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Linseed oil and poly(urea-formaldehyde)-based microcapsules with an 82% weight ratio of core/shell and a mean outer diameter of about 100 μm were synthesised by in-situ polymerisation. These microcapsules were dispersed in polyester paint and then primer-coated Galvalume sheets were painted with microcapsule loaded (MC) and neat (no microcapsules) paints. These painted samples were scribed and examined using various characterisation techniques to evaluate their self-healing properties. SST and CCT showed that the electrolyte diffusion was suppressed in the MC sample, whereas the neat sample was noticeably blistered due to under-film corrosion. Scanning Kelvin Probe microscopy, SKP supported this finding wherein the Volta potential of the neat sample increased in the positive direction indicating cathodic delamination, whereas no significant change occurred in the MC sample. SEM-EDAX revealed the surface morphology and composition of the samples. Furthermore, EIS showed that microcapsule addition increased the pore resistance and decreased the coating capacitance of the polyester paint. [ABSTRACT FROM AUTHOR]

UV sensors possess high importance for modern electronics such as environmental monitoring, health diagnostics, and optoelectronic devices. Thus UV-sensing-materials with high stability has drawn significant interest for next generation UV sensors. Herein, a simple synthesis method of SbPS 4 has been proposed. Then the SbPS 4 crystals are effectively delaminated by micromechanical exfoliation into a few-nanometer-scale nanowires, which is the first demonstration of the material's possibility of exfoliation down to one-molecular-layer thickness. Weak van der Waals (vdW) interaction within the crystal lattice can be easily overcome. The exfoliated SbPS 4 nanowires showed one-dimensional tube structure, and the work function of SbPS 4 showed strong thickness dependence and was confirmed through Scanning Kelvin probe microscopy. The bandgap of 2.54 eV of SbPS 4 , showed great sensitivity to UV lights, depicting SbPS 4 as a promising future UV sensing material for future optoelectronic application. [Display omitted] • Synthesis of one-dimensional van der Waals material SbPS 4 with a tubular molecular structure • Single chain exfoliation of SbPS 4 and its thickness-dependency of work function • Optical property of SbPS 4 as UV-detecting material [ABSTRACT FROM AUTHOR]

In this work, the effect of the ion fluence-dependent defect formation on the modification of surface electronic and optical properties of graphene has been investigated. The chemical vapor deposited (CVD) graphene samples were irradiated with 70 MeV Si+5 swift heavy ions (SHI) with varying fluence to study the defect formation mechanism and the role of ion beam fluence in modulating its surface electronic property such as work function. At a low ion dose, acceptor doping via vacancy creation was observed. The redshift in absorption peak position, the blueshift in Raman peak position, and the enhancement in work function values are indicators of such doping effect at low fluence. In contrast, the dense electronic excitation-dominated extended defects were realized at a higher ion dose showing strain-induced modifications in the optoelectronic properties of graphene. This work offers an effective strategy to control defect formation and systematically alter graphene's optical and electronic properties. The experimental findings will be useful for the applicability of graphene under extreme radiation conditions and space research. [ABSTRACT FROM AUTHOR]

Two-dimensional ultrathin ferroelectrics have attracted much interest due to their potential application in high-density integration of non-volatile memory devices. Recently, 2D van der Waals ferroelectric based on interlayer translation has been reported in twisted bilayer h-BN and transition metal dichalcogenides (TMDs). However, sliding ferroelectricity is not well studied in non-twisted homo-bilayer TMD grown directly by chemical vapor deposition (CVD). In this paper, for the first time, experimental observation of a room-temperature out-of-plane ferroelectric switch in semiconducting bilayer 3R MoS 2 synthesized by reverse-flow CVD is reported. Piezoelectric force microscopy (PFM) hysteretic loops and first principle calculations demonstrate that the ferroelectric nature and polarization switching processes are based on interlayer sliding. The vertical Au/3R MoS 2 /Pt device exhibits a switchable diode effect. Polarization modulated Schottky barrier height and polarization coupling of interfacial deep states trapping/detrapping may serve in coordination to determine switchable diode effect. The room-temperature ferroelectricity of CVD-grown MoS 2 will proceed with the potential wafer-scale integration of 2D TMDs in the logic circuit., (© 2024 Wiley‐VCH GmbH.)

