scholarly journals Local contact potential difference of molecular self-assemblies investigated by Kelvin probe force microscopy

2011 ◽  
Vol 99 (23) ◽  
pp. 233102 ◽  
Author(s):  
Evan J. Spadafora ◽  
Mathieu Linares ◽  
Wan Zaireen Nisa Yahya ◽  
Frédéric Lincker ◽  
Renaud Demadrille ◽  
...  
Keyword(s):  
Contact Potential Difference ◽  
Kelvin Probe Force Microscopy ◽  
Potential Difference ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Force Microscopy ◽  
Local Contact

scholarly journals Imaging the surface potential at the steps on the rutile TiO2(110) surface by Kelvin probe force microscopy

2019 ◽  
Vol 10 ◽  
pp. 1228-1236 ◽  
Author(s):  
Masato Miyazaki ◽  
Huan Fei Wen ◽  
Quanzhen Zhang ◽  
Yuuki Adachi ◽  
Jan Brndiar ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Surface Potential ◽  
Active Sites ◽  
Contact Potential Difference ◽  
Kelvin Probe Force Microscopy ◽  
Potential Difference ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Force Microscopy ◽  
First Time

Although step structures have generally been considered to be active sites, their role on a TiO2 surface in catalytic reactions is poorly understood. In this study, we measured the contact potential difference around the steps on a rutile TiO2(110)-(1 × 1) surface with O2 exposure using Kelvin probe force microscopy. A drop in contact potential difference was observed at the steps, indicating that the work function locally decreased. Moreover, for the first time, we found that the drop in contact potential difference at a <1−11> step was larger than that at a <001> step. We propose a model for interpreting the surface potential at the steps by combining the upward dipole moment, in analogy to the Smoluchowski effect, and the local dipole moment of surface atoms. This local change in surface potential provides insight into the important role of the steps in the catalytic reaction.

scholarly journals Open-loop amplitude-modulation Kelvin probe force microscopy operated in single-pass PeakForce tapping mode

2021 ◽  
Vol 12 ◽  
pp. 1115-1126
Author(s):  
Gheorghe Stan ◽  
Pradeep Namboodiri
Keyword(s):  
Amplitude Modulation ◽  
Contact Potential Difference ◽  
Open Loop ◽  
Kelvin Probe Force Microscopy ◽  
Potential Difference ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Force Microscopy ◽  
Single Pass ◽  
Afm Probe

The open-loop (OL) variant of Kelvin probe force microscopy (KPFM) provides access to the voltage response of the electrostatic interaction between a conductive atomic force microscopy (AFM) probe and the investigated sample. The measured response can be analyzed a posteriori, modeled, and interpreted to include various contributions from the probe geometry and imaged features of the sample. In contrast to this, the currently implemented closed-loop (CL) variants of KPFM, either amplitude-modulation (AM) or frequency-modulation (FM), solely report on their final product in terms of the tip–sample contact potential difference. In ambient atmosphere, both CL AM-KPFM and CL FM-KPFM work at their best during the lift part of a two-pass scanning mode to avoid the direct contact with the surface of the sample. In this work, a new OL AM-KPFM mode was implemented in the single-pass scan of the PeakForce Tapping (PFT) mode. The topographical and electrical components were combined in a single pass by applying the electrical modulation only in between the PFT tip–sample contacts, when the AFM probe separates from the sample. In this way, any contact and tunneling discharges are avoided and, yet, the location of the measured electrical tip–sample interaction is directly affixed to the topography rendered by the mechanical PFT modulation at each tap. Furthermore, because the detailed response of the cantilever to the bias stimulation was recorded, it was possible to analyze and separate an average contribution of the cantilever to the determined local contact potential difference between the AFM probe and the imaged sample. The removal of this unwanted contribution greatly improved the accuracy of the AM-KPFM measurements to the level of the FM-KPFM counterpart.

scholarly journals Imaging Hydrogen in Stainless Steel Alloys by Kelvin Probe Force Microscopy

2018 ◽  
Author(s):  
J. D. McNamara ◽  
A. J. Duncan ◽  
M. J. Morgan ◽  
P. S. Korinko
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Contact Potential Difference ◽  
Kelvin Probe Force Microscopy ◽  
Grain Structure ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Steel Alloys ◽  
Force Microscopy ◽  
Net Shaping

Kelvin probe force microscopy (KPFM) was used to image austenitic stainless steel (SS) samples (Type 304L) fabricated by the laser engineered net shaping (LENS®) process. The samples were hydrogen charged (H-charged) and subsequently cut and polished. The surface contact potential difference (CPD) of the samples was measured using the KPFM technique, a form of atomic force microscopy. A set of uncharged samples was also studied for reference and changes in the CPD were on the noise level. For H-charged samples fabricated by the LENS® process, the resulting surface potential images show a change in CPD of about 10 – 20mV around cell-like boundaries (5–10 μm in size) and grain boundaries (50–100 μm in size). The significant change in the CPD is affected by variation of the local work function, which indicates the presence of hydrogen. The elemental composition of the LENS® samples was studied using energy dispersive spectroscopy (EDS) which showed an increase in the atomic percentage of Cr and a decrease in Ni around the cell-like boundaries. The existence of intercellular ferrite on the sub-grain boundaries may explain the propensity of hydrogen to segregate around these regions. The finer grain structure of LENS® samples compared to that of forged or welded samples suggests that the hydrogen can be dispersed differently throughout this material than in traditionally forged austenitic SS. This study is conducted to elucidate the behavior of hydrogen with respect to the microstructure of additively manufactured stainless steel alloys.

