Multimode Scanning Probe Microscopy Research Articles

Correlative imaging with multi-modal scanning probe microscopy

Correlative imaging with multi-modal scanning probe microscopy

Resolution-enhanced X-ray fluorescence microscopy via deep residual networks

Multimodal hard X-ray scanning probe microscopy has been extensively used to study functional materials providing multiple contrast mechanisms. For instance, combining ptychography with X-ray fluorescence (XRF) microscopy reveals structural and chemical properties simultaneously. While ptychography can achieve diffraction-limited spatial resolution, the resolution of XRF is limited by the X-ray probe size. Here, we develop a machine learning (ML) model to overcome this problem by decoupling the impact of the X-ray probe from the XRF signal. The enhanced spatial resolution was observed for both simulated and experimental XRF data, showing superior performance over the state-of-the-art scanning XRF method with different nano-sized X-ray probes. Enhanced spatial resolutions were also observed for the accompanying XRF tomography reconstructions. Using this probe profile deconvolution with the proposed ML solution to enhance the spatial resolution of XRF microscopy will be broadly applicable across both functional materials and biological imaging with XRF and other related application areas.

2D graphene oxide and MXene nanosheets at carbon fiber surfaces

Carbon fibers, which are known for their high strength to weight ratio and thermal and chemical stability, are key components in advanced structural composites. Controlling the fiber-matrix interface is key to achieving required physical performance. Functional two-dimensional (2D) materials that can conformally coat the fiber surface facilitate interface and interphase engineering for enhanced mechanical properties and added functionalities. Understanding how 2D flakes bond, integrate, and perform at carbon fiber interfaces is key to developing multifunctional high-strength composites. In this study, we focus on the surface interactions of graphene oxide (GO) and Ti3C2Tx MXene nanoflakes at the surface of low-tension carbon fibers with and without amine functionalization by in-depth multimode scanning probe microscopy. We suggest that beyond strengthening the interfaces, GO and MXene provide efficient charge transfer with MXene also adding conductivity to the fiber surface, extending potential applications of composites to broad areas including structural supercapacitors and battery cooling/packaging materials. GO and MXene modified fibers not only create opportunities for increased interfacial adhesion in composites via increased surface roughness, but also act as anchors for bonding, energy dissipation, charge transport, and local interface stiffening.

Spinodal Decomposition-Driven Endurable Resistive Switching in Perovskite Oxides.

Common pursuits of developing nanometric logic and neuromorphic applications have motivated intensive research studies into low-dimensional resistive random-access memory (RRAM) materials. However, fabricating resistive switching medium with inherent stability and homogeneity still remains a bottleneck. Herein, we report a self-assembled uniform biphasic system, comprising low-resistance 3 nm-wide (Bi0.4,La0.6)FeO3-δ nanosheets coherently embedded in a high-resistance (Bi0.2,La0.8)FeO3-δ matrix, which were spinodally decomposed from an overall stoichiometry of the (Bi0.24,La0.76)FeO3-δ parent phase, as a promising nanocomposite to be a stable and endurable RRAM medium. The Bi-rich nanosheets accommodating high concentration of oxygen vacancies as corroborated by X-ray photoelectron spectroscopy and electron energy loss spectroscopy function as fast carrier channels, thus enabling an intrinsic electroforming-free character. Surficial electrical state and resistive switching properties are investigated using multimodal scanning probe microscopy techniques and macroscopic I-V measurements, showing high on/off ratio (∼103) and good endurance (up to 1.6 × 104 cycles). The established spinodal decomposition-driven phase-coexistence BLFO system demonstrates the merits of stability, uniformity, and endurability, which is promising for further application in RRAM devices.

