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Percorrer por autor "Blom, P. W. M."

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  • Dynamics of charge carrier trapping in NO2 sensors based on ZnO field-effect transistors
    Publication . Andringa, Anne-Marije; Vlietstra, N.; Smits, E. C. P.; Spijkman, Mark-Jan; Gomes, Henrique L.; Klootwijk, J. H.; Blom, P. W. M.; De Leeuw, Dago M.
    Nitrogen dioxide (NO2) detection with ZnO field-effect transistors is based on charge carrier trapping. Here we investigate the dynamics of charge trapping and recovery as a function of temperature by monitoring the threshold voltage shift. The threshold voltage shifts follow a stretched-exponential time dependence with thermally activated relaxation times. We find an activation energy of 0.1 eV for trapping and 1.2 eV for detrapping. The attempt-to-escape frequency and characteristic temperature have been determined as 1 Hz and 960 K for charge trapping and 1011 Hz and 750 K for recovery, respectively. Thermally stimulated current measurements confirm the presence of trapped charge carriers with a trap depth of around 1 eV. The obtained functional dependence is used as input for an analytical model that predicts the sensor’s temporal behavior. The model is experimentally verified and a real-time sensor has been developed. The perfect agreement between predicted and measured sensor response validates the methodology developed. The analytical description can be used to optimize the driving protocol. By adjusting the operating temperature and the duration of charging and resetting, the response time can be optimized and the sensitivity can be maximized for the desired partial NO2 pressure window.
    2012Artigo científico Acesso restrito Ver mais
  • Low frequency electric current noise in glioma cell populations
    Publication . Rocha, P. R. F.; Schlett, P.; Schneider, L.; Dröge, M.; Mailänder, V.; Gomes, Henrique L.; Blom, P. W. M.; De Leeuw, Dago M.
    Measuring the electrical activity of large and defined populations of cells is currently a major technical challenge to electrophysiology, especially in the picoampere-range. For this purpose, we developed and applied a bidirectional transducer based on a chip with interdigitated gold electrodes to record the electrical response of cultured glioma cells. Recent research determined that also non-neural brain glia cells are electrically active and excitable. Their transformed counterparts, e.g. glioma cells, were suggested to partially retain these electric features. Such electrophysiological studies however are usually performed on individual cells and are limited in their predictive power for the overall electrical activity of the multicellular tumour bulk. Our extremely low-noise measuring system allowed us to detect not only prominent electrical bursts of neuronal cells but also minute, yet constantly occurring and functional, membrane capacitive current oscillations across large populations of C6 glioma cells, which we termed electric current noise. At the same time, tumour cells of non-brain origin (HeLa) proved to be electrically quiescent in comparison. Finally, we determined that the glioma cell activity is primarily caused by the opening of voltage-gated Na+ and K+ ion channels and can be efficiently abolished using specific pharmacological inhibitors. Thus, we offer here a unique approach for studying electrophysiological properties of large cancer cell populations as an in vitro reference for tumour bulks in vivo.
    2015Artigo científico Acesso aberto Ver mais