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.


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

Trends in micro nano event in Bienne

On Oct. 25th, the Trend in Micro Nano event organized by the Swiss mnt network took place at the Innocampus in Bienne.  Among other speakers reporting about applied research or applications, we reported there on our work with Silicon-based biochemical sensors and its potential for applications.



Congratulations to Jan for the Best Poster award on the SNI Annual event.

Jan Overbeck with SNI Best poster award - 2016
Jan Overbeck won SNI Best poster award – 2016

In September 2016, SNI members met for their third annual conference in Lenzerheide, where 80 participants were treated to a diverse mixture of lectures and posters to encourage scientific exchange. 

Jan Oberbeck, an SNI doctoral student from Michel Calame’s group, won over the audience with his poster, for which he picked up a prize. 

Press release


Just accepted: paper on single and multi-domain CVD graphene by Kishan Thodkar et al.

fig2We systematically investigate the impact of granularity in CVD graphene films by performing Raman mapping and electrical characterization of single (SD) and multi domain (MD) graphene. In order to elucidate the quality of the graphene film, we study its regional variations using large area Raman mapping and compare the G and 2D peak positions of as-transferred Chemical Vapor Deposited (CVD) graphene on SiO2 substrate. We find a similar upshift in wavenumber in both SD and MD graphene in comparison to freshly exfoliated graphene. In our case, doping could play the dominant role behind the observation of such upshifts rather than the influence due to strain. Interestingly, the impact of the polymer assisted wet transfer process is the same in both the CVD graphene types. The electrical characterization shows that SD graphene exhibits a substantially higher (a factor 5) field-effect mobility when compared to MD graphene. We attribute the low sheet resistance and mobility enhancement to a decrease in charge carrier scattering thanks to a reduction of the number of grain boundaries and defects in SD graphene.

Figure Large area Raman scans of D, G and 2D bands (a-c, g-i) and peak position-histograms of SD (d-f) and MD (j-l) graphene. The average peak positions are marked with black dotted lines for D, G and 2D bands. Features in the large area scans are marked using white arrows. Scale bars: 4 µm (SD) and 2 µm (MD)

Comparative study of single and multi domain CVD graphene using large area Raman mapping and electrical transport characterization
Kishan Thodkar, Maria El Abbassi, Felix Lüönd, Frédéric Overney, Christian Schönenberger, Blaise Jeanneret and Michel Calame
pss-RRL (2016), DOI: 10.1002/pssr.201600211