Frequency Response of Graphene Electrolyte-Gated Field-Effect Transistors

This work develops the first frequency-dependent small-signal model for graphene electrolyte-gated field-effect transistors (EGFETs). Graphene EGFETs are microfabricated to measure intrinsic voltage gain, frequency response, and to develop a frequency-dependent small-signal model. The transfer function of the graphene EGFET small-signal model is found to contain a unique pole due to a resistive element, which stems from electrolyte gating. Intrinsic voltage gain, cutoff frequency, and transition frequency for the microfabricated graphene EGFETs are approximately 3.1 V/V, 1.9 kHz, and 6.9 kHz, respectively. This work marks a critical step in the development of high-speed chemical and biological sensors using graphene EGFETs.United States. Office of Naval Research (Grant N00014-12-1-0959)United States. Office of Naval Research (Grant N0014-16-1-2230)United States. National Aeronautics and Space Administration (Award NNX14AH11A)United States. Army Research Office (Contract W911NF-13-D-0001

Marcona Sostenible. Propuesta Urbana para el desarrollo de la ciudad de San Juan de Marcona

El principal problema de la ciudad de San Juan de Marcona está representado por el crecimiento desmedido de la ciudad. El Plan de Desarrollo Urbano (PDU) de la Municipalidad propone la expansión de ésta para contener a la población en el año 2030. Esto representa un peligro para su territorio pues la expansión de la ciudad, en términos de dimensiones, representa un peligro para la sostenibilidad urbana. El proyecto propone para la ciudad de San Juan de Marcona un Desarrollo Urbano Sostenible que le permita crecer sin representar una amenaza para su territorio. Esto se logra aplicando los principios del Urbanismo Ecológico, planteado por Salvador Rueda, en donde se busca una ciudad que sea compacta y diversa y donde el peatón sea el principal actor. Asimismo, la propuesta busca otorgar espacios que permitan conectar a la ciudad con su paisaje y su clima. Se elabora un plan maestro para el desarrollo de la ciudad hasta el 2050 y se profundiza la primera fase de éste. Esta fase implica el desarrollo urbano de un sector de borde de la ciudad. Para lograrlo se plantean supermanzanas cuyas piezas urbanas son producto de la relación entre sol y aire con la ciudad. El espacio público, las redes viales, la vegetación y su ordenamiento en tres niveles es pensado para favorecer al peatón. De esta manera el plan maestro para esta zona logra reconectar la ciudad, diversificarla a través de un programa variado, y naturalizarla a partir de la implementación de una red de espacios públicos y productivos

Validation of a Measuring Instrument for the Relationship between Knowledge Transfer and Entrepreneurial Orientation in Family Firms

Family businesses are created due to the entrepreneurial behavior of one or more founders, who find and exploit one opportunity. It is necessary that this Entrepreneurial Orientation (EO) is transmitted to the next generation. We argue that knowledge management within the family business is positively related to entrepreneurial orientation and, therefore, related to firm performance. A scale for measuring the knowledge transfer has been defined in order to determine the degree of relationship between the above elements. The measuring instrument is original because previous measuring scales do not exist in the literature which measure, on the one hand, the subconstructs that might lead knowledge transfer and, on the other hand, the relationship between this and the other variables. As a result of causal relationship analysis, it concludes with a scale, with a sample of Spanish family firms, and it is the first empirical validation of these dimensions we know so far

Threshold voltage control by gate oxide thickness in fluorinated GaN metal-oxide-semiconductor high-electron-mobility transistors

This paper demonstrates the compensation of the intrinsic positive charges in Al₂O₃ gate dielectric by fluorine ions in GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs). Negatively-charged fluorine ions diffused into the oxide from the AlGaN barrier during the 250 °C atomic layer deposition compensate the intrinsic positive charge present in the Al₂O₃. This compensation is key to control the threshold voltage (Vth) of enhancement-mode (E-mode) transistors. A comprehensive analytical model for the V[subscript th] of fluorinated MOS-HEMTs was established and verified by experimental data. This model allows the calculation of the different charge components in order to optimize the transistor structure for E-mode operation. Using the proposed charge compensation, the V[subscript th] increases with gate dielectric thickness, exceeding 3.5V for gate dielectrics 25 nm thick

Quorum Sensing is essential for an effective symbiosis in R. leguminosarum UPM791.

