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Femtosecond laser ablation has found wide-ranging applications in the surface structuring of nanoelectronics and nanophotonics devices. Traditionally, the inspection of the fabricated three-dimensional (3D) morphology was performed using a scanning electron microscope or atomic force microscopy in an ex situ manner after processing was complete. To quickly monitor and efficiently optimize the quality of surface fabrication, we developed an in situ method to accurately reconstruct the 3D morphology of surface micro-structures. This method is based on a triangulation optical system that utilizes structured illumination. The approach offers a super-resolution capacity, making it a powerful and non-invasive tool for quick in situ monitoring of surface ablation structures. [ABSTRACT FROM AUTHOR]

Thin films of silver were deposited on nonalkali glass substrates at substrate temperatures ranging from room temperature (28 °C) to 150, 200, 300, 400, and 500 °C at discharge pressures of 0.40, 1.20, and 2.00 Pa using direct current magnetron sputtering. On the basis of the measured cross-sectional and surface morphologies, crystallographic structures, and film properties, I discuss the dependence of the film structure and properties on the substrate temperature. The x-ray diffraction measurements showed that the <111> orientation was preferred for all deposition conditions. Scanning electron microscope observations revealed a microstructure of convex-shaped fine grains for a substrate at room temperature, while laterally growing, mound-shaped grains with flat-topped surfaces appeared at substrate temperatures of 400 and 500 °C. Atomic force microscopy also showed an increase in the lateral size and height of the mound-shaped structures with increasing substrate temperature. The lateral grain size evaluated from the areal particle density obtained from atomic force microscopy increased significantly with increasing substrate temperature, reaching 600–800 nm at a substrate temperature of 500 °C. The film stress also changed from compressive to tensile with increasing substrate temperature. The relative density, defined as the ratio of the deposited amount-of-substance to the physical-thickness, decreased significantly with increasing substrate temperature and, at a substrate temperature of 500 °C, was approximately 0.6 times as large as that obtained for thin films deposited at room temperature. The high surface diffusivity of the Ag adatoms induces the growth of laterally growing, mound-shaped grains. Besides, the energy accumulated in the thin films during sputter deposition induces the void formation to increase the efficiency of energy release in the form of heat. [ABSTRACT FROM AUTHOR]

GaN nanowires are potential candidates for use in scanning probe microscopy due to their well-defined, reproducible, geometric shapes, their hardness, and their light guiding properties. We have developed and investigated probes for high resolution atomic force microscopy and scanning tunneling microscopy utilizing GaN nanowires as probes. The nanowires are n-doped and the morphology of the nanowires has been tailored for scanning probe microscopy by growing them with a sharp tip for measurements and high thickness for robustness. The individual GaN nanowires were removed from their growth substrate and attached onto commercial atomic force microscopy cantilevers or etched tungsten wires for scanning tunneling microscopy. A standard scanning electron microscope equipped with a nanoprobe, a focused ion beam column and a gas injection system was used to locate, transfer, and attach the nanowires. We evaluated the properties of the GaN probes on different substrates including HOPG, Au, SiO2, InAs, and GaAs. We demonstrate both atomic force microscopy and scanning tunneling microscopy measurements with single atomic layer resolution and evaluate the robustness of the tips by monitoring them before and after scanning. Finally, we explore the use of the tips for scanning tunneling spectroscopy demonstrating that reliable results, which can reveal information on the electronic properties of the surface-tip system, are obtainable. The fundamental properties of these probes, which are demonstrated in this work, show promise for future use of the probes in exploring semiconductor-semiconductor tunneling junctions at the nanoscale as well as for other scanning probe techniques where high resolution is required. [ABSTRACT FROM AUTHOR]

