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Single-photon detection has emerged as a method of choice for ultra-sensitive measurements of picosecond optical transients. In the short-wave infrared, semiconductor-based single-photon detectors typically exhibit relatively poor performance compared with all-silicon devices operating at shorter wavelengths. Here we show a new generation of planar germanium-on-silicon (Ge-on-Si) single-photon avalanche diode (SPAD) detectors for short-wave infrared operation. This planar geometry has enabled a significant step-change in performance, demonstrating single-photon detection efficiency of 38% at 125 K at a wavelength of 1310 nm, and a fifty-fold improvement in noise equivalent power compared with optimised mesa geometry SPADs. In comparison with InGaAs/InP devices, Ge-on-Si SPADs exhibit considerably reduced afterpulsing effects. These results, utilising the inexpensive Ge-on-Si platform, provide a route towards large arrays of efficient, high data rate Ge-on-Si SPADs for use in eye-safe automotive LIDAR and future quantum technology applications. By incorporating germanium, single-photon avalanche diode detectors using silicon-based platforms are applied to infrared light detection. Here, a cost-effective planar detector geometry is presented yielding high detection efficiency suitable for applications such as sparse photon imaging or LIDAR.

Flash memories are essential for modern electronics; here a selenium-templated polyoxometalate is used to engineer new metal–oxide–semiconductor devices. Flash memory goes molecular Flash memory is becoming standard for smart phones, cameras, memory sticks and other devices. Its achievable data storage densities are ultimately limited by the minimum size of the individual data cells that can be fabricated, so molecule-based flash memory is an attractive proposition for stretching these limits. Christoph Busche and colleagues report the design, synthesis and electronic characterization of a family of metal-oxide cluster molecules that are compatible with current technology. The new materials are highly configurable at the atomic-level and show promise for implementation in practical devices. Flash memory devices—that is, non-volatile computer storage media that can be electrically erased and reprogrammed—are vital for portable electronics, but the scaling down of metal–oxide–semiconductor (MOS) flash memory to sizes of below ten nanometres per data cell presents challenges. Molecules have been proposed to replace MOS flash memory 1 , but they suffer from low electrical conductivity, high resistance, low device yield, and finite thermal stability, limiting their integration into current MOS technologies. Although great advances have been made in the pursuit of molecule-based flash memory 2 , there are a number of significant barriers to the realization of devices using conventional MOS technologies 3 , 4 , 5 , 6 , 7 . Here we show that core–shell polyoxometalate (POM) molecules 8 can act as candidate storage nodes for MOS flash memory. Realistic, industry-standard device simulations validate our approach at the nanometre scale, where the device performance is determined mainly by the number of molecules in the storage media and not by their position. To exploit the nature of the core–shell POM clusters, we show, at both the molecular and device level, that embedding [(Se( iv )O 3 ) 2 ] 4− as an oxidizable dopant in the cluster core allows the oxidation of the molecule to a [Se( v ) 2 O 6 ] 2− moiety containing a {Se( v )–Se( v )} bond (where curly brackets indicate a moiety, not a molecule) and reveals a new 5+ oxidation state for selenium. This new oxidation state can be observed at the device level, resulting in a new type of memory, which we call ‘write-once-erase’. Taken together, these results show that POMs have the potential to be used as a realistic nanoscale flash memory. Also, the configuration of the doped POM core may lead to new types of electrical behaviour 9 , 10 , 11 . This work suggests a route to the practical integration of configurable molecules in MOS technologies as the lithographic scales approach the molecular limit 12 .

Junction-less nanowire transistors are being investigated to solve short channel effects in future CMOS technology. Here we demonstrate 8 nm diameter silicon nanowire junction-less transistors with metallic doping densities which demonstrate clear 1D electronic transport characteristics. The 1D regime allows excellent gate modulation with near ideal subthreshold slopes, on- to off-current ratios above 10 8 and high on-currents at room temperature. Universal conductance scaling as a function of voltage and temperature similar to previous reports of Luttinger liquids and Coulomb gap behaviour at low temperatures suggests that many body effects including electron-electron interactions are important in describing the electronic transport. This suggests that modelling of such nanowire devices will require 1D models which include many body interactions to accurately simulate the electronic transport to optimise the technology but also suggest that 1D effects could be used to enhance future transistor performance.

