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Dive into the research topics where Stefan Dan Costea is active.

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Featured researches published by Stefan Dan Costea.


international semiconductor conference | 2008

Surface acoustic wave CO 2 sensing with polymer-amino carbon nanotube composites

Bogdan-Catalin Serban; A. K. Sarin Kumar; Stefan Dan Costea; Mihai N. Mihaila; Octavian Buiu; Mihai Brezeanu; Nicolae Varachiu; Cornel Cobianu

The synthesis of two new types of nanocomposite matrices, the first based on polyallylamine (PAA) and aminocarbon nanotubes, the second on polyethyleneimine (PEI) and aminocarbon nanotubes, are reported. The surface acoustic wave (SAW) sensors, coated with the two selected nanocomposites, showed good sensitivities when varying the CO2 concentrations in the range (500-5000) ppm. The sensor sensitivity is larger when using polyethyleneimine aminocarbon nanotubes than in the case when only a pure polyethyleneimine layer is considered for coating.


Sensors | 2013

InN Based Water Condensation Sensors on Glass and Flexible Plastic Substrates

Viorel Georgel Dumitru; Stefan Dan Costea; Mihai Brezeanu; G.E. Stan; C. Besleaga; A.C. Galca; Gabriela Cristina Ionescu; Octavian Ionescu

In this paper, we report the realization and characterization of a condensation sensor based on indium nitride (InN) layers deposited by magnetron sputtering on glass and flexible plastic substrates, having fast response and using potentially low cost fabrication technology. The InN devices work as open gate thin film sensitive transistors. Condensed water droplets, formed on the open gate region of the sensors, deplete the electron accumulation layer on the surface of InN film, thus decreasing the current of the sensor. The current increases back to its initial value when water droplets evaporate from the exposed InN film surface. The response time is as low as 2 s.


international semiconductor conference | 2010

A novel concept for low drift chemical sensing at micro and nano-scale

Cornel Cobianu; Bogdan Catalin Serban; Ion Georgescu; Stefan Dan Costea; Cazimir G. Bostan

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 response to humidity and temperature variations are shown for the SAW sensors, with the sensor signal kept independent of their changes.


international semiconductor conference | 2012

SOI membrane-based pressure sensor in stress sensitive differential amplifier configuration

Mihai Brezeanu; Viorel-Georgel Dumitru; Stefan Dan Costea; Syed Zeeshan Ali; Florin Udrea; Mihai Gologanu; Cazimir G. Bostan; Ion Georgescu; Viorel Avramescu; Octavian Buiu

This paper introduces a pressure sensing structure configured as a stress sensitive differential amplifier (SSDA), built on a Silicon-on-Insulator (SOI) membrane. Theoretical calculation show the significant increase in sensitivity which is expected from the pressure sensors in SSDA configuration compared to the traditional Wheatstone bridge circuit. Preliminary experimental measurements, performed on individual transistors placed on the membrane, exhibit state-the-art sensitivity values (1.45mV/mbar).


international semiconductor conference | 2014

Materials selection for gas sensing. An HSAB perspective

Bogdan-Catalin Serban; Mihai Brezeanu; Cornel Cobianu; Stefan Dan Costea; Octavian Buiu; Alisa Stratulat; Nicolae Varachiu

This paper introduces the Hard Soft Acid Base (HSAB) concept as a promising tool for the selection of gas sensing layers. Target gas molecule - sensitive layer tandems are discussed and interpreted in the terms of this theory. Sensing layers suitable for carbon dioxide, nitrogen dioxide, sulphur dioxide, and hydrogen sulphide detection are presented and classified according to this concept. For oxygen and mineral acids detection, an indirect HSAB approach is discussed. The paper explains how the HSAB principle can be useful in designing gas sensing layers for different types of sensing structures, such as: surface acoustic waves (SAW), colorimetric, chemoresistive, etc.


Archive | 2010

METHODS OF OPERATION OF ELECTROCHEMICAL GAS SENSORS

Keith Francis Edwin Pratt; John Chapples; Martin Geoffrey Jones; Stefan Dan Costea; Mihai Gologanu


Archive | 2008

SURFACE ACOUSTIC WAVE BASED SENSOR APPARATUS AND METHOD UTILIZING SEMI-SYNCHRONOUS SAW RESONATORS

Cazimir G. Bostan; Stefan Dan Costea; Viorel Avramescu; Cornel Cobianu


Archive | 2008

Patterned dielectric elastomer actuator and method of fabricating the same

Mihai Gologanu; Viorel Avramescu; Stefan Dan Costea; Li Wang


Archive | 2007

Mems based battery monitoring technical field

Cornel Cobianu; Viorel-Georgel Dumitru; Ion Georgescu; Mihai Gologanu; Stefan Dan Costea


Archive | 2009

Checking electrochemical gas sensors

Keith Francis Edwin Pratt; John Chapples; Martin Geoffrey Jones; Stefan Dan Costea; Mihai Gologanu

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