Visible and infrared photocurrent enhancement in a graphene-silicon Schottky photodetector through surface-states and electric field engineering

The design of efficient graphene-silicon (GSi) Schottky junction photodetectors requires detailed understanding of the spatial origin of the photoresponse. Scanning-photocurrent-microscopy (SPM) studies have been carried out in the visible wavelengths regions only, in which the response due to silicon is dominant. Here we present comparative SPM studies in the visible ($\lambda$ = 633nm) and infrared ($\lambda$ = 1550nm) wavelength regions for a number of GSi Schottky junction photodetector architectures, revealing the photoresponse mechanisms for silicon and graphene dominated responses, respectively, and demonstrating the influence of electrostatics on the device performance. Local electric field enhancement at the graphene edges leads to a more than ten-fold increased photoresponse compared to the bulk of the graphene-silicon junction. Intentional design and patterning of such graphene edges is demonstrated as an efficient strategy to increase the overall photoresponse of the devices. Complementary simulations and modeling illuminate observed effects and highlight the importance of considering graphene's shape and pattern and device geometry in the device design

Bistability and oscillatory motion of natural nano-membranes appearing within monolayer graphene on silicon dioxide

The recently found material graphene is a truly two-dimensional crystal and exhibits, in addition, an extreme mechanical strength. This in combination with the high electron mobility favours graphene for electromechanical investigations down to the quantum limit. Here, we show that a monolayer of graphene on SiO2 provides natural, ultra-small membranes of diameters down to 3 nm, which are caused by the intrinsic rippling of the material. Some of these nano-membranes can be switched hysteretically between two vertical positions using the electric field of the tip of a scanning tunnelling microscope (STM). They can also be forced to oscillatory motion by a low frequency ac-field. Using the mechanical constants determined previously, we estimate a high resonance frequency up to 0.4 THz. This might be favorable for quantum-electromechanics and is prospective for single atom mass spectrometers.Comment: 9 pages, 4 figure

Anisotropic photoconductivity in graphene

We investigate the photoconductivity of graphene within the relaxation time approximation. In presence of the inter-band transitions induced by the linearly polarized light the photoconductivity turns out to be highly anisotropic due to the pseudospin selection rule for Dirac-like carriers. The effect can be observed in clean undoped graphene samples and be utilized for light polarization detection.Comment: 4 pages, 2 figure

Growth and properties of few-layer graphene prepared by chemical vapor deposition

The structure, and electrical, mechanical and optical properties of few-layer graphene (FLG) synthesized by chemical vapor deposition (CVD) on a Ni coated substrate were studied. Atomic resolution transmission electron microscope (TEM) images show highly crystalline single layer parts of the sample changing to multilayer domains where crystal boundaries are connected by chemical bonds. This suggests two different growth mechanisms. CVD and carbon segregation participate in the growth process and are responsible for the different structural formations found. Measurements of the electrical and mechanical properties on the centimeter scale provide evidence of a large scale structural continuity: 1) in the temperature dependence of the electrical conductivity, a non-zero value near 0 K indicates the metallic character of electronic transport; 2) the Young's modulus of a pristine polycarbonate film (1.37 GPa) improves significantly when covered with FLG (1.85 GPa). The latter indicates an extraordinary Young modulus value of the FLG-coating of TPa orders of magnitude. Raman and optical spectroscopy support the previous conclusions. The sample can be used as a flexible and transparent electrode and is suitable for special membranes to detect and study individual molecules in high resolution TEM

Pengaruh Varietas dan Pupuk Petroganik Terhadap Pertumbuhan, Produksi dan Viabilitas Benih Jagung (Zea mays L.)

