Tag Archives: Platinum Silicide AFM probes

Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation

Controlling the work function of transition metal oxides is of key importance with regard to future energy production and storage. As the majority of applications involve the use of heterostructures, the most suitable characterization technique is Kelvin probe force microscopy (KPFM), which provides excellent energetic and lateral resolution.*

In their study “Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation» Dominik Wrana, Karol Cieślik, Wojciech Belza, Christian Rodenbücher, Krzysztof Szot and Franciszek Krok present the advantages and limitations of the FM-KPFM technique using the example of a newly discovered TiO/SrTiO3(100) (metal/insulator) heterostructure, which has potentially high technological relevance.*

In the same article a combined conductivity and work function study from the same surface area is presented, showing the possibility of obtaining full information on the electronic properties when the KPFM technique is accompanied by local conductivity atomic force microscopy (LC-AFM).*

The authos present the measurement of the crystalline TiO work function and its dependence on the gaseous pressure of air using Kelvin probe force microscopy.

In order to ensure reproducible FM-KPFM results, two different types of AFM cantilevers were used: NANOSENSORS™ PointProbe® Plus PPP-ContPt (PtIr-coated) and NANOSENSORS™ Platinum Silicide PtSi-FM.*

Such cantilevers are widely used as conducting tips in a contact mode AFM, allowing for a high lateral resolution in conductivity measurements. The remarkable mechanical stability of the selected cantilevers allowed for the noncontact mode measurements (with a Kelvin loop) using the very same tip, maintaining oscillations at the higher harmonics of the fundamental frequency (≈75 kHz). Hence, in order to record current and CPD maps from the very same sample area, KPFM measurements were first performed with the soft cantilever forced to oscillate at higher harmonics, then the tip was retracted tens of nanometers from the surface, all feedback loops were turned down and a contact mode AFM scan was performed when approached with a single loop maintaining a deflection set point of 10–30 mV. The high conductivity of both TiO and STO materials enabled a low sample bias of +1 mV for the LC-AFM measurements to be used.*

Figure 4 from “Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation”: KPFM lateral resolution on high TiO/STO structures. a) Topography and b) work function of TiO nanowire array on SrTiO3(100). c) Height (black line) and work function (green line) profiles of two adjacent TiO nanowires, showing high KPFM contrast. d) Dependence of the CPD resolution (estimated as ΔCPD/CPD, see c) on the separation between TiO nanowires, with A + B/X asymptote fit. Insets show the SEM images of the actual PtSi cantilever used in the experiments with a tip radius of 15 nm.

*Dominik Wrana, Karol Cieślik, Wojciech Belza, Christian Rodenbücher, Krzysztof Szot, Franciszek Krok
Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation
Beilstein Journal of Nanotechnology 2019, 10, 1596–1607
DOI: 10.3762/bjnano.10.155

Please follow this external link to read the full article: https://www.beilstein-journals.org/bjnano/articles/10/155

Open Access The article “Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation” by Dominik Wrana, Karol Cieślik, Wojciech Belza, Christian Rodenbücher, Krzysztof Szot and Franciszek Krok 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/.

Conductive-probe atomic force microscopy and Kelvin-probe force microscopy characterization of OH-terminated diamond (111) surfaces with step-terrace structures

Diamond has a high breakdown field, high carrier mobilities and the highest thermal conductivity. That is why diamond is a promising material for next generation high-power devices such as field effect transistors.*

In their paper “Conductive-probe atomic force microscopy and Kelvin-probe force microscopy characterization of OH-terminated diamond (111) surfaces with step-terrace structures”, Masatsugu Nagai, Ryo Yoshida, Tatsuki Yamada, Taira Tabakoya, Christoph E. Nebel, Satoshi Yamasaki, Toshiharu Makino, Tsubasa Matsumoto, Takao Inokuma and Norio Tokuda report about a detailed characterization of OH-terminated diamond (111) surfaces with step-terrace (ST) and bunching-step (BS) regions. In order to obtain the OH-terminated diamond (111) surfaces, they combined three techniques: anisotropic diamond etching by thermochemical reaction between Ni and diamond in high-temperature water vapor, hydrogen plasma treatment24) and water vapor annealing.
For characterization of the topography as well as electronic surface properties, atomic force microscopy (AFM), Kelvin-probe force microscopy (KPFM) and conductive-prove AFM (CPAFM) were applied.*

They found that the contact potential difference (CPD) and current were highly correlated with the surface topography and concluded that the interface states were generated around steps on the OH-terminated diamond (111) surfaces.*

The results presented in this paper indicate that atomically flat diamond surfaces with minimal step densities are required to form ideal MOS structures with minimized interface state densities.*

The CPD maps of the OH-terminated diamond (111) surfaces were obtained by the KPFM measurements, using NANOSENSORS™ Platinum Silicide ( PtSi ) AFM probes. *

 Fig. 2 from “Conductive-probe atomic force microscopy and Kelvin-probe force microscopy characterization of OH-terminated diamond (111) surfaces with step-terrace structures” by Masatsugu Nagai et al.:
 (Color online) (a) The topographic image and CPD map of the OH-terminated diamond (111) surface with ST and BS regions. (b) the cross sectional image and CPD profile corresponding to the line A-A' in the Fig. 2(a).

