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For understanding the ubiquitous photoemission charging of solid surface in planetary environments, it is important to characterize the photoemission charging properties of silicate minerals such as the work function. In this study, we measured the work function of olivine mineral based on the measurements of contact potential difference by using an ultrahigh vacuum Kelvin probe force microscopy. Our results showed that work function on olivine mineral surface is mainly affected by surface morphology and crystal orientation and that the variation range of work function is 7.3–8.5 eV. It implicates that photoemission of the olivine mineral occurs under the X-ray and solar ultraviolet irradiation with wavelength of

Dodecyl benzene sulfonic acid (DBSA) doped polyaniline (PANI-DBSA) has been synthesized by chemical oxidative polymerization of aniline monomer in the presence of DBSA. The UV-visible spectroscopy and X-ray diffraction measurements confirm the formation of PANI and its doping by DBSA. SEM images show the formation of submicron size rod shaped PANI particles. A vibrating capacitor based ammonia gas sensor was prepared by spin coating PANI-DBSA film over copper (Cu) substrate. The sensor exploited Kelvin probe technique to monitor contact potential difference between PANI and Cu as a function of time and ammonia concentration. Upon exposure to 30 ppm ammonia, the sensor displays response time of 329 s, recovery time of 3600 s, and sensitivity value of 1.54 along with good repeatability.

© 2015 Elsevier B.V. Contact electrification is generally referred to as the charge transfer process between particles during collisions. The transferred charge can be accumulated on the surface of the particles especially for insulating materials with irregular shapes, which can lead to a non-uniform charge distribution and eventually affects the charge accumulation process. In this study, in order to investigate the influence of the particle shape on contact electrification, a sphere-tree multi-sphere method and a contact electrification model are implemented into the discrete element method (DEM) to model the charging process of irregular particles in a rotating drum. Irregular particles with various Sauter mean diameters but the same maximum diameter and equivalent volume diameters are considered. The charge distribution and accumulation on the particles are investigated. It is found that the charge transfer originates from the contact between the particle and the drum due to the contact potential difference and initially takes place primarily at the region near the wall of the drum. The charge eventually propagates to the entire granular bed. The charge of the particles increases exponentially to an equilibrium value. For particles with the same maximum diameter, a larger charging coefficient is obtained for the particles with smaller Sauter mean diameters and sphericities, which leads to a faster charge accumulation, while for particles with the same equivalent volume diameter and fill ratio, similar charging coefficients are observed. A non-uniform intra-particle charge distribution is induced on each individual multi-sphere particle.

Mg doped GaN nanorods were grown on undoped n-type GaN nanorods uniaxial on monolayer graphene by hydride vapor phase epitaxy (HVPE) method. The monolayer graphene used as the bottom electrode and a substrate as well provides good electrical contact, acts as a current spreading layer, well suitable for the growth of hexagonal GaN nanorod. In addition it has a work function suitable to that of n-GaN. The formed p–n nanorods show a Schottky behavior with a turn on voltage of 3 V. Using graphene as the substrate, the resistance of the nanorod is reduced by 700 times when compared with the case without using graphene as the current spreading layer. The low resistance of graphene acts in parallel with the resistance of the GaN buffer layer, and reduces the resistance drastically. The formed p–n junction in a single GaN nanorod is visualized by Kelvin Force Probe Microscopy (KPFM) to have distinctively contrast p and n regions. The measured contact potential difference of p-and n-region has a difference of 103 mV which well confirms the formed regions are electronically different. Low temperature photoluminescence (PL) spectra give evidence of dopant related acceptor bound emission at 3.2 eV different from 3.4 eV of undoped GaN. The crystalline structure, compositional purity is confirmed by X-ray diffraction (XRD), Transmission and Scanning electron microcopies (SEM), (TEM), Energy dispersive analysis by X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS) as well.

The photovoltaic (PV) characteristics of bulk-heterojunction (BHJ) solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl-C 61 -butyric acid methyl ester (P3HT:PC 61 BM) were improved using indium-tin-oxide (ITO) anode electrodes modified chemically with CH 3 O-, H-, Cl-, CF 3 -, and NO 2 -terminated benzenesulfonyl chlorides as a self-assembled monolayer (SAM). The ITO electrode surfaces were easily treated through the chemical modification of the reactive –SO 2 Cl binding group, and the work function (WF) of the modified ITO was effectively changed depending on the permanent dipole moments introduced in the para -position of benzenesulfonyl chloride. We examined the correlation between the ITO WFs corrected by the change in the contact potential difference and the calculated dipole moments of the SAM models. Moreover, we examined the PV characteristics of the P3HT:PC 61 BM based BHJ organic PV cells using the SAMs or poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-treated ITOs with different WFs lying within ±0.2 eV from the highest occupied molecular orbital (HOMO) level of P3HT. We found that the enhancement effect of the SAMs on the power-conversion efficiency ( η P ) reached a maximum with Cl ( η P = 3.72%), and became larger than that of PEDOT:PSS ( η P = 3.62%). Two distinct J sc dependencies, increasing and decreasing with the increasing WF of the anode ITO, were observed at higher and lower WFs than the HOMO level of the donor, respectively. Almost constant V oc values (around 0.6 V) were observed with different SAM-modified ITOs, which suggested that Fermi level pinning was achieved by aligning the anode Fermi level and positive polaronic level of the donor polymer.