This paper deals with the interfacial adhesion properties of Ti-6Al-4V alloy substrates, prepared by using different treatment protocols selected on the basis of their different effectiveness, and bonded using a structural, high-strength epoxy adhesive. The alternative pre-bonding treatments were sodium hydroxide anodization and low-pressure-plasma treatment, the effects of which were compared to that of a base preparation via solvent degreasing of the substrates’ surface. The treated surfaces were joined according to standard protocols, and then tested for shear strength. The mechanical results were then correlated to surface characteristics of the substrates such as oxidation state and wettability. Parallel scanning Kelvin-probe measurements allowed us to focus our attention on the possible role of the electrical properties of the substrates. We observed that each treatment entails different behavior of the electrical potential of the surface, which correlates with the mechanical strength of the joints. The results suggest that an evaluation of the surface potential of titanium-alloy substrates might be a promising, indicative supplementary parameter for the evaluation of their pre-bonding surface conditions, allowing correlations with presence/absence of an oxide layer at the resin-substrate interface.

The devices based on SiO2 electret have significant applications in various MEMS sensors. However, the charge stability of SiO2 electret suffered from the water percolation, which seriously restricts its application. In this work, the long‐term charge stability of the SiO2 nanoarray electret (SiO2 NAE) without any water repellent treatment is demonstrated. When the oxidation time is 1.5 h, the potential decay of the SiO2 NAE is less than 46% during 60 days with an original potential of −120 V. The long‐term charge stability of the SiO2 NAE is attributed to its unique charge decay process and the large H2O diffusion barrier in the SiO2 NAE: firstly, the charge trapped in the planar part of the SiO2 NAE decays rapidly. Then, residual charge stored in the SiO2 nanoarray. Eventually, the large H2O diffusion barrier in the interface of Si/SiO2 effectively hinders the charge decay. In addition, we demonstrate the unique charge stability of nanoelectret, which has a promising application in developing high performance electret‐based devices. [ABSTRACT FROM AUTHOR]

The domain structure on the surface of 2-methylbenzimidazole (MBI) crystals is studied using various modes of atomic-force microscopy, which made it possible to visualize the surface potential distribution. MBI crystals are grown by evaporation from a saturated ethanol solution. Using the scanning Kelvin probe microscopy mode, the potential distribution is visualized on the (001) cleavages of a single crystal, which is a periodic structure of charged stripes oriented along the 〈110〉tetr axis. This pattern can be explained by the presence of a system of ferroelastic domains with charged domain walls on the surface, which compensates deformation in the surface layers occurring during cleavage. An equilibrium structure of ferroelectric domains with a polarization component perpendicular to the surface is found on the {110} microcrystal surface using the scanning Kelvin probe microscopy mode. The electrostatic force microscopy mode makes it possible to visualize ferroelastic domain walls. It is shown that, in the case of a microcrystal, the action of a locally applied electric pulse causes the displacement of both ferroelectric and ferroelastic domain walls. The potential distribution over the (001) cleavage surface of the single crystal after external action remains unchanged. [ABSTRACT FROM AUTHOR]

Charge-carrier transport in the channel of bottom gate, top contact organic field effect transistors with anisotropic layers of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pentacene) obtained by zone casting was investigated using scanning Kelvin probe microscopy combined with atomic force microscopy. The TIPS-Pentacene continuous layers consisted of thin crystals unidirectionally oriented in the channel. Devices with perpendicular and parallel charge flow in the transistor channel were prepared. It was found that irregularities in the surface morphology at the semiconductor layer in the transistor channel are correlated with the local potential profile, and that the channel resistance strongly depends on the orientation of the TIPS-Pentacene crystals. [ABSTRACT FROM AUTHOR]

