Browsing by Author "Smits, E. C. P."
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- Determining carrier mobility with a metal–insulator–semiconductor structurePublication . Stallinga, Peter; Benvenho, A. R. V.; Smits, E. C. P.; Mathijssen, S. G. J.; Cölle, M.; Gomes, Henrique L.; De Leeuw, Dago M.The electron and hole mobility of nickel-bis(dithiolene) (NiDT) are determined in a metal– insulator–semiconductor (MIS)structure using admittance spectroscopy. The relaxation times found in the admittance spectra are attributed to the diffusion time of carriers to reach the insulator interface and via Einstein’s relation this yields the mobility values. In this way, an electron mobility of 1:9 104 cm2=Vs and a hole mobility of 3:9 106 cm2=Vs were found. It is argued that the low mobility is caused by an amphoteric mid-gap trap level. The activation energy for electrons and holes from these traps is found to be 0.46 eV and 0.40 eV, respectively.
- Dynamics of charge carrier trapping in NO2 sensors based on ZnO field-effect transistorsPublication . 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.
- Dynamics of threshold voltage shifts in organic and amorphous silicon field-effect transistorsPublication . Mathijssen, S. G. J.; Colle, M.; Gomes, Henrique L.; Smits, E. C. P.; de Boer, B.; McCulloch, I.; Bobbert, P. A.; de Leeuw, D. M.The electrical instability of organic field-effect transistors is investigated. We observe that the threshold-voltage shift (see figure) shows a stretched-exponential time dependence under an applied gate bias. The activation energy of 0.6 eV is common for our and all other organic transistors reported so far. The constant activation energy supports charge trapping by residual water as the common origin.
- Ultralow Power Microfuses for Write-Once Read-Many Organic Memory ElementsPublication . de Brito, B. C.; Smits, E. C. P.; van Hal, P. A.; Geuns, T. C. T.; de Boer, B.; Lasance, C. J. M.; Gomes, Henrique L.; de Leeuw, D. M.Ultralow power microfuses for write-once read-many organic memory elements that rely on electrolysis of water rather than conventional Joule heating are presented. Gasses formed upon electrolysis cannot escape, the pressure rises, the top electrode delaminates and the electrical contact is lost. The voltage-driven fuses are ideally suited for low-end applications such as in electronic bar codes.