The catalytic decomposition of ammonia on (C2B10H4)n organoboron nanoparticles deposited onto SiO2, Al2O3, and graphite substrates at 750 K and 10–6 Torr is studied. The effect of the substrate material on the rate of NH3 decomposition is established. It is demonstrated that the replacement of SiO2 by Al2O3 or graphite increases the decomposition rate 1.9- and 2.3-fold, respectively. The catalytic activity of the nanoparticles increases with the contact potential difference between the nanoparticles and the substrate. The potential difference between the nanoparticles particles and the SiO2, Al2O3 and graphite substrates are found to be–0.5,–0.2, and 0.0 V, respectively.

The corrosion properties of a neodymium modified titanium alloy, Ti6Al4V2Nd were investigated in 1.5 wt% NaCl and compared with Ti6Al4V. The modified alloy contains neodymium precipitates mainly located at grain boundaries. Ti6Al4V2Nd differs in corrosion behavior from Ti6Al4V by the oxidation of the neodymium precipitates. Electrochemical investigation by polarization measurements and cyclic voltammetry indicate that the precipitates undergo an oxidation process in the early stages of exposure. This is confirmed by SEM investigation and atomic force microscopy (AFM) investigation. Scanning Kelvin probe force microscopy (SKPFM) and electrochemical AFM (EC-AFM) investigation were used to investigate localized corrosion phenomena. SKPFM shows clearly a high Volta potential difference between the precipitates and the matrix, indicating that the precipitates act as local anodes during corrosion. EC-AFM shows that during exposure to NaCl solution the precipitates undergo a strong change in height, owing their oxidation with subsequent formation of an oxide or oxyhydride due to their low stability in NaCl solution.

Boron-doped nanocrystalline diamond (NCD) exhibits extraordinary mechanical properties and chemical stability, making it highly suitable for biomedical applications. For implant materials, the impact of boron-doped NCD films on the character of cell growth (i.e., adhesion, proliferation) is very important. Boron-doped NCD films with resistivity of 10−2 Ωcm were grown on Si substrates by the microwave plasma chemical vapor deposition (MPCVD) process with H2 bubbled B2O3. The crystal structure, diamond character, surface morphology, and surface roughness of the boron-doped NCD films were analyzed using different characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope (SKFM). The cytotoxicity of films was studied by in vitro tests, including fluorescence microscopy, SEM and MTT assay. Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates. MG-63 cells adhered well and exhibited a significant growth on the surface of films, suggesting that the boron-doped NCD films were non-toxic to cells.

In this work PeakForce Kelvin Probe Force Microscopy (PF-KPFM) at ambient environment is used to characterize both oxidation states of copper (Cu) surfaces, cupric oxide CuO and cuprous oxide Cu2O, with high lateral resolution. Characteristic values of the Contact Potential Difference were obtained for the copper oxide states. By this means, PF-KPFM measurements enabled to distinguish between the different types of Cu oxide with nanometer resolution and to correlate the oxidation states to local topography features. It was even possible to identify single oxide grains on top of the Cu surface. As a result, PF-KPFM is able to address the needs for nanoscale characterization methods in semiconductor manufacturing or other related technologies where the local oxidation behavior of copper is a critical issue.

We present a local spectroscopy study of thin MgO films on Mo(001), investigated with a combined noncontact atomic force microscope (nc-AFM) and scanning tunneling microscope (STM). The work function of Mo(001) and MgO/Mo(001) was measured with field emission resonance (FER) spectroscopy. The work function of the clean Mo(001) surface ΦMo was determined to be 4.5 eV. After the deposition of an 8 atomic layer thick MgO film, it decreased to ΦMgO/Mo = 3.2 eV (ΔΦFER = −1.3 eV). This work function shift ΔΦFER, introduced by the oxide film on the metal work function, was also investigated with contact potential difference (CPD) measurements. Here, a lowering of the work function by ΔΦCPD = −1.1 eV was measured. Furthermore, the influence of line defects, present in the MgO film, on the local work function was investigated and compared to pristine terrace sites of the oxide film. Here, we measured a slightly higher local work function of +200 meV above line defects as compared to pristine oxide terrace sites.

