The present study covers the nanoanalysis methods for four key material characteristics: electrical and electronic properties, optical, stress and strain, and chemical composition. With the ...downsizing of the geometrical dimensions of the electronic, optoelectronic, and electromechanical devices from the micro to the nanoscale and the simultaneous increase in the functionality density, the previous generation of microanalysis methods is no longer sufficient. Therefore, the metrology of materials' properties with nanoscale resolution is a prerequisite in materials' research and development. The article reviews the standard analysis methods and focuses on the advanced methods with a nanoscale spatial resolution based on atomic force microscopy (AFM): current‐sensing AFM (CS‐AFM), Kelvin probe force microscopy (KPFM), and hybrid optical techniques coupled with AFM including tip‐enhanced Raman spectroscopy (TERS), photothermal‐induced resonance (PTIR) characterization methods (nano‐Vis, nano‐IR), and photo‐induced force microscopy (PIFM). The simultaneous acquisition of multiple parameters (topography, charge and conductivity, stress and strain, and chemical composition) at the nanoscale is a key for exploring new research on structure–property relationships of nanostructured materials, such as carbon nanotubes (CNTs) and nano/microelectromechanical systems (N/MEMS). Advanced nanocharacterization techniques foster the design and development of new functional materials for flexible hybrid and smart applications.
Combining different methods with scanning probe microscopy allows the breaking limitations of conventional microanalytics. Such a powerful combination is illustrated by an atomic force microscopy combined with plasmonics that makes breaking the diffraction limit of light possible. This synergistic combination of different methods gives access to a large number of sample properties at the nanoscale in a single experiment.
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•We found stress reduction in silicon in the vicinity of the TSVs after post-annealing.•We show more stress relaxation in the direction where the neighboring TSVs exist.•We report ...lower Cu protrusion height at high annealing temperatures of about 380°C.
Thermo-mechanical reliability of through-silicon via (TSV) structures is affected by the residual stress, which is generated during thermal cycling in back end of line (BEOL) stack manufacturing, and by the 3D bonding processes. In this study, micro-Raman spectroscopy is employed for characterization of the local residual surface layer stress in Si due to the proximity of copper vias. We found that stress reduction in silicon in the vicinity of the TSVs is due to the relaxation after post-annealing. The residual thermal stress is relaxed more in the direction where the neighboring TSVs exist. Re-crystallization due to grain growth and also plastic and viscous behavior after annealing at high temperature might lead to higher stress relaxation that can impact on decreasing the keep-out zone (KOZ) size. Furthermore, the effect of post-annealing of Cu-TSVs in the generation of via protrusion is investigated. Cu protrusion mainly occurs due to the plastic and viscous behavior of Cu in the TSV. It was predicted from earlier publications, that the protrusion height is increasing with increasing the annealing temperature. However, we show that it might decrease at higher annealing temperatures of about 380°C. This result can be associated with large modification of the copper grain growth and/or stress-induced grain sliding.
Structural electronics, as well as flexible and wearable devices are applications that are possible by merging polymers with metal nanoparticles. However, using conventional technologies, it is ...challenging to fabricate plasmonic structures that remain flexible. We developed three-dimensional (3D) plasmonic nanostructures/polymer sensors via single-step laser processing and further functionalization with 4-nitrobenzenethiol (4-NBT) as a molecular probe. These sensors allow ultrasensitive detection with surface-enhanced Raman spectroscopy (SERS). We tracked the 4-NBT plasmonic enhancement and changes in its vibrational spectrum under the chemical environment perturbations. As a model system, we investigated the sensor's performance when exposed to prostate cancer cells' media over 7 days showing the possibility of identifying the cell death reflected in the environment through the effects on the 4-NBT probe. Thus, the fabricated sensor could have an impact on the monitoring of the cancer treatment process. Moreover, the laser-driven nanoparticles/polymer intermixing resulted in a free-form electrically conductive composite that withstands over 1000 bending cycles without losing electrical properties. Our results bridge the gap between plasmonic sensing with SERS and flexible electronics in a scalable, energy-efficient, inexpensive, and environmentally friendly way.
We report the high-powered laser modification of the chemical, physical, and structural properties of the two-dimensional (2D) van der Waals material GaSe. Our results show that contrary to ...expectations and previous reports, GaSe at the periphery of a high-power laser beam does not entirely decompose into Se and Ga2O3. In contrast, we find unexpectedly that the Raman signal from GaSe gets amplified around regions where it was not expected to exist. Atomic force microscopy (AFM), dielectric force microscopy (DFM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) results show that laser irradiation induces the formation of nanoparticles. Our analyses demonstrate that, except for a fraction of Ga2Se3, these nanoparticles still belong to the GaSe phase but possess different electrical and optical properties. These changes are evidenced in the increased Raman intensity attributed to the near-resonance conditions with the Raman excitation laser. The elemental analysis of nanoparticles shows that the relative selenium content increased to as much as 70% from a 50:50 value in stoichiometric GaSe. This elemental change is related to the formation of the Ga2Se3 phase identified by Raman spectroscopy at some locations near the edge. Further, we exploit the localized high-power laser processing of GaSe to induce the formation of Ag–GaSe nanostructures by exposure to a solution of AgNO3. The selective reaction of AgNO3 with laser-irradiated GaSe gives rise to composite nanostructures that display photocatalytic activity originally absent in the pristine 2D material. The photocatalytic activity was investigated by the transformation of 4-nitrobenzenethiol to its amino and dimer forms detected in situ by Raman spectroscopy. This work improves the understanding of light–matter interaction in layered systems, offering an approach to the formation of laser-induced composites with added functionality.
