1. 中国科学院 重庆绿色智能技术研究院 Zhongbo Yang等
Near-Field Nanoscopic Terahertz Imaging of Single Proteins. Small.
Figure 1. Schematic illustration of the THz s-SNOM setup and its use for single biomolecule imaging.
Figure 2. THz near-field signals collected on different substrates. a) Time-domain THz electric field signals, and b) corresponding frequency-domain signals collected on graphene, Au, Si, and mica surfaces, respectively. The signals were demodulated at the second harmonics (2 Ω) of the probe oscillation frequency. c,d) The AFM topography images of graphene and Au substrates with 200 × 200 pixels, respectively. The height scale bars of (c) and (d) are the same.
摘要：太赫兹生物成像因其能以无标记、无创伤和非电离的方式获取样品的物理化学信息而颇受瞩目。但是，低介电常数生物分子的反射率问题，使得单分子精度的太赫兹成像仍是一个挑战。针对于此，作者开发了一种方法，利用石墨烯介导的太赫兹频率散射型扫描近场光学显微镜，对单个蛋白分子直接成像。此项研究发现，拥有较高太赫兹反射率和原子平整度的石墨烯基底可以为蛋白分子提供较高的太赫兹对比度。另外，我们还发现对铂探针的轴长优化能增强太赫兹散射近场信号中的振幅信号强度。基于这两个效应，作者同时获得了尺寸只有数纳米的免疫球蛋白G（IgG）和铁蛋白分子的形貌以及太赫兹散射图像。本文中所用的方法为单生物分子的太赫兹成像提供了新思路。
2. 华中科技大学 Chao Chen等
Terahertz Nanoimaging and Nanospectroscopy of Chalcogenide Phase-Change Materials. ACS Photonics2020.
Figure 2. THz near-field setup and imaging experiments. (a) Schematics of the THz s-SNOM setup with a bolometer used as a detector. The inset shows an illustration of the finite dipole model for the layered sample. (b) Approach curve, showing the amplitude signal s2 on c-GST as a function of tip–sample distance. The mark h1/e represents the position at which the signal decays to 1/e of its maximum. The inset displays an optical microscope image of the AFM tip above the sample. The red dotted squares mark the c-GST areas. (c) AFM topography image (top panel) of GST on a silicon oxide substrate, which includes amorphous and crystalline states. Near-field amplitude (s2, middle panel) and phase (φ2, bottom panel) images at 1.89 THz. (d) Topography, (e) near-field amplitude, and (f) phase line profiles (shown as solid symbols) taken from the corresponding images in c. The red solid lines are smoothed curves based on the experimental data. Horizontal dashed gray lines are a guide for the eye.
摘要：硫属化物相变材料（PCMs）在太赫兹（THz）频率下会发生光学声子共振现象，这个效应可被用于研究相变的基本特性，并产生很强的介电对比度，使其可被用于太赫兹的光子学应用。在本文中，我们证明可以通过频率可调的太赫兹散射型扫描近场光学显微镜（s-SNOM）研究PCM的声子。其具体方法为对包含非晶相和结晶相的PCM样品进行太赫兹纳米光谱成像。我们观察到材料的声子特征使其产生了很强的s-SNOM信号，以及重要的是，非晶态和结晶态PCM的光谱之间存在明显的差异，这使我们可以在纳米尺度上高信度地区分PCM的不同相。我们还发现可以通过增加针尖的半径来增强以信号强度和频谱对比度为标志的光谱特征。综上所述，我们用太赫兹s-SNOM成功构建了基于局部声子光谱的纳米结构以及化学组成的图谱。
3. 中国地质大学-武汉 Zhigao Dai等人
Edge-oriented and steerable hyperbolic polaritons in anisotropic van der Waals nanocavities. Nat. Commun..
Figure 1. a Schematic diagram of edge-tailored PhPs in α-MoO3. The edge orientation is defined as angle θ with respect to the [001] direction. Green arrows indicate the incident PhPs waves launched by the laser-illuminated (purple curve arrows) AFM tip and reflected by the edge (red line). b Angle-dependent ke isofrequency contour of PhPs in α-MoO3at ω = 889.8 cm−1. The solid lines and points stand for experimental results concluded from Fig. 1c. The green and black dotted arrows illustrate the incidence wavevector ki and Poynting vector Si, respectively. Generally, ki and Si are non-collinear. The reflected Poynting vector Se (solid arrows) is not parallel to the reflected wavevector ke (different color solid arrows) but antiparallel to Si. σ is the open angle. c Real-space imaging of edge-tailoring PhPs at angle-dependent α-MoO3edges (length L: 2.5 µm; width W: 200 nm; sample thickness d: 210 nm, L and W defined in the Ed1). d s-SNOM line traces along the direction perpendicular to the edges in Ed1-Ed5. e Near-field amplitude s(ω) of PhPs on isosceles triangle α-MoO3nanocavities with bottom edge perpendicular to the [001] crystal direction (height length: 4.33 μm; thickness: d = 175 nm); The angles between adjacent sides of the series of triangles with respect to the [001] direction are approximately 7.5°, 15°, 30°, 45°, and 60°, respectively.