We report the fabrication of sandwich-type metal/TiO 2 nanotube (TNT) array/metal structures as well as their betavoltaic effects under build-in voltage through contact potential difference. The sandwiched structure is integrated by immobilized TNT arrays on Ti foil with radioisotope 63 Ni planar source on Ni substrate (Ni– 63 Ni/TNT array/Ti). Under irradiation of the 63 Ni source with activity of 8 mCi, the structure (TNT diameter ∼ 130 nm, length ∼ 11 μm) presents optimum energy conversion efficiency of 7.30% with open-circuit voltage of 1.54 V and short-circuit current of 12.43 nA. The TNT arrays exhibit a highly potential for developing betavoltaic batteries due to its wide band gap and nanotube array configuration. The TNT-betavoltaic concept offers a facile solution for micro/nano electronics with high efficiency and long life-time instead of conventional planar junction-type batteries.

Most traditional techniques to recover latent fingermarks from metallic surfaces do not consider the metal surface properties and instead focus on the fingermark chemistry. The scanning Kelvin probe (SKP) technique is a non-contact, non-destructive method, used under ambient conditions, which can be utilised to recover latent prints from metallic surfaces and does not require any enhancement techniques or prevent subsequent forensic analysis. Where a fingermark ridge contacted the metal, the contact potential difference (CPD) contrast between the background surface and the fingermark contact area was 10–50 mV. Measurements were performed on the untreated brass, nickel-coated brass and copper metal surfaces and compared to traditional forensic enhancement techniques such as Vacuum Metal Deposition (VMD) using Au–Zn and Au–Ag. Using VMD, the CPD change ranged from 0 to 150 mV between the dissimilar metal surfaces affected by the fingermark. In general, SKP worked best without additional enhancement techniques. Scanning Electron Microscope (SEM) scans were used to identify the fingermark contact areas through a sodium, chlorine and oxygen electron probe micro-analyzer (EPMA). The fingermark was observed in the backscattered electron image as the carbon deposits scattered the electrons less than the surrounding metal surface. The fingermark is shown clearly in a Cathodoluminescence scan on the copper sample as it blocks the photon emission at band gap (2.17 eV) from the underlying copper oxide (Cu2O) surface. For the first time, SEM, EPMA and Cathodoluminescence techniques were compared to SKP data. Visible and latent fingermarks were tested with latent, eccrinous fingermarks more easily imaged by SKP. Results obtained were very encouraging and suggest that the scanning Kelvin probe technique, which does not need vacuum, could have a place as a first stage analysis tool in serious crime investigation.

We review a new experimental implementation of Kelvin probe force microscopy (KPFM) in which the dissipation signal of frequency modulation atomic force microscopy (FM-AFM) is used for dc bias voltage feedback (D-KPFM). The dissipation arises from an oscillating electrostatic force that is coherent with the tip oscillation, which is caused by applying the ac voltage between the tip and sample. The magnitude of the externally induced dissipation is found to be proportional to the effective dc bias voltage, which is the difference between the applied dc voltage and the contact potential difference. Two different implementations of D-KPFM are presented. In the first implementation, the frequency of the applied ac voltage, \(f_\mathrm {el}\), is chosen to be the same as the tip oscillation (\(f_\mathrm {el} = f_\mathrm {m}\): \(1\omega \)D-KPFM). In the second one, the ac voltage frequency, \(f_\mathrm {el}\), is chosen to be twice the tip oscillation frequency (\(f_\mathrm {el}= 2 f_\mathrm {m}\): \(2\omega \)D-KPFM). In \(1\omega \)D-KPFM, the dissipation is proportional to the electrostatic force, which enables the use of a small ac voltage amplitude even down to \({\approx }10\) mV. In \(2\omega \)D-KPFM, the dissipation is proportional to the electrostatic force gradient, which results in the same potential contrast as that obtained by FM-KPFM. D-KPFM features a simple implementation with no lock-in amplifier and faster scanning as it requires no low frequency modulation. The use of a small ac voltage amplitude in \(1\omega \)D-KPFM is of great importance in characterizing of technically relevant materials in which their electrical properties can be disturbed by the applied electric field. \(2\omega \)D-KPFM is useful when more accurate potential measurement is required. The operations in \(1\omega \) and \(2\omega \)D-KPFM can be switched easily to take advantage of both features at the same location on a sample.

