Tag Archives: PPP-EFM

Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching

Happy #NanotechnologyDay!

The date, 10/9, is a nod to the nanometer scale, where objects span only billionths of a meter (10⁻⁹ meters).

We celebrate it with the nanotechnology community by featuring an article on AFM-Based Electrochemical Etching in today’s blogpost.

Nanomanufacturing involves scaled-up, reliable, and cost-effective manufacturing of nanoscale materials, structures, devices, and systems. It leads to the production of improved materials and new products, and manufactured structures with unique properties in the nanoscale are capable of enabling quantum leaps and improvement in high-performance technologies, from new sensors, high-density data storage, and drug delivery to high-strength materials and energy-efficient solar cells. These applications lead to significant demand in the future research and development of nanomanufacturing. Based on material properties, nanomanufacturing can be performed by additive, subtractive, and mass conservation. Several nanomanufacturing technologies, such as laser ablation, etching, ultraviolet light lithography, and focused ion beam (FIB), have been widely utilized to obtain functional structures and surfaces with nanoscale features. Although exciting results have been achieved, many challenges are still encountered in nanomanufacturing relative to the nanoscale, nano accuracy, complex shape/structure, and novel materials. *

Scanning probe microscopy (SPM)-based lithography, as a promising nanolithography approach for the fabrication at the nanometer scale, has attracted significant attention because of its simplicity and precise control of a structure and location. *

Atomic force microscopy (AFM), as a kind of SPM, shows more advantages in nanomanufacturing than STM, especially because AFM can work in ambient environments. Moreover, many different approaches, such as chemical and electrical methods, can be easily combined on AFM to improve the nanomanufacturing ability. AFM-based electrochemical machining was first used to modify hydrogen-passivated n-Si(111) surfaces via chemical oxidization in ambient conditions. Accordingly, the kinetics and mechanism of oxidation have attracted great interest due to the major contributions in the machining process, and other papers have hoped to improve the reproducibility of the process by studying the dynamic force microscopy modes. The comprehensive understanding and control of the oxidation mechanism are of critical importance for the application of the SPM technique. However, the complexity of challenges remains open, and the oxidation process of the sample is still complicated. Furthermore, atomic and close-to-atomic scale manufacturing (ACSM) has become the leading trend in global manufacturing development. To achieve ACSM, AFM and STM work as vital instruments due to the atomic and close-to-atomic scale resolution in all three spatial dimensions. For decades, scientists have been inspired to develop relevant techniques to ACSM to directly visualize and manipulate an individual atom using SPM. *

In their article “Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching “ Wei Han, Paven Thomas Mathew, Srikanth Kolagatla, Brian J. Rodriguez and Fengzhou Fang describe how, an AFM-based electrochemical machining method was used to etch a highly oriented pyrolytic graphite  (HOPG) surface to single-atomic-layer precision.*

Atomic force microscopy (AFM)-based electrochemical etching of a highly oriented pyrolytic graphite (HOPG) surface is studied toward the single-atomic-layer lithography of intricate patterns. Electrochemical etching is performed in the water meniscus formed between the AFM tip apex and HOPG surface due to a capillary effect under controlled high relative humidity (~ 75%) at otherwise ambient conditions. The conditions to etch nano-holes, nano-lines, and other intricate patterns are investigated. The electrochemical reactions of HOPG etching should not generate debris due to the conversion of graphite to gaseous CO and CO2 based on etching reactions. However, debris is observed on the etched HOPG surface, and incomplete gasification of carbon occurs during the etching process, resulting in the generation of solid intermediates. Moreover, the applied potential is of critical importance for precise etching, and the precision is also significantly influenced by the AFM tip wear. This study shows that the AFM-based electrochemical etching has the potential to remove the material in a single-atomic-layer precision. This result is likely because the etching process is based on anodic dissolution, resulting in the material removal atom by atom.*

The experiments were performed under ambient conditions with a commercial atomic force microscope using NANOSENSORS PtIr5 coated PointProbePlus® PPP-EFM AFM probes. The AFM tip side coating enhances the conductivity of the AFM tip and allows electrical contacts, and the opposite side coating enhances the laser reflex.