Mass production of one-dimensional, V2Se9 crystals, was successfully synthesized using the solid-state reaction of vanadium and selenium. Through the mechanical exfoliation method, the bulk V2Se9 crystal was easily separated to nanoribbon structure and we have confirmed that as-grown V2Se9 crystals consist of innumerable single V2Se9 chains linked by van der Waals interaction. The exfoliated V2Se9 flakes can be controlled thickness by the repeated-peeling method. In addition, atomic thick nanoribbon structure of V2Se9 was also obtained on a 300 nm SiO2/Si substrate. Scanning Kelvin probe microscopy analysis was used to explore the variation of work function depending on the thickness of V2Se9 flakes. We believe that these observations will be of great help in selecting suitable metal contacts for V2Se9 and that a V2Se9 crystal is expected to have an important role in future nano-electronic devices. [ABSTRACT FROM AUTHOR]

Abstract: Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The fine control of the interfacial properties of functionalized graphene is a key point for its applications, especially in biosensing devices. We have here used an in-house developed technique to fabricate microsized patterned graphene via laser ablation and then we have functionalized the interface with poly- d -lysine, a biocompatible polyelectrolyte normally used as a promoter for cell adhesion. Scanning Kelvin probe microscopy shows that a surface potential contrast appears at the patterned regions, with ablated regions of silicon substrate exhibiting higher surface potential than the surrounding background, whereas both levels have negative values. By subsequent coating with the poly- d -lysine it is possible to change stepwise the surface potential levels, while keeping the contrast at the patterned regions constant, up to neutralizing the initial negative values. With further dipping in a polyelectrolyte solution of opposite sign, such as polystyrene sulfonate, it is then possible to decrease the surface potential shifting it again back to negative values. The starting substrate chosen for graphene transfer allows deciding the sign of the surface potential contrast between two adjacent regions of the pattern. [ABSTRACT FROM AUTHOR]

In this paper, Scanning Kelvin Probe Microscopy (SKPM) was applied in combination with standard current-voltage measurements to assess the contact resistance ( R C ) effects and to estimate the contact-free charge carrier mobility in n-type transistors based on evaporated films of PDIF-CN 2 . This analysis was carried out in particular as a function of the applied polarization voltages. The separate contributions to the R C phenomenon coming from the injecting (source) and extracting (drain) electrodes were investigated with the possibility to separately analyze the specific electrical behaviour of these two regions. In agreement with previous results, the experimental data here discussed show that the devices under analysis are not simply injected limited. Voltage drops at both the injecting and extracting contacts must be taken into consideration. However, it is worth to mention that for the bottom-contact devices here investigated, a minimum R C of 5.5 kΩ cm was found in linear regime. These values are significantly lower (i.e. by a factor 5×) than those previously reported for other perylene dimiide thin-film devices with bottom-contact configuration. [ABSTRACT FROM AUTHOR]

Electronic disorder in organic semiconductor single crystals, manifested as parallel surface potential domains with potential variations ranging from tens to hundreds of mV, is observed by scanning Kelvin probe microscopy. Chemical etching and X-ray diffraction indicate that the potential domains are correlated with planar defects such as stacking faults. The results have important implications for understanding structure-transport relationships in organic semiconductor single crystals. [ABSTRACT FROM AUTHOR]

The work function of nano-materials is important for a full characterization of their electronic properties. Because the band alignment, band bending and electronic noise are very sensitive to work function fluctuations, the dependence of the work function of nano-scale crystals on facet orientation can be a critical issue in optimizing optoelectronic devices based on these materials. We used scanning Kelvin probe microscopy to assess the local work function on samples of silver nano-plates at sub-micrometric spatial resolution. With the appropriate choice of the substrate and based on statistical analysis, it was possible to distinguish the surface potential of the different facets of silver nano-plates even if the measurements were done in ambient conditions without the use of vacuum. A phenomenological model was used to calculate the differences of facet work function of the silver nano-plates and the corresponding shift in Fermi level. This theoretical prediction and the experimentally observed difference in surface potential on the silver nano-plates were in good agreement. Our results show the possibility to sense the nano-crystal facets by appropriate choice of the substrate in ambient conditions. [ABSTRACT FROM AUTHOR]

