A double toroidal analyzer for scanning probe electron energy spectrometer

An ultra-high vacuum （UHV） compatible electron spectrometer employing a double toroidal analyzer has been de- veloped. It is designed to be combined with a custom-made scanning tunneling microscope （STM） to study the spatially localized electron energy spectrum on a surface. A tip-sample system composed of a piezo-driven field-emission tungsten tip and a sample of highly ordered pyrolytic graphite （HOPG） is employed to test the performance of the spectrometer. Two-dimensional images of the energy-resolved and angle-dispersed electrons backscattered from the surface of HOPG are obtained, the performance is optimized and the spectrometer is calibrated. A complete electron energy loss spectrum covering the elastic peak to the secondary electron peaks for the HOPG surface, acquired at a tip voltage of -140 V and a sample current of 0.5 pA, is presented, demonstrating the viability of the spectrometer.

Measurement and Analysis of Three-Dimensional Surface Topography of Sawn Timber Based on Scanning Probe Method

In order to explore the characteristics of the three-dimensional surface morphology of sawn timber,a three-dimensional wood surface morphology tester based on the scanning probe method and the principle of atomic force microscope was used to test the three-dimensional sur face morphology of three kinds of sawn timber and calculate its surface roughness.This study also analyzed the reasonable plan for the value of wood surface roughness and the advantages of the three dimensional shape tester,as well as the influence of tree species,three sections,air dry density and other factors on the surface roughness of the specimen after mechanical processing.The results have shown that it is a more appropriate method to select the calculated values of S。and Sq as the evaluation of the surface roughness of wood with random surface characteristics.The three dimensional wood surface topo-graphy tester can efficiently,conveniently and accurately display the three dimensional topography of wood at a micron-level resolution,and is characterized by high eficiency and good durability.The three dimensional surface morphology characteristics of the three sawn woods correspond to their roughness.The surface roughness of woods is arranged as follows:Sitka spruce>Larch>Beech.For the same tree species,the roughness of the corresponding section after sawing is as follows:chordwise section>crosswise section>radial section.The radial section has lower roughness than the other surfaces.The surface roughness of the wood after sawing is mainly related to its air-dry density.The above is intended to provide a useful reference for the application of measuring and evaluating the surface roughness of sawn timber using the three dimensional surface topography test method.

Scanning probe lithography on calixarene towards single-digit nanometer fabrication

Cost effective patterning based on scanning probe nanolithography(SPL)has the potential for electronic and optical nano-device manufacturing and other nanotechnological applications.One of the fundamental advantages of SPL is its capability for patterning and imaging employing the same probe.This is achieved with self-sensing and self-actuating cantilevers,also known as‘active'cantilevers.Here we used active cantilevers to demonstrate a novel path towards single digit nanoscale patterning by employing a low energy(<100 eV)electron exposure to thin films of molecular resist.By tuning the electron energies to the lithographically relevant chemical resist transformations,the interaction volumes can be highly localized.This method allows for greater control over spatially confined lithography and enhances sensitivity.We found that at low electron energies,the exposure in ambient conditions required approximately 10 electrons per single calixarene molecule to induce a crosslinking event.The sensitivity was 80-times greater than a classical electron beam exposure at 30 keV.By operating the electro-exposure process in ambient conditions a novel lithographic reaction scheme based on a direct ablation of resist material(positive tone)is presented.

Correlating the Interfacial Polar-Phase Structure to the Local Chemistry in Ferroelectric Polymer Nanocomposites by Combined Scanning Probe Microscopy

Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.

Combination of Instrumented Nanoindentation and Scanning Probe Microscopy for Adequate Mechanical Surface Testing

The elastic indentation modulus and hardness of standard bulk materials and advanced thin films were determined by using the nanoindentation technique followed by the Oliver- Pharr post-treatment. After measurements with different loading/unloading schemes on chemically polished bulk titanium a substantial decrease of both modulus and hardness vs an increasing loading time was found. Then, hard nanostructured TiBN and TiCrBN thin films deposited by magnetron sputtering （using multiphase targets） on substrates of high roughness （sintered hard metal） and low roughness （silicon） were studied. Experimental modulus and hardness characterized by using two different nanoindenter tools were within the limits of standard deviation. However, a strong effect of roughness on the spread of the experimental values was observed and it was found that hardness and elastic indentation modulus obeyed a Gaussian distribution. The experimental data were discussed together with scanning probe microscopy （SPM） images of typical imprints taken after the nanoindentation tests and the local topographyls strong correlation with the results of nanoindentation was described.

