Interfacial Resistive Properties of Nickel Silicide Thin Films to Doped Silicon

Improved means of electrical access to nanotechnology devices and accurate nanoscale characterization of electrical properties of ultrathin layers constituting such electrical contacts is of utmost interest to nanoelectronics researchers. This paper reports on the characterization of interfacial resistive properties of ohmic contacts to doped silicon, incorporating thin films of nickel silicide. Silicon doping was achieved by carefully designed ion implantation of antimony ͑for n-type͒ and boron ͑for p-type͒. Cross Kelvin resistor test structures were used to extract the specific contact resistivity ͑SCR͒ values for the different ohmic contacts fabricated. SCR values, which are quantitative characteristics of interfacial resistive properties, as low as 5.0 ϫ 10 −9 ⍀ cm 2 for contacts to antimony-doped silicon and 3.5 ϫ 10 −9 ⍀ cm 2 to boron-doped silicon were estimated. These experimental results, representing the lowest such values measured, were based on a rigorous evaluation technique and verified by finite element modeling

Pathways into services for offenders with intellectual disabilities : childhood experience, diagnostic information and offence variables

The patterns and pathways into intellectual disability (ID) offender services were studied through case file review for 477 participants referred in one calendar year to community generic, community forensic, and low, medium, and maximum secure services. Data were gathered on referral source, demographic information, index behavior, prior problem behaviors, diagnostic information, and abuse or deprivation. Community referrers tended to refer to community services and secure service referrers to secure services. Physical and verbal violence were the most frequent index behaviors, whereas contact sexual offenses were more prominent in maximum security. Age at first incident varied with security, with the youngest in maximum secure services. Attention-deficit/hyperactivity disorder or conduct disorder was the most frequently recorded diagnosis, and severe deprivation was the most frequent adverse developmental experience. Fire starting, theft, and road traffic offenses did not feature prominently. Generic community services accepted a number of referrals with forensic-type behavior and had higher proportions of both women and people with moderate or severe ID

USING A TWO-CONTACT CIRCULAR TEST STRUCTURE TO DETERMINE THE SPECIFIC CONTACT RESISTIVITY OF CONTACTS TO BULK SEMICONDUCTORS

We present a numerical method to extract specific contact resistivity (SCR) for three-dimensional (3-D) contact structures using a two-electrode test structure. This method was developed using Finite Element Modeling (FEM). Experimental measurements were performed for contacts of 200 nm nickel (Ni) to p+-type germanium (Ge) substrates and 200 nm of Titanium (Ti) on 4H-Silicon Carbide (SiC). The SCR obtained was (2.3-27) ×10-6 Ω·cm2 for the Ni-Ge contacts and (1.3-2.4）×10-3 Ω·cm2 for the Ti-SiC

CIRCULAR TEST STRUCTURES FOR DETERMINING THE SPECIFIC CONTACT RESISTANCE OF OHMIC CONTACTS

Though the transport of charge carriers across a metal-semiconductor ohmic interface is a complex process in the realm of electron wave mechanics, such an interface is practically characterised by its specific contact resistance. Error correction has been a major concern in regard to specific contact resistance test structures and investigations by finite element modeling demonstrate that test structures utilising circular contacts can be more reliable than those designed to have square shaped contacts as test contacts become necessarily smaller. Finite element modeling software NASTRAN can be used effectively for designing and modeling ohmic contact test structures and can be used to show that circular contacts are efficient in minimising error in determining specific contact resistance from such test structures. Full semiconductor modeling software is expensive and for ohmic contact investigations is not required when the approach used is to investigate test structures considering the ohmic interface as effectively resistive

Organic Field-Effect Transistors as Flexible, Tissue-Equivalent Radiation Dosimeters in Medical Applications

Radiation therapy is one of the most prevalent procedures for cancer treatment, but the risks of malignancies induced by peripheral beam in healthy tissues surrounding the target is high. Therefore, being able to accurately measure the exposure dose is a critical aspect of patient care. Here a radiation detector based on an organic field‐effect transistor (RAD‐OFET) is introduced, an in vivo dosimeter that can be placed directly on a patient\u27s skin to validate in real time the dose being delivered and ensure that for nearby regions an acceptable level of low dose is being received. This device reduces the errors faced by current technologies in approximating the dose profile in a patient\u27s body, is sensitive for doses relevant to radiation treatment procedures, and robust when incorporated into conformal large‐area electronics. A model is proposed to describe the operation of RAD‐OFETs, based on the interplay between charge photogeneration and trapping

Unusually High Thermal Conductivity of Carbon Nanotubes

Combining equilibrium and non-equilibrium molecular dynamics simulations with accurate carbon potentials, we determine the thermal conductivity $\lambda$ of carbon nanotubes and its dependence on temperature. Our results suggest an unusually high value ${\lambda}{\approx}6,600$~W/m$\cdot$K for an isolated (10,10) nanotube at room temperature, comparable to the thermal conductivity of a hypothetical isolated graphene monolayer or diamond. Our results suggest that these high values of $\lambda$ are associated with the large phonon mean free paths in these systems; substantially lower values are predicted and observed for the basal plane of bulk graphite.Comment: 4 pages 3 figures (5 postscript files), submitted for publicatio