Important issues in optoelectronic devices based on exfoliated graphene are the electronic noise due to the interaction between graphene flakes and the substrate, and the accumulation of electrical charge at the flake edges. These effects, in addition to the distribution of flakes in the composites, being random and locally showing multiple overlaps, cause significant Inhomogeneity in the measured work function of the graphene-based materials. To shed light on the above effects, we investigated both graphene flakes and single-layer graphene by means of scanning Kelvin probe microscopy in ambient conditions. The graphene materials were deposited on rough substrates of silver with a top layer of titanium dioxide. The roughness caused the random disorder of interest for characterization, while the thin dielectric layer of titanium dioxide helped in keeping the electric field localized and provided better contrast in the surface potential images. It is demonstrated that proper engineering of the substrate can minimize the work function inhomogeneity. Additionally, SKPM allows for local mapping of graphene flakes overlaps and thus effective thickness, for possible quality control in produced devices. [ABSTRACT FROM AUTHOR]

Mass production of one-dimensional, V2Se9 crystals, was successfully synthesized using the solid-state reaction of vanadium and selenium. Through the mechanical exfoliation method, the bulk V2Se9 crystal was easily separated to nanoribbon structure and we have confirmed that as-grown V2Se9 crystals consist of innumerable single V2Se9 chains linked by van der Waals interaction. The exfoliated V2Se9 flakes can be controlled thickness by the repeated-peeling method. In addition, atomic thick nanoribbon structure of V2Se9 was also obtained on a 300 nm SiO2/Si substrate. Scanning Kelvin probe microscopy analysis was used to explore the variation of work function depending on the thickness of V2Se9 flakes. We believe that these observations will be of great help in selecting suitable metal contacts for V2Se9 and that a V2Se9 crystal is expected to have an important role in future nano-electronic devices.

The process of charge transfer based on triboelectrification (TE) and contact electrification (CE) has been recently utilized as the basis for a new and promising energy harvesting technology, i.e., triboelectric nanogenerators, as well as selfpowered sensors and systems. The electrostatic charge transfer between two surfaces can occur in both the TE and the CE modes depending on the involvement of relative sliding friction. Does the sliding behavior in TE induce any fundamental difference in the charge transfer from the CE? Few studies are available on this comparison because of the challenges in ruling out the effect of the contact area using traditional macro-scale characterization methods. This paper provides the first study on the fundamental differences in CE and TE at the nanoscale based on scanning probe microscopic methods. A quantitative comparison of the two processes at equivalent contact time and force is provided, and the results suggest that the charge transfer from TE is much faster than that from CE, but the saturation value of the transferred charge density is the same. The measured frictional energy dissipation of ∼11 eV when the tip scans over distance of 1 Å sheds light on a potential mechanism: The friction may facilitate the charge transfer process via electronic excitation. These results provide fundamental guidance for the selection of materials and device structures to enable the TE or the CE in different applications; the CE mode is favorable for frequent moderate contact such as vibration energy harvesting and the TE mode is favorable for instant movement such as harvesting of energy from human walking. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate for the first time that the bulk InSeI crystals can be effectively delaminated by micromechanical exfoliation into a few nanometer-scale InSeI nanowires, due to the presence of weak van der Waals (vdWs) interaction within the crystal lattice. The exfoliated InSeI nanowires show one-dimensional (1D) bundle structure, and the work function of InSeI measured by Scanning Kelvin probe microscopy shows strong dependency on its thickness. The InSeI has a large bandgap corresponding to 2.12 eV, and when applied to a UV-detecting device, it was confirmed that the device with excellent sensitivity can be obtained, because there is little interference in the infrared and visible light regions. Based on these results, InSeI could be a excellent candidate as an additional 1D vdWs material for optoelectronics, including photodetectors or photovoltaic devices. • Synthesis of 1D van der Waals InSeI crystals and single chain exfoliation. • Thickness dependent work functions confirmed via scanning Kelvin probe microscopy. • Optical band gap and its potential application to UV detectors.. [ABSTRACT FROM AUTHOR]

