Research Highlights 2018

Boron nitride passivation layers

Passivation of metals using protective coatings is a widespread technology and represents a huge market that generates billions of US dollars every year. 2D material offer the possibility to provide efficient protection against environment while the properties of the metal being protected are retained.

The high spatial resolution chemical analysis performed at CEITEC Nano Core facility provides insight in the mechanism of surface passivation against water and air oxidation.

The results revealed that when exposed to H2O2, a monolayer h-BN film is as inefficient as graphene as a protective coating. In contrary, 5–7 layers-thick h-BN film showed good protection, probably because of the higher resistance to transverse electron transfer from the metal to the electrolyte.

L. Jiang, N. Xiao, B. Wang, E. Grustan-Gutierrez, X. Jing, P. Bábor, M. Kolíbal, G. Lu, T. Wu, H. Wang, F. Hui, Y. Shi, B. Song, X. Xie, M. Lanza: High-resolution characterization of hexagonal boron nitride coatings exposed to aqueous and air oxidative environments, Nano Res. 2017, 10, 2046.


3D phase imaging

Phase-altering metasurfaces comprise a new class of artificial materials that allow to manipulate the wavefront of passing light and thus provide unprecedented functionalities in optics and nanophotonics.

On the metallic nanostructures fabricated at CEITEC Nano Core facility two CEITEC groups were able to perform quantitative 3D phase retrieval.

Using coherence-controlled holographic microscopy authors can obtain information about the phase of light from the whole field of view of an optical microscope in a single measurement. Quantitative 3D phase map of fabricated plasmonic zone plate shows functional phase lens with thickness below 50 nm.

J. Babocký, A. Křížová, L. Štrbková, L. Kejík, F. Ligmajer, M. Hrtoň, P. Dvořák, M. Týč, J. Čolláková, V. Křápek, R. Kalousek, R. Chmelík, T. Šikola: Quantitative 3D Phase Imaging of Plasmonic Metasurfaces, ACS Photonics 2017, 4, 1389.


Memristive memories

Resistive random access memories (RRAM) have emerged as the flagship element allowing future massive data storage due to their excellent performance and easy fabrication. To fulfill the information storage needs of modern societies, the performance of electronic nonvolatile memories (NVMs) should be continuously improved.

The devices fabricated at CEITEC Nano Core facility show the way how to further extend the performance of RRAMs.

Ti/2-nm-TiO2/1.5-nm-SiOX/n++Si memristors exhibit unprecedented I–V characteristics with double hysteresis. This behavior is related to the coexistence of filamentary and distributed resistive switching. The simplicity of our design and the good compatibility of all the materials used (Ti, TiO2, SiOX, and n++Si), with the silicon technology give promise that these findings will be quickly implemented in real devices.

N. Xiao, M. A. Villena, B. Yuan, S. Chen, B. Wang, M. Eliáš, Y. Shi, F. Hui, X. Jing, A. Scheuermann, K. Tang, P. C. McIntyre, M. Lanza: Resistive Random Access Memory Cells with a Bilayer TiO2/SiOX Insulating Stack for Simultaneous Filamentary and Distributed Resistive Switching, Adv. Funct. Mater. 2017, 27, 1700384.


Remote Graphene doping

Graphene is a zero bandgap semiconductor. In this respect, applying external electric field it is possible to control the charge carrier type (negative or positive) and concertation in graphene, therefore to change it transport properties (e.g. resistance).  This usually requires several fabrication steps, i.e. fabrication of graphene effect transistor device. 

Employing the graphene devices fabricated in CEITEC Nano Core Facility Pavel Procházka and his colleagues have found that the graphene can be doped using the X-ray radiation.

In this way, the graphene properties can be remotely defined without need for any contacts. Moreover, results of the study define the framework for correct X-ray characterization of graphene and can be developed into graphene radiation sensors.

P. Procházka, D. Mareček, Z. Lišková, J. Čechal, T. Šikola: X-ray induced electrostatic graphene doping via defect charging in gate dielectric, Sci. Rep. 7 (2017), 563.


Nano Letters article

Mira Kolíbal used NanoSAM at CEITEC Nano to reveal the essential role of atomic hydrogen in determining the growth direction of Ge nanowires with an Au catalyst.

M. Kolíbal,  T. Pejchal, T. Vystavěl, T. Šikola: The synergic effect of atomic hydrogen adsorption and catalyst spreading on Ge nanowire growth orientation and kinking, Nano Lett. 16 (8), (2016), 4880–4886.

 


ACS Editors Choice and Cover

The paper resulting from work on TOF-SIMS QTAC by Stan Průša, Pavel Procházka, Petr Bábor, Tomáš Šikola and their coworkers was chosen by Langmuir editor as the Editors choice!​

S. Průša, P. Procházka, P. Bábor, T. Šikola, R. ter Veen, M. Fartmann, T. Grehl , P. Brüner, D. Roth, P. Bauer, H. H. Brongersm: Highly Sensitive Detection of Surface and Intercalated Impurities in Graphene by LEIS, Langmuir 31 (2015), 9628.


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