Injection charge dynamics on the Pb(Zr0.52Ti0.48)O3 surface by scanning probe microscopy

The origin of an injected charge and its temperature dependence in ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films is studied by multimode scanning probe microscopy. During the poling process in scanning probe microscope (SPM) measurement, which is a local bias applied by using a conductive tip on a film’s surface to induce polarization orientation, a strong charge injection is always observed in oxide ferroelectric films; therefore, the surface potential is dominated by injection charge rather than polarization and screening charge. The surface potential shows an increase with the increase in the applied bias and saturation at a higher bias, which is much higher than the coercive field in PZT films. The positive surface potential shows a clear increase after oxygen plasma treatment, suggesting that the injection behavior is significantly enhanced. Subsequent heating could recover the surface condition to the initial state. Charge injection could be weakened but could not be completely eliminated by heat treatment. The current results suggest that charge injection behavior could not be easily relaxed, and a careful control of the localized poling process using an SPM conductive tip is required especially for studying the charge state on the surfaces of ferroelectric thin films.

Atomic defect classification of the H-Si(100) surface through multi-mode scanning probe microscopy.

The combination of scanning tunnelling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) allows enhanced extraction and correlation of properties not readily available via a single imaging mode. We demonstrate this through the characterization and classification of several commonly found defects of the hydrogen-terminated silicon (100)-2 × 1 surface (H–Si(100)-2 × 1) by using six unique imaging modes. The H–Si surface was chosen as it provides a promising platform for the development of atom scale devices, with recent work showing their creation through precise desorption or placement of surface hydrogen atoms. While samples with relatively large areas of the H–Si surface are routinely created using an in situ methodology, surface defects are inevitably formed reducing the area available for patterning. By probing the surface using the different interactivity afforded by either hydrogen- or silicon-terminated tips, we are able to extract new insights regarding the atomic and electronic structure of these defects. This allows for the confirmation of literature assignments of several commonly found defects, as well as proposed classifications of previously unreported and unassigned defects. By combining insights from multiple imaging modes, better understanding of their successes and shortcomings in identifying defect structures and origins is achieved. With this, we take the first steps toward enabling the creation of superior H–Si surfaces through an improved understanding of surface defects, ultimately leading to more consistent and reliable fabrication of atom scale devices.

Visualization of Functional Components in a Lithium Silicon Titanium Phosphate–Natural Graphite Composite Anode

Here, a multimodal scanning probe microscopy study of a composite anode with a dispersed lithium silicon titanium phosphate (LSTP) lithium ion conductor for all-solid-state batteries is presented. ...

Defect Reconstruction Triggered Full-Color Photodetection in Single Nanowire Phototransistor

The coherent developments of high performance broadband photodetection and a discrimination technique are highly essential for multiscene imaging and optical communication applications. The integration of traditional bandpass filters or stacking other spectral absorber in photodetectors often complicates the device design and leads to asymmetric photogain for each waveband. Herein, we report on ultraviolet–visible (UV-vis) multispectral photodetection based on a single ZnO nanowire (NW) phototransistor, where defect reconstructions can be reliably induced by a two-step annealing that leads to the observed broadband photodetection. Electron paramagnetic resonance and photoluminescence spectra reveal the reconstructions of zinc-atom-related defects (i.e., zinc interstitials and vacancies). Combined microdifferential reflectance and multimode scanning probe microscope (SPM) technique confirm the presence of a unique visible-sensitive Zn-rich ZnO shell layer and a trap-free UV-sensitive ZnO core. We achieve not only an ultrahigh carrier mobility (212.4 cm2 V–1 s–1), but also a concurrent improvement for UV-vis photodetection with superior responsivities and detectivities on the orders of 105 AW–1 and 1015 Jones at 100 mV, respectively, and response speeds less than one second. Moreover, photocurrents under blue, green, and red stimuli can be selectively switched on/off by tuning the gate stress. These high performances in all figures of merit have opened new routes to tailor intrinsic properties of a single NW for optoelectronic applications.