Figure 2 from Wei Han et al. “Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching” Schematic diagram of the AFM-based electrochemical etching apparatus with an RH-controlled environment. The experiments were performed under ambient conditions with a commercial atomic force microscope using NANOSENSORS PtIr5 coated PointProbePlus® PPP-EFM AFM probes. The AFM tip side coating enhances the conductivity of the AFM tip and allows electrical contacts, and the opposite side coating enhances the laser reflex.
Figure 2 from Wei Han et al. “Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching”
Schematic diagram of the AFM-based electrochemical etching apparatus with an RH-controlled environment

*Wei Han, Paven Thomas Mathew, Srikanth Kolagatla, Brian J. Rodriguez AND Fengzhou Fang
Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching
Nanomanufacturing and Metrology volume 5, pages 32–38 (2022)
DOI: https://doi.org/10.1007/s41871-022-00127-9

Please follow this external link to read the full article: https://rdcu.be/cXcCi

Open Access: The article “Toward Single-Atomic-Layer Lithography on Highly Oriented Pyrolytic Graphite Surfaces Using AFM-Based Electrochemical Etching” by Wei Han, Paven Thomas Mathew, Srikanth Kolagatla, Brian J. Rodriguez and Fengzhou Fang is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes

Solid state electrolytes (SSEs) are interesting materials that could potentially replace the currently used organic electrolytes in lithium‐ion batteries (LIBs). *

Electrochemical strain microscopy (ESM), a research technique based on atomic force microscopy (AFM), was developed to locally probe ion movement in electrodes based on electro-chemo-mechanical coupling measure through the AFM cantilever deflection. It can be used to characterize Li-ion mobility in energy materials with extremely high spatial resolution. *

The main challenge with ESM is its nonquantitative nature due to complex AFM cantilever dynamics in contact mode when performed on resonance as well as signal contribution that are not necessarily related to ions such as electrostatic forces.*

In the article “ Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes “ Nino Schön, Roland Schierholz, Stephen Jesse, Shicheng Yu, Rüdiger‐A. Eichel, Nina Balke and Florian Hausen investigate the exact signal formation process of electrochemical strain microscopy (ESM) when it is applied on sodium super ionic conductor (NASCIO)-type solid state electrolytes containing Na- and Li-ions.*

In their research the authors correlatively use various scanning probe microscopy (SPM) based microscopy techniques together with scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy ( EDX ) at identical positions of the solid state electrolyte LATP.*

They find that changes in the dielectric properties are responsible for the detected contrast in the deflection of the AFM cantilever instead of a physical volume change as a result of Vegard’s Law. The AFM cantilever response is strongly reduced in areas of high sodium content which is attributed to a reduction of the AFM tip-sample capacitance in comparison with areas with high lithium content.*

This is the first time a direct link between electrostatic forces in contact mode and local chemical information is demonstrated on SSEs. The results presented in the article open up the possibility to learn more since dielectric properties are sensitive to subtle changes in local chemical composition.*

NANOSENSORS conductive Platinum-Iridium coated PointProbe® Plus PPP-EFM AFM probes were primarily used in the research for this article.

Figure 1 from Nino Schön et al. «Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes”:
a) Topography, b) deflection error, and c) corresponding cantilever deflection change (Dac) map of a 30 µm × 30 µm area of LATP. d) Noncontact EFM amplitude map in the same area.
NANOSENSORS conductive platinum-iridium coated PointProbe Plus PPP-EFM AFM probes were used.
Figure 1 from Nino Schön et al. «Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes”:
a) Topography, b) deflection error, and c) corresponding cantilever deflection change (Dac) map of a 30 µm × 30 µm area of LATP. d) Noncontact EFM amplitude map in the same area.

