Valentin CHESARU, Cristian NEACŞU, Claudius DAN, Mircea BODEA
Abstract. This paper presents the design of a low power discontinuous time comparator that saves its state in a digital latch circuit when entering shut-down mode. The designed low power comparator can be used in any integrated circuit to decrease power consumption in shut-down mode. The design is based on a simple and efficient idea: while the comparator is in shut-down mode, its previous state is stored in a latch. This idea can be easily applied to any “already designed” discontinuous – time comparator. Read the pdf
George S. KLIROS
Abstract. Graphene nanostructures exhibit an intrinsic advantage in relation to the gate delay in three-terminal devices and provide additional benefits when operate in the quantum capacitance limit. In this paper, we developed a simple model that captures the Fermi energy and temperature dependence of the quantum capacitance for monolayer and bilayer graphene devices. Quantum capacitance is calculated from the broadened density of states taking into account electron-hole puddles and possible finite lifetime of electronic states through a Gaussian broadening distribution. The obtained results are in agreement with many features recently observed in quantum capacitance measurements on both gated monolayer and bilayer graphene devices. The temperature dependence of the minimum quantum capacitance around the charge neutrality point is also investigated. Read the pdf
Cornel COBIANU, Bogdan ŞERBAN, Ion GEORGESCU, Ştefan COSTEA, Cazimir BOSTAN
Abstract. It is the purpose of this paper to present a novel generic concept for low drift chemical sensing which is applicable at micro and nanometer scale, based on a new, all-differential approach. At micrometer level, our principle is explained by means of surface acoustic wave (SAW) chemical sensing, while at nano level, we are using the resonant sensing principle to develop our genuine differential concept. Unlike the traditional differential approaches based on functionalized sensing layer in the sensing loop, and on a uncoated surface in the reference loop, our all differential concept provides a better response subtraction between the two paths, as the sensing loop consists of a functionalized sensing layer, as before, but, the reference loop consists of a functionalized non-sensing layer, with the same ageing and humidity behavior as the sensing layer. Twinned electronic reading is used for both loops, and thus all the common mode signals are subtracted in the differential reading, assuring the minimum base line drift of the sensor. Preliminary results of all differential sensor eliminating the effects of humidity and temperature variations are shown for the SAWsensors, with the sensor signal kept independent of their changes. Finally, the application of the novel concept for the humidity sensing with all differential resonant nanosensor is presented. Read the pdf
Adina BRAGARU, Mihaela MIU, Monica SIMION, Andra IORDĂNESCU,
Abstract. This work is based on platinum nanoparticles preparation protected by a polycation- PDDA- poly (diallyldimethylammonium chloride) and to embed them in a Nafion 117 membrane matrix in order to obtain a nanocomposite structure, which can be used as alternative polymer electrolyte membrane for direct methanol fuel cells (DMFC). Read the pdf.
Mona MIHĂILESCU1, Arcadie SOBETKII, Mihaela PELTEACU
Abstract. The aim of our study is to find a simple design for the two-steps profile diffractive micro-lenses (DMLs) which will generate binary focal points on the propagation axis at monochromatic plane wave incidence. Their fabrication steps include e-beam lithography (for mask pattern) and reactive ion etching (for transparent DMLs). For the two-steps profile, the fabrication process is simpler because it doesn’t introduce errors due to masks alignment. In the design algorithm, developed in MATLAB, we start with simple DMLs which generate one single focal point at a given distance. We propose a method which uses some sections from different simple DMLs to built one DML with special properties. We investigate the influence of the missing zones in the diffraction pattern. The propagation was simulated in the Fresnel approximation. To visualize their transparent binary microrelief and the phase profile, we employ the digital holographic microscopy technique. Experimental and simulation results are presented. Read the pdf.
Mariana-Dana DAMACEANU, Radu-Dan RUSU, Mihaela OLARU,
Abstract. Here we present a study of the polyimide films nanostructuring by KrF laser beam irradiation and the investigation of the mechanism of cone-like structure formation at two laser fluences, 57 and 240 mJ/cm2. These films were prepared from fluorinated containing oxadiazole rings, by casting polymer solutions onto glass plates and gradually heating. Their morphology before and after laser ablation was investigated by using various techniques such as infrared spectroscopy (FTIR), atom force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Read the pdf.
Marius VOLMER, Marioara AVRAM
Abstract. The manipulation and detection of magnetic carriers used for biosensing represent key features in a lab-on-a-chip (LOC) device. In this contribution we present some results regarding the analysis of a manipulation system and the interaction between the magnetic nanoparticles (MNPs) and the spin valve sensor used for detection. We found that the detection sensitivity is strongly related with the position of the magnetic particles on the sensor’s surface. A net signal can be obtained for a single magnetic nanoparticle of 100 nm in diameter. For micromagnetic simulations the employed program was SimulMag. Read the pdf.
Adrian RUSU, Cristian RAVARIU, Alexandru RUSU, Dragos DOBRESCU, Mihai CRACIUN, Dan COZMA
Abstract. This paper presents the simulation results of the gate-controlled diode, working in the analog regime. The aim of the paper is to find the device macromodel that provides an optimum linearity of the junction breakdown voltage versus the gate voltage, at a given current. The lateral pn junction is simulated in the breakdown regime and the gate voltage biases the MOS capacitor in deep depletion. Finally, linearity under 1% was accomplished, being in agreement with the theory. An emulator based on equivalent circuit was developed according to these simulations in order to be implemented in Spice-like programs. Read the pdf.