We show the first direct measurement of the potential distribution within organic light emitting diodes (OLEDs) under operation and hereby confirm existing hypotheses about charge transport and accumulation in the layer stack. Using a focused ion beam to mill holes in the diodes we gain access to the cross section of the devices and explore the spatially resolved potential distribution in situ by scanning Kelvin probe microscopy under different bias conditions. In bilayer OLEDs consisting of tris(hydroxyquinolinato) aluminum (Alq3)/ N, N ′-bis(naphthalene-1-yl)- N, N ′-bis(phenyl) benzidine (NPB) the potential exclusively drops across the Alq3 layer for applied bias between onset voltage and a given transition voltage. These findings are consistent with previously performed capacitance-voltage measurements. The behavior can be attributed to charge accumulation at the interface between the different organic materials. Furthermore, we show the potential distribution of devices with different cathode structures and degraded devices to identify the cathode interface as main culprit for decreased performance. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Highlights: [•] We observed an influence of Ga+ Focused Ion Beam (FIB) exposure on TIPS-pentacene. [•] Mobility and conductivity increase significantly, threshold voltage decreases. [•] XPS analysis shows a clear Ga signature and an evidence for p-doping. [•] SKPM data show local p-doping and local conductivity increase. [•] An application can be local doping and nanopatterned contacts in organic devices [ABSTRACT FROM AUTHOR]

Abstract: In ambipolar organic field effect transistors (OFET) the shape of the channel potential is intimately related to the recombination zone width W, and hence to the electron–hole recombination strength. Experimentally, the recombination profile can be assessed by scanning Kelvin probe microscopy (SKPM). However, surface potentials as measured by SKPM are distorted due to spurious capacitive couplings. Here, we present a (de)convolution method with an experimentally calibrated transfer function to reconstruct the actual surface potential from a measured SKPM response and vice versa. Using this scheme, we find W =0.5μm for a nickel dithiolene OFET, which translates into a recombination rate that is two orders of magnitude below the value expected for Langevin recombination. [Copyright &y& Elsevier]

Abstract: The electrical properties of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) thin films deposited from aqueous dispersion using different concentrations of sorbitol have been studied in detail. Although it is well known that sorbitol enhances the conductivity of PEDOT:PSS thin films by three orders of magnitude, the origin and consequences of sorbitol treatment are only partly understood and subject of further study. By thermal annealing of spin coated PEDOT:PSS/sorbitol films and simultaneously monitoring the conductivity, we demonstrate that the strong increase in conductivity coincides with evaporation of sorbitol from the film. Hence, sorbitol is a processing additive rather than a (secondary) dopant. Scanning Kelvin probe microscopy reveals that sorbitol treatment causes a reduction of the work function from 5.1eV to 4.8–4.9eV. Sorbitol also influences the environmental stability of the films. While the conductivity of the pristine PEDOT:PSS films increases by about one order of magnitude at ∼50% RH due to an ionic contribution to the overall conductivity, films prepared using sorbitol exhibit an increased environmental stability with an almost constant conductivity up to 45% RH and a slight decrease at 50% RH. The higher stability results from a reduced tendency to take up water from the air, which is attributed to a denser packing of the PEDOT:PSS after sorbitol treatment. [Copyright &y& Elsevier]

• Reduction of cantilever crosstalk in amplitude-modulation scanning Kelvin probe microscopy. • Verification of accuracy of measurements using interdigitating electrodes calibration samples and numerical simulation. • Determination of built-in potential of wafer-bonded GaAs/GaN heterojunction using quantitative AM-SKPM. Amplitude modulation scanning Kelvin probe microscopy (AM-SKPM) is widely used to measure the contact potential difference (CPD) between probe and samples in ambient or dry inert atmosphere. However, AM-SKPM is generally considered quantitatively inaccurate due to crosstalk between the cantilever and the sample. Here we demonstrate that the accuracy of AM-SKPM-based CPD measurements is drastically improved by exciting the SKPM probe at its second eigenmode. In the second eigenmode of oscillation, there exists a stationary node at the cantilever towards its free end, across which the displacement bears opposite signs; therefore driving the SKPM probe at its second eigenmode helps to partially cancel the virtual work done by the cantilever and reduce the crosstalk effect. The improvement in accuracy is experimentally confirmed with interdigitating electrodes calibration samples as well as practical samples such as the cross-section of wafer-bonded GaAs/GaN heterojunction. [ABSTRACT FROM AUTHOR]