摘要：高度受限和低损耗的化子在石墨烯和六方氮化硼上是沿平面各向同性传播的，这使得对光的控制被限制在了有限的自由度内。而以α-MoO3and V2O5为代表的新兴双轴范德华材料则展现出了特的化传播特性，它们的辅助光轴是在平面上的。利用这种强平面各向异性，作者通过空间纳米成像观测到了α-MoO3纳米腔的图样内有着受边界导向的双曲化子。并且发现边界的夹角和结晶方向对其光学响应信号有着举足轻重的影响，这对调整化图样的参数是至关重要的。基于此，通过调整α-MoO3纳米腔的几何构型，我们观测到了双曲化子会延边界传播并且会调整自身传播方向的特性以及与之对应的化子绕行禁区。而这种双曲化子的寿命和性能指数则受到纳米腔边界宽高比的限制。
4. 国防科学技术大学 Jiangyu Zhang 等人
Light-induced irreversible structural phase transition in trilayer graphene. Sci. & App..
Figure 4. Raman mapping and s-SNOM imaging of the light-induced structural phase transition in MLG. (a) Optical microscopy image of MLG sample #125. (b) AFM image and height profile of graphene. (c) Raman maps of the integrated G peak intensity (position: 1576 cm−1, width: 5 cm−1) before laser irradiation and (d) after laser irradiation. The laser power is 20 mW, and the exposure time is 34 min. (e) s-SNOM image of graphene after laser irradiation. (f) Magnified s-SNOM image of graphene. Graphene domains with different stacking orders show different contrasts in the s-SNOM image. The marked regions I, II, and III correspond to ABC stacking, ABA stacking and mixed ABC + ABA stacking domains, respectively. The red arrows in (e, f) highlight the additional mixed ABC + ABA stacking domains that were not resolved in the Raman maps. (g) Raman spectra of different graphene regions taken from the marked solid dots before laser irradiation and (h) after laser irradiation
摘要：晶体结构对相关材料的物理性质有着深刻的影响。因此，即使化学组成相同（比如石墨烯和金刚石），我们也可以通过生成具有特定对称性的晶体，来很大范围内调整它们的特性。而当晶体的结构相可以通过外部刺激动态改变时，更多有意思的可能性出现在了我们面前。这样的材料特性虽不常见，但却能引发很多喜人的现象，例如相变记忆效应。具体到三层石墨烯，它有两种常见的堆叠结构（ABA和ABC），二者都具有特的电子能带结构，并展现出了与众不同的特性。而这两种堆叠结构的三层石墨烯里的畴壁，则展现出了新的迷人的物理效应，比如说量子谷霍尔效应。科研工作者在三层石墨烯的相工程上投入了大量的精力。不过，操纵畴壁以实现对材料局部结构和特性的调控仍然是一个难题。本文通过实验表明，通过激光照射可以实现结构相之间的转换，并在三层石墨烯中构建各种形状的畴壁。这种能够控制畴壁位置和方向的能力，使得我们能够更好地调整石墨烯的局部结构相和特性，并为可定制原子结构，电子以及光学特性的人造二维材料的生成提供了一种简洁且有效的路径。
5. 华中科技大学 Peining Li等人
Collective near-field coupling and nonlocal phenomena in infrared-phononic metasurfaces for nano-light canalization. Nat.Commun..
Figure 2. Near-field imaging of polariton evolution in a hBN metasurface. a Schematic of the near-field nanoimaging experiment. b, c Near-field images measured at two different frequencies, ω = 1415 cm−1(HPhP region) and ω = 1510 cm−1(EPhP region). White arrows indicate the polariton fringes observed on the metasurface.
摘要：通过光子耦合激发和偶物质激发所产生的化子可以沿具有双曲线色散或椭圆色散的各向异性超表面传播。而在双曲线色散与椭圆色散之间的转换过程中（对应拓扑结构的转换），有各种有趣的现象被观测到，比如光子态密度的增强、化子的沟道效应和超透镜效应。在本文中，作者从理论角度和实验角度分别研究了这种拓扑结构的转换，单轴红外声子超表面中的化耦合和其强烈的非局域响应信号，以及六方氮化硼 (hBN) 纳米带的光栅。 通过超高分辨红外10纳米成像，研究者观察到了六方氮化硼中余辉带里合成的横向光学声子的共振（即纳米带强烈的集体性近场耦合），这触发了从双曲线色散向椭圆色散的拓扑转换。作者还表征并可视化了跃迁频率附近深亚波长通道模式的空间演化，该模式作为一种准直化子为超透镜和无衍射传播打下了基础。
6. 山西大学 PengjuYang 等人
Rational electronic control of carbon dioxide reduction over cobalt oxide. J. Cat..