Conductive atomic-force microscopy (C-AFM) writing is attracting attention as a technique for clarifying the switching mechanism of resistive random-access memory by providing a wide area filled with filaments, which can be regarded as one filament with large radius. The writing area on a nickel-oxide (NiO) film formed by conductive atomic-force microscopy was observed by scanning electron microscope, and a correlation between the contrast in a secondary-electron image (SEI) and the resistance written by C-AFM was revealed. In addition, the dependence of the SEI contrast on the beam accelerating voltage (Vaccel) suggests that the resistance-change effect occurs near the surface of the NiO film. As for the effects of electron irradiation and vacuum annealing on the C-AFM writing area, it was shown that the resistance-change effect is caused by exchange of oxygen with the atmosphere at the surface of the NiO film. This result suggests that the low-resistance and high-resistance areas are, respectively, p-type Ni1+δO (δ < 0) and insulating (stoichiometric) or n-type Ni1+δO (δ ≥ 0). [ABSTRACT FROM AUTHOR]

The spin Hall angle (SHA) represents the efficiency of the conversion between spin current into charge current and vice-versa. In this paper, we report the experimental detection of large enhancement of the effective SHA in heterostructures of yttrium iron garnet (YIG)/[Pt-Ag]/Pt and YIG/[Pt-Ag], when compared with measurements in YIG/Pt bilayers. The notation [Pt-Ag] represents the nanoparticles island formation of Ag in the Pt film. In order to investigate the role played by the metallic nanoparticles in the spin-to-charge conversion process, we carried out microwave spin pumping measurements in the following samples: YIG/Ag(3 nm)/Pt(6 nm), YIG/[Pt(3 nm)-Ag(3 nm)]/Pt(3 nm) and YIG/[Pt(6 nm)-Ag(3 nm)]. By means of high-resolution scanning electron microscope (HR-SEM) investigation, we confirmed that layers of Ag exhibit islands nanoparticle structures when grown on the surface of the Pt, which are characterized by the Volmer-Weber mode. The spin pumping results show that the Ag nanoparticles can enhance the charge current created by the inverse spin Hall effect (IISHE) up to three times larger than the single Pt layer. Also, by analyzing atomic force microscopy (AFM) images, obtained for samples with different thickness of the Ag layer, we conclude that the roughness plays an important role in the enhancement of the IISHE. Therefore, taking advantage of poor wetting properties of Ag over Pt layer, it was possible to create nanoscopic particles of Ag randomly grown in the Pt layer. The nanoparticles serve as nanoscopic molds to locally increase the SHA. This feature represents an improvement in searching more efficient methods of the spin-to-charge conversion and opens up the possibility of tuning the SHA by controlling the size and shape of the Ag nanoparticles. [ABSTRACT FROM AUTHOR]

More than 40 years after its invention, the atomic force microscopy (AFM) can be integrated with scanning electron microscope (SEM) instruments as an increasingly capable and productive characterization tool with sub-nanometer spatial resolution. The authors have designed and developed an AFM instrument capable to be integrated into any SEM or in a combination of SEM with a focused ion-beam (FIB) tool. The combination of two or more different types of techniques like SEM, energy dispersive x-ray spectroscopy, and AFM is called correlative microscopy because analytical information from the same place of the sample can be obtained and correlated. For the first time, they introduced to the SEM/FIB tool correlative nanofabrication methods like field-emission scanning probe lithography, tip-based electron beam induced deposition, and nanomachining. The combination of all these methods provides a completely new nanotechnology instrument, which should be seen as a tool for correlative nanofabrication and microscopy. Thus, it provides for the first time the capabilities of a stand-alone instrument with the capabilities of nondestructive three-dimensional tip-based metrology and nanofabrication into the combined SEM/FIB tool. In this article, the authors describe all these methods in detail and present a brief example of the results obtained. They demonstrate that the self-sensing, self-actuating cantilevers (called active cantilevers) equipped with Diamond tip are a versatile toolkit for fast imaging and emerging nanofabrication. The AFM integrated into SEM is using active cantilevers that can characterize and generate nanostructures all in situ without the need to break-vacuum or contaminate the sample. [ABSTRACT FROM AUTHOR]

Presents information on a study which applied a variant of the scanning capacitance microscope which is based on the atomic force microscope, to determine charge storage in a nitride-oxide-silicon medium. Methods; Results; Discussion.

Focuses on a study concerning the radical etching of bromine and the material system of indium, gallium, arsenic and aluminum. Discussion of the process of photochemical etching; Use of atomic force microscope and scanning electron microscope; Effect of the desorption process on etching.