ANALYTICAL TEST STRUCTURE MODEL FOR DETERMINING LATERAL EFFECTS OF TRI-LAYER OHMIC CONTACT BEYOND THE CONTACT EDGE

Contact test structures where there is more than one non-metal layer, are significantly more complex to analyse compared to when there is only one such layer like active silicon on an insulating substrate. Here, we use analytical models for complex test structures in a two contact test structure and compare the results obtained with those from Finite Element Models (FEM) of the same test structures. The analytical models are based on the transmission line model and the tri-layer transmission line model in particular, and do not include vertical voltage drops except for the interfaces. The comparison shows that analytical models for tri-layer contacts to dual active layers agree well with FEM when the Specific Contact Resistances (SCR) of the contact interfaces is a significant part of the total resistance. Overall, there is a broad range of typical dual-layer-to-TLTLM contacts where the analytical model works. The insight (and quantifying) that the analytical model gives on the effect of the presence of the contact, on the distribution of current away from the contact is shown

Review: Placental derived biomarkers of pregnancy disorders

Pregnancy is one of the greatest physiological challenges that a women can experience. The physiological adaptations that accompany pregnancy may increase the risk of developing a number of disorders that can lead to both acute and chronic physiological outcomes. In addition, fetal development may be impaired and, if the fetus survives, the child may be at an increased risk of disease throughout life. Pregnancy disorders are poorly predicted by traditional risk factors and maternal history alone. The identification of biomarkers that can predict incidence and severity of disease would allow for improved and targeted prophylactic therapies to prevent adverse maternal and fetal outcomes. Many of these pregnancy disorders, including preeclampsia, intrauterine growth restriction, gestational diabetes mellitus and preterm birth are known to be regulated at least in part by poor trophoblast invasion and/or dysregulated placental function. Cellular stress within the placenta increases the release of a number of factors into the maternal circulation. While many of these factors minimally impact maternal biology, others affect key physiological systems and contribute to disease. Importantly, these factors may be detected in physiological fluids and have predicative capacity making them ideal candidates as biomarkers of pregnancy disorders. This review will discuss what is known about these placental derived biomarkers of pregnancy disorders and highlight potential clinical opportunities for disease prediction and diagnosis

Transcutaneous vagus nerve stimulation (t-VNS): A novel effective treatment for temper outbursts in adults with Prader-Willi Syndrome indicated by results from a non-blind study.

Temper outbursts are a severe problem for people with Prader-Willi Syndrome (PWS). Previous reports indicate that vagus nerve stimulation (VNS) may reduce maladaptive behaviour in neurodevelopmental disorders, including PWS. We systematically investigated the effectiveness of transcutaneous VNS (t-VNS) in PWS. Using a non-blind single case repeat measures modified ABA design, with participants as their own controls, t-VNS was evaluated in five individuals with PWS [three males; age 22-41 (M = 26.8)]. After a baseline phase, participants received four-hours of t-VNS daily for 12 months, followed by one month of daily t-VNS for two-hours. The primary outcome measure was the mean number of behavioural outbursts per day. Secondary outcomes included findings from behavioural questionnaires and both qualitative and goal attainment interviews. Four of the five participants who completed the study exhibited a statistically significant reduction in number and severity of temper outbursts after approximately nine months of daily four-hour t-VNS. Subsequent two-hour daily t-VNS was associated with increased outbursts for all participants, two reaching significance. Questionnaire and interview data supported these findings, the latter indicating potential mechanisms of action. No serious safety issues were reported. t-VNS is an effective, novel and safe intervention for chronic temper outbursts in PWS. We propose these changes are mediated through vagal projections and their effects both centrally and on the functioning of the parasympathetic nervous system. These findings challenge our present biopsychosocial understanding of such behaviours suggesting that there is a single major mechanism that is modifiable using t-VNS. This intervention is potentially generalizable across other clinical groups. Future research should address the lack of a sham condition in this study along with the prevalence of high drop out rates, and the potential effects of different stimulation intensities, frequencies and pulse widths

Learning Mazes with Aliasing States: An LCS Algorithm with Associative Perception

Learning classifier systems (LCSs) belong to a class of algorithms based on the principle of self-organization and have frequently been applied to the task of solving mazes, an important type of reinforcement learning (RL) problem. Maze problems represent a simplified virtual model of real environments that can be used for developing core algorithms of many real-world applications related to the problem of navigation. However, the best achievements of LCSs in maze problems are still mostly bounded to non-aliasing environments, while LCS complexity seems to obstruct a proper analysis of the reasons of failure. We construct a new LCS agent that has a simpler and more transparent performance mechanism, but that can still solve mazes better than existing algorithms. We use the structure of a predictive LCS model, strip out the evolutionary mechanism, simplify the reinforcement learning procedure and equip the agent with the ability of associative perception, adopted from psychology. To improve our understanding of the nature and structure of maze environments, we analyze mazes used in research for the last two decades, introduce a set of maze complexity characteristics, and develop a set of new maze environments. We then run our new LCS with associative perception through the old and new aliasing mazes, which represent partially observable Markov decision problems (POMDP) and demonstrate that it performs at least as well as, and in some cases better than, other published systems