W. Moritz

Humboldt-Universität zu Berlin, Berlín, Berlin, Germany

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Publications (68)137.66 Total impact

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    ABSTRACT: The aim of this research is to find a CO2 sensor with high value of the response to CO2 concentrations in a range of several hundreds of ppm. The sensor investigated in this work is based on metal/solid electrolyte/insulator/silicon structure with fluorine conducting solid electrolyte LaF3 layer. It is characterized by rather with short response and recovery time of about 1 min (t90) at room temperature. The application of such gas sensor seems to be very promising for the measurement of CO2 concentration in a range from atmospheric background (300 ppm) to maximum permissible concentration (2000 ppm).
    Procedia Engineering 12/2014; 87:1047-1050. DOI:10.1016/j.proeng.2014.11.341
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    ABSTRACT: A hydrogen sensor based on a silicon Metal/Solid Electrolyte/Insulator/Semiconductor (MEIS) structure with thin layers of the super-ionic conductor LaF3 and Pd gate metal was investigated in a hybrid structure on a resistance heater mounted on a ceramic substrate. The sensor was operated at room temperature, however, a short heating impulse once a day ensures a fast and reproducible dynamic behavior. The sensor was characterized in the concentration range typical for alarm levels up to 40% of the lower flammability limit and shows a logarithmic dependency of the sensor signal from the hydrogen concentration and a mean sensitivity of about 140 mV/decade. The response time (t90) is about 8 s. In a long term test for a period of three month, the sensor was exposed to hydrogen every two weeks. The sensor signal was shown to be stable in dynamic behavior, sensitivity and signal difference.
    Sensors and Actuators B Chemical 10/2013; 187:395-400. DOI:10.1016/j.snb.2012.12.081 · 3.84 Impact Factor
  • 01/2013; 2(2):171-177. DOI:10.5194/jsss-2-171-2013
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    ABSTRACT: A new silicon-based hydrogen sensor for measurements at high concentrations near the lower flammable limit of hydrogen (40,000 ppm) is presented. Due to operation at room temperature the power consumption of the sensor is smaller than that of other sensors on the market by several orders magnitude. Further development of the sensor system could lead to battery powered or even energy-independent operation. As sensor fabrication is based on semiconductor technology, low-cost production can be achieved for the mass market. The sensor investigated showed good long-term stability combined with a fast response on the basis of cyclic thermal activations. This was demonstrated by a stress test that simulated the activation and measurement cycles experienced by the sensor in one year. Finite element method was used to further reduce the power consumption of the thermal activation. This resulted in an average power consumption of 2 × 10−6 W for the sensor activation.
    International Journal of Hydrogen Energy 11/2012; 37(22):17523–17528. DOI:10.1016/j.ijhydene.2012.07.072 · 2.93 Impact Factor
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    ABSTRACT: Ternary thin film alloys based on Pd, Ni and Co on silicon wafers have been characterized in order to determine elemental composition and thickness. A broad variety of alloy compositions was obtained on one and the same substrate by magnetron dc-co-sputter deposition. Energy-dispersive electron probe X-ray microanalysis of these ‘multi’ alloy composition samples is performed in a non-destructive, precise and, if optimized, also in a time-saving way. The local thickness of the layers under study was in between 50 nm and 250 nm. Pure element bulk materials have been employed as reference specimens. The results attained in this study are compared to those obtained by other analytical methods as Auger electron spectroscopy and X-ray photo electron spectroscopy. Copyright © 2012 John Wiley & Sons, Ltd.
    Surface and Interface Analysis 11/2012; 44(11-12):1456-1458. DOI:10.1002/sia.4974 · 1.39 Impact Factor