The implications of Quorum Sensing in the establishment of a successful symbiosis of Rhizobium leguminosarum bv. viciae (Rlv) with legume plants are discussed in this work. In order to analyze the significance and regulation of the production of AHL signal molecules, mutants deficient in each of the two QS systems present in Rlv UPM791 were constructed. A detailed analysis of the effect of these mutations on growth, AHL production, biofilm formation and symbiosis with pea, vetch and lentil plants has been carried out

Efecto de los sistemas de Quorum Sensing sobre la eficiencia simbiótica de R. leguminosarum UPM791

Rhizobium leguminosarum bv viciae (Rlv) es una alfa-proteobacteria capaz de establecer una simbiosis diazotrófica con distintas leguminosas. Uno de los factores implicados en el establecimiento de la simbiosis es el sistema de comunicación intercelular conocido como Quorum Sensing (QS). Mediante este sistema, las bacterias actúan de manera coordinada en respuesta a cambios en la densidad de población a través de la producción y detección de señales extracelulares. El genoma de Rlv UPM791 contiene dos sistemas tipo luxRI mediados por señales de tipo N-acyl-homoserina lactonas (AHLs): el sistema rhiRI, codificado en el plásmido simbiótico, produce C6-HSL, C7-HSL y C8-HSL; y el sistema cinRI, localizado en el cromosoma, produce 3-OH-C14:1-HSL. Con el fin de analizar el significado y la regulación de los sistemas de QS en esta bacteria endosimbiótica se generaron mutantes defectivos en cada uno de los sistemas de QS, y se llevó a cabo un análisis detallado sobre la producción de AHLs y la simbiosis con plantas de guisante, veza y lenteja. El sistema rhiRI se necesita para un comportamiento simbiótico normal, dado que la mutación en rhiI reduce considerablemente la eficiencia simbiótica. rhiR es esencial para la fijación de nitrógeno en ausencia del plásmido pUPM791d. Asimismo, mutaciones en el sistema cinRIS mostraron también un importante efecto en simbiosis. El mutante ?cinRIS no produce la señal 3-OH-C14:1-HSL, y da lugar a nódulos blancos e inefectivos, carentes de bacteroides. El mutante ?cinI, incapaz de producir AHLs, no forma nódulos en ninguna de las leguminosas utilizadas. El análisis genético reveló que dicha mutación origina la inestabilización del plásmido simbiótico por un mecanismo dependiente de cinI que no ha sido aclarado. Los resultados obtenidos sugieren un papel relevante de los sistemas de Quorum Sensing de Rlv UPM791 en los primeros estadíos de la simbiosis, e indican la existencia de un modelo de regulación dependiente de QS significativamente distinto a los que se han descrito previamente en otras cepas de R. leguminosarum

Trench formation and corner rounding in vertical GaN power devices

Trench formation and corner rounding are the key processes to demonstrate high-voltage trenchbased vertical GaN devices. In this work, we developed a damage-free corner rounding technology combining Tetramethylammonium hydroxide wet etching and piranha clean. By optimizing the inductively coupled plasma dry etching conditions and applying the rounding technology, two main trench shapes were demonstrated: flat-bottom rounded trench and tapered-bottom rounded trench. TCAD simulations were then performed to investigate the impact of trench shapes and round corners on device blocking capability. GaN trench metal-insulator-semiconductor barrier Schottky rectifiers with different trench shapes were fabricated and characterized. A breakdown voltage over 500V was obtained in the device with flat-bottom rounded trenches, compared to 350V in the device with tapered-bottom rounded trenches and 150V in the device with nonrounded trenches. Both experimental and simulation results support the use of rounded flat-bottom trenches to fabricate high-voltage GaN trench-based power devices

Delay Analysis of Graphene Field-Effect Transistors

In this letter, we analyze the carrier transit delay in graphene field-effect transistors (GFETs). GFETs are fabricated at the wafer-scale on sapphire substrate. For a device with a gate length of 210 nm, a current gain cut-off frequency fT of 18 GHz and 22 GHz is obtained before and after de-embedding. The extraction of the internal (Cgs,i, Cgd,i) and external capacitances (Cgs,ex and Cgd,ex) from the scaling behavior of the gate capacitances Cgs and Cgd allows the intrinsic ({\tau}_int), extrinsic ({\tau}_ext) and parasitic delays ({\tau}_par) to be obtained. In addition, the extraction of the intrinsic delay provides a new way to directly estimate carrier velocity from the experimental data while the breakdown of the total delay into intrinsic, extrinsic, and parasitic components can offer valuable information for optimizing RF GFETs structures.Comment: 3 pages, 3 figures, accepted for publication in IEEE Electron Device Letter