Intrinsic and Atomic Layer Etching Enhanced Area-Selective Atomic Layer Deposition of Molybdenum Disulfide Thin Films

For continual scaling in microelectronics, new processes for precise high volume fabrication are required. Area-selective atomic layer deposition (ASALD) can provide an avenue for self-aligned material patterning and offers an approach to correct edge placement errors commonly found in top-down patterning processes. Two-dimensional transition metal dichalcogenides also offer great potential in scaled microelectronic devices due to their high mobilities and few-atom thickness. In this work, we report ASALD of MoS2 thin films by deposition with MoF6 and H2S precursor reactants. The inherent selectivity of the MoS2 atomic layer deposition (ALD) process is demonstrated by growth on common dielectric materials in contrast to thermal oxide/ nitride substrates. The selective deposition produced few layer MoS2 films on patterned growth regions as measured by Raman spectroscopy and time-of-flight secondary ion mass spectrometry. We additionally demonstrate that the selectivity can be enhanced by implementing atomic layer etching (ALE) steps at regular intervals during MoS2 growth. This area-selective ALD process provides an approach for integrating 2D films into next-generation devices by leveraging the inherent differences in surface chemistries and providing insight into the effectiveness of a supercycle ALD and ALE process

A high-resolution map of human evolutionary constraint using 29 mammals.

The comparison of related genomes has emerged as a powerful lens for genome interpretation. Here we report the sequencing and comparative analysis of 29 eutherian genomes. We confirm that at least 5.5% of the human genome has undergone purifying selection, and locate constrained elements covering ∼4.2% of the genome. We use evolutionary signatures and comparisons with experimental data sets to suggest candidate functions for ∼60% of constrained bases. These elements reveal a small number of new coding exons, candidate stop codon readthrough events and over 10,000 regions of overlapping synonymous constraint within protein-coding exons. We find 220 candidate RNA structural families, and nearly a million elements overlapping potential promoter, enhancer and insulator regions. We report specific amino acid residues that have undergone positive selection, 280,000 non-coding elements exapted from mobile elements and more than 1,000 primate- and human-accelerated elements. Overlap with disease-associated variants indicates that our findings will be relevant for studies of human biology, health and disease

Setting our sights on infectious diseases

In May 2019, the Wellcome Centre for Anti-Infectives Research (WCAIR) at the University of Dundee, UK, held an international conference with the aim of discussing some key questions around discovering new medicines for infectious diseases and a particular focus on diseases affecting Low and Middle Income Countries. There is an urgent need for new drugs to treat most infectious diseases. We were keen to see if there were lessons that we could learn across different disease areas and between the preclinical and clinical phases with the aim of exploring how we can improve and speed up the drug discovery, translational, and clinical development processes. We started with an introductory session on the current situation and then worked backward from clinical development to combination therapy, pharmacokinetic/pharmacodynamic (PK/PD) studies, drug discovery pathways, and new starting points and targets. This Viewpoint aims to capture some of the learnings

An evaluation of thermal imaging as a tool for assessing occupancy of enclosed nests

Thermal cameras are being used increasingly in the bird-ringing community and preliminary reports suggest they have a wide range of relevant applications. However, there has been little quantitative assessment of these methods. In this study we tested the use of a thermal imager to assess the occupancy of enclosed nests, using nest-box populations of small passerines. Based on a thermal image of each nest box, observers were able to predict nest-box occupancy with a combined success rate of 85.9%. The observers were able to identify when nest boxes contained a heat source relating to an active nest but unable to differentiate between warm clutches and live broods. The age of the brood significantly influenced the predictions, reflecting the limited ability of young broods to maintain their body temperatures independently. There were no significant effects from potential confounding variables relating to solar exposure, nest-box design or ambient temperature, although these may have accounted for a small number of incorrect predictions. Overall, it was found that thermal imagers provide an effective, non-invasive and efficient method for monitoring nest-box occupancy, with inferences about suitability for other types of enclosed nest

Towards Plasma Enhanced Atomic Layer Deposition

The fabrication of microelectronics relies on thin film technologies. As the demand for improved performance of microchips continues to escalate, atomic layer deposition (ALD) has emerged as a crucial technique in enabling precise and controlled thin film deposition. Plasma-enhanced ALD in particular is an energy-enhanced method for synthesizing thin films with mono-layer resolution. Unlike conventional thermal ALD processes where chemical precursors react with a heated substrate to deposit the thin film, forming a plasma of the ALD precursors allows for alternate reaction paths, potentially leading to improved film density, crystallinity, and mechanical properties at lower deposition temperatures. Plasma exposure during ALD can also assist in the removal of surface contaminants during the deposition process. In this project, a capacitively coupled plasma is generated by applying a direct current (DC) bias between the powered and grounded electrodes in a quartz chamber, inducing an electric field. This couples with the precursor gas to create a high-energy plasma that produces energetic reactive species, which can then be directed to the substrate, providing novel reaction pathways having a more desired thermal budget to achieve the desired film properties. This chamber will be integrated into an ALD system to enable plasma-enhanced ALD. The chemical, physical, and electrical properties of the resulting films will be characterized