The Effect of Varieties and Petroganik Fertilizer to Growth, Production, and SeedViability of Corn (Zea mays L) ABSTRACT The purpose of this study was to determine the effect of varieties and Petroganik fertilizer on the growth , production, and seed viability of corn as well as the interaction that occurbetween the two treatments . This study was conducted in the Experimental Laboratory of theFaculty of Agriculture and Laboratory of Seed Science and Technology, Syiah Kuala University from March to August 2013. The design used both in the field and the laboratory wasRandomized Block Design (RBD ) factorial with 2 treatment. The first treatment was doses ofPetroganik fertilizer with 4 levels , namely 0 kg / ha ( P0 ) , 500 kg / ha ( P1 ) , 750 kg / ha ( P2 )and 1000 kg / ha ( P3 ) and the second was varieties with 3 different varieties namely Srikandi(V1) , Lamuru ( V2 ) and Bisma ( V3 ), and repeated three times. The parameters observed in the field include plant height ( cm ) , stem diameter ( mm ) , number of leaves ( strands ) , leaf length( cm ), width of leaf ( cm ) , number of cobs per plant , cob weight with cornhusk (g) , cob weight without cornhusk ( g ) , cob length without cornhusk ( cm ) , cob without cornhusk diameter ( mm ) , dried shelled weight ( g ) and the potential yield / ha ( kg ) . For observations in the laboratory include growth potential, germination, growth speed , growth simultaneity and dry weight of normal seedling ( g ). The results showed that the use of Petroganik fertilizers witha dose of 1000 kg / ha showed the best results in almost every parameter of observation , whereas for varieties , use of Srikandi varieties showed the best results in almost all parameters of the observations in terms of growth , yield and seed viability in laboratory level. Keyword : Varities, Petroganik Fertilizer, Corn PENGARUH VARIETAS DAN PUPUK PETROGANIK TERHADAP PERTUMBUHAN,PRODUKSI DAN VIABILITAS BENIH JAGUNG (Zea mays L.). ABSTRAK Tujuan dari penelitian ini adalah untuk mengetahui pengaruh varietas dan pemberian pupuk Petroganik terhadap pertumbuhan, produksi, dan viabilitas benih jagung serta interaksi yang terjadi diantara perlakuan pupuk Petroganik dan perlakuan varietas. Penelitian inidilaksanakan di Kebun Percobaan Fakultas Pertanian dan Laboratorium Ilmu dan TeknologiBenih Universitas Syiah Kuala. Penelitian dilaksanakan dari bulan Maret sampai dengan Agustus2013, Rancangan yang digunakan baik di lapangan maupun di laboratorium adalah RancanganAcak Kelompok (RAK) pola faktorial dengan 2 perlakuan yaitu dosis pupuk Petroganik dengan4 taraf, yaitu 0 kg/ha (P0), 500 kg/ha (P1), 750 kg/ha (P2) dan 1000 kg/ha (P)dan perlakuankedua yaitu varietas dengan 3 varietas yang berbeda yaitu Srikandi (V1),Lamuru (V2) dan Bisma(V3) dengan tiga ulangan. Parameter yang diamati di lapangan meliputi tinggi tanaman (cm),diameter pangkal batang (mm), jumlah daun (helai), panjang daun (cm) lebar daun (cm), jumlah tongkol per tanaman, bobot tongkol berkelobot (g), bobot tongkol tanpa kelobot (g), panjang tongkol tanpa kelobot (cm), diameter tongkol tanpa kelobot (mm), berat pipilan kering (g) danpotensi hasil/ha (kg). Untuk pengamatan di laboratorium antara lain potensi tumbuh, daya berkecambah, kecepatan tumbuh, keserempakan tumbuh dan berat kering kecambah normal (g). Hasil penelitian menunjukkan bahwa penggunaan pupuk Petroganik dengan dosis 1000 kg/hamenunjukkan hasil terbaik hampir pada setiap parameter pengamatan, sedangkan untuk varietas, penggunaan varietas Srikandi menunjukkan hasil terbaik hampir di seluruh parameter pengamatan baik dari segi pertumbuhan, hasil dan tingkat viabilitas benih di laboratorium.Banda Ace

