Tag Archives: Nanotechnology

Insights into dynamic sliding contacts from conductive atomic force microscopy

Friction in nanoscale contacts is determined by the size and structure of the interface that is hidden between the contacting bodies. One approach to investigating the origins of friction is to measure electrical conductivity as a proxy for contact size and structure. However, the relationships between contact, friction and conductivity are not fully understood, limiting the usefulness of such measurements for interpreting dynamic sliding properties.*

In their study “Insights into dynamic sliding contacts from conductive atomic force microscopy” Nicholas Chan, Mohammad R. Vazirisereshk, Ashlie Martini and Philip Egberts used atomic force microscopy (AFM) to simultaneously acquire lattice resolution images of the lateral force and current flow through the tip–sample contact formed between a highly oriented pyrolytic graphite (HOPG) sample and a conductive diamond AFM probe to explore the underlying mechanisms and correlations between friction and conductivity. Both current and lateral force exhibited fluctuations corresponding to the periodicity of the HOPG lattice.

Unexpectedly, while lateral force increased during stick events of atomic stick-slip, the current decreased exponentially.*

The results presented in the study by Nicholas Chan et al. confirm that the correlation between conduction and atom–atom distance previously proposed for stationary contacts can be extended to sliding contacts in the stick-slip regime.*

A NANOSENSORS™ conductive diamond coated AFM probe CDT-CONTR was used to obtain all experimental data presented in their manuscript.*

Figure 1 (a) from “Insights into dynamic sliding contacts from conductive atomic force microscopy” by Nicholas Chan et al:
A schematic of the experimental setup is shown in Fig. 1(a). The experiment was conducted using an ultra-high vacuum (UHV) (RHK) AFM at room temperature at a pressure of <1109Torr. A doped diamond coated cantilever (NANOSENSORS CDT-CONTR) with a normal bending spring constant of 0.86 N m1and lateral spring constant of 10 N m1was used to obtain all experimental data presented in this manuscript.

Figure 1 (a) from “Insights into dynamic sliding contacts from conductive atomic force microscopy” by Nicholas Chan et al:
A schematic of the experimental setup is shown in Fig. 1(a). The experiment was conducted using an ultra-high vacuum (UHV)AFM at room temperature at a pressure of <1109Torr. A doped diamond coated cantilever (NANOSENSORS CDT-CONTR) with a normal bending spring constant of 0.86 N m1and lateral spring constant of 10 N m1was used to obtain all experimental data presented in this manuscript.

*Nicholas Chan, Mohammad R. Vazirisereshk, Ashlie Martini and Philip Egberts
Insights into dynamic sliding contacts from conductive atomic force microscopy
Nanoscale Advances., 2020, Advance Article
DOI: 10.1039/d0na00414f

Please follow this external link to read the whole article: https://pubs.rsc.org/en/content/articlepdf/2020/na/d0na00414f

Open Access: The article “Insights into dynamic sliding contacts from conductive atomic force microscopy” by Nicholas Chan, Mohammad R. Vazirisereshk, Ashlie Martini and Philip Egberts 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/.

Gentle plasma process for embedded silver-nanowire flexible transparent electrodes on temperature-sensitive polymer substrates

In the article “Gentle plasma process for embedded silver-nanowire flexible transparent electrodes on temperature-sensitive polymer substrates “ Lukas Kinner, Emil J W List-Kratochvil and Theodoros Dimopoulos investigate processing routes to obtain highly conductive and transparent electrodes of silver nanowires (AgNWs) on flexible polyethylene terephthalate (PET) substrate.*

Their study shows that both thermally stable polyimide, as well as temperature-sensitive PET can be used as flexible host substrates, combined with a gentle, AgNW plasma curing. This is possible by adjusting the fabrication sequence to accommodate the plasma curing step, depending on the host substrate. As a result, embedded AgNW electrodes, transferred from polyimide-to-PET and from PET-to-PET are obtained, with optical transmittance of ~80% (including the substrate) and sheet resistance of ~13 Ω/sq., similar to electrodes transferred from glass-to-glass substrates.*

The embedded AgNW electrodes on PET show superior performance in bending tests, as compared to indium-tin-oxide electrodes and can be easily combined with metal oxide films for device implementation. The introduced approach, involving low-cost flexible substrates, AgNW spray-coating and plasma curing, is compatible with high-throughput, roll-to-roll processing.*

The impact of the introduced processes concerns therefore applications where high-throughput production must be combined with sensitive, flexible substrates and ultra-thin device architectures, like OLEDs and organic- or perovskite-based photovoltaics.*

The sample surfaces were characterized with atomic force microscopy (AFM) in tapping mode, using high-resolution NANOSENSORS™ SuperSharpSilicon™ SSS-NCHR AFM probes.