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    ABSTRACT: A new high throughput screening method to characterise alloys used as gate metal of Metal/solid Electrolyte/Insulator/Semiconductor (MEIS) gas-sensors was developed. Samples with continuous gradients in alloy concentration for the system Pd1-x-yNiyCoy were analysed regarding H-2 sensitivity. First results showed reduced poisoning effects of H2S for Ni concentrations between 4-11 at-% in Pd. (C) 2012 Elsevier Ltd .... Selection and/or peer-review under responsibility of the Symposium Cracoviense Sp. z.o.o.
    EUROSENSOR 2012, Krakow, Poland; 09/2012
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    ABSTRACT: Frequency-dependent capacitance–voltage (C–V) and impedance-spectroscopy characteristics of nanoplate capacitive field-effect electrolyte-insulator-silicon-on-insulator (EISOI) structures with various thicknesses (30, 60 and 350 nm) of the top p-Si layer are investigated for the first time. The frequency-dependent C–V curves of EISOI structures show an unusual behaviour, which significantly differs from that of conventional EIS structures. Due to the large series resistance of the nanoplate top Si, the C–V curves of the EISOI structures show stronger frequency dependence in the accumulation region. In addition, C–V curves show typical low-frequency behaviour even at higher frequencies (up to 8 kHz). An equivalent circuit of an EISOI structure is discussed taking into account the series resistance of the nanoplate top Si.
    Physica Status Solidi (A) Applications and Materials 06/2011; 208(6):1327 - 1332. DOI:10.1002/pssa.201001211 · 1.53 Impact Factor
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    ABSTRACT: Ternary alloys have been studied as the gate metal of chemical sensors based on the field effect in silicon. The investigation of reduced poisoning of hydrogen sensors by H2S is presented in the alloy system PdxNiyCo1−x−y. A new method in high throughput screening of alloys is applied. Not singular sample compositions but a continuous gradient in alloy concentrations was produced on a semiconductor sample. A laser scanning system produces a photo current in the semiconductor to map the sensor signal and provide a quasi continuous alloy characterization. The new system is therefore called Continuous Gradient-High Throughput Screening Macroscope (CG-HTSM). Typically 625 alloys are characterized in 15 minutes. The resolution of our set-up allows distinguishing 100.000 alloy compositions.
    Sensor Letters 04/2011; 9(2):662-664. DOI:10.1166/sl.2011.1586 · 0.56 Impact Factor
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    ABSTRACT: An array of individually addressable nanoplate field-effect capacitive (bio-)chemical sensors based on an SOI (silicon-on-insulator) structure has been developed. The isolation of the individual capacitors was achieved by forming a trench in the top Si layer with a thickness of 350 nm. The realized sensor array allows addressable biasing and electrical readout of multiple nanoplate EISOI (electrolyte-insulator-silicon-on-insulator) capacitive biosensors on the same SOI chip as well as differential-mode measurements. The feasibility of the proposed approach has been demonstrated by realizing sensors for the pH and penicillin concentration detection as well as for the label-free electrical monitoring of polyelectrolyte multilayers formation and DNA (deoxyribonucleic acid)-hybridization event. A potential change of ∼ 120 mV has been registered after the DNA hybridization for the sensor immobilized with perfectly matched single-strand DNA, while practically no signal changes have been observed for a sensor with fully mismatched DNA. The realized examples demonstrate the potential of the nanoplate SOI capacitors as a new basic structural element for the development of different types of field-effect biosensors.
    Biosensors & Bioelectronics 02/2011; 26(6):3023-8. DOI:10.1016/j.bios.2010.12.006 · 6.45 Impact Factor
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    ABSTRACT: A thin-film amorphous silicon (a-Si) deposited on a glass substrate was employed as a semiconductor material for the chemical imaging sensor, which can visualize the distribution of ion concentration in a solution. The sensing properties and the spatial resolution of the a-Si sensors were investigated. Nearly-Nernstian pH sensitivities and submicron resolution were demonstrated, which suggests the superior performance of the chemical imaging sensor based on thin-film a-Si.