Fabrication of grating-like polystyrene latex monolayer structure as three-dimensional calibration standards for scanning probe microscope

This paper illuminates the preparation of grating-like polystyrene latex monolayer structure, which can minimize the effects of the size deviation of spheres and the defect transfer on the accuracy as calibration samples for micro-scopes. The latex films are grown on freshly cleaved mica substrates by vertical deposition method. The concentration dependence of the structure and the topography of latex films is characterized by optical microscope, ultraviolet- visible transmission spectrum and scanning probe microscope. The origination of such a grating-like structure is also discussed.

EXPERIMENTAL RESEARCH OF NANO-CUTTING BY USING SCANNING PROBE MICROCOPE

An experimental study on cutting amorphous alloy at nanometer scale is conducted by applying the principle and technology of scanning probe microscope(SPM) It is revealed from the experiments that cutting inside SPM is an excellent and direct way to research the material removal process at small size Based on the experimental results,the chip formation mechanism for the cutting of amorphous alloy is discussed It is found that the deformation along the direction of chip flow occurs ahead of the appearance of localized shear,and a simplified geometrical model is proposed to illustrate the deformation.

Accelerating the Feedback Loop in Scanning Probe Microscopes without Loss of Height Measurement Accuracy by Using Pixel Forecast Methods

Scanning probe microscopes (SPM) are limited in their speed of data acquisition by the mechanical stability of the scanner. Therefore many types of scanners have been developed to achieve a rigid setup while maintaining an acceptable image size. We have followed here a different path to accelerate data acquisition by improving the feedback loop to achieve the same SPM image quality in a shorter time. While the feedback loop in a scanning probe microscope typically starts to probe a new pixel starting from the previous position, we have reduced the total control time by using an improved starting point for the feedback loop at each pixel. By exploiting the information of the already scanned pixels a forecast for the new pixel is created. We have successfully used several simple methods for a prognosis in MATLAB simulations like one dimensional linear or cubic extrapolation and others. Only scanning tunnelling microscope data from real experiments were used to test the forecasts. A doubling of the speed was achieved in the most favourable cases.

Observations of Wood Cell Walls with a Scanning Probe Microscope

Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical characteristics such as stiffness, adsorptive properties, and viscoelasticity. These features make it easy to identify the surface structure of complex materials;therefore, the use of SPMs has increased in recent years. Wood cell walls are primarily composed of cellulose, hemicellulose, and lignin. It is believed that hemicellulose and lignin surround the cellulose framework;however, their detailed formation remains unknown. Therefore, we observed wood cell walls via scanning probe microscopy to try to reveal the formation of the cellulose framework. We determined that the size of the cellulose microfibril bundle and hemicellulose lignin module composite was 18.48 nm based on topography and that the size of the cellulose microfibril bundle was 15.33 nm based on phase images. In the viscoelasticity image, we found that the viscoelasticities of each cell wall of the same cell were not the same. This is because the cellulose microfibrils in each cell wall lean in different directions. The angle between the leaning of the cellulose microfibril and the cantilever affects the viscoelasticity measurement.

Surface Properties of Cement Paste Evaluated by Scanning Probe Microscopy

The microscopic physical properties of Hardened Cement Paste (HCP) surfaces were evaluated by using Scanning Probe Microscopy (SPM). The cement pastes were cured under a hydrostatic pressure of 400 MPa and the contacting surfaces with a slide glass during the curing were studied. Scanning Electron Microscope (SEM) observation at a magnification of 7000 revealed smooth surfaces with no holes. The surface roughness calculated from the SPM measurement was 4 nm. The surface potential and the frictional force measured by SPM were uniform throughout the measured area 24 h after the curing. However, spots of low surface potential and stains of low frictional force and low viscoelasticity were observed one month after curing. This change was attributed to the carbonation of hydrates.

Toward augmenting tip-enhanced nanoscopy with optically resolved scanning probe tips

A thorough understanding of biological species and emerging nanomaterials requires,among other efforts,their in-depth characterization through optical techniques capable of nanoresolution.Nanoscopy techniques based on tip-enhanced optical effects have gained tremendous interest over the past years,given their potential to obtain optical information with resolutions limited only by the size of a sharp probe interacting with focused light,irrespective of the illumination wavelength.Although their popularity and number of applications is rising,tip-enhanced nanoscopy(TEN)techniques still largely rely on probes that are not specifically developed for such applications,but for atomic force microscopy.This limits their potential in many regards,e.g.,in terms of signal-to-noise ratio,attainable image quality,or extent of applications.We take the first steps toward next-generation TEN by demonstrating the fabrication and modeling of specialized TEN probes with known optical properties.The proposed framework is highly flexible and can be easily adjusted to be used with diverse TEN techniques,building on various concepts and phenomena,significantly augmenting their function.Probes with known optical properties could potentially enable faster and more accurate imaging via different routes,such as direct signal enhancement or facile and ultrafast optical signal modulation.We consider that the reported development can pave the way for a vast number of novel TEN imaging protocols and applications,given the many advantages that it offers.