Figure 5. from “Gentle plasma process for embedded silver-nanowire flexible transparent electrodes on temperature-sensitive polymer substrates “ by Lukas Kinner et al.: The sample surfaces were characterized with atomic force microscopy (AFM) in tapping mode, using high-resolution NANOSENSORS™ SuperSharpSilicon™ SSS-NCHR AFM probes.
AFM images of the AgNW electrodes for: (a) G2G SP, (b) G2G IP, (c) height profile for the dashed line marked in (b), (d) K2P SP, (e) P2P IP, (f) height profile for the dashed line marked in (e).
Figure 5. from “Gentle plasma process for embedded silver-nanowire flexible transparent electrodes on temperature-sensitive polymer substrates “ by Lukas Kinner et al.:
AFM images of the AgNW electrodes for: (a) G2G SP, (b) G2G IP, (c) height profile for the dashed line marked in (b), (d) K2P SP, (e) P2P IP, (f) height profile for the dashed line marked in (e).

*Lukas Kinner, Emil J W List-Kratochvil and Theodoros Dimopoulos
Gentle plasma process for embedded silver-nanowire flexible transparent electrodes on temperature-sensitive polymer substrates
Nanotechnology, Volume 31, Number 36 (2020)
DOI: https://doi.org/10.1088/1361-6528/ab97aa

Please follow this external link to read the full article: https://iopscience.iop.org/article/10.1088/1361-6528/ab97aa

Open Access: The article “Gentle plasma process for embedded silver-nanowire flexible transparent electrodes on temperature-sensitive polymer substrates” by Lukas Kinner, Emil J W List-Kratochvil and Theodoros Dimopoulos 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/.

Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface

Carbon-based layers play an important role in boundary lubrication, from graphite as commercial solid lubricant in a spray can over diamond-like carbon coatings in automotive industries all the way to graphitic layers found in metal-metal hip implants. With increasing availability of graphene, the two-dimensional building block of graphite, its possible role in lubrication is being explored. *

After the discovery of friction and wear reduction on steel surfaces by graphene in a variety of environments, graphene is now emerging as new lubricant. Polymer composites with graphene exhibit improved tribological properties due to wear reduction by efficient transfer layers. The composite approach has been successfully extended to multilayers of polymer and graphene. The use of graphene as additive in formulated lubricant oils is also promising after functionalization to improve solubility. *

In their letter “Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface” G. Krämer, C. Kim, K-S. Kim and R. Bennewitz report experimental results for fundamental lubrication properties of the interface between a hexadecane model lubricant and a steel surface modified by a single layer graphene. Using high-resolution force microscopy, they quantify that the reduction of friction on graphene is connected to an ordered layer of adsorbed hexadecane molecules and that the graphene induces an ordering in molecular layers in the confined liquid above graphene patches. *

A single layer of graphene on steel surfaces causes a change in the near-surface structure of the model lubricant hexadecane. Hexadecane adsorbs in an ordered layer aligned straight molecules, and this layer is stable under scanning in contact with the tip of an atomic force microscope, while no such layer is observed on the steel substrate. Graphene and hexadecane layer reduce friction at the nanoscale by a factor of three compared to the bare steel in hexadecane. *

All AFM measurements described in this letter were performed using a NANOSENSORS™ PointProbe® Plus PPP-CONTR AFM probe at room temperature with a home-built fluid cell where the cantilever was fully immersed in hexadecane.*

 Figure 3 from “Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface” by G Krämer et al.:
 High-resolution lateral force maps recorded in hexadecane with a normal force of 3 nN. (a) On graphene, the adsorbed hexadecane molecules arrange in form of lamellae with a width of 2.1 nm. The cross-section was taken along the line indicated. The schematic depiction of the orientation of one hexadecane molecule is informed by the results in [21]. (b) On the steel substrate, an irregular stick-slip pattern with a characteristic slip length of about 1 nm is observed. The two cross-sections are taken the along the lines indicated in the respective color.
Figure 3 from “Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface” by G Krämer et al.:
High-resolution lateral force maps recorded in hexadecane with a normal force of 3 nN. (a) On graphene, the adsorbed hexadecane molecules arrange in form of lamellae with a width of 2.1 nm. The cross-section was taken along the line indicated. The schematic depiction of the orientation of one hexadecane molecule is informed by the results in [21]. (b) On the steel substrate, an irregular stick-slip pattern with a characteristic slip length of about 1 nm is observed. The two cross-sections are taken the along the lines indicated in the respective color.

*G. Krämer, C. Kim, K-S. Kim and R. Bennewitz
Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface
Nanotechnology, Volume 30, Number 46, 2019, 46LT01
DOI: https://doi.org/10.1088/1361-6528/ab3cab

Please follow this external link to read the full article: https://iopscience.iop.org/article/10.1088/1361-6528/ab3cab

Open Access: The letter “Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface” by G Krämer, C Kim, K-S Kim and R Bennewitz 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/.