Presents a study that examined yttrium compound superconducting thin films by using laser-deposition. Information on the structure and morphology of the films; Discussion on the surface morphology and electron channeling patterns of the thin films; Use of scanning electron microscope and atomic force microscope.

With rapidly increasing numbers of studies of new and exotic material uses for perovskites and quasicrystals, these demand newer instrumentation and simulation developments to resolve the revealed complexities. One such set of observational mechanics at the nanoscale is presented here for somewhat simpler material systems. The expectation is that these approaches will assist those materials scientists and physicists needing to verify atomistic potentials appropriate to the nanomechanical understanding of increasingly complex solids. The five following segments from nine University, National and Industrial Laboratories both review and forecast where some of the important approaches will allow a confirming of how in situ mechanics and nanometric visualization might unravel complex phenomena. These address two-dimensional structures, temporal models for the nanoscale, atomistic and multiscale friction fundamentals, nanoparticle surfaces and interfaces and nanomechanical fracture measurements, all coupled to in situ observational techniques. Rapid future advances in the applicability of such materials science solutions appear guaranteed. [ABSTRACT FROM AUTHOR]

In low energy scanning electron microscope (SEM) with primary electron energy less than 1.0 keV, the dependence of SEM contrast on crystallographic orientation within a range of 1.0 nm in depth has been investigated by utilizing 4H-SiC (0001) as a standard sample having a definitive electron penetration depth marker layer at hexagonal sites. Reflecting the difference of the direction of topmost two Si-C bilayers stacking sequence (0.50 nm in depth), clear bright and dark SEM contrast has been observed by adjusting the sample tilting and rotation angles by a conventional Everhart-Thornley type in-chamber detector. It is revealed that the brighter signal emission arises when the incident primary electron beam direction is almost parallel to the topmost stacking sequence direction. This angular coincidence was verified separately by correlating low energy SEM contrast from 3C-SiC (111) of no hexagonal sites with its electron back scattered diffraction pattern for identifying stacking sequence direction. The obtained results suggest a potential of low energy electron to characterize the crystallographic orientation just beneath the surface without using any special detector. [ABSTRACT FROM AUTHOR]

Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model which can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics. [ABSTRACT FROM AUTHOR]

Tuning of the Fermi level is investigated in graphene channels using two in-plane gates with significantly different-sized isolating gaps. While the n-type tuning was achievable in both schemes, the wide-gap device had an enhanced minimum drain current and less prominent current modulation than the narrow-gap device. In addition, further p-type tuning was not observed in the wide-gap device at negative gate biases. These phenomena indicated that both devices had distinct field-strength dependences and Fermi level tuning effects, which may be critical for the practical design of devices. [ABSTRACT FROM AUTHOR]

We report on AlxGa1-xN-based solar-blind ultraviolet (UV) photodetector (PD) grown on Si(111) substrate. First, Si(111) substrate is patterned, and then metalorganic chemical vapor deposition is implemented for a fully-coalesced ∼8.5 μm AlN template layer via a pulsed atomic layer epitaxial growth technique. A back-illuminated p-i-n PD structure is subsequently grown on the high quality AlN template layer. After processing and implementation of Si(111) substrate removal, the optical and electrical characteristic of PDs are studied. Solar-blind operation is observed throughout the array; at the peak detection wavelength of 290 nm, 625 μm2 area PD showed unbiased peak external quantum efficiency and responsivity of ∼7% and 18.3 mA/W, respectively, with a UV and visible rejection ratio of more than three orders of magnitude. Electrical measurements yielded a low-dark current density below 1.6 × 10-8 A/cm2 at 10 V reverse bias. [ABSTRACT FROM AUTHOR]

Growth of large-scale graphene is still accompanied by imperfections. By means of a four-tip scanning tunneling and electron microscope (4-tip STM/SEM), the local structure of graphene grown on SiC(0001) was correlated with scanning electron microscope images and spatially resolved transport measurements. The systematic variation of probe spacings and substrate temperature has clearly revealed two-dimensional transport regimes of Anderson localization as well as of diffusive transport. The detailed analysis of the temperature dependent data demonstrates that the local on-top nano-sized contacts do not induce significant strain to the epitaxial graphene films. [ABSTRACT FROM AUTHOR]

