New paper on SiOx-graphene memristors is just appeared in Nano Letters! Congratulations to Maria!

Congratulations to Maria!

Her paper on the  study of memristive behavior in SiOx-graphene nanojunction is just appeared in Nano Letters!

  • Multiple physical timescales and dead time rule in few-nm sized graphene-SiOx-graphene memristors
    Laszlo Posa, Maria El Abbassi, Peter Makk, Botond Santa, Cornelia Nef, Miklos Csontos, Michel Calame, and Andras Halbritter.
    Nano Letters, , null, 2017. [DOI]

New paper on nanogap formation in graphene is accepted to Nanoscale! Congratulations to Maria!

Congratulations to Maria!

Paper about the  study of environmental effects on the nanogap in graphene formation was just accepted for publication to Nanoscale!

  • From Electroburning to Sublimation: Substrate and Environmental Effects in the Electrical Breakdown Process of Monolayer Graphene
    Maria El Abbassi, Laszlo Posa, Peter Makk, Cornelia Nef, Kishan Thodkar, Andras Halbritter, and M. Calame.
    Nanoscale, , -, 2017. [DOI]
    [Abstract]

    We report on the characterization of the Electrical Breakdown (EB) process for the formation of tunneling nanogaps in single-layer graphene. In particular{,} we investigated the role of oxygen in the breakdown process by varying the environmental conditions (vacuum and ambient conditions). We show that the density of oxygen molecules in the chamber is a crucial parameter that defines the physical breakdown process: at low density{,} the graphene lattice is sublimating{,} whereas at high density the process involved is oxidation{,} independent on the substrate material. To estimate the activation energies of the two processes{,} we use a scheme which consists of applying voltage pulses across the junction during the breaking. By systematically varying the voltage pulse length{,} and estimating the junction temperature from a 1D thermal model{,} we extract activation energies which are consistent with the sublimation of graphene in high vacuum and the electroburning process in air. Our study indicates that a better control of the gaps formation is suitable in the sublimation regime.

Welcome Mathias and Mickael!

We are happy to welcome two new postdocs in our group.

Mathias Wipf
Mickael Perrin

Dr. Mathias Wipf during his doctoral (2010-2014, University of Basel) studies and postdoctoral research job (2015-2016, Yale University, Mark Reed group) worked with silicon nanowire based sensors.

Dr. Mickael Perrin was working in the field of single molecular junctions (as PhD student in 2011-2015 and as a postdoctoral researcher in 2015-2016 at Delft Technical University in the group of Herre van der Zant).

Just accepted: Charge noise in organic electrochemical transistors

Congratulations to Ralph Stoop and Michele Sessolo. Their paper on “Charge noise in organic electrochemical transistors” will appear in Phys. Rev. Applied.

Abstract

Organic electrochemical transistors (OECTs) are increasingly studied as transducers in sensing applications. While much emphasis has been placed on analyzing and maximizing the OECT signal, noise has been mostly ignored, although it determines the resolution of the sensor. The major contribution to the noise in sensing devices is the 1/f noise, dominant at low frequency. In this work, we demonstrate that the 1/f noise in OECTs follows a charge-noise model, which reveals that the noise is due to charge fuctuations in proximity or within the bulk of the channel material. We present the noise scaling behavior with gate voltage, channel dimensions and polymer thickness. Our results suggest the use of large area channels in order to maximize the signal-to-noise-ratio
(SNR) for biochemical and electrostatic sensing applications. Comparison with literature shows that the magnitude of the noise in OECTs is similar to that observed in graphene transistors, and only slightly higher compared to Carbon nanotubes and Silicon nanowire devices. In a model ion-sensing experiment with OECTs, we estimate crucial parameters such as the characteristic SNR and corresponding limit of detection.

 

Device schematic and measurement setup for the noise characterization. (b) Conductance G (black, left axis) and transconductance gm(red, right axis) versus liquid gate potential V_lg measured for a 25 um x 25 um OECT. (c) Power spectral density of the voltage fluctuations S_V versus frequency f for the OECT in (b) gated to different conductance values as given in the legend. The black dashed line indicates a 1/f dependence. The scattering peaks are due to the intrinsic noise of the power line matching 50 Hz and multiples of it.

 

Charge Noise in Organic Electrochemical Transistors
Ralph L. Stoop, Kishan Thodkar, Michele Sessolo and Henk Bolink, Christian Schonenberger and Michel Calame
to appear in Phys. Rev. Applied