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Disentangling topographic contributions to near-field scanning microwave microscopy images
摘要： We develop empirical models to predict the contribution of topographic variations in a sample to near-field scanning probe microwave microscopy (NSMM) images. In particular, we focus on |S11| images of a thin Perovskite photovoltaic material and a GaN nanowire. The difference between the measured NSMM image and this prediction is our estimate of the contribution of material property variations to the measured image. Prediction model parameters are determined from either a reference sample that is nearly free of material property variations or directly from the sample of interest. The parameters of the prediction model are determined by robust linear regression so as to minimize the effect of material property variations on results. For the case where the parameters are determined from the reference sample, the prediction is adjusted to account for instrument drift effects. Our statistical approach is fully empirical and thus complementary to current approaches based on physical models that are often overly simplistic.
关键词： Near-field scanning probe microwave microscopy,Signal extraction,GaN nanowire,Statistical methods,Perovskite materials,Atomic force microscopy
更新于2025-09-23 15:23:52
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Template-driven dense packing of pentagonal molecules in monolayer films
摘要： The integration of molecules with irregular shape into a long-range, dense and periodic lattice represents a unique challenge for the fabrication of engineered molecular scale architectures. The tiling of pentagonal molecules on a 2D plane can be used as a proof-of-principle investigation to overcome this problem since basic geometry dictates that a two-dimensional (2D) surface cannot be filled with a periodic arrangement of pentagons, a fundamental limitation that suggests that pentagonal molecules may not be suitable as building blocks for dense films. However, here we show that the 2D covalent organic framework (COF) known as COF-1 can direct the growth of pentagonal guest molecules as dense crystalline films at the solution/solid interface. We find that the pentagonal molecule corannulene adsorbs at two different sites on the COF-1 lattice, and that multiple molecules can adsorb into well-defined clusters patterned by the COF. Two types of these dense periodic packing motifs lead to a five-fold symmetry reduction compatible with translational symmetry, one of which gives an unprecedented high molecular density of 2.12 molecules/nm2.
关键词： host-guest system,fivefold symmetry,scanning probe microscopy,pentagonal molecules
更新于2025-09-23 15:21:21
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Electrode-free anodic oxidation nanolithography of low-dimensional materials
摘要： Scanning probe lithography based on local anodic oxidation (LAO) provides a robust and general nanolithography tool for a wide range of applications. Its practical use, however, has been strongly hampered due to the requirement of a pre-fabricated micro-electrode to conduct the driving electrical current. Here we report a novel electrode-free LAO technique, which enables in-situ patterning of as-prepared low-dimensional materials and heterostructures with great flexibility and high precision. Unlike conventional LAO driven by a DC current, the electrode-free LAO is driven by a high-frequency (>10 kHz) AC current applied through capacitive coupling, which eliminates the need of a contacting electrode and can be used even for tailoring insulating materials. Using this technique, we demonstrated flexible nanolithography of graphene, hexagonal boron nitride (hBN), and carbon nanotubes (CNTs) on insulating substrates with ~10-nanometer precision. In addition, the electrode-free LAO exhibits high etching quality without oxide residues left. Such an in-situ and electrode-free nanolithography with high etching quality opens up new opportunities for fabricating ultraclean nanoscale devices and heterostructures with great flexibility.
关键词： electrode-free local anodic oxidation,graphene,high-frequency AC voltage,low-dimensional materials,Scanning probe lithography
更新于2025-09-23 15:21:21
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[IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Nano C-V imaging of Semiconductor Devices with Scanning Microwave Impedance Microscopy
摘要： Two doped semiconductor samples are measured using probe-based Scanning Microwave Impedance Microscopy (sMIM). One is a plan-view polished CMOS image sensor and the other is a cross-section polished power device. Both samples are imaged with sMIM using two different approaches: the first using a dual pass method with dC/dV images acquired simultaneously with sMIM during the first pass in contact mode, and the second pass at a fixed offset from the surface. The second method uses a non-resonant mode where C-V are acquired at specific lateral locations. The C-V curves are used to determine polarity compared to dC/dV and also to distinguish p-n junctions, characterize doping concentration, and build images at constant DC values to discern subtle changes not evident in traditional SCM imaging.
