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Multiple research articles fabricate large electronic devices (with lateral sized 大于10 µm2) and claim that the behaviors observed are “promising” for applications like data storage or computing. Such claims are highly misleading because those technologies employ ultra-scaled electronic devices (e.g., transistors, memristors) with lateral sizes 小于0.01 µm2. In small-size devices, the number of local defects in the materials can be remarkably different, which almost always affects switching voltages, energies and times, as well as state resistances may be remarkably different than in larger devices, which also affects yield, variability and reliability. Hence, the fact that a large device (大于10 µm2) shows whatever performance does not imply that a small device (小于0.01 µm2) with identical materials composition will also exhibit it. In this seminar, I will show multiple methods to characterize the electronic properties of different materials and devices at the nanoscale. I will describe some of the properties I have analyzed in metal-oxides, graphene, molybdenum disulfide, hexagonal boron nitride, and nanowires. I will describe the setups that I have developed in order to carry out these studies, with special emphasis in conductive atomic force microscopy. The main properties that I will discuss are related to leakage current, dielectric breakdown and resistive switching in thin dielectrics, as well as piezoelectricity in two-dimensional materials and nanowires.
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On-surface chemical reactions on single molecules leads to fundamental chemical insights, such as better understanding bond-order relationships in reaction intermediates and products. Here, based on high-resolution atomic force microscopy/scanning tunnelling microscopy experiments, we will demonstrate the power of atom manipulation in two contexts: on conductive and on non-conductive substrates. On conductive substrates we will show how atom manipulation can generate a Diels-Alder reaction and couple terminal alkynes, on non-conductive substrates we will demonstrate how controlling the charge state of individual molecules can promote the reversible dissociation of a single molecule.
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Scanning Probe Lithography tools have opened a new paradigm in the creation of biomimetic structures, as they enable direct writing of lipid membranes or other biomaterials with spatial resolution down to 100 nm, that can be used as building blocks for chemical or biological sensors.1
We have used Dip-Pen Nanolithography with Phospholipids (l-DPN), which deposits nanosized elements, by transferring absorbed molecules on the AFM tip through a water meniscus onto the substrate, to create an in-vitro platform for the study of lipid membrane curvature driven effects.2 Although l-DPN has generally being conceived as a 2D lithography technique, by tuning the substrate properties, we have recently achieved to extend its capabilities to 3D writing.
On the other hand, we have proposed the use of the Fluid Force Microscopy (FluidFM) technology to overcome some inherent limitations of l-DPN. FluidFM features a hollow AFM cantilever with submicron sized aperture that locally disperses a chosen solution3, combines the accuracy of force control positioning and the versatility of microfluidics. This allowed us to create other types of structures, which can mimic the extracellular matrix for in-vitro cell experiments.4
[1] Liu, H. Y.; Kumar, R.; Zhong, C.; Gorji, S.; Paniushkina, L.; Masood, R.; Wittel, U. A.; Fuchs, H.; Nazarenko, I.; Hirtz, M. Adv. Mater. 33, 2008493 (2021)
[2] Berganza, E.; Ebrahimkutty, M. P.; Vasantham, S. K.; Zhong, C.; Wunsch, A.; Navarrete, A.; Galic, M.; Hirtz, M. Nanoscale, 13, 12642– 12650, (2021).
[3] Berganza, E.; Hirtz, M. Direct-Write Patterning of Functional Biomimetic Lipid Membranes with FluidFM. ACS Appl. Mat. Int. 13, 43, 50774–50784 (2021).