Germanium‐containing short‐wave infrared (SWIR) avalanche photodiode (APD) arrays on silicon platforms have the potential for monolithic integration into complementary metal‐oxide‐semiconductor (CMOS) integrated circuits, making them mass‐manufacturable, high‐performance, arrayed optical detectors operating at wavelengths beyond the silicon cut‐off wavelength. Here, the first high‐performance, surface‐illuminated, 10‐pixel linear array of pseudoplanar geometry germanium‐on‐silicon (Ge‐on‐Si) APDs operating at 1550 nm wavelength and at temperatures up to 378 K are demonstrated. At room temperature, the dark current, avalanche gain, responsivity, and avalanche breakdown of the devices show good uniformity. Array A exhibits a mean dark current density of 198 ± 62 mA cm−2 at 90% of the breakdown voltage. The excess noise factor is less than half that of InP‐based SWIR APD arrays, which allows Ge‐on‐Si devices to operate at a higher avalanche gain. A responsivity of 8.2 A W−1 at a gain of 20 and excess noise of 3.3 is achieved when illuminated with 1550 nm wavelength light. The detector array also demonstrates stable performance at 378 K with a maximum avalanche gain of 24. This device architecture will be applicable for the design of large‐scale APD arrays on Si platforms for SWIR detection which can be used in imaging, sensing, and optical communication applications. The fabrication and characterization of a new type of surface‐illuminated Si‐based avalanche photodiode array operating in the short‐wave infrared region using germanium as the absorber and silicon as the multiplier is reported. The demonstration of an avalanche gain of 24 at a temperature of 378 K allows the devices to operate in outdoor environments.

There is discordance among studies assessing the impact of race on outcome of patients with Triple Negative Breast Cancer (TNBC). We assessed survival outcomes for African American (AA) versus Caucasian (CA) women with TNBC treated at an urban cancer center in Memphis, TN with a predominant AA patient population. Patients with Stage I-III TNBC were identified from our breast database. Event free survival (EFS) and Breast cancer specific survival (BCSS) were the primary outcome measures. Cox proportional hazards models were fitted for EFS and BCSS. Of the 124 patients, 71% were AA. No significant association between race and stage (P = 0.21) or menopausal status (P = 0.15) was observed. Median age at diagnosis was significantly lower for AA versus CA women (49.5 vs. 55 years, P = 0.024). 92% of the patients received standard neo/adjuvant chemotherapy, with no significant difference in duration and type of chemotherapy between the races. With a median follow up of 23 months, 28% of AA vs. 19% of CA women had an event (P = 0.37). 3 year EFS and BCSS trended favorably towards CA race (77% vs. 64%, log rank P = 0.20 and 92% vs. 76%, P = 0.13 respectively) with a similar trend noted on multiple variable modeling (EFS: HR 0.62, P = 0.29; BCSS: HR 0.36, P = 0.18). AA women >/=50 years at diagnosis had a significantly worse BCSS than the CA women in that age group (P = 0.012). Older AA women with TNBC have a significantly worse breast cancer specific survival than their CA counterparts. Overall, there is a trend towards lower survival for AA women compared to Caucasians despite uniformity of tumor phenotype and treatment. The high early event rate, irrespective of race, underscores the need for effective therapies for women with TNBC.