关键词： Nano-C-V,SCM,Scanning Probe Microscopy,doping characterization,Scanning Microwave Impedance Microscopy,Scanning Capacitance Microscopy,sMIM
更新于2025-09-23 15:21:01
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Hybrid gate dielectrics: a comparative study between polyvinyl alcohol/ $$\hbox {SiO}_{2}$$ SiO 2 nanocomposite and pure polyvinyl alcohol thin-film transistors
摘要： Polyvinyl alcohol (PVA) thin films as polymer gate dielectrics, with and without SiO2 nanoparticles were fabricated using spin-coating. Surface roughness and hydrophilicity of PVA and PVA/SiO2 thin films were studied by contact-angle measurements and atomic force microscopy. The dielectric properties were characterized via capacitance and leakage-current measurements on metal–insulator–metal structures. In order to further investigate the application potential of such materials as a replacement for conventional inorganic dielectrics such as SiO2 in organic thin-film transistors, devices were fabricated based on these polymers using α, ω-dihexylquaterthiophene as an active layer. Performance of the devices was realized by electrical measurements and Kelvin probe force microscopy. All transistors showed hole and electron mobilities in the low-voltage range. PVA/SiO2 films showed larger capacitance, less hydrophilicity, rougher surfaces and considerable leakage currents compared with those with neat PVA. Although integrating nanoparticles modified surface electronic properties and showed a shift in surface potential as observed in Kelvin probe force measurements, it appears that non-polymeric and neat polymeric dielectric materials could still be a privilege to nanocomposite polymeric dielectrics for optoelectronic applications.
关键词： ambipolar thin-film transistor,scanning probe microscopy (SPM),surface chemistry,electrical and structural properties,Polymer dielectrics
更新于2025-09-19 17:15:36
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Self‐Assembled Room Temperature Multiferroic BiFeO <sub/>3</sub> ‐LiFe <sub/>5</sub> O <sub/>8</sub> Nanocomposites
摘要： Multiferroic materials have driven significant research interest due to their promising technological potential. Developing new room-temperature multiferroics and understanding their fundamental properties are important to reveal unanticipated physical phenomena and potential applications. Here, a new room temperature multiferroic nanocomposite comprised of an ordered ferrimagnetic spinel α-LiFe5O8 (LFO) and a ferroelectric perovskite BiFeO3 (BFO) is presented. It is observed that lithium (Li)-doping in BFO favors the formation of LFO spinel as a secondary phase during the synthesis of LixBi1?xFeO3 ceramics. Multimodal functional and chemical imaging methods are used to map the relationship between doping-induced phase separation and local ferroic properties in both the BFO-LFO composite ceramics and self-assembled nanocomposite thin films. The energetics of phase separation in Li doped BFO and the formation of BFO-LFO composites are supported by first principles calculations. These findings shed light on Li’s role in the formation of a functionally important room temperature multiferroic and open a new approach in the synthesis of light element doped nanocomposites for future energy, sensing, and memory applications.
关键词： light element doping,thin film nanostructures,multiferroics,nanoferroic properties,scanning probe microscopy,self-assembled nanocomposites
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE/MTT-S International Microwave Symposium - IMS 2019 - Boston, MA, USA (2019.6.2-2019.6.7)] 2019 IEEE MTT-S International Microwave Symposium (IMS) - Borrowing from Microwave Holography a Technique for Broad-band Nano Imaging at Infrared Wavelengths
摘要： Scanning Probe Microscopy (SPM) for Nano imaging includes different techniques, ranging from Atomic Force Microscopy (AFM) and Scanning Near-Field Optical Microscopy (able to acquire images beyond diffraction limit), up to Scanning Microwave Microscopy developed to achieve imaging and characterization of a sample at Microwaves. In the present work we describe a technique which implements the concept of “Synthetic Reference Wave”, borrowed from Microwave Holography and already introduced in Synthetic Aperture Radars (SAR), to perform Nano scale quantitative imaging at infrared wavelengths. Although this approach was already combined in the past with AFM, in the following paper we proposed a different implementation, potentially suitable for wide-band imaging at Nano scale.
