Nanoscale Hybrid Electronic Systems

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.

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

On December 1st 2016, Oliver Braun joined our group as a PhD student under the joint supervision of Michel Calame and Prof. Dr. Ilaria Zardo (Uni Basel). Oliver will work on electronic transport and thermopower in nanoscale devices. 

We’re happy to welcome Maria back from Netherlands!
Within the MOLESCO Marie Curie ITN, Maria spent 1 month in the group of Prof. Herre van der Zant at TU Delft working on low-temperature characterization of graphene nanojunctions.

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.

• Laser-Schneiden von komplexen mikro-mechanischen Konturen ohne Taperwinkel, Janko Auerswald, TRUMPF Maschinen AG
• MEMS et Micromechanique pour les montres, Olivier Dubochet, CSEM
• Transistors à nanofils de silicium pour la détection de ions et protéines, Michel Calame, SNI – Universität Basel
• Dünne Hochleistungsschichten mit HiPIMS, Jörg Patscheider, EMPA
• Additives Manufacturing für optische 3D-Mikrostrukturen, Dr. Helmut Schift, PSI

We are happy to welcome Yves Mermoud who will join the group on October. 1st. Yves will work on Si nanoribbon transistors for sensing in the framework of the NCCR MSE project.

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

We 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

Michel Calame, staff member at the Swiss Nanoscience Institute and the Department of Physics at the University of Basel, has accepted to lead a laboratory at the Empa (Swiss Federal Laboratories for Materials Science and Technology) with a new focus on “Nanoscale Transport Phenomena”, starting Oct. 1st, 2016. The activities of the group in Basel continue and will be progressively transferred to the Empa. The whole Nanoscale Hybrid Electronic Systems group will be integrated in the Empa lab and based in Dübendorf from August 2017 on.

Announcement at Empa: link.

New address
Michel Calame
Empa
Swiss Federal Laboratories for Materials Science and Technology
Ueberlandstrasse 129
CH-8600 Dübendorf
Tel: +41 58 765 4260
michel.calame@empa.ch

For administrative matters
Silvia Eppenberger (Mo-Th)
Silvia.Eppenberger@empa.ch
+41 58 765 4272

Béatrice Spoerri (Tu, Fr):
Beatrice.Spoerri@empa.ch
+41 58 765 4407

At the 8th International Conference on Molecular Electronics “Elecmol–2016” (August 22−26, Université Pierre et Marie Curie, Paris):

• Anton gave a talk “Controlled formation of organometallic molecular junctions in liquid environment”; 
• Jan presented a poster “Investigation of Electron Transport in Molecular and Optoelectronic Nanojunctions” – won a poster prize!
• Maria presented a poster “Graphene molecular junctions”.