In this work, a well-controllable, direct-write, resistless, and crystallinity-retaining etching process for germanium using a focused electron beam with nanometer resolution has been developed. This process allows for precise, local, and efficient removal of germanium from a surface without showing any spontaneous etching effects. This focused electron beam induced etching process of germanium substrates employs pure chlorine gas as etchant. The presented process was carried out in a conventional scanning electron microscope equipped with a custom-tailored gas injection system. The etch rate of this etching process was observed to be up to 0.32 μm3 min-1 or 12 nm min-1 for an area of 1.5×1.5 μm2. The influence of various etching parameters such as electron beam current, acceleration voltage and chlorine gas flow on the etch rate as well as the shape of the etch pits have been studied systematically by atomic force microscopy analysis. It is demonstrated that etching of amorphous germanium films can be performed significantly faster (∼8 times) than etching of crystalline germanium. Finally, a comparison between silicon etching and germanium etching by chlorine is presented. [ABSTRACT FROM AUTHOR]

A novel method for cleaning a high vacuum chamber is presented. This method is based on concurrent in situ high-energetic UV light activation of contaminants located in the residual gas and at the vacuum chamber surfaces as well as the in situ generation of highly reactive ozone. Ozone oxidizes the contaminants to volatile species. Investigations by energy-dispersive x-ray analysis of residual gas depositions and mass-spectroscopy measurements of the residual gas in the vacuum chamber identify the contaminant species as hydrocarbons. After a cleaning period of 8 h, a decrease in measured chamber contamination by about 90% could be achieved according to atomic force microscope analysis. Mass spectroscopy measurements using a residual gas analyzer indicate the creation of volatile, carbonaceous species during the cleaning process. [ABSTRACT FROM AUTHOR]

Details of the fabrication and characterization of hybrid green light emitting diodes, composed of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN on AlN/sapphire, are reported. Scanning electron microscope, atomic force microscopy, high resolution x-ray diffraction, and photoluminescence were used to study the hybrid device. The effects of solvents, annealing, and etching on n-ZnO are discussed. Successful hybridization of ZnO and (In)GaN into a green light emitting diode was realized. [ABSTRACT FROM AUTHOR]

The 4 in. wafer-scale production of probes tipped with single carbon nanofibers (CNF probes) for scanning probe microscope was achieved by an Ar+-ion-irradiation method. For the wafer-scale production, an arrangement of commercial-type Si cantilevers (tetrahedral Si tips), onto which single CNFs are grown, was optimized to contain 288 cantilevers in a 4 in. wafer. The ion-induced CNFs were then batch grown in the wafer scale. Scanning electron microscope observation of 50 of 288 probes randomly selected revealed that the CNFs were linear shaped, ∼400 nm in average length and ∼9 nm in average radius, and that ∼80% of the probes batch grown were suitable for practical use as qualified probes. Atomic force microscope image of a densely distributed plastic nanocolumn array obtained by the batch-grown CNF probe was clearer and less distorted, compared to that attained by a conventional Si probe. Thus, the ion-irradiation method opened up new route for the wafer-scale production of CNF probes for practical daily use. [ABSTRACT FROM AUTHOR]

Piezoelectrical actuators widely used in scanning devices for highly resolved displacement generation exhibit a number of known nonlinear effects as hysteresis and creep. This article describes an attempt to minimize those nonlinearities by recognizing the relation between scan range and voltage magnitude in a scanner specific function. In addition, by utilizing a strain gauge sensor system, a forward displacement correction is realized. The mathematical procedure behind the hysteresis correction is described in detail. The dependence of the higher order correction factors on parameters such as scan speed, scan range, or center position is studied carefully to extract their influence on the result. Finally, integral nonlinearities of about 1% are proven in experiments with an atomic force microscope. [ABSTRACT FROM AUTHOR]