关键词： Nano Imaging,Scanning Probe Microscopy,Microwave Holography
更新于2025-09-16 10:30:52
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Charge Carrier Dynamics in Electron-Transport-Layer-Free Perovskite Solar Cells
摘要： Better understanding the carrier dynamics process in electron transport layer (ETL) -free perovskite solar cells (PSCs) enables the further exploration of the perovskite potential and corresponding device structure design. Herein, ETL-free perovskite/transparent conductive film SnO2:F(FTO) contact with different perovskite thickness illuminated by varied light intensity was investigated by scanning probe microscopy technology. Strong charge transfer is occurred at the perovskite/FTO contact, evidenced by the variations of both surface contact potential and local current value. Mott-Schottky analysis based on capacitance-voltage measurements suggests that the interface property of perovskite/FTO contact is similar to the perovskite/TiO2/FTO structure, make it ideal to fabricate ETL-free PSCs. The cross-sectional surface potential drop was found to be mainly located at the CH3NH3PbI3/FTO heterojunction, suggesting a single diode junction in the ETL -free PSCs. Furthermore, a single-side abrupt p-n++ junction model is employed to illustrate the energy level alignment at the perovskite/FTO contact. This study will be helpful for understanding the carrier dynamics process and thus achieving high device efficiency in the ETL-free PSCs.
关键词： perovskite solar cells,Carrier dynamics,surface potential,scanning probe microscopy,heterojunction
更新于2025-09-11 14:15:04
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Microscopy: Hasten high resolution
摘要： The best electron and scanning probe microscopes today can resolve individual atoms and chemical bonds. Views of materials such as graphene, catalysts and oxides on these scales — around 0.5 ?ngstr?ms — reveal structures and the impacts of crystal defects on their properties. To truly understand materials’ chemical and physical properties, atomic arrangements need to be mapped with much greater precision. Resolutions of 0.1 ? — the goal set by physicist Richard Feynman in his 1959 American Physical Society lecture, ‘There’s Plenty of Room at the Bottom’ — would take us to the physical limit of microscope vision, set by the thermal vibrations of atoms. Small structural distortions that determine magnetism, valence (the number of chemical bonds an atom can form) and spin state would become apparent.
关键词： atomic resolution,materials science,scanning probe microscopy,electron microscopy,microscopy
更新于2025-09-11 14:15:04
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Exploration of Interfacial Porphine Coupling Schemes and Hybrid Systems by Bond-Resolved Scanning Probe Microscopy
摘要： The templated synthesis of porphyrin-based oligomers and heterosystems is of considerable interest for materials with tunable electronic gaps, photovoltaics, or sensing device elements. In this work, temperature-induced dehydrogenative coupling between unsubstituted free-base porphine units and their attachment to graphene nanoribbons on a well-defined Ag(111) support are scrutinized by bond-resolved scanning probe microscopy techniques. The detailed inspection of covalently fused porphine dimers obtained by in vacuo on-surface synthesis clearly reveals atomistic details of coupling motifs, whereby also putative reaction intermediates are identified. Moreover, the covalent attachment of porphines at preferred locations of atomically precise armchair-type graphene nanoribbons is demonstrated.
关键词： porphyrins,graphene nanoribbons,scanning probe microscopy,surface chemistry,C–C coupling
更新于2025-09-10 09:29:36