*Nino Schön, Roland Schierholz, Stephen Jesse, Shicheng Yu, Rüdiger‐A. Eichel, Nina Balke, Florian Hausen
Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes
Small Methods, Early View, Online Version of Record before inclusion in an issue 2001279
DOI: https://doi.org/10.1002/smtd.202001279

Please follow this external link to read the full article: https://onlinelibrary.wiley.com/doi/10.1002/smtd.202001279

Open Access The article “Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes” by Nino Schön, Roland Schierholz, Stephen Jesse, Shicheng Yu, Rüdiger‐A. Eichel, Nina Balke, Florian Hausen is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Engineering work function of graphene oxide from p to n type using a low power atmospheric pressure plasma jet

Graphene, since its discovery in 2004 has attracted enormous interest due to its physical and chemical properties, and wide applications. *

Graphene oxide (GO) has emerged as an attractive alternative to graphene due to low cost, large scale production and solution processability. GO is prepared by oxidative exfoliation of graphite.*

The work function is a fundamental electronic property of a material and can be used to interpret the relative position of the Fermi level.*

For efficient transport of electrons or holes in a heterojunction device, the work function of the materials plays a crucial role, since work function determines how the bands will align at the contacts.*

Recently there has been an increased interest in applications of GO for interfacial layers and transparent electrode materials in optoelectronic devices e.g. liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), touch screens, dye-sensitized solar cells (DSSCs) and as supercapacitor electrodes. Tuning the work function of GO is key to achieving high performance devices. *

In the article “Engineering work function of graphene oxide from p to n type using a low power atmospheric pressure plasma jet” by Avishek Dey, Paheli Ghosh, James Bowen, Nicholas St. J. Braithwaite and Satheesh Krishnamurthy, the authors demonstrate doping graphene oxide (GO) films using a low power atmospheric pressure plasma jet (APPJ) with subsequent tuning of the work function.*

The surface potential of the plasma functionalized GO films could be tuned by 120 ± 10 mV by varying plasma parameters. *

Scanning Kelvin probe microscopy ( SKPM ) also known as Kelvin probe force microscopy ( KPFM ) measurements were carried out to realize changes in work function of the GO films with plasma functionalization.*

NANOSENSORS™ PointProbe® Plus PPP-EFM AFM probes with a platinum iridium coating were used to perform surface potential measurements. *

The Kelvin probe studies showed that the bonding configuration can influence the work function of GO. Pyridinic nitrogen transforms GO to p-type while graphitic nitrogen increases the electron density of GO and transforming it to n type. Pointing to the fact that a low power APPJ can effectively tune the work function of GO and hence the conductivity. *

The findings presented in the article are extremely useful in fabricating heterojunction devices like sensors and optoelectronic devices where band structure alignment is key to device performance when GO is used as a charge transport layer. This technique can be extended to other known 2D systems.*

Fig. 10 (a) from “Engineering work function of graphene oxide from p to n type using a low power atmospheric pressure plasma jet” by Avishek Dey et al.:

a) KPFM surface potential map of reference GO thin film ( please have a look at https://pubs.rsc.org/image/article/2020/CP/c9cp06174f/c9cp06174f-f10_hi-res.gif for the full figure.)
Figure 10 (a) from “Engineering work function of graphene oxide from p to n type using a low power atmospheric pressure plasma jet” by Avishek Dey et al.:

a) KPFM surface potential map of reference GO thin film ( please have a look at https://pubs.rsc.org/image/article/2020/CP/c9cp06174f/c9cp06174f-f10_hi-res.gif for the full figure.)

*Avishek Dey, Paheli Ghosh, James Bowen, Nicholas St. J. Braithwaite and Satheesh Krishnamurthy
Engineering work function of graphene oxide from p to n type using a low power atmospheric pressure plasma jet
Physical Chemistry Chemical Physics, 2020, 22, 7685-7698
DOI: 10.1039/C9CP06174F

Please follow this external link for the full article: https://pubs.rsc.org/en/content/articlehtml/2020/cp/c9cp06174f

Open Access: The article “Engineering work function of graphene oxide from p to n type using a low power atmospheric pressure plasma jet” by Avishek Dey, logoa, Paheli Ghosh, James Bowen, Nicholas St. J. Braithwaite and Satheesh Krishnamurthy is licensed under a Creative Commons Attribution 3.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/.