The surface potential distribution measured using Kelvin probe force microscopy (KPFM) is influenced by the contact potential difference (CPD) between the tip and surface, the stray capacitance of the cantilever, and fixed monopole charges on the surface and tip. The interpretation of atomic-scale KPFM contrast studies has been controversial. Here, we investigate the contrast mechanism in KPFM with atomic resolution. First, the effect of stray capacitance on potential measurements is explored in the FM-, AM-, and heterodyne AM-KPFM modes. The distance dependence of the modulated electrostatic force in AM-KPFM is much weaker than that in FM- and heterodyne AM-KPFM, and the stray capacitance of the cantilever, which strongly affects potential measurements in AM-KPFM, is almost completely eliminated in FM- and heterodyne AM-KPFM. The very small local contact potential difference (LCPD) corrugation in AM-KPFM is attributed to an artefact induced by the topographic feedback. Next, an investigation of the LCPD on a TiO2 (110)-1 × 1 surface and atom-dependent bias-distance spectroscopic mapping are performed. The LCPD of TiO2 (110) is dominated not only by the permanent surface dipole between the tip apex atom and the surface, but also by the dipoles induced by the chemical interaction between the tip and sample. Finally, we propose a new multiple-image method for obtaining the frequency shift, tunneling current, and LCPD images. For the first time, we obtain three images on a TiO2(110) surface with atomic resolution at 78 K. The LCPD has a higher value on a defect site than on the nearby O rows because excess electrons caused by surface defects are delocalized on the nearby Ti rows. The multiple-image method can be used to investigate the charge transfer phenomena between nanoparticles and surface sites and to elucidate the mechanisms of catalytic reactions.

We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metal and semiconductor surfaces (Al, Ag, Au, Si) illuminated by a Deep Ultra-Violet (DUV) source at ambient pressure. In Constant Final State Yield Spectroscopy (CFSYS) the incident photon energy is rastered rather than applying a variable retarding electric field as in conventional UPS. For both ambient- and near ambient pressure-photoemission spectroscopy (NAP-PES) the CFSYS configuration overcomes the limitation of inelastic electron scattering in air. This arrangement can be applied in several operational modes: using the DUV source to determine the absolute work function (ϕ) of the metal with 50-100 meV resolution and also the Kelvin probe, under dark conditions, to measure Contact Potential Difference (CPD) with an accuracy of 1-3 meV. We show that the metal photoresponse agrees with Fowler theory. We have used CPD and linear extrapolated photoemission measurements to produce an energy level diagram for the native-oxide covered Si. We propose a model of photoemission in air involving atmospheric ions. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The nanofiltration (NF) process is electrostatically governed and the surface free energy plays a key role in the separation of particulates, macromolecules, and dissolved ionic species. Streaming potential measurement and the surface charge mapping by Kelvin probe atomic force mircoscopy (AFM) have been carried out. Forces of interaction near the surface of nanofiltration membranes were further studied by a force spectroscopy using atomic force microscopy. The two membranes used are more negatively charged at high pH values; hence the higher the solution chemistry, the higher and faster will be adhesion of ions on the surface of the nanofiltration membranes. It was observed that the three acquired signals from non-contact AFM (contact potential difference, amplitude and phase) were rigorously connected to the surface structure of the nanofiltration membranes. In addition to the surface structure (roughness), electrostatic interactions can also enhance initial particle adhesion to surfaces of nanofiltration membranes. The performance of the NF membranes was further investigated for the removal of nickel ions from aqueous solution, and the results were correlated to the mechanical responses of the nanofiltration membranes obtained from AFM and the streaming potential measurement.

The reversible interaction of CO 2 gas with sensing material is very difficult to achieve at room temperature. In this work we present copper oxide nanoparticles (CuO-NPs) as CO 2 gas sensitive material. The CO 2 interaction with CuO-NPs is investigated with the help of capacitance based Kelvin probe measurements, reflecting the adsorption induced changes in contact potential difference or work function alterations. Moreover, cross-sensitivity to humidity and the dependency of CO 2 gas sensing on nanoparticles layer thickness has also been investigated. It is shown that CuO-NPs sensing layer depicts high sensitivity to CO 2 gas exposure (400–4000 ppm) at room temperature and can be effectively used for the development of low cost CO 2 gas sensors.

The variations of work functions in Mn1.56Co0.96Ni0.48O4 (MCN) thin films are investigated in the temperature range from 30 to 80 °C. The high resolution images of the contact potential difference (CPD) of MCN thin films were obtained through Kelvin probe force microscopy (KPFM) and the correlations between the work functions and temperatures were demonstrated through the imaginary part of the dielectric functions. The complex dielectric spectra are temperature dependent while their intensities have the inverse trend according to the work functions. The phenomenon can be interpreted by different chemical states that relate to the Mn3+ state.