    MRS Online Proceeding Library 01/2011; 910. DOI:10.1557/PROC-0910-A20-01
  • Fred Lisdat, Werner Moritz, Lothar Müller
    12/2010; 30(12):427 - 433. DOI:10.1002/zfch.19900301203
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    ABSTRACT: A novel strategy for enhanced field-effect biosensing using capacitive electrolyte–insulator–semiconductor (EIS) structures functionalised with pH-responsive weak polyelectrolyte/enzyme or dendrimer/enzyme multilayers is presented. The feasibility of the proposed approach is exemplarily demonstrated by realising a penicillin biosensor based on a capacitive p-Si–SiO2 EIS structure functionalised with a poly(allylamine hydrochloride) (PAH)/penicillinase and a poly(amidoamine) dendrimer/penicillinase multilayer. The developed sensors response to changes in both the local pH value near the gate surface and the charge of macromolecules induced via enzymatic reaction, resulting in a higher sensitivity. For comparison, an EIS penicillin biosensor with adsorptively immobilised penicillinase has been also studied. The highest penicillin sensitivity of 100 mV/dec has been observed for the EIS sensor functionalised with the PAH/penicillinase multilayer. The lower and upper detection limit was around 20 µM and 10 mM, respectively. In addition, an incorporation of enzymes in a multilayer prepared by layer-by-layer technique provides a larger amount of immobilised enzymes per sensor area, reduces enzyme leaching effects and thus, enhances the biosensor lifetime (the loss of penicillin sensitivity after 2 months was 10–12%).
    Physica Status Solidi (A) Applications and Materials 04/2010; 207(4):884 - 890. DOI:10.1002/pssa.200983317 · 1.53 Impact Factor
  • Jan Szeponik, Werner Moritz, Farid Sellam
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    ABSTRACT: A new kind of semiconductor based fluoride sensor was prepared by growing thin polycrystalline LaF3 films directly on silicon substrates using vacuum vapour deposition technique. The EICS (Electrolyte Ion Conductor Semiconductor) structure was investigated by means of impedance spectroscopy, CV measurements and exchange measurements with labeled ions (18F). Whereas charge and potential conditions at the LaF3/ electrolyte interface are governed by the fast fluoride exchange the LaF3 bulk and the blocked Si/LaF3 interface determine the electrical behavior. Although the Si/LaF3 contact is not reversible the potential stability of the EICS structure is surprisingly high. Additional results at epitaxial LaF3 layers, prepared by MBE, were taken into account for comparision with those at polycrystalline layers.
    03/2010; 95(11):1448 - 1453. DOI:10.1002/bbpc.19910951125
  • W. MORITZ, A. HERBST, K.-H. HECKNER
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 02/2010; 23(8):24-24. DOI:10.1002/chin.199208024
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    ABSTRACT: A capacitive field-effect EDIS (electrolyte–diamond–insulator–semiconductor) sensor with improved pH and penicillin sensitivity has been realised using a nanocrystalline-diamond (NCD) film as sensitive gate material. The NCD growth process on SiO2 as well as an additional surface treatment in oxidising medium have been optimised to provide high pH-sensitive, non-porous O-terminated films without damage of the underlying SiO2 layer. The surface morphology of O-terminated NCD thin films and the layer structure of EDIS sensors have been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. To establish the relative coverage of the surface functional groups generated by the oxidation of NCD surfaces, X-ray photoelectron spectroscopy analysis was carried out. The hydrophilicity of NCD thin films has been studied by water contact-angle measurements. A nearly Nernstian pH sensitivity of 54–57 mV/pH has been observed for O-terminated NCD films treated in an oxidising boiling mixture for 80 min and in oxygen plasma. The high pH-sensitive properties of O-terminated NCD have been used to develop an EDIS-based penicillin biosensor. A freshly prepared penicillin biosensor possesses a high sensitivity of 85 mV/decade in the concentration range of 0.1–2.5 mM penicillin G. The lower detection limit is 5 μM.