Fig. 2 from “Conductive-probe atomic force microscopy and Kelvin-probe force microscopy characterization of OH-terminated diamond (111) surfaces with step-terrace structures” by Masatsugu Nagai et al.:
(Color online) (a) The topographic image and CPD map of the OH-terminated diamond (111) surface with ST and BS regions. (b) the cross sectional image and CPD profile corresponding to the line A-A’ in the Fig. 2(a).

*Masatsugu Nagai, Ryo Yoshida, Tatsuki Yamada, Taira Tabakoya, Christoph E. Nebel, Satoshi Yamasaki, Toshiharu Makino, Tsubasa Matsumoto, Takao Inokuma and Norio Tokuda
Conductive-probe atomic force microscopy and Kelvin-probe force microscopy characterization of OH-terminated diamond (111) surfaces with step-terrace structures
Japanese Journal of Applied Physics, 2019, Volume 58, Number SIIB08
DOI: https://doi.org/10.7567/1347-4065/ab1b5c

Please follow this external link for the full article: https://iopscience.iop.org/article/10.7567/1347-4065/ab1b5c

Open Access: The article “Conductive-probe atomic force microscopy and Kelvin-probe force microscopy characterization of OH-terminated diamond (111) surfaces with step-terrace structures” by Masatsugu Nagai, Ryo Yoshida, Tatsuki Yamada, Taira Tabakoya, Christoph E. Nebel, Satoshi Yamasaki, Toshiharu Makino, Tsubasa Matsumoto, Takao Inokuma and Norio Tokuda 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/

Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy

The dielectric permittivity of membranes is important for many fundamental electrophysiological functions like selective transport in ion channels, action potential propagation and energy generation.*

In their article “Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy” George Gramse, Andreas Schönhals and Ferry Kienberger investigate the nearfield dipole mobility of protein membranes in a wide frequency range from 3 kHz to 10 GHz.*

They achieved their results by adding the frequency as a second fundamental dimension to quantitative dielectric microscopy thereby demonstrating the possibilities of broadband dielectric microscopy for the investigation of dynamic processes in cell bioelectricity at the individual molecular level. Furthermore, the technique may also shed light on local dynamic processes in related materials science applications like semiconductor research or nano-electronics.*

All AFM measurements were carried out at 25 °C using a NANOSENSORS Platinum Silicide AFM probe ( PtSi-FM ).

Fig. 2 from “Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy” by Gramse et al.: image a) shows the AFM topography and image b) shows the corresponding C′′(z)/C′′dry(z) image obtained in lift mode at z = 10 nm above the last scan line and at a frequency of ω = 10 kHz (inset at 1 MHz). The corresponding topography and C′′(z)/C′′dry(z) profile lines are shown in  image c). Solid lines correspond to profile lines at 10 kHz and the dashed line to 1 MHz. Image d) shows the normalized dielectric spectra on the substrate and protein membrane at constant height z′ = 15 nm and lift mode z = 15 nm. Black solid lines represent fitting with eqn (1) and (2). image e) shows the resulting complex dielectric functions ε′r(f) and ε′′r(f)2 (using the relation ε′′r(f) = −(π/2∂)ε′r/∂ln(2πf)38). All measurements are carried out at 25 °C using conductive and wear-resistant Platinum Silicide AFM probes  (PtSi-FM ) from NANOSENSORS (Germany). Humidity was changed and left to stabilize for 2–3 hours. Imaging conditions were adjusted to maintain the lift distance for the dielectric images identical.

Fig. 2 from “Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy” by Gramse et al.: (a) AFM topography and (b) corresponding C′′(z)/C′′dry(z) image obtained in lift mode at z = 10 nm above the last scan line and at a frequency of ω = 10 kHz (inset at 1 MHz). The corresponding topography and C′′(z)/C′′dry(z) profile lines are shown in (c). Solid lines correspond to profile lines at 10 kHz and the dashed line to 1 MHz. (d) Normalized dielectric spectra on the substrate and protein membrane at constant height z′ = 15 nm and lift mode z = 15 nm. Black solid lines represent fitting with eqn (1) and (2). (e). Resulting complex dielectric functions ε′r(f) and ε′′r(f)2 (using the relation ε′′r(f) = −(π/2∂)ε′r/∂ln(2πf)38).
All measurements are carried out at 25 °C using PtSi-FM tips from NANOSENSORS (Germany). Humidity was changed and left to stabilize for 2–3 hours. Imaging conditions were adjusted to maintain the lift distance for the dielectric images identical.

*Georg Gramse, Andreas Schönhals, Ferry Kienberger
Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy
Nanoscale, 2019, 11, 4303-4309
DOI: 10.1039/C8NR05880F

Please follow this external link for the full article: https://pubs.rsc.org/en/content/articlehtml/2019/nr/c8nr05880f

Open Access The article “Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy” by George Gramse, Andreas Schönhals and Ferry Kienberger 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. To view a copy of this license, visit https://creativecommons.org/licenses/by/3.0/