Investigating and tailoring surface potential changes of a system at the interfaces is of significance in the fundamental understanding and application of semiconductor devices. Thus the surface potential of zinc oxide (ZnO) nanowires is a vital factor to tune the performance of devices. In this paper, Kelvin probe force microscopy (KPFM) is used to measure the surface potential of single conical ZnO nanowires with different diameters. A size dependence of the surface potential in single conical ZnO nanowires is experimentally revealed. As the diameter decreases, the surface potential of the ZnO nanowires is found to decrease linearly under 400 nm. At large diameters (≥400 nm), the surface potential remains almost constant. The contact potential difference of the ZnO–PtIr tip increases to saturation after 40 min UV illumination and remains stable. An energy band theory is introduced to explore the surface potential change of ZnO nanowires under UV illumination. This study provides an understanding of the surface electrical properties of semiconductors at the nanoscale, which is valuable for optimizing functional nanodevices based on semiconductor nanowires.

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 notrequire a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid-liquid interface. UCD Research NANOREMEDIES Programme for Research in Third Level Institutions Cycle 5 European Regional Development Fund

The objective of the study research was to obtain bimodal structured ultrafine-grained ferrite steel with outstanding mechanical properties and excellent corrosion resistance. The bimodal microstructure was fabricated by the cold rolling and annealing process of a dual-phase steel. The influences of the annealing process on microstructure evolution and the mechanical properties of the cold-rolled dual-phase steel were investigated. The effect of bimodal microstructure on corrosion resistance was also studied. The results showed that the bimodal characteristic of ferrite steel was most apparent in cold-rolled samples annealed at 650 °C for 40 min. More importantly, due to the coordinated action of fine-grained strengthening, back-stress strengthening, and precipitation strengthening, the yield strength (517 MPa) of the bimodal microstructure improved significantly, while the total elongation remained at a high level of 26%. The results of corrosion experiments showed that the corrosion resistance of bimodal ferrite steel was better than that of dual-phase steel with the same composition. This was mainly because the Volta potential difference of bimodal ferrite steel was smaller than that of dual-phase steel, which was conducive to forming a protective rust layer.

Scanning Kelvin probe force microscopy has been employed to examine the behaviour of second phase carbide particles in beryllium at different relative humidity levels and after exposure to deionised water. Carbides are believed to have a role in the localised corrosion of beryllium as a result of their hydrolysis when exposed at the metal surface. The presence of beryllium carbide was confirmed by means of Auger electron spectroscopy and the particles were further characterised by scanning electron microscopy, energy/wavelength dispersive x-ray spectroscopy and scanning Kelvin probe force microscopy. The particles were found to have a more noble Volta potential than the beryllium matrix and a decrease in the Volta potential difference between the second phase particles and the matrix was observed as the humidity was increased. A thick beryllium oxide/hydroxide layer then formed on the particles following exposure to water significantly reducing their potential.

We studied the effective contact potential difference (ECPD) of thin film nanostructures and its role in self-powered X-ray sensors, which use the high-energy current detection scheme. We compared the response to kilovoltage X-rays of several nanostructures made of disparate combinations of conductors (Al, Cu, Ta, ITO) and oxides (SiO2, Ta2O5, Al2O3). We measured current–voltage curves in parallel-plate configuration separated by an air gap and determined three characteristic parameters: current at zero voltage bias I0, the voltage offset for zero current ECPD, and saturation current Isat. We found that the metals’ ECPD values measured with our technique were higher than the CPD values measured with photoelectron spectroscopy in situ, i.e., no air contact. These differences are related to natural oxidization and to the presence of photo-/Auger-electron current leaking from the high-Z toward the low-Z electrode, as suggested by additional experiments carried out in vacuum. Further, the deposition of the 40...

We report high-resolution multiparametric kelvin probe force microscopy (MP-KPFM) measurements for the simultaneous quantitative mapping of the contact potential difference (CPD) and nanomechanical properties of the sample in single-pass mode. This method combines functionalities of the force-distance-based atomic force microscopy and amplitude-modulation (AM) KPFM to perform measurements in single-pass mode. During the tip-sample approach-and-retract cycle, nanomechanical measurements are performed for the retract part of nanoindentation, and the CPD is measured by the lifted probe with a constant tip-sample distance. We compare the performance of the proposed method with the conventional KPFMs by mapping the CPD of multilayer graphene deposited on n-doped silicon, and the results demonstrate that MP-KPFM has comparable performance to AM-KPFM. In addition, the experimental results of a custom-fabricated polymer grating with heterogeneous surfaces validate the multiparametric imaging capability of the MP-KPFM. This method can have potential applications in finding the inherent link between nanomechanical properties and the surface potential of the materials, such as the quantification of the electromechanical response of the deformed piezoelectric materials.