Role of Post-Deposition Annealing on Defectivity in 2D Materials

With the increasing complexity of microelectronics, the development of new forward-looking materials and processes has become imperative to enable their functionality. Among the potential pathways to further miniaturize devices, two-dimensional (2D) materials offer great promise due to their outstanding electrical properties even at the atomic level. Molybdenum disulfide (MoS2) is a notable example of a 2D material that exhibits these desirable characteristics and can be synthesized through chemical vapor deposition (CVD) at elevated temperatures. For deposition temperatures below 300°C, atomic layer deposition (ALD) shows promise for synthesis of MoS2 films, but film quality is generally lower than CVD films, and ALD films often employ post-deposition annealing (PDA) to improve their quality. Ultimately, electrical performance of 2D materials is of primary interest, yet device fabrication can be time consuming and expensive. Thus, there arises a need for the ability to rapidly evaluate the quality of ALD thin films prior to test device fabrication. Raman spectroscopy, a powerful analytical technique widely employed for the characterization of 2D thin films, presents itself as a promising approach for efficient metrology. Variations in the crystallinity and defect density of MoS2 can induce peak shifts or broadening in the corresponding Raman spectra. Establishing a quantitative correlation between these changes and the film properties would enable a swift and non-destructive method for characterizing thin films to evaluate which processing conditions produce films of sufficient quality for device fabrication. To establish this approach, ALD MoS2 films will be deposited on a variety of substrates and subsequently subjected to various annealing conditions, including different temperatures, durations, and environments. The Raman spectra of the annealed samples will be evaluated using deconvolution of the phonon modes giving rise to the peaks in the spectra. These data, along with processing conditions, will be correlated with defect densities acquired through transmission electron and scanning probe microscopies and film conductivity. This approach will establish a quantitative relationship between Raman spectral features and film mobilities, which will enable high-throughput metrology for ALD process development of high quality 2D materials

Treatment patterns and costs of patients with ankylosing spondylitis initiating biologic therapy in taiwan – a population-based analysis

International audienc

Estimating the response and economic burden of rheumatoid arthritis patients treated with biologic disease-modifying antirheumatic drugs in Taiwan using the National Health Insurance Research Database (NHIRD).

BACKGROUND:Previous studies in Taiwan utilizing the Taiwan's National Health Insurance Database (NHIRD) have estimated the direct healthcare costs of RA patients, but they have not focused on patients on bDMARDs, or considered patients' response to therapy. OBJECTIVES:The objective of this study was to estimate the rate of inadequate response for patients newly treated with biologic disease-modifying antirheumatic drugs (bDMARDs) as well as their costs and resource use. METHODS:Data were from the catastrophic illness file within the NHIRD from 1/1/2009 to 12/31/2013. Patients with RA, which was categorized by the presence of a catastrophic illness card, that were previously bDMARD-naïve, were included in this study if they initiated their first bDMARD during the index period. The index period included all of 2010, a pre-index period consisting of the index date- 365 days, and a follow-up period including the index date to 365 days post-index, were also included. Previously biologically-naïve patients were indexed into the study on the date of their first claim for a bDMARD. A validated algorithm was used to examine the rate of inadequate response (IR) in the biologically-naïve cohort of patients. Inadequate responders met one or more of the following criteria during their year of follow-up: low adherence (proportion of days covered <0.80); switched to or added a second bDMARD; added a new conventional synthetic DMARD (csDMARD); received ≥1 glucocorticoid injection; or increased oral glucocorticoid dosing. All-cause mean annual direct costs and resource use were measured in the year of follow-up. Costs were converted from NT$to USD using 1 NT$ = 0.033 USD. RESULTS:A total of 818 patients with RA initiated their first bDMARD (54% etanercept and 46% adalimumab) in 2010. After one year of follow-up, 32% (n = 258) were classified as stable, 66% (n = 540) had an IR, and 2% (n = 20) were lost to follow-up. During the follow-up period mean annual total direct costs were $16,136 for stable patients compared to$14,154 for patients with IR. Mean annual non-medication direct costs were $937 for stable patients and$1,574 for patients with IR. Mean annual hospitalizations were higher for patients with IR (0.46) compared to stable patients (0.10) during the one year follow-up period. CONCLUSIONS:The majority of patients that were previously naïve to bDMARDs had an IR to their first bDMARD during the year of follow-up. Patients with an IR had numerically increased all-cause resource utilization and non-medication costs during the follow-up period compared to patients with stable disease. This level of IR suggests an unmet need in the RA treatment paradigm

Metallic 1T phase source/drain electrodes for field effect transistors from chemical vapor deposited MoS2

Two dimensional transitionmetal dichalcogenides (2D TMDs) offer promise as optoelectronic materials due to their direct band gap and reasonably good mobility values. However, most metals form high resistance contacts on semiconducting TMDs such as MoS2. The large contact resistance limits the performance of devices. Unlike bulk materials, low contact resistance cannot be stably achieved in 2D materials by doping. Here we build on our previous work in which we demonstrated that it is possible to achieve low contact resistance electrodes by phase transformation. We show that similar to the previously demonstrated mechanically exfoliated samples, it is possible to decrease the contact resistance and enhance the FET performance by locally inducing and patterning the metallic 1T phase of MoS2 on chemically vapor deposited material. The device properties are substantially improved with 1T phase source/drain electrodes