The authors have investigated the dry etch mechanisms of complex poly-Si/TiN/HfO2 gate stacks and the issues that are correlated with the introduction of a thin metal layer in the gate stack. Based on atomic force microscopy (AFM) and scanning electron microscope measurements, they will first show that a mixture of HBr and Cl2 at low rf bias power is required to successfully pattern the TiN layer without damaging the HfO2 gate oxide. Second, it is demonstrated that the introduction of a metal layer in the gate stack prevents charging effects during the last etching steps of the silicon part of the gate. Transmission electron microscope measurements and x-ray photoelectron spectroscopy analyses of the gate sidewalls show that the thickness of the silicon sidewall passivation layer decreases during the O2 free metal etching step potentially inducing silicon gate profile distortion such as notch. However, the notch can be eliminated by etching the Si/TiN gate in a single step process instead of stopping at the TiN surface. Finally, AFM measurements show that during the TiN etching step, a low rf bias power is required to prevent damage (punching through) of the HfO2 layer. However, even under these conditions, a significant silicon recess (oxidation of the c-Si beneath the HfO2 layer) is observed even if TiN is etched in an O2-free chemistry. [ABSTRACT FROM AUTHOR]

An atomic force microscope that mounts on a sample stage of a scanning force microscope (SEMAFM) was developed. It was implemented for measurement of static mechanical properties of three-dimensional nanometric objects. The sample stage of the AFM was equipped with piezoelectric actuators enabling raster scanning as well as three degrees of freedom positioning with sub nm resolution and mm movable range. This enabled centering the AFM tip to the field of view of the SEM. Measurement of the spring constant and rupture force of three-dimensional nanometric structures was made possible. The SEMAFM also functioned as a conventional AFM. [ABSTRACT FROM AUTHOR]

The strain dependence of conductance of monolayer graphene has been studied experimentally here. The results illustrate the notable transitions: the slight increase, the dramatic decrease, and the sudden dropping of the conductance by gradually increasing the uniaxial strain. The graphene conductance behaves reversibly by tuning of the elastic tensile strain up to 4.5%, while it fails to recover after the plastic deformation at 5%. The change in conductance due to strain is surprisingly high, which indicates the potential applications in electromechanical devices. [ABSTRACT FROM AUTHOR]

As an emerging optical material, graphene's ultrafast dynamics are often probed using pulsed lasers yet the region in which optical damage takes place is largely uncharted. Here, femtosecond laser pulses induced localized damage in single-layer graphene on sapphire. Raman spatial mapping, SEM, and AFM microscopy quantified the damage. The resulting size of the damaged area has a linear correlation with the optical fluence. These results demonstrate local modification of sp2-carbon bonding structures with optical pulse fluences as low as 14 mJ/cm2, an order-of-magnitude lower than measured and theoretical ablation thresholds. [ABSTRACT FROM AUTHOR]

We report on an in-situ monitoring of graphite oxidation using a high temperature environmental scanning electron microscope. A morphological transition is clearly identified around 1040 K between hexagonal pits at low temperatures and circular pits at high temperatures, with apparently no change in the kinetic law. A kinetic Monte Carlo model allows rationalizing these findings in terms of the competitive oxidation of armchair and zig-zag edge sites and provides an estimate of the rate laws associated to these two events. Extended to three dimensions, the model also explains the 'in-depth' transition between the stepwise hexagons and the hemispheres observed by atomic force microscopy. [ABSTRACT FROM AUTHOR]

A simple approach to fabricate two-dimensional nanobump arrays on silicon (Si) substrate is reported. In the process, a single 248 nm excimer laser pulse was applied on a self-assembled monolayer of 1.5-μm-diameter silica microspheres on a n-doped (100) Si wafer. After laser irradiation at a fluence of 300 mJ/cm2, a regular array of conical Si nanobumps surrounded by a ring shaped trench were fabricated. The structure of the nanobump arrays was characterized by scanning electron microscope, and atomic force microscope. The formed nanobumps were determined to be Si-based bumps with energy disperse spectroscopy. The mechanisms involved in the formation of nanobumps were discussed. [ABSTRACT FROM AUTHOR]

Mn1.56Co0.96Ni0.48O4 films with spinel structure were prepared on Al2O3 substrate by chemical solution deposition method. The microstructure of the films was studied by atomic force microscope and field-emission scanning electron microscope. The current-voltage characteristics showed Ohmic conductivity in the temperature range of 245–295 K. The conduction was described by a variable range hopping model for a parabolic density of states. The advantages of high characteristic temperature, as well as high transition temperature (201 K) between ferromagnetic and paramagnetic phases make the Mn1.56Co0.96Ni0.48O4 films very promising for infrared detection, especially for functional devices by integrating magnetic and electronic properties of the materials. [ABSTRACT FROM AUTHOR]