The work function difference (WFD) between the two electrode materials has a positive effect on the potential window for the asymmetric supercapacitors (ASCs) theoretically, but there is no relevant investigation. Here, we use the kelvin probe force microscope to detect contact potential difference (CPD) which can well represent the WFD between carbon@K0·5Mn2O4 positive material and four metal oxides anode materials, namely MoO3, V2O5, Fe2O3 and WO3 respectively. What’s more, the relationship between WFD and the potential window is studied by combining contact potential difference with electrochemical testing. We find that the as-fabricated carbon@K0·5Mn2O4//MoO3 device exhibits the widest potential window of 2.42 V with the maximum WFD. As a result, the carbon@K0·5Mn2O4//MoO3 have a high energy density of 66.7 Wh kg−1 at the power density of 5.95 kW kg−1. Our study provides a new experimental reference for constructing supercapacitor devices with wide potential window and high energy density.

a b s t r a c t We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metallic surfaces (Au, Ag, Cu, Fe, Ni, Ti, Zn, Al) illuminated by a deep ultra-violet (DUV) source under ambient pressure. To surmount the limitation of electron scattering in air the incident photon energy is rastered rather than applying a variable retarding electric field as is used with UPS. This arrangement can be applied in several operational modes: using the DUV source to determine the photoemission threshold (˚) with 30–50 meV resolution and also the Kelvin probe, under dark conditions, to measure contact potential difference (CPD) between the Kelvin probe tip and the metallic sample with an accuracy of 1–3 meV. We have studied the relationship between the photoelectric threshold and CPD of metal surfaces cleaned in ambient conditions. Inclusion of a second spectroscopic visible source was used to confirm a semiconducting oxide, possibly Cu2O, via surface photovoltage measurements with the KP. This dual detection system can be easily extended to controlled gas conditions, relative humidity control and sample heating/cooling.

Transformations in nickel nanofilms as a function of thickness (d = 3–60 nm) and temperature of heat treatment (T = 373–873 K) are studied via optical spectroscopy, microscopy, and gravimetry. It is found that, depending on the thickness of nickel films and temperature of heat treatment, the kinetic curves of the degree of transformation are satisfactorily described in terms of the linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference for Ni and NiO films and the photovoltage for Ni-NiO systems are measured. An energy band diagram for Ni-NiO systems is constructed. A model of the thermal transformation of Ni films, including the stages of oxygen adsorption, charge carrier redistribution in a Ni-NiO contact field, and the formation of nickel(II) oxide, is proposed.

Transformations of gallium nanofilms have been studied by optical spectroscopy, optical microscopy, and gravimetry at film thicknesses d = 2–74 nm and heat treatment temperatures T = 423–873 K. Kinetic curves of the degree of conversion in the films are adequately represented by a linear, inverse logarithmic, parabolic, or logarithmic rate law. We have measured the contact potential difference across the Ga and Ga2O3 films and the photovoltage in the Ga-Ga2O3 system and constructed the energy band diagram of the Ga-Ga2O3 films. A model has been proposed for the thermal transformation of Ga films which includes oxygen adsorption, carrier redistribution in the Ga-Ga2O3 interfacial field, and gallium(III) oxide formation.

In the article is examined new physical phenomenon the electrocurent contact potential difference, whose value depends on the current, which flows along the conductor. Unfortunately, the computed values of electrocurent contact a potential difference proved to be considerably lower than the potentials, observed in the experiment. The carried out experiments and calculations showed that the discovered electrization of the superconductive windings and tori finds its explanation in the concept of scalar-vector potential, developed by the author. This concept assumes the dependence of the scalar potential of charge on its relative speed.

The influence of post-deposition annealing (PDA) temperature condition on charge distribution behavior of HfO2 thin films was systematically investigated by various-temperature Kelvin probe force microscopy technology. Contact potential difference profiles demonstrated that charge storage capability shrinks with decreasing annealing temperature from 1,000 to 500 °C and lower. Compared to 1,000 °C PDA, it was found that 500 °C PDA causes deeper effective trap energy level, suppresses lateral charge spreading, and improves the retention characteristics. It is concluded that low-temperature PDA can be adopted in 3D HfO2-based charge trap flash memory to improve the thermal treatment compatibility of the bottom peripheral logic and upper memory arrays.

AA2024 clad with AA1050 was immersed in CeCl 3 solution to promote deposition of cerium species. The deposition occurs on the entire sample surface for the alkaline etched substrate, while it is very limited for the degreased substrate. The surface potential (Volta potential) was investigated by scanning Kelvin probe force microscopy after different immersion times in CeCl 3 solution. The preferential deposition of Ce compounds at Al–Fe intermetallic sites progressively reduces their Volta potential difference relative to the matrix in the alkaline etched substrate. This reduces the susceptibility to localized attack of the intermetallics as proven by potentiodynamic polarization measurements.

