9 research outputs found
Feasibility of 4H-SiC p-i-n Diode for Sensitive Temperature Measurements between 20.5 K and 802 K
No full textFor the first time, we report on the performances of 4H-SiC p-i-n-diode temperature sensors for operating temperatures between 20.5 and 802 K. In this huge temperature range, three ranges of performance were identified with the limit temperatures at 78.2 and 176.3 K. In each of these ranges, a different dominant current transport mechanism is shown and in this paper, a detailed analysis and discussion are reported. The sensor performances were extracted from VD - T characteristics at different fixed ID values. In particular, at ID = 1 μ A and in the temperature range between 78.2 and 802 K, we found a sensor sensitivity of 2.3-3.4 mV/K with a rms temperature error, eT , of less than 4.2 K and the sensor shows an excellent linearity - quantified by the coefficient of determination R2 higher than 0.9993. For even lower temperatures (below 78.2 K), low measurement currents like 10 nA are required leading to a sensitivity of 5.8 mV/K, but a lower linearity (R2 = 0.9095) and an rms temperature error of 9.7 K which makes the sensor only partially usable in the temperature range between 20.5 and 78.2 K. Finally, the sensor performances are compared with other state-of-the-art solutions
Performance of 4H-SIC bipolar diodes as temperature sensor at low temperatures
No full textIn this paper we report on the performance of 4H-SiC bipolar diodes as temperature sensors far beyond 273K. The sensor is measured from 150K to 445K covering a temperature range of 295K. In this operating temperature range, the sensor characteristic VD-T is highly linear and it is dominated by the typical dependence of the p-i-n diode voltage on the temperature. The sensor sensitivity is-4.48mV/K for a diode current of 2nA with a maximum error of 4.3K across the full temperature range. Although 4H-SiC p-i-n are mainly focused on very high temperature applications, our analysis on the performance of bipolar diodes at low temperatures highlights its feasibility as temperature sensor for aerospace and high altitude applications where cryogenic temperatures are achieved
Author Correction: Highly accurate determination of heterogeneously stacked Van-der-Waals materials by optical microspectroscopy
No full textThe original version of this Article contained an error in Equation 1. (Formula Presented.).now reads:(Formula Presented.)As a result, Equation 2 was incorrect.(Formula Presented.).now reads:(Formula Presented.).The original Article has been corrected.13
Generalized approach to design multi-layer stacks for enhanced optical detectability of ultrathin layers
No full textLarge-Area Layer Counting of Two-Dimensional Materials Evaluating the Wavelength Shift in Visible-Reflectance Spectroscopy
No full textS.9192-9201An advanced and highly scalable approach for determining the number of layers of two-dimensional (2D) materials via optical spectroscopy is introduced. Based on appropriate subjacent layer stacks, the reflectance spectra of the 2D material assemblies exhibit wavelength shifts in distinct minima, which are linearly related to the number of layers. A linear correlation enables straightforward data interpretation, which is essential for implementing simple and comparatively fast measurement routines for process control on wafer scale. The structure of the optical layer stacks as well as the complex refractive indices of 2D materials were found to strongly influence the spectral position of the reflectance minima as well as the magnitude and the linearity of the wavelength shifts. We experimentally prove this method to be applicable for large-area layer counting of subsequently stacked chemical vapor deposition graphene films on a layer stack consisting of silicon nitride and silicon oxide. The measurement results confirm the calculated wavelength shift of the reflection minimum around 540 nm equaling approx. 3 nm per layer. Numerical analysis shows that comparable behavior is also achievable by the tailored design of subjacent layer stacks for graphene oxide, hexagonal boron nitride, and more complex 2D materials like transition-metal dichalcogenides. For the achievement of linear relations between wavelength shifts of the respective minimum and the layer count of the 2D material, analytical design rules are derived considering the optical properties of the underlying layer stack as well as oscillator frequencies within the complex refractive index of the 2D material. The largest signal response of 12 nm per layer was calculated for MoSe2 on an optimized layer stack.123Nr.1