    Electrochimica Acta 10/2009; 54:5981-5985. DOI:10.1016/j.electacta.2009.03.011 · 4.09 Impact Factor
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    ABSTRACT: An array of individually addressable nanoplate field-effect capacitive (bio-)chemical sensors based on an SOI (silicon-on-insulator) structure has been developed for multi-parameter detection. An isolation of the individual capacitors was achieved by forming a trench in the top Si layer with various thicknesses of 30-350 nm. The feasibility of the proposed approach has been demonstrated by realising sensors for the detection of pH as well as for the label-free electrical monitoring of adsorption and binding of charged macromolecules.
    09/2009; 1(1):670-673. DOI:10.1016/j.proche.2009.07.167
  • 7th International Conference on Semiconductor Micro- and Nanoelectronics, TSAKHCADZOR, ARMENIA; 07/2009
  • W. Moritz, K.-H. Heckner
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    ABSTRACT: Eine Apparatur für radiochemische Adsorptionsuntersuchungen aus Lösungen an kompakten Oberflächen (insbesondere an Elektrodenmaterialien) wird vorgestellt und ihre Funktion erläutert. Die entwickelte Zellenvariante zeichnet sich besonders durch die Möglichkeit einer automatisierten Aufnahme der Adsorptionskinetik mit Hilfe einer Programmsteuerung aus. Die Separationsmöglichkeiten verschiedener Strahlenanteile werden diskutiert. Zur Berechnung der Oberflächenkonzentration der absorbierten Ionen werden zwei unabhängige Methoden angegeben. Die Amwendung der Apparatur wird am Beispiel der Chloridadsorption an thermisch präparierien Platin-Iridium-Elektroden mit Titangrundkörper dargestellt. Im Bereich der Ausbildung der Oberflächenoxide ergab sich in der Potentialabhängigkeit eine deutliche Hysteresis.
    08/2008; DOI:10.1080/10256018208544772
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    ABSTRACT: Application of solid electrolytes as undergate layers accelerates the response of a sensor at room temperature as compared with ordinary hydrogen sensors manufactured on the basis of the metal-insulator-semiconductor (MIS) structures with a palladium gate. The proton-conducting solid electrolytes under study include NAFION, zirconium hydrophosphate, and etherified polyvinyl alcohol (PVA) with heteropolyacids and phenoldisulfonic acid, which can be deposited under the platinum gate. Sensors based on the MIS structures with these solid electrolytes show a high sensitivity toward hydrogen (∼120 mV per concentration decade). The response time τ0.63 of a freshly manufactured sensor with a layer of zirconium hydrophosphate amounts to about 2 min. The maximum mechanical stability, especially at relative humidities in excess of 80% is intrinsic to sensors containing layers of PVA with heteropolyacids. The response time of such sensors is nearly 10 min.
    Russian Journal of Electrochemistry 04/2007; 43(5):561-569. DOI:10.1134/S1023193507050096 · 0.66 Impact Factor
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    ABSTRACT: An increase in the number of gases detectable by sensors based on Pd-SiO<sub>2</sub>-Si (MIS) and Pt-LaF<sub>3</sub>-Si<sub>3</sub>N<sub>4 </sub>-SiO<sub>2</sub>-Si (MEIS) structures was achieved by the application of an external catalyst element (CE). It was shown that as a result of the decomposition of hydrocarbon and fluorocarbon molecules on a Ni coil (CE), the products detectable by metal-insulator-semiconductor (MIS) and metal-electrolyte-insulator-semiconductor (MEIS) sensors are formed. The simultaneous catalytic oxidation of hydrocarbons and their thermal decomposition result in an optimum CE temperature of about 1050 K for propane. The kinetics of the thermal decomposition of gases on Ni were investigated. The activation energy of the reaction for C<sub>3 </sub>H<sub>8</sub> and the enthalpy in the case of CF<sub>3</sub>-CCl were estimated
    IEEE Sensors Journal 03/2007; DOI:10.1109/JSEN.2006.882778 · 1.85 Impact Factor

Publication Stats

431 Citations
137.66 Total Impact Points

Institutions

  • 1988–2014
    • Humboldt-Universität zu Berlin
      • Department of Chemistry
      Berlín, Berlin, Germany
  • 1993
    • Bundesanstalt für Materialforschung und -prüfung
      Berlín, Berlin, Germany