Direct imaging of atomic step morphologies and individual threading dislocations in on-axis epitaxial 4H-SiC surfaces is presented. Topographically sensitive electron images of the crystalline surfaces were obtained through forescattered electron detection inside a conventional scanning electron microscope. This technique, termed electron channeling contrast imaging (ECCI), has been utilized to reveal the configuration of highly stepped, homoepitaxial 4H-SiC films grown on 4H-SiC mesa structures. Individual threading dislocations have been consistently imaged at the core of spiral atomic step morphologies located on the 4H-SiC surfaces. The ability of ECCI to image atomic steps was verified by atomic force microscopy. [ABSTRACT FROM AUTHOR]

We describe a nanolithography process for a polymethylmethacrylate (PMMA) surface using scanning contact atomic force microscopy. Parallel furrows were scribed with a pyramidal silicon tip using the same scan mechanism as used to image samples. The PMMA was first electron beam irradiated using a scanning electron microscope and developed. The topography formed is reproducible and predictable. Material from the region where the tip scribes is moved to nearby regions, and aligned, elongated PMMA fragments are seen to decorate the valleys between furrows. [ABSTRACT FROM AUTHOR]

The simultaneous presence of hexagonal and quadratic arrangements of polystyrene microspheres in the top layers of polystyrene and gold-polystyrene composite colloidal crystals has been evidenced by both atomic force microscopy and scanning electron microscopy. It is thought that the formation of layers with the two different packing modes is in agreement with the phase transformations found in systems with confined geometries. The results of this study are relevant to the fabrication of high quality photonic crystals. [ABSTRACT FROM AUTHOR]

A characterization device was developed for nanomechanical testing on one-dimensional micro/nanostructures. The tool consists of a nanomanipulator, a three-plate capacitive transducer, and associated probes, and is operated inside a scanning electron microscope. The transducer independently measures force and displacement with micronewton and nanometer sale resolutions, respectively. Tensile testing of a polyaniline microfiber (diameter ∼1 μm) demonstrated the capabilities of the system. Engineering stress versus strain curves exhibited two distinct regions with different Young’s moduli. Failure at the probe-sample weld occurred at ∼67 MPa, suggesting that polyaniline microfibers exhibit a yield stress that is higher than most comparable bulk polymers. [ABSTRACT FROM AUTHOR]

Gold and tungsten were deposited on silicon wafer and/or glass substrates by using random incidence sputtering deposition and thermal vapor deposition techniques. Two-dimensional tungsten nanotriangle and gold nanoring arrays were obtained on the silicon wafer substrate and examined using scanning electron microscope and atomic force microscope analysis. The size of the equal tungsten nanotriangles is within 100 nm per side and 210 nm apart from each other. The size of gold nanorings is 220 nm diameter, 40 nm wide, 10 nm thick, and 560 nm apart from each other. No nanorings were found on the glass substrate. Mechanisms for the formation of nanoring arrays are discussed. [ABSTRACT FROM AUTHOR]

Examines the use of piezoresistive cantilevers with an atomic force microscope operating with a scanning electron microscope. Compatibility of the microscopes; Presentation of grating and integrated circuit images; Methods for the detection of lever deflection.

Examines the fabrication of electron-beam-deposited tips. Use of atomic force microscope integrated with a scanning electron microscope; Benefits of the integrated microscope; Reduction of the curvature radius.

The line-edge roughness obtained from top-view scanning electron microscope (SEM) images is decomposed into three components; parallel shift, cross-sectional shape deformation, and surface roughness. The local slope angle of the pattern surface is estimated from the surface roughness component, which corresponds to the projection of the surface roughness onto the substrate plain. Cross-sectional profiles reconstructed by scanning this procedure across top-view SEM images show good agreement with the results obtained by other metrology methods, such as atomic force microscopy. [ABSTRACT FROM AUTHOR]