This project developed a robust and reliable process to pattern < 5 nm features in negative tone Hydrogen silsesquioxane (HSQ) resist using high resolution electron beam lithography and developed a low damage reactive ion etch (RIE) process to fabricate silicon nanowires on degenerately doped n-type silicon-on-insulator (SOI) substrates. A process to thermally grow high quality silicon dioxide (SiO2) (between 5-15 nm) is also developed to passivate onto the etched silicon nanowire devices to serve the purposes of gate dielectric and a diffusion barrier to minimize the donor deactivation. The measured interface state trap density (Dit) of the 10 nm thermally grown oxide is 1.3x1010 cm−2 eV−1 with a breakdown voltage of ~7 V. Using optimized processes for lithography, dry etch and thermal oxidation, Hall bar and Greek cross devices are fabricated with mean widths from 45 to 4 nm on SOI substrates with a doping density ~ 2x1019, 4x1019, 8x1019 and 2x1020 atoms/cm3 and electronically characterized at room and cryogenic temperatures (from 1.4 to 300 K) to allow resistivity, mobility and carrier density to be extracted directly as a function of temperature. This allowed to probe electron transport and scattering mechanisms in degenerately doped silicon nanowires. The mean free path is theoretically calculated and directly compared with the widths of the nanowires by which it can be approximated that the electron transport is 3 dimensional (3D) for the 12 nm wide nanowire which has likely to be changed to 2D and 1D for the 7 nm and 4 nm wide nanowires respectively. Moreover the experimental mobility is directly compared with a number of theoretically calculated mobilities using Matthiessen’s rule, where it has been determined that the neutral impurity scattering is the dominant scattering mechanism limiting the performance of silicon nanowires. Using silicon nanowires, junctionless transistors are fabricated on SOI substrate with a doping density ~ 4x1019 atoms/cm3 and electronically characterized at room and cryogenic temperatures (from 1.4 to 300 K). It was observed that reducing the width of channel from 24 to 8 nm, the transistor changed their operation from depletion to enhancement mode due to increase in the surface depletion at smaller length scales. Since the drain current in a junctionless transistor is proportional to the doping density, a high on-state drive current ~ 1.28 mA/µm has been observed with sub-threshold slope (SS) ~ 66 mV/decade at 300 K. Moreover temperature dependent measurements revealed a low SS ~ 39 mV/decade at 70 K and single electron oscillations at 1.4 K. Finally, independent arrays of 2 terminal nanowires devices with mean widths from 45 to 4 nm are fabricated on SOI substrate with a doping density ~ 8x1019 atoms/cm3 to detect polyoxometalate (POM) molecules [W18O54(SeO3)2]4−. A change in resistivity has been observed ~ 3.6 m ohm-cm (corresponds to ~ 13 % increase) when POM molecules are coated around the nanowires, shown n-type behaviour of molecules. POM molecules exhibit highly redox properties, therefore side-gated FETs with mean width ~ 4 nm were fabricated on SOI substrate with a doping density ~ 4x1019 atoms/cm3 where side-gate was used to apply alternative ± pulses of 20 V to charge and discharge the POM molecules to demonstrate flash memory operation. The average change in the threshold voltage was ~ 1.2 V between the charging (program) and the discharging (erase) cycles. The program/erase time is currently limited to 100 ms for a reasonable single-to-noise ratio. Moreover no significant decay in the stored charge has yet been measured over a period of 2 weeks (336 hours).

We investigate the low temperature transport in 8 nm diameter Si junctionless nanowire field effect transistors fabricated by top down techniques with a wrap-around gate and two different activated doping densities. First we extract the intrinsic gate capacitance of the device geometry from a device that shows Coulomb blockade at 13 mK with over 500 Coulomb peaks across a gate voltage range of 6 V indicating the formation of a single island in the entire nanowire channel. In two other devices, doped Si:P \\(4\\times10^{19}\\,\\text{cm}^{-3}\\) and \\(2\\times10^{20}\\,\\text{cm}^{-3}\\), we observe quantum interference and use the extracted gate coupling to determine the dominant energy scale and the corresponding mean-free paths. For the higher doped device the analysis yields a mean free path of \\(4\\pm2\\,\\text{nm}\\), which is on the order of the average dopant spacing and suggests scattering on unactivated or activated dopants. For the device with an activated dopant density of \\(4\\times10^{19}\\,\\text{cm}^{-3}\\) the quantum interference effects suggest a mean free path of \\(10\\pm2\\,\\text{nm}\\), which is comparable to the nanowire width, and thus quasi-ballistic transport. A temperature dependent analysis of Universal Conductance Fluctuations suggests a coherence length above the nanowire length for temperatures below 1.9 K and decoherence from 1D electron-electron interactions for higher temperatures. The mobility is limited by scattering on impurities rather than the expected surface roughness scattering for nanowires with diameters larger or comparable to the Fermi wavelength. Our measurements therefore provide insight into the performance limitations from dominant scattering and dephasing mechanisms in technologically relevant silicon device geometries.