Kelvin probe force microscopy at air in the dark and under illumination by visible light was performed for electrodeposited porous ZnO films, which were sensitized by the indoline dye D149. A contact potential difference was measured that confirmed electron injection into the semiconductor matrix and their subsequent stabilization in trap states. A locally widely homogenous signal was observed speaking in favor of a well-crystallized sample. The rise and decay times of the photovoltage in the ms to s timescale could be analyzed by use of individual scan lines or scanned images, respectively. The results are discussed in the context of recent pump–probe spectroscopy results as well as such from photoelectrochemical experiments with such electrodes and implications will be deduced for their use in dye-sensitized solar cells.

Recent researches in thermal energy harvesting have revealed the remarkable efficiency of thermionic energy converters comprising very low work function electrodes. From room temperature and above, this kind of converter could supply low power devices such as autonomous sensor networks. In this type of thermoelectric converters, current injection is mainly governed by a mechanism of thermionic emission at the hot electrode which explains the interest for low work function coating materials. In particular, alkali metal oxides have been identified as excellent candidates for coating converter electrodes. This paper is devoted to the synthesis and characterization of potassium peroxide K2O2 onto silicon surfaces. To determine optimal synthesis conditions of K2O2, we present diagrams showing the different oxides as a function of temperature and oxygen pressure from which phase stability characteristics can be determined. From the experimental standpoint, we present results on the synthesis of potassium oxide under ultra high vacuum and controlled temperature. The resulting surface is characterized in situ by means of photoemission spectroscopy (PES) and contact potential difference (CPD) measurements. A work function of 1.35 eV is measured which and the expected efficiency of the corresponding converter is discussed. It is generally assumed that the decrease of the work function in the alkali/oxygen/ silicon system, is attributed to the creation of a surface dipole resulting from a charge transfer between the alkali metal and oxygen.

In this paper, the crosstalk in potential measurements caused by the topographic feedback and the resonance frequency in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM), amplitude modulation (AM) and heterodyne amplitude modulation (heterodyne AM) modes. We showed theoretically that the distance-dependence of the modulated electrostatic force in AM-KPFM is significantly weaker than in FM-and heterodyne AM-KPFMs. We experimentally confirmed that the crosstalk in FM-KPFM and heterodyne AM-KPFM is weak than that in AM-KPFM due to the bigger difference of the modulated frequencies in topographic and potential measurements in FM and heterodyne AM-KPFMs. We also compared the corrugations in the local contact potential difference (LCPD) on the surface of Si (001) show that difference on topographic (potential) images is approximately 15 pm (10 mV) between the faulted and unfaulted parts using heterodyne AM-KPFM, on the other hand, this difference cannot be observed using AM-KPFM mode. Original of this was attributed to the low crosstalk between the topographic and the LCPD measurements in heterodyne AM-KPFM.

Transformations of cobalt nanofilms have been studied by optical spectroscopy, optical microscopy, and gravimetry at film thicknesses d = 2–35 nm and heat treatment temperatures T = 473–873 K. Kinetic curves of the degree of conversion in the films are adequately represented by a linear, inverse logarithmic, cubic, or logarithmic rate law. We have measured the contact potential difference across the Co and Co2O3 films and the photovoltage across the interface and constructed the energy band diagram of the Co and Co2O3 films. A model has been proposed for the thermal transformation of Co films which includes oxygen adsorption, carrier redistribution in the Co-Co2O3 interfacial field, and cobalt(III) oxide formation.

HP steels are commonly used in steam reforming tubes, which are exposed to harsh operational conditions causing microstructural changes. These microstructural changes cause variations in the magnetic properties, which can be measured by different techniques. This work aims at the measurement of the magnetic and electric variations in HP-Nb modified alloys with different chemical composition using scanning probe microscopy (SPM) techniques. The results show that, despite the microstructural change due to variation of chemical composition, samples with aging state I exhibit a magnetic response at the carbides boundary, while for advanced aging states, the magnetic response is not evidenced.

In this study, indium concentration dependence on Volatile Organic Compounds (VOCs) interaction were examined in InGaN-GaN multi quantum well structures (MQWs) grown on sapphire substrate at different quantum well (InGaN) growth temperatures. The periodicity, structural properties and indium dependent dislocation density was deduced from high resolution X-ray diffraction pattern. The variation of energy bandgap of InGaN quantum well clearly depicts that the bandgap decreases with increase in indium concentration in InGaN well layer. The interaction properties of the device with various VOCs such as ethanol, benzene, n-hexane and triethylamine were examined using Scanning Kelvin Probe (SKP) system and they are correlated with dislocation density. The change in contact potential difference (CPD) in dark and visible light illumination, as well as the variation of CPD with respect to various VOCs is observed. The difference in contact potential difference clearly suggests that the InGaN-GaN multi quantum well structure can be one of the suitable candidates for novel gas sensor applications.