Figure 2. (a) XPS Co 2p of Co3O4and Co3O4/Al-1(1 wt% Co3O4), (b) XPS Al 2p of Co3O4/Al-1 and Al-1, (c-d) the S-SNOM optical image of Co3O4/Al-1(1 wt% Co3O4) and SNOM amplitude S3 of lines A-E.
摘要：选择性地将二氧化碳(CO2)还原为燃料和化学品是通过碳中和发展可持续性能源经济的重点所在。而其中CO2的活化则是重中之重。考虑到电子迁移是这一过程的决速步骤，通过调节CO2还原催化剂的电子结构来增强其活性则显得更为关键。不过，人们对催化剂的电子特性与活性的内在关系的理解还不是很深入，这也限制了高效CO2还原催化剂的有理论支撑的设计。本文中，作者设计了一种以铝作为电子供体的催化剂-绝缘体-金属系统，并以此来调节氧化钴(Co3O4)催化剂的电子结构。这样，铝中的电子便可以高效地通过一种超薄且自主形成的Al2O3绝缘层穿入Co3O4。实验和理论结果毫无疑问确证了Co3O4的高电子密度有利于CO2的吸收和活化，并同时降低了COOH的生成能垒，尤其是CO*中间体的解吸能垒，这大大加速了CO2到CO的光还原反应的动力学进程。相比Co3O4，Co3O4/Al2O3-Al中的Co的周转频率要高出很多。其表观量子产率在420纳米处能高达3.8%，这一数字超越了绝大部分文献中对催化剂的记述。另外，Co3O4中电子密度的提高也有效地抑制了析氢竞相反应。同时对CO的筛选性也从Co3O4的57.9%提高到了Co3O4/Al2O3-Al的82.4%。值得注意的是，通过控制Al的含量和粒径我们还可以合理调节催化剂的催化效率。综上，该项研究建立了催化剂的电子结构与其对 CO2还原反应的催化活性之间的联系。并且，作者提出的这种Al2O3-Al结构，还有潜力成为其他非均相催化剂电子效应研究的全新平台。
7. 中山大学 Yan Shen等人
Pyramid-Shaped Single-Crystalline Nanostructure of Molybdenum with Excellent Mechanical, Electrical, and Optical Properties. ACS Appl. Mater. Interfaces.
Figure 6. Optical properties of the pyramid-shaped single-crystalline Mo nanostructures. (a, b) AFM topography and the corresponding optical near–field amplitude (third harmonics, at excitation of 633 nm) images of a typical individual, respectively; the insets are the structural models that help to understand this sample’s geometric features.
摘要：特定的几何形貌与改进过的晶体特性对微纳米尺度材料的开发来说是举足轻重的。不过，对于高熔点钼来说，想高质量地生成同时具有单晶特性和预设形貌的结构是很困难的。在本文中，作者通过一种热蒸发技术和与之对应的实验调控，生成了金字塔形的单晶结构钼。而之后细致的材料表征工作则表明其生长机理遵循的是一个包括MoO2分解、Mo 沉积、岛状单晶形成、层状成核和竞争性生长在内的连续性过程。此外，经测量还发现这种生成物有着非常的物理性能。比如通过机械性能的测量，发现纳米结构的钼展现出了远高于其块体材料的纳米压痕硬度、弹性模量和拉伸强度。而在电子特性的测量中，这种材料的单体结构则展现出了非常的电传输特性，其电导能达到约0.16 S。所制备的0.02平方厘米的膜材料展现出了大电流电子发射特性，其大电流达到了33.6毫安，其电流密度则达到了1.68安每平方厘米。同时，通过光学特性的测量，该团队发现这种结构展现了明显的电磁场定位和增强效应，这使其作为基底材料，非常适合应用于表面增强拉曼散射（SERS）。作者还进一步讨论了对应的结构与响应信号之间的关系。文章中提到的，包括微纳米尺度，每个晶粒中所蕴含的单晶特性，以及材料的金字塔尖形貌在内的，这些纳米结构钼的基础特性，都对其物理特性有着正面的影响。
8. 香港理工大学 Xin Hu等人
Infrared Nanoimaging of Surface Plasmons in Type-II Dirac Semimetal PtTe2 Nanoribbons. ACS Nano..