Insulin amyloid structures and their influence on neural cells

Peptide aggregation into oligomers and fibrillar architectures is a hallmark of severe neurodegenerative pathologies, diabetes mellitus or systemic amyloidoses. The polymorphism of amyloid forms and their distribution are both effectors that potentially modulate the disease, thus it is important to understand the molecular basis of protein amyloid disorders through the interaction of the different amyloid forms with neural cells and tissues. Here we explore the effect of amyloid fibrils on the human neuroblastoma (SH-SY5Y) cell line in vitro. We control the kinetic of fibrillization of insulin at low pH and higher temperature. We use a multiscale characterization via fluorescence microscopy and multimodal scanning probe microscopy to correlate the number of cells and their morphology, with the finer details of the insulin deposits. Our results show that insulin aggregates deposited on neuroblastoma cell cultures lead to a progressive modification and decreased number of cells that correlates with the degree of fibrillization. SPM unravels that the aggregates strongly interact with the cell membrane, forming a stiff encase that possibly leads to an increased cell membrane stiffness and deficit in the metabolic exchanges between the cells and their environment. The presence of fibrils does not affect the number of cells at 24h whereas drop down to 60% is observed after 48h of incubation.

Nanoscale Probing of Elastic-Electronic Response to Vacancy Motion in NiO Nanocrystals.

Measuring the diffusion of ions and vacancies at nanometer length scales is crucial to understanding fundamental mechanisms driving technologies as diverse as batteries, fuel cells, and memristors; yet such measurements remain extremely challenging. Here, we employ a multimodal scanning probe microscopy (SPM) technique to explore the interplay between electronic, elastic, and ionic processes via first-order reversal curve I-V measurements in conjunction with electrochemical strain microscopy (ESM). The technique is employed to investigate the diffusion of oxygen vacancies in model epitaxial nickel oxide (NiO) nanocrystals with resistive switching characteristics. Results indicate that opening of the ESM hysteresis loop is strongly correlated with changes to the resonant frequency, hinting that elastic changes stem from the motion of oxygen (or cation) vacancies in the probed volume of the SPM tip. These changes are further correlated to the current measured on each nanostructure, which shows a hysteresis loop opening at larger (∼2.5 V) voltage windows, suggesting the threshold field for vacancy migration. This study highlights the utility of local multimodal SPM in determining functional and chemical changes in nanoscale volumes in nanostructured NiO, with potential use to explore a wide variety of materials including phase-change memories and memristive devices in combination with site-correlated chemical imaging tools.

RETRACTED: A study approach on ferroelectric domains in BaTiO3

Abstract Atomic Force Acoustic Microscopy (AFAM) and Piezoresponse Force Microscopy (PFM) were used to study local elastic and electromechanical response in BaTiO 3 ceramics. A commercial multi-mode Scanning Probe Microscopy (SPM) and AFAM mode to image contact stiffness were employed to accomplish the aforementioned purposes. Stiffness parameters along with Young's moduli and piezo coefficients were quantitatively determined. PFM studies were based on electrostatic and electromechanical response from localized tip-surface contact. Comparison was made regarding the Young's moduli obtained by AFAM and PFM. In addition, phase and amplitude images were analyzed based on poling behavior, obtained via the application of − 10 V to + 10 V local voltage.

Changes in morphology and local conductance of GeTe–Sb2Te3 superlattice films on silicon observed by scanning probe microscopy in a lithography mode

Changes in the morphology and conductance state of [(GeTe)2(Sb2Te3)] superlattice (SL) films on Si(100) caused by external voltage were investigated by multimode scanning probe microscopy (MSPM) and scanning probe lithography (SPL) at room temperature in vacuum. After SPL patterning at a write voltage exceeding a threshold value, grain-dependent changes in transverse film conductance appeared in the MSPM current maps at a low voltage. Specific details of the conductance state switching were dependent on the film growth process. In uniform films grown in a two-step process, a threshold voltage of 1.6 V and a minimum switching power of ∼15 pW were obtained for conductance switching activated by high-energy electrons injected from the probe. Above 3.0 V, thermally driven regrowth of the SL films was observed. The results demonstrate a simple and appropriate method of optimizing topological SL films as recording media without device fabrication.

