full return to pre-injury employment, home duties and/or study. -- Participants and Methods: Participants comprised 56 mTBI patients and 57 trauma controls (TC). Assessments were conducted at a mean of 5 days (SD 2.8) and again at 102 days (SD 14.2) post-injury. Logistic regression analyses were conducted to determine whether pre-injury, injuryrelated, post-injury and neuropsychological variables (including verbal learning, attention and information processing) were predictive of return to productivity. -- Results: At three months post-injury, both groups reported a significant reduction in paid employment hours relative to pre-injury, with the TC group reducing their hours significantly more than the mTBI group (p = .026). Hours spent performing home duties were significantly reduced for both groups, with the TC group again reducing their hours significantly more than the mTBI group (p = .011). Neither group reported a significant reduction in the number of hours devoted to study post-injury. Multivariable analysis revealed that participants who reported higher levels of subjective pain were less likely to have returned to their pre-injury productivity by three months post-injury (OR: .75, 95% CI: .58-.98, p = .034). MTBI patients with a shorter length of hospital stay were more likely to report full productivity (OR: .57, 95% CI: .58-.98, p = .012), whereas for TC there was no significant relationship between length of hospital stay and productivity (OR: 1.69, 95% CI: 1.07-2.68, p = .607). With each unit increase in verbal learning, individuals with mTBI were 1.10 times more likely to report full productivity (95% CI: 1.02-1.19) whereas for TC there was no significant relationship between verbal learning and return to productivity (OR: 1.01, 95% CI: .98-1.04). Participants involved in litigation or who were seeking compensation were significantly less likely to have returned to their pre-injury productivity levels by three months post-injury (OR: .14, 95% CI: .047-.435, p = .001). -- Conclusion: Post-injury pain may preclude both mTBI and trauma patients from returning to full productivity. Within an mTBI sample length of hospital stay and verbal learning (as measured prior to discharge) may help predict return to early productivity. Involvement in litigation or compensation-seeking has a strong, negative relationship with return to pre-injury productivity level at three months post-injury.Mode of access: World Wide Web.1 online resource (xii, 201 pages) illustration