RECENT ACHIEVEMENTS

Length separation of single-walled carbon nanotubes and its impact on structural and electrical properties of wafer-level fabricated carbon nanotube–field-effect transistors

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

On the way towards a reproducible waver-level technology for high performance FETs, we have applied a length separation process for SWCNTs and conducted a systematic study with FETs using different length fractions on the statistical level. It could be shown that sorted long SWCNTs outperform in FETs and give a device yield of > 95%. Moreover, compared to unsorted sc-SWCNTs, performance parameters such as subthreshold swing and hole mobility of FETs could be improved significantly. (S.Böttger et al. in Nanotechnology (2016) 10.1088/0957-4484/27/43/435203)

Enhancement of carbon nanotube FET performance via direct synthesis of poly (sodium 4-styrenesulfonate) in the transistor channel

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

Particularly in dense CNT assemblies, FET device performance is crucially determined by the topology of SWCNTs. Therefore we have explored a new approach allowing to tune channel properties by a direct post synthesis of poly (sodium 4-styrenesulfonate) (P(NaSS)) on SWCNTs. It reveals to be highly beneficial in improving the device parameters such as improved device-to-device consistency, higher drain currents and higher on/off ratios. Moreover, this treatment may serve also as a long-term passivation of SWCNT transistor devices. (M.Toader et al. in Chemical Physics Letter (2016) 10.1016/j.cplett.2016.07.049)

Effect of cleaning procedures on the electrical properties of carbon nanotube transistors

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

Unintentional memory effects in CNTFETs due to e.g. traps and surfactant molecules lead to unpredictable device and circuit performance and needs to be avoided. Four chemical cleaning procedures for a successful removal of surfactant molecules from carbon nanotubes in field-effect transistors are evaluated statistically. (J. Tittmann-Otto et al. in Journal of Applied Physics, 10.1063/1.4944835)

Towards an optimal contact metal for CNTFETs

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

Using the so-called ‘modular approach’, we have investigated a representative set of ten metals with various work functions and bond strengths to a CNT. This analysis reveals the physical mechanisms determining the metal/CNT resistance and identifying optimal contact metals in terms of contact resistance and its scaling. (A. Fediai et al. in Nanoscale, doi: 10.1039/C6NR01012A)

Impact of incomplete metal coverage on the electrical properties of metal-CNT contacts: A large-scale ab-initio study

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

Understanding the physics behind the contact resistance at metal-CNT interfaces is of crucial importance for the development of high-performance CNTFETs. Using parameter-free model, we show how the contact resistance and on-current of a carbon nanotube FET depend on the quality of the metal/CNT contact for a variety of three metals representing week, medium and week metal-CNT interaction strength. (A. Fediai et al. in Applied Physics Letters, doi: 10.1063/1.4962439)

Electrical Characterization of Emerging Transistor Technologies: Issues and Challenges

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

Emerging transistor technologies are very often affected by traps leading to unintentional memory effects and inconsistent device characteristics by means of conventional characterization techniques. Pulsed measurements with narrow pulses and very small duty cycles allow a trap-free electrical device characterization preventing false conclusions for technology development and device performance. (M. Haferlach et al. in IEEE Transactions on Nanotechnology, 10.1109/TNANO.2016.2564925)

Electron Back Scattering in CNTFETs

Published on in CARBON PATH (RECENT ACHIEVEMENTS)

Physics-based compact models for CNTFETs have failed so far to correctly predict the transistor behavior above the onset of optical scattering. By considering analytically that carrier injection from the drain is suppressed once source injected carriers are accumulated at the band edge due to optical phonon scattering, the applicability of the compact models has successfully been extended beyond the onset of optical phonon scattering. (I. Bejenari et al. in Transactions of Electron Devices, 10.1109/TED.2015.2512180)