Nanofabrication of the gold scanning probe for the STM-SECM coupling system with nanoscale spatial resolution

Scanning probe is the key issue for the electrochemical scanning probe techniques(EC-SPM) such as EC-scanning tunnel microscopy(STM), EC-atomic force microscopy(AFM) and scanning electrochemical microscopy(SECM), especially the insulative encapsulation of the nanoelectrode probe for both positioning and electrochemical feedbacks. To solve this problem,we develop a novel fabrication method of the gold nanoelectrodes: firstly, a micropipette with nanomter-sized orifice was prepared as the template by a laser puller; secondly, the inside wall of micropipette apex was blocked by compact and conic Au nano-piece through electroless plating; thirdly, the Au nano-piece was grown by bipolar electroplating and connected with a silver wire as a current collector. The fabricated Au nanoelectrode has very good voltammetric responses for the electrodic processes of both mass transfer and adsorption. The advantage lies in that it is well encapsulated by a thin glass sealing layer with a RG value lowered to 1.3, which makes it qualified in the SECM-STM coupling mode. On one hand, it can serve as STM tip for positioning which ensures the high spatial resolution; on the other hand, it is a high-quality nanoelectrode to explore the local chemical activity of the substrate. The nanofabrication method may promote the SPM techniques to obtain simultaneously the physical and chemical images with nanoscale spatial resolution, which opens a new approach to tip chemistry in electrochemical nanocatalysis and tip-enhanced spectroscopy.

Progress of electrode/electrolyte interfacial investigation of Li-ion batteries via in situ scanning probe microscopy

The electrode/electrolyte interface plays a cri- tical role in the performance of a Li-ion battery. In view of the dynamic and complex nature of the interface, in situ research approaches can provide valuable information of interfacial phenomena during battery operation. In situ scanning probe microscopy （SPM） is a powerful technique used for the interfacial investigation of the Li-ion batteries. The versatile SPM techniques and their various operation modes have been utilized to measure the morphology and other properties of the electrode interface at high resolu- tion. Herein, we discuss the related SPM techniques to study the topography, mechanics and electrochemistry re- search of electrodes. Recent progresses of in situ SPM research on the electrode/electrolyte interface are summa- rized. Finally, the outlook of the technique is discussed.

Electrochemical scanning probe microscopies for artificial photosynthesis

The rational design of efficient artificial photosynthetic components requires thorough understandings towards(photo)electrochemical properties and kinetic processes at the solid/liquid interface.Electrochemical scanning probe microscopy(EC-SPM),which enables the high-spatial resolution imaging in an electrolyte environment,becomes an indispensable experimental technique for operando studies of(photo)electrochemistry.This review summarizes the latest results of relevant ECSPM techniques to study the interfacial properties of electrocatalysts and photoelectrodes.Covered methods include atomic force microscopy,Kelvin probe force microscopy,conductive atomic force microscopy,scanning tunneling microscopy,scanning electrochemical microscopy,and other advanced SPM-based operando techniques.Finally,we offer some perspectives on the future outlook in this fascinating research area.

A Comprehensive FIB Lift-out Sample Preparation Method for Scanning Probe Microscopy

In this work,we investigate cross-sectional sample preparation for atomic force microscopy and general scanning probe microscopy(SPM)characterization.In light of traditional cross-sectional sample preparation solutions for transmission electron microscopy,mechanical polishing and focused ion beam(FIB)milling have been employed to prepare cross-sectional samples for SPM.We present an optimized solution for thin films and oxide heterostructures that allows for examining the prepared surfaces using various SPM techniques.In particular,post-cleaning after FIB milling is shown to be crucial and precision ion polishing was conducted to remove rough layers on mechanically polished samples.We also study SPM mechanical milling to remove amorphous layers on FIB-milled samples.Consequently,a reliable solution for making cross sections suitable for SPM has been achieved providing a useful methodology that can also be employed for other material systems with different hardness,such as polymers and metals.