Although they are important disease vectors mosquito biodiversity in Pakistan is poorly known. Recent epidemics of dengue fever have revealed the need for more detailed understanding of the diversity and distributions of mosquito species in this region. DNA barcoding improves the accuracy of mosquito inventories because morphological differences between many species are subtle, leading to misidentifications. Sequence variation in the barcode region of the mitochondrial COI gene was used to identify mosquito species, reveal genetic diversity, and map the distribution of the dengue-vector species in Pakistan. Analysis of 1684 mosquitoes from 491 sites in Punjab and Khyber Pakhtunkhwa during 2010-2013 revealed 32 species with the assemblage dominated by Culex quinquefasciatus (61% of the collection). The genus Aedes (Stegomyia) comprised 15% of the specimens, and was represented by six taxa with the two dengue vector species, Ae. albopictus and Ae. aegypti, dominant and broadly distributed. Anopheles made up another 6% of the catch with An. subpictus dominating. Barcode sequence divergence in conspecific specimens ranged from 0-2.4%, while congeneric species showed from 2.3-17.8% divergence. A global haplotype analysis of disease-vectors showed the presence of multiple haplotypes, although a single haplotype of each dengue-vector species was dominant in most countries. Geographic distribution of Ae. aegypti and Ae. albopictus showed the later species was dominant and found in both rural and urban environments. As the first DNA-based analysis of mosquitoes in Pakistan, this study has begun the construction of a barcode reference library for the mosquitoes of this region. Levels of genetic diversity varied among species. Because of its capacity to differentiate species, even those with subtle morphological differences, DNA barcoding aids accurate tracking of vector populations.

Study of monogenic forms of obesity has demonstrated the pivotal role of the central leptin–melanocortin pathway in controlling energy balance, appetite and body weight 1 . The majority of loss-of-function mutations (mostly recessive or co-dominant) have been identified in genes that are directly involved in leptin–melanocortin signaling. These genes, however, only explain obesity in <5% of cases, predominantly from outbred populations 2 . We previously showed that, in a consanguineous population in Pakistan, recessive mutations in known obesity-related genes explain ~30% of cases with severe obesity 3 , 4 – 5 . These data suggested that new monogenic forms of obesity could also be identified in this population. Here we identify and functionally characterize homozygous mutations in the ADCY3 gene encoding adenylate cyclase 3 in children with severe obesity from consanguineous Pakistani families, as well as compound heterozygous mutations in a severely obese child of European-American descent. These findings highlight ADCY3 as an important mediator of energy homeostasis and an attractive pharmacological target in the treatment of obesity. Genetic analysis of children with severe obesity identifies mutations in the ADCY3 gene (encoding adenylate cyclase 3). These variants are rare in public databases and affect the functional activity of the protein, indicating that ADCY3 is a potential pharmacological target for obesity treatment.

Jute (Corchorus capsularis) is a widely cultivated fibrous species with important physiological characteristics including biomass, a deep rooting system, and tolerance to metal stress. Furthermore, Corchorus species are indigenous leafy vegetables and show phytoremediation potential for different heavy metals. This species has been used for the phytoremediation of different toxic pollutants such as copper (Cu), cadmium (Cd), zinc (Zn), mercury (Hg) and lead (Pb). The current literature highlights the physiological and morphological characteristics of jute that are useful to achieve successful phytoremediation of different pollutants. The accumulation of these toxic heavy metals in agricultural regions initiates concerns regarding food safety and reductions in plant productivity and crop yield. We discuss some innovative approaches to increase jute phytoremediation using different chelating agents. There is a need to remediate soils contaminated with toxic substances, and phytoremediation is a cheap, effective, and in situ alternative, and jute can be used for this purpose.