Two-dimensional layer materials have been of great interest in the promising application of novel nano-electronics in recent years. In this study, we demonstrated the modification on electronic properties of bilayer MoS2 field-effect transistor (FET) by low-temperature oxygen plasma treatment with different radio frequency (RF) power. According to the I-V measurement with Cascade semi-automatic probe station, it was observed that the electronic properties of bilayer MoS2 FET could be improved effectively after low-power oxygen plasma treatment. The analysis of transport properties in MoS2 revealed the modification mechanism of sulphur (S) vacancies by low-power oxygen plasma. Nevertheless, electronic properties of MoS2 FET were degenerated after high-power oxygen plasma treatment for the increase of defect in MoS2, which has been characterized by Raman spectrum and XPS spectrum. Furthermore, it was found that the signal distributions of surface contact potential difference (CPD) and capacitance of MoS2 mono-crystal samples prepared by chemical vapor deposition (CVD) were heterogeneous, which demonstrates that the edge region of MoS2 can be interacted by oxygen plasma more easily owing to the defect and active sites. This study will provide a theoretical basis in the research of next-generation high-performance electronic device.

The effect of Ca additions on the microstructure and corrosion resistance of Mg–9Al and Mg–9Al-0.5Mn alloys is investigated. Model alloys were used instead of a commercial AZ91 alloy in order to avoid masking effects from other alloying elements. Grain size and secondary phases were characterised with special interest in their Volta potential. Corrosion performance was evaluated by hydrogen evolution and electrochemical methods. A synergetic effect was found when Ca and Mn were added in small amounts (0.5 wt%), reaching corrosion rates up to two orders of magnitude lower than the model Mg–9Al alloy. Such improvement was associated with Ca decreasing the Volta potential of the β-phase and with Ca and Mn decreasing the galvanic activity of Fe-rich intermetallics. Precipitation of Al2Ca decreased the amount of β-phase and had a negative impact on the corrosion resistance due to its cathodic behaviour.

In this work, different pretreatment condition on AA6061 was investigated by altering the alkaline cleaning time in NaOH, the concentration and composition of acidic pickling solution, respectively. The corrosion resistance of ZrCC was evaluated, and the surface property of the pretreated surface was measured by SKPFM. Results demonstrate that a longer alkaline cleaning time is detrimental to the corrosion resistance of ZrCC since it will decrease the Volta potential difference (ΔE); the acidic pickling in HNO3 improves the corrosion resistance of ZrCC, but an increased concentration will not remarkably further improve the quality of ZrCC, due to the accompanying of increased ΔE; the addition of HF will lead to the overactivation of alloy surface since it will decrease ΔE and increase ΔH. An ideal pretreated surface shown exhibit a combination of mediate ΔH and high ΔE.

We carry out the surface potential (SP) measurements of Si-doped InN nanorods (NRs) grown by plasma-assisted molecular beam epitaxy. Photoluminescence and photoemission spectroscopic studies reveal that the Si-doped InN nanorods possess surface electron accumulation. To estimate the SP value of the InN nanorods, a contact potential difference is measured using Kelvin probe force microscopy (KPFM). In order to avoid the influence of the surface adsorbed species, KPFM measurements were carried out at a high vacuum condition of ∼7.5 × 10−7 mbar. The SP value of the Si-doped InN nanorods is found to depend on the size of nanorods. The size-dependent SP value of the Si-doped InN nanorods is attributed to the variation in the downward surface band bending caused by the change in the sheet carrier density of surface electron accumulation. The change in surface band bending is the result of the variation in the free-electron distribution with a size of the NRs.

Interfaces between organic semiconductors and dielectrics may exhibit interfacial electronic polarization, which is equivalently quantified as a contact potential difference (CPD), an interface dipole, or a vacuum level shift. Here we report quantitative measurements by scanning Kelvin probe microscopy (SKPM) of surface potentials and CPDs across ultrathin (1–2 monolayer) crystalline islands of the benchmark semiconductor pentacene thermally deposited on a variety of polymer dielectrics (e.g., poly(methyl methacrylate), polystyrene). The CPDs between the pentacene islands and the polymer substrates are in the range of −10 to +50 mV, they depend strongly on the polymer type and deposition temperature, and the CPD magnitude is correlated with the dipole moment of the characteristic monomers. Surface potential variations within 2 monolayer (3 nm) thick pentacene islands are ∼15 mV and may be ascribed to microstructure (epitaxial) differences. Overall, the microscopy results reveal both strong variations in i...