A sensitive charge scanning probe based on silicon single electron transistor

Single electron transistors（SETs） are known to be extremely sensitive electrometers owing to their high charge sensitivity. In this work, we report the design, fabrication, and characterization of a silicon-on-insulatorbased SET scanning probe. The fabricated SET is located about 10 m away from the probe tip. The SET with a quantum dot of about 70 nm in diameter exhibits an obvious Coulomb blockade effect measured at 4.1 K. The Coulomb blockade energy is about 18 me V, and the charge sensitivity is in the order of 10^-（5）–10（^-3）e/Hz^（1/2）. This SET scanning probe can be used to map charge distribution and sense dynamic charge fluctuation in nanodevices or circuits under test, realizing high sensitivity and high spatial resolution charge detection.

Scanning probe microscopy in probing low-dimensional carbon-based nanostructures and nanomaterials

Carbon,as an indispensable chemical element on Earth,has diverse covalent bonding ability,which enables construction of extensive pivotal carbon-based structures in multiple scientific fields.The extraordinary physicochemical properties presented by pioneering synthetic carbon allotropes,typically including fullerenes,carbon nanotubes,and graphene,have stimulated broad interest in fabrication of carbon-based nanostructures and nanomaterials.Accurate regulation of topology,size,and shape,as well as controllably embedding target sp^(n)-hybridized carbons in molecular skeletons,is significant for tailoring their structures and consequent properties and requires atomic precision in their preparation.Scanning probe microscopy(SPM),combined with on-surface synthesis strategy,has demonstrated its capabilities in fabrication of various carbon-based nanostructures and nanomaterials with atomic precision,which has long been elusive for conventional solution-phase synthesis due to realistic obstacles in solubility,isolation,purification,etc.More intriguingly,atom manipulation via an SPM tip allows unique access to local production of highly reactive carbon-based nanostructures.In addition,SPM provides topographic information of carbon-based nanostructures as well as their characteristic electronic structures with unprecedented submolecular resolution in real space.In this review,we overview recent exciting progress in the delicate application of SPM in probing low-dimensional carbon-based nanostructures and nanomaterials,which will open an avenue for the exploration and development of elusive and undiscovered carbon-based nanomaterials.

Characterization of stress corrosion crack growth of 304 stainless steel by electrochemical noise and scanning Kelvin probe

The fatigue pre-cracking 304 stainless steel （SS） specimens with lengths of 1.002 mm （L-crack） and 0.575 mm （S-crack） were prepared. Their corrosion behavior was studied by electrochemical noise （EN） in 4 mol/L NaC1 ＋ 0.01 mol/L Na2S203 solution under slow-strain-rate-testing （SSRT） conditions. Moreover, the characteristics of L-crack＇s surface morphology and potential distribution with scanning Kelvin probe （SKP） before and after SSRT were also discussed. Compared with S-crack, L-crack is propagated and the features of crack propagation can be obtained. After propagation, the noise amplitudes increase with increasing stress and accelerating corrosion, the white noises at low and high frequencies （WE and WH） of the later stage are one order of magnitude larger than that at early stage in the current power spectral densities （PSDs）. The potential PSDs also increase, but WH disappears. In addition, the crack propagation can be demonstrated according to variation of probability distribution, surface morphology and potential distribution.

Corrosion of Carbon Steel under Epoxy-varnish Coating Studied by Scanning Kelvin Probe

The corrosion behavior of partly coated carbon steel was investigated by salt spray test and scanning Kelvin probe （SKP） in order to understand the long-term corrosion behavior of coated carbon steel in marine atmosphere environment. The localized corrosion was accurately characterized by SKP in both coated and uncoated regions. The SKP results showed that Volta potential varied with the test time, and the more the corrosion products, the more positive the potential. The borderline between coated and uncoated regions of partly coated steel shifted towards the coated side with the increasing of test time. The coating disbonding rate could be determined according to the shift of potential borderline measured by SKP. The corrosion mechanism of partly coated steel in NaCl salt spray was discussed according to the potential maps and corrosion morphologies.

Sensitization behavior of welded 304L austenitic stainless steel using scanning vibrating probe

The sensitization behavior of special structures such as weld seams reduces the resistance of materials to intergranular corrosion and intergranular stress corrosion cracking. How ever,the degree of sensitization in the seams could not be detected by the traditional electrochemical potentiokinetic reactivation（ EPR） measurement using the double loop method. Results based on non-effective tests bring risks to the application of these materials. In this study,the degree of sensitization in w eld seams are determined by using the scanning vibrating probe（ SVP）method.