Conductance switching behavior of GeTe/Sb2Te3 superlattice upon hot-electron injection: a scanning probe microscopy study

ABSTRACTTopological (GeTe)/(Sb2Te3) superlattices (SL) are of practical interest for memory applications because of different mechanism of electric conductance switching in the crystalline phase. In the work, electrical switching behavior of individual SL grains was examined employing a multimode scanning probe microscope (MSPM) in a lithography mode at room temperature. Using programmed bias voltage with different amplitude and pulse duration, we observed the position-dependent variations of the switching voltage and the current injection delay for [(GeTe)2 (Sb2Te3)]4 SLs on Si(100). The results shed a light on the role of electric field and hot-electron injection on the SL conductance switching.

Multimodal scanning probe imaging: nanoscale chemical analysis from biology to renewable energy

Multimodal scanning probe microscopy enables analysis of not only surface topography, but also surface chemistry, electrical, magnetic, and mechanical properties.

Nanometric Magnetic and Piezo Domain Studies on Multiferroic BTO–CFO Based-Nanostructures

Multiferroic BTO-CFO was chosen for this study to understand multifunctional properties at the nanometer scale. The bulk pellet and nano-structured thin films of these compounds were synthesized. The films fabricated by pulsed laser deposition (PLD) technique, using the same material as target, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). About 100-nm-thick films showed different nanostructures of BTO-CFO which PLD grown at deposited in same conditions on various substrates like silicon, quartz, and strontium titanate (STO). Morphological studies revealed the presence of about ~ 50 nm sized nanostructured pillars. The multiferroic properties in these nanocomposite films were characterized using multimode scanning probe microscopy (SPM). Magnetic force microscopy studies revealed the distribution of magnetic domains with a diameter of <; 50 nm range in BTO matrix while using a silicon substrate. Piezo force microscopy available as a special SPM mode provided the evidence on the presence of piezoelectric domain and their behavior. Spatially, varying piezoelectric response was observed. Among the films with composite architectures, nanostructure BTO-CFO film on STO yielded maximum piezo response. Domain interfaces in both cases involving thin films and pellets are bestowed with special features.

Quantitative Evaluation of Dopant Concentration in Shallow Silicon p–n Junctions by Tunneling Current Mapping with Multimode Scanning Probe Microscopy

Quantitative evaluation of the dopant concentration across silicon p–n junctions has been performed on oxide-passivated surfaces by using tunneling current mapping in the constant-gap mode of a multimode scanning probe microscope (MSPM). A distinct difference between regions with different impurity concentrations was observed in tunneling current maps when a constant tunneling gap was maintained by using repulsive force acting on the MSPM probe. To extract impurity profiles, the results of three-dimensional device simulations within the current continuity model were compared with measured bias-dependent current profiles. The obtained impurity profiles showed agreement with the actual donor concentration in the p–n junction region. The results demonstrate the applicability of the method for quantitative analysis of the local impurity distribution in modern semiconductor devices with improved sensitivity and nanometer spatial resolution.

Nanoscale Characterization of Silicon-On-Insulator Nanowires by Multimode Scanning Probe Microscopy

Nanoscale Characterization of Silicon-On-Insulator Nanowires by Multimode Scanning Probe Microscopy

Built-in Potential Mapping of Silicon Field Effect Transistor Cross Sections by Multimode Scanning Probe Microscopy

Built-in Potential Mapping of Silicon Field Effect Transistor Cross Sections by Multimode Scanning Probe Microscopy

Spatial Distribution of Photocurrent in Si Stripes under Tilted Illumination Measured by Multimode Scanning Probe Microscopy

Spatial distribution of photocurrent in Si stripes of 50–1000 nm in width were investigated as a function of optical excitation wavelength by multimode scanning probe microscopy (MSPM). Inhomogeneous distribution of the MSPM photocurrent in the Si stripe interior was attributed to the light intensity profile. A model that included light absorption depth profile and the probe-induced band-bending region reproduced the photocurrent profile for tilted illumination of the stripes. An effective spatial resolution of ∼10 nm was deduced from the photocurrent measurements with multimode SPM in the constant-force mode.

Spatial Distribution of Photocurrent in Si Stripes under Tilted Illumination Measured by Multimode Scanning Probe Microscopy

Spatial Distribution of Photocurrent in Si Stripes under Tilted Illumination Measured by Multimode Scanning Probe Microscopy