scholarly journals Kelvin probe force microscopy in liquid using electrochemical force microscopy

2015 ◽  
Vol 6 ◽  
pp. 201-214 ◽  
Author(s):  
Liam Collins ◽  
Stephen Jesse ◽  
Jason I Kilpatrick ◽  
Alexander Tselev ◽  
M Baris Okatan ◽  
...  
Keyword(s):  
Contact Potential Difference ◽  
Liquid Interface ◽  
Kelvin Probe Force Microscopy ◽  
Physical Models ◽  
Mapping Technique ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Force Microscopy ◽  
Solid Liquid Interface ◽  
Solid Liquid

Conventional closed loop-Kelvin probe force microscopy (KPFM) has emerged as a powerful technique for probing electric and transport phenomena at the solid–gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid–liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe–sample gap, a condition which is violated for ionically-active liquids (e.g., when diffuse charge dynamics are present). Here, electrostatic and electrochemical measurements are demonstrated in ionically-active (polar isopropanol, milli-Q water and aqueous NaCl) and ionically-inactive (non-polar decane) liquids by electrochemical force microscopy (EcFM), a multidimensional (i.e., bias- and time-resolved) spectroscopy method. In the absence of mobile charges (ambient and non-polar liquids), KPFM and EcFM are both feasible, yielding comparable contact potential difference (CPD) values. In ionically-active liquids, KPFM is not possible and EcFM can be used to measure the dynamic CPD and a rich spectrum of information pertaining to charge screening, ion diffusion, and electrochemical processes (e.g., Faradaic reactions). EcFM measurements conducted in isopropanol and milli-Q water over Au and highly ordered pyrolytic graphite electrodes demonstrate both sample- and solvent-dependent features. Finally, the feasibility of using EcFM as a local force-based mapping technique of material-dependent electrostatic and electrochemical response is investigated. The resultant high dimensional dataset is visualized using a purely statistical approach that does not require a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid–liquid interface.

scholarly journals High-resolution noncontact AFM and Kelvin probe force microscopy investigations of self-assembled photovoltaic donor–acceptor dyads

2016 ◽  
Vol 7 ◽  
pp. 799-808 ◽  
Author(s):  
Benjamin Grévin ◽  
Pierre-Olivier Schwartz ◽  
Laure Biniek ◽  
Martin Brinkmann ◽  
Nicolas Leclerc ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Contact Potential Difference ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Structural Variations ◽  
Contact Potential ◽  
Force Microscopy ◽  
Donor Acceptor ◽  
Dark Conditions ◽  
Self Assembled

Self-assembled donor–acceptor dyads are used as model nanostructured heterojunctions for local investigations by noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). With the aim to probe the photo-induced charge carrier generation, thin films deposited on transparent indium tin oxide substrates are investigated in dark conditions and upon illumination. The topographic and contact potential difference (CPD) images taken under dark conditions are analysed in view of the results of complementary transmission electron microscopy (TEM) experiments. After in situ annealing, it is shown that the dyads with longer donor blocks essentially lead to standing acceptor–donor lamellae, where the acceptor and donor groups are π-stacked in an edge-on configuration. The existence of strong CPD and surface photo-voltage (SPV) contrasts shows that structural variations occur within the bulk of the edge-on stacks. SPV images with a very high lateral resolution are achieved, which allows for the resolution of local photo-charging contrasts at the scale of single edge-on lamella. This work paves the way for local investigations of the optoelectronic properties of donor–acceptor supramolecular architectures down to the elementary building block level.

scholarly journals Kelvin probe force microscopy for local characterisation of active nanoelectronic devices

2015 ◽  
Vol 6 ◽  
pp. 2193-2206 ◽  
Author(s):  
Tino Wagner ◽  
Hannes Beyer ◽  
Patrick Reissner ◽  
Philipp Mensch ◽  
Heike Riel ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Contact Potential Difference ◽  
Kelvin Probe Force Microscopy ◽  
Local Surface ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Nanoelectronic Device ◽  
Force Microscopy ◽  
Nanoelectronic Devices ◽  
Direct Demodulation

Frequency modulated Kelvin probe force microscopy (FM-KFM) is the method of choice for high resolution measurements of local surface potentials, yet on coarse topographic structures most researchers revert to amplitude modulated lift-mode techniques for better stability. This approach inevitably translates into lower lateral resolution and pronounced capacitive averaging of the locally measured contact potential difference. Furthermore, local changes in the strength of the electrostatic interaction between tip and surface easily lead to topography crosstalk seen in the surface potential. To take full advantage of the superior resolution of FM-KFM while maintaining robust topography feedback and minimal crosstalk, we introduce a novel FM-KFM controller based on a Kalman filter and direct demodulation of sidebands. We discuss the origin of sidebands in FM-KFM irrespective of the cantilever quality factor and how direct sideband demodulation enables robust amplitude modulated topography feedback. Finally, we demonstrate our single-scan FM-KFM technique on an active nanoelectronic device consisting of a 70 nm diameter InAs nanowire contacted by a pair of 120 nm thick electrodes.

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