Interoperability between heterogeneous Blockchains for Supply Chains

Det er et behov for interoperabilitet i det nåværende blokkjeder miljøet for a skape et mindre fragmentert blokkjeder økosystem. I de siste årene har det vært et økt fokus på interoperabilitet mellom homogene blokkjeder. Med de unike fordelene gitt av tillatede og tillatelsesløse blokkjeder, er det usannsynlig at homogen interoperabilitet vil løse interoperabilitetsproblemet. Derfor må det settes fokus på heterogen interoperabilitet. Denne oppgaven utviklet to produkter etter det designvitenskapelige paradigmet, og løste våre tre forskningsspørsmål: Er det en måte å interoperere data mellom to heterogene blokkjeder? Hva er ytelsen, og hva er problemene med den valgte interoperabilitetsløsningen? Kan Self-sovereign identiteter brukes til å deanonymisere krysskjededata mellom to heterogene blokkjeder? Ved å svare på disse tre spørsmålene ble dagens eksisterende heterogene interoperabilitetsløsninger funnet, og en fungerende løsning ble bygget basert på den overlegne løsningen. Eksperimenter ble utført ved bruk av de utviklede produktene, med fokus på løsningens ytelse og avdekket problemer den hadde. Et annet produkt ble opprettet for å løse anonymiseringsproblemet som ble oppdaget, ved å bruke Self-sovereign identitet, noe som ga det ønskede resultatet av deanonymisering av dataene sendt over krysskjedeløsningen.There is a need for interoperability in the current blockchain environment to shape a less fragmented blockchain ecosystem. In recent years there has come a focus on interoperability between homogenous blockchains. With the unique benefits provided by permissioned and permissionless blockchains, it is unlikely that homogenous interoperability will solve the interoperability issue. Therefore a focus has to be placed on heterogeneous interoperability. This thesis developed two products following the design science paradigm, solving our three research questions: Is there a way to interoperate data between two heterogeneous blockchains? What is the performance, and what are the issues of the selected interoperability solution? Can Self-sovereign identities be used to deanonymize cross-chain data between two heterogeneous blockchains? By answering these three questions, the current existing heterogeneous interoperability solutions were found, and a working solution was built based on the superior solution. Experiments were done using the developed products, focusing on the solution's performance and exposing problems it had. A second product was created to solve the anonymization issue discovered, using Self-sovereign identity, yielding the desired result of deanonymizing the data sent over the cross-chain solution

Minimum Information about a Neuroscience Investigation (MINI) Electrophysiology

This module represents the formalized opinion of the authors and the CARMEN consortium, which identifies the minimum information required to report the use of electrophysiology in a neuroscience study, for submission to the CARMEN system (www.carmen.org.uk).
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Generation of photovoltage in graphene on a femtosecond time scale through efficient carrier heating

Graphene is a promising material for ultrafast and broadband photodetection. Earlier studies addressed the general operation of graphene-based photo-thermoelectric devices, and the switching speed, which is limited by the charge carrier cooling time, on the order of picoseconds. However, the generation of the photovoltage could occur at a much faster time scale, as it is associated with the carrier heating time. Here, we measure the photovoltage generation time and find it to be faster than 50 femtoseconds. As a proof-of-principle application of this ultrafast photodetector, we use graphene to directly measure, electrically, the pulse duration of a sub-50 femtosecond laser pulse. The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat. To study this, we examine the spectral response and find a constant spectral responsivity between 500 and 1500 nm. This is consistent with efficient electron heating. These results are promising for ultrafast femtosecond and broadband photodetector applications.Comment: 6 pages, 4 figure

Filament wound composite fatigue mechanisms investigated with full field DIC strain monitoring

Fatigue of filament wound materials was investigated using Digital Image Correlation DIC monitoring every 50th cycle of a high cycle fatigue test of a split disk ring sample. The ring was cut from a filament wound glass fiber reinforced polymer pressure vessel and had a hole. The strain field redistributed over time, lowering and moving strain concentrations. The redistributive behavior was most extensive in areas that later developed local fiber failure, which soon led to catastrophic failure. Microscopy was carried out on partially fatigued material. Damage evolved as matrix cracks and matrix splitting of groups of fibers and complete debonding of single fibers. This occurred at borders of voids and matrix cracks, easing progressive fiber failure. It was concluded that fatigue in filament wound composites has an extensive matrix damage phase before final failure. Fibers could locally withstand strains close to and above the static failure strain for considerable number of cycles if little local strain field redistribution was observed. The used method was able to detect changes in the strain fields that preceded catastrophic failure. It was concluded that DIC combined with the post processing methods presented may serve as a valuable tool for structural integrity monitoring of composite pressure vessels over time.publishedVersio