A method to determine the van der Waals forces from phase–distance curves recorded by atomic force microscopy (AFM) in tapping mode is presented. The relationship between the phase shift and the ...tip–sample distance is expressed as a function of the product of the Hamaker constant by tip radius. Silica-covered silicon tips are used to probe silica-covered silicon substrate in dry conditions to avoid capillary effects. Tips being assumed spherical, radii are determined in situ by averaging profiles recorded in different directions on hematite nanocrystals acting as nanotemplates, thus accounting for tip anisotropy. Through a series of reproducible measurements performed with tips of various radii (including the in-situ characterization of a damaged tip), a value of (6.3±0.4)×10−20J is found for the Hamaker constant of interacting silica surfaces in air, in good agreement with tabulated data. The results demonstrate that the onset of the tip–surface interaction is dominated by the van der Waals forces and that the total force can be modeled in the framework of the harmonic approximation. Based on the tip radius and the Hamaker constant associated to the tip–substrate system, the model is quite flexible. Once the Hamaker constant is known, a direct estimate of the tip size can be achieved whereas when the tip size is known, a quantitative evaluation of the van der Waals force becomes possible on different substrates with a spatial resolution at the nanoscale.
► Van der Waal forces in tapping mode atomic force microscopy. ► Harmonic approximation model of phase–distance curves probed by simulations. ► Silica tips and surfaces as a model case. ► Tip geometry determined in situ by nanoparticles as nanotemplates. ► Method to derive the Hamaker constant for any tip/surface system.
Two-dimensional (2D) materials have been utilized to design flexible field-effect transistors (FETs) with promising performance. However, flexible FETs still face challenges with poor switching ...features and ultra-low drive current. In this paper, a facile and repeatable large-area integration process is presented for inkjet-printed FETs with 2D materials active channels and PI films as gate dielectrics. The MoS
2
FETs reported here exhibit
n
-type channel feature with an outstanding average subthreshold swing of 75 mV/dec, an on-state/off-state current ratio of 10
4
, and on-state current up to 10 μA at a power supply voltage of 3.0 V. Besides, MoS
2
–rGO FETs also exhibit
n
-type semiconductor features with good electrical properties by the inkjet-printing technology.
Carbon nanomaterials are important for future sensors and electronics. Defects determine the material properties, therefore, it is critical to find new ways to investigate defects at the nanoscale. ...In this context, Raman spectroscopy (RS) is the tool of choice to study defects in carbon nanomaterials. On the other hand, Kelvin probe force microscopy (KPFM) provides structural and surface potential information at the nanoscale. Here, the authors demonstrate the synergistic application of these methods in the investigation of ion‐beam‐induced defects in graphite. KPFM and RS imaging are used for visualizing ion‐induced defects in a wide range of ion doses from 1010 to 1016 ions cm−2. For the lower range of ion dose, the authors find that RS provides image contrast for the different defect regions in graphite up to a dose of 5 × 1013 ions cm−2. For higher doses, the sp2 carbon concentration becomes so small that the Raman spectra get dominated by broad amorphous carbon bands. For this dose range, the KPFM contrast allows the defective regions to be differentiated. This contrast in KPFM originates from sp3 carbons that act as charge traps. The results show that KPFM and Raman microscopy make a powerful and necessary combination for studying the spatial distribution of defects in carbon.
Focused ion beam technology and techniques leveraged to control defect generation in graphite. The combination of Kelvin probe force microscopy and Raman spectroscopy imaging makes visualizing these defects in a broad range of ion dose possible, from the pristine graphite up to complete carbon amorphization.
While most of the research in graphene-based materials seeks high electroactive surface area and ion intercalation, here, we show an alternative electrochemical behavior that leverages graphene's ...potential in biosensing. We report a novel approach to fabricate graphene/polymer nanocomposites with near-record conductivity levels of 45 Ω sq
and enhanced biocompatibility. This is realized by laser processing of graphene oxide in a sandwich structure with a thin (100 μm) polyethylene terephthalate film on a textile substrate. Such hybrid materials exhibit high conductivity, low polarization, and stability. In addition, the nanocomposites are highly biocompatible, as evidenced by their low cytotoxicity and good skin adhesion. These results demonstrate the potential of graphene/polymer nanocomposites for smart clothing applications.
A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow ...diverse metallic nanowire arrays with extreme regularity in only two steps. First, III–V semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a “reverse epitaxy” process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays (Au, Fe, Ni, Co, FeAl alloy) are fabricated on these III–V templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances (LSPRs) of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine (CoPc) in surface-enhanced Raman scattering (SERS). Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.
The properties and applications of Ag nanowires (AgNWs) are closely related to their morphology and composition. Therefore, controlling the growth process of AgNWs is of great significance for ...technological applications and fundamental research. Here, silver nanowires (AgNWs) were synthesized via a typical polyol method with the synergistic effect of Cl−, Br−, and Fe3+ mediated agents. The synergistic impact of these mediated agents was investigated intensively, revealing that trace Fe3+ ions provided selective etching and hindered the strong etching effect from Cl− and Br− ions. Controlling this synergy allowed the obtainment of highly uniform AgNWs with sub-30 nm diameter and an aspect ratio of over 3000. Transparent conductive films (TCFs) based on these AgNWs without any post-treatment showed a very low sheet resistance of 4.7 Ω sq−1, a low haze of 1.08% at a high optical transmittance of 95.2% (at 550 nm), and a high figure of merit (FOM) of 1210. TCFs exhibited a robust electrical performance with almost unchanged resistance after 2500 bending cycles. These excellent high-performance characteristics demonstrate the enormous potential of our AgNWs in the field of flexible and transparent materials.
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