Sensing glucose concentrations at GHz frequencies with a fully embedded Biomicro-electromechanical system (BioMEMS)
No full textSensing glucose concentrations at GHz frequencies with a fully embedded biomicro-electromechanical system
No full textThe progressive scaling in semiconductor technology allows for advanced miniaturization of intelligent systems like implantable biosensors for low-molecular weight analytes. A most relevant application would be the monitoring of glucose in diabetic patients, since no commercial solution is available yet for the continuous and drift-free monitoring of blood sugar levels. We report on a biosensor chip that operates via the binding competition of glucose and dextran to concanavalin A. The sensor is prepared as a fully embedded micro-electromechanical system and operates at GHz frequencies. Glucose concentrations derive from the assay viscosity as determined by the deflection of a 50 nm TiN actuator beam excited by quasi-electrostatic attraction. The GHz detection scheme does not rely on the resonant oscillation of the actuator and safely operates in fluidic environments. This property favorably combines with additional characteristics—(i) measurement times of less than a second, (ii) usage of biocompatible TiN for bio-milieu exposed parts, and (iii) small volume of less than 1 mm3—to qualify the sensor chip as key component in a continuous glucose monitor for the interstitial tissue
Sensing glucose concentrations at GHz frequencies with a fully embedded biomicro-electromechanical system
No full textAceite de buriti de la Amazonia: Caracterización química y potencial antioxidante
No full textBuriti oil is an example of an Amazonian palm oil of economic importance. The local population uses this oil for the prevention and treatment of different diseases; however, there are few studies in the literature that evaluate its properties. In this study, detailed chemical and antioxidant properties of Buriti oil were determined. The predominant fatty acid was oleic acid (65.6%) and the main triacylglycerol classes were tri-unsaturated (50.0%) and di-unsaturated-mono-saturated (39.3%) triacylglycerols. The positional distribution of the classes of fatty acids on the triacylglycerol backbone indicated a saturated and unsaturated fatty acid relationship similar in the three-triacylglycerol positions. All tocopherol isomers were present, with a total content of 2364.1 mg·kg−1. α-tocopherol constitutes 48% of the total tocopherol content, followed by γ- tocopherol (45%). Total phenolic (107.0 mg gallic acid equivalent·g−1 oil) and β-carotene (781.6 mg·kg−1) were particularly high in this oil. The highest antioxidant activity against the free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) was obtained at an oil concentration of 50 mg·mL−1 (73.15%). The antioxidant activity evaluated by the Oxygen Radical Absorbance Capacity (ORAC) was 95.3 μmol Trolox equivalent·g−1 oil. These results serve to present Buriti oil as an Amazonian resource for cosmetic, food and pharmaceuticals purposes.El aceite de Buriti es un ejemplo de aceite de palma amazónica de gran importancia económica. La población local utiliza este aceite para la prevención y el tratamiento de diferentes enfermedades; sin embargo, hay pocos estudios científicos que evalúen sus propiedades. En este estudio, se determinaron las propiedades antioxidantes del aceite de Buriti. El ácido graso predominante fue el oleico (65,6 %) y las principales clases de triglicéridos fueron tri-insaturadas (50,0 %) y Di-insaturados-mono-saturada (39,3 %). La distribución posicional de las clases de ácidos grasos en el esqueleto de triacilglicerol indicó una relación de ácidos grasos saturados e insaturados similar en las tres posiciones del triacilglicerol. Todas las isoformas de tocoferol estaban presentes, con un contenido total de 2364.1 mg·kg−1. El α-tocoferol constituye el 48 % del contenido total de tocoferol, seguido de γ-tocoferol (45 %). El contenido fenólico total (107,0 mg equivalente ácido gálico·g−1 de aceite) y β-caroteno (781,6 mg·kg−1) fueron particularmente altos en este aceite. La mayor actividad antioxidante contra el radical 1,1-difenil-2-picrilhidrazil libre (DPPH) se obtuvo a una concentración de aceite de 50 mg·mL−1 (73,15 %). La actividad antioxidante evaluadas por la capacidad de absorción de radicales de oxígeno (ORAC) fue 95,3 mmol Trolox equivalente·g−1 de aceite. Estos resultados presentan al aceite de Buriti amazónico como buen recurso con fines cosmético, alimenticio y farmacéutico