[4] Berganza, E.; Apte, G.; Vasantham, S. K.; Nguyen, T-H.; Hirtz, M. Polymers, 14, 7, 1327 (2022)
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探针材料:纳米尺度局部功能的定量成像
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The search of ultrathin and robust ferroelectrics leads to few promising two-dimensional (2D) materials. Among those, α-phase In2Se3 has drawn a special attention owing to the existence of intercoupled in-plane (IP) and out-of-plane (OOP) ferroelectricity in monolayer form, which makes it a potential candidate for emerging artificial intelligence, information processing and memory applications[1]. Mostly, Piezoelectric force microscopy (PFM) is used to identify the ferroelectricity in 2D materials, where the polarization direction changes under the applied electric field is reflected as phase contrast[2]. However, the contact-mode PFM causes layer damages, in particular if any steps or roughness are present in the topography. Therefore, an alternative non-contact mode characterization technique, like Kelvin-probe force microscopy (KPFM), can be useful to identify the electric field direction in non-destructive way[1]. To provide a proof-of-concept demonstration in device level, we performed KPFM measurements on a ferroelectric-semiconductor field-effect transistors (FeS-FET) under operational conditions[3-5]. Here, we showed a repeatable and reversible IP ferroelectric switching across the device channel, realized by a vertical electric field applied through gate electrode, which also established the inherent orthogonal dipole coupling[3]. Moreover, the interfacial band formations between all the dissimilar materials (including metal electrodes), respective CB and VB offsets, junctions type, effect of ferroelectric dipoles, are deduced via KPFM for coplanar In2Se3-In2O3 heterostructure FETs[4-5]. In conclusion, KPFM is an effective non-destructive method with high spatial resolution over domain orientation, for fast detection of 2D ferroelectricity, which becomes beneficial for research and device innovation.
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Ion hydration and transport at interfaces are relevant to a wide range of applied fields and natural processes. Interfacial effects are particularly profound in confined geometries such as nanometre-sized channels, where the mechanisms of ion transport in bulk solutions may not apply. To correlate atomic structure with the transport properties of hydrated ions, both the interfacial inhomogeneity and the complex competing interactions among ions, water and surfaces require detailed molecular-level characterization. Using a noncontact atomic force microscopy (AFM) system, we were able to image the individual ion hydrates at surfaces with atomic resolution [1-3]. We found that the alkali ion with specific hydration numbers diffuses orders of magnitude more quickly than other ion hydrates, arising from the degree of symmetry match between the hydrates and the surface lattice. In addition, we found that the alkali ions can come into close contact with each other through the dehydration and water rearrangement process, which is driven by the effective ionic attraction due to the interplay between the water-ion and water-water interactions. These results not only help us to understand the nature of biological ion channels, but may also provide general design principles for artificial ion channels towards high permeation rate and selectivity.
1. Peng et al., Nature 557, 701 (2018)
2. Tian et al., Science 377, 315 (2022)
3. Tian et al., submitted (2022)
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扫描扩展电阻显微镜(SSRM)原理及应用介绍
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高分辨扫描电化学池显微镜(SECCM)设计为同时记录样品的形貌和电化学活性信息,进而在微观尺度直接关联结构-性能。探针尺寸和稳定性决定了图像测试分辨率。这里报道了一种装配自制小探针(~50 nm直径)的SECCM测试系统,得到了几十纳米的高分辨率。同时获得了~45 nm金纳米颗粒的形貌和电化学活性图像。在纳米尺度实现SECCM的常规化测试,进一步扩展SECCM在不同领域的应用。
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介绍日立荧光光度计和紫外可见近红外分光光度计对光电材料的表征点击进入活动专题:追光逐电 与日俱新——日立光电行业主题网络会议_专题-仪器信息网 欢迎访问:日立科学仪器(北京)有限公司_首页
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电子显微镜作为重要的微观表征设备,已经广泛的应用于光电行业。本报告将重点介绍日立各类电镜及其相关产品的特点以及其在光电相关行业的应用案例,包括各类光电材料的形貌观察和成分分析,光电器件的三维形貌观察和失效分析,光电薄膜的粗糙度测量及界面分析等。欢迎访问:日立科学仪器(北京)有限公司_首页 (instrument.com.cn)欢迎浏览会议页面:追光逐电 与日俱新——日立光电行业主题网络会议更多内容查看专题:追光逐电 与日俱新——日立光电行业主题网络会议_专题-仪器信息网 (instrument.com.cn)