Figure 6. Near-field images and plasmonic properties of sub-10 nm PtTe2tapers. (a) Topography of the PtTe2taper (NT1) with a thickness of 10.4 nm. The inset is the height profile along the white dashed line. (b) Experimental near-field image of NT1 at the laser frequency of 2500 cm–1(λ0= 4 μm). (c) Simulated image of the near-field standing-wave pattern corresponding to (b). The standing-wave patterns in the PtTe2tapers are mimicked by Enf= E0+ r1exp(2iksp·x1) + r2exp(2iksp·x2), where x1and x2are the perpendicular distances from an arbitrary point in the taper to its two edges. The propagation constant ksp= (2.264 + 0.884i)k0, supposing the permittivity of the 10.4 nm PtTe2film is identical to the bulk permittivity, and E0= 1, r1= r2= 0.2. (d) Topography of NT2with a thickness of 5–7 nm. The inset is the height profile along the black dashed line. (e) Near-field optical image of NT2at the laser frequency of 1400 cm–1(λ0= 7.14 μm). (f) Near-field optical image of NT2at the laser frequency of 2500 cm–1. The domains in NT2have different layers (L) ranging from 10L (∼5 nm) to 13L (∼7 nm). All scale bars are 1 μm.
摘要：由二维过渡金属二硫属化物制成的拓扑狄拉克半金属(TMDCs)，因其电子传输特性，在电子和光电设备领域的应用得到了广泛的关注。作为具有强层间相互作用的范德华材料，这种半金属被期望可以用于支持尚未被实验证明的层相关等离子体化激元的存在。在本研究中，作者利用近场纳米成像展示了II型铂碲狄拉克半金属（PtTe2）纳米带和纳米薄片中的中红外等离子体波的延迟和衰减。从近场驻波图像中总结出的PtTe2纳米带（厚度为15到25纳米）的等离子体模式衰减色散关系被应用于MIR区的PtTe2介电常数拟合，其结果表明自由载流子和狄拉克费米子都参与了中红外光和物质的相互作用。而对超薄（小于10纳米）PtTe2等离子体模式的湮灭的观察和分析使作者发现是PtTe2与本征层相关的光电特性导致了其无近场共振图像的现象。以上结果为应用TMDC进行MIR区的光电探测和调制铺展了道路。
9. 上海微系统所&长春光机所 Weiliang Ma等人
Broad spectral tuning of ultra-low-loss polaritons in a van der Waals crystal by intercalation. Nat. Mater..
Figure 2. a–c, Near-field amplitude images s3of an α-V2O5flake with thickness d = 105 nm at incident frequencies ω0= 1,031 (a), 1,026 (b) and 1,020 cm−1(c). Scale bar in c, 2 μm. d–f, Profiles along the [100] (green lines) and [001] (blue lines) directions, extracted from the near-field amplitude images in a–c, respectively. λp[100] and λp[001] are the polariton wavelengths along the [100] and [001] directions, respectively. g, Dispersion of PhPs along the [100] (green symbols) and [001] (blue symbols) directions in the RB1. Grey lines are guides for the eye. Grey shaded areas indicate the spectral regions outside the RB. a.u., arbitrary units.
Figure 3. a, Illustration of the α-V2O5lattice structure (orthorhombic) where the red spheres represent oxygen atoms, the blue atoms represent vanadium atoms, and the blue pyramids show the polyhedral structure defined by the oxygen atoms. The crystal structure consists of bilayers of distorted VO5pyramids stacked along the [010] direction via vdW interactions (interlayer distance c = 0.44 nm). b, nanoFTIR spectral line scans along the [100] and [001] directions of a α-V2O5flake showing s3/s3, Au (near-field amplitude s3normalized on Au, s3,Au) as a function of distance between the tip and the flake edge. Solid horizontal lines mark the approximate transversal optic (TO) phonon modes in α-V2O5(TO1, 975 cm−1; TO2, 770 cm−1), separating RB1–3. Dashed lines are guides for the eye of signal maxima. The flake thickness is d = 245 nm. c, Illustration of the α’-(Na)V2O5lattice structure (orthorhombic) where the red spheres represent oxygen atoms, the blue atoms represent vanadium atoms, the yellow atoms represent sodium atoms and the blue pyramids show the polyhedral structure defined by the oxygen atoms. The crystal structure consists of bilayers of distorted VO5pyramids with sodium atoms intercalated and stacked along the [010] direction via vdW interactions (interlayer distance c = 0.48 nm). d, nanoFTIR spectral line scans along the [100] and [001] directions of a α’-(Na)V2O5flake showing s3/s3, Au (near-field amplitude s3normalized on Au, s3,Au) as a function of distance between the tip and the flake edge. The solid horizontal line approximately mark the transversal optic phonon mode in α’-(Na)V2O5(TO, 950 cm−1), defining RB’1. The flake thickness is d = 150 nm. The scales in the colour bars of b and d are linear.
摘要：性范德华晶体中的声子化子——一种光与晶格振动的耦合——是有在纳米尺度上控制能量流动的有力候选者，因为它们有着很强的限制场、各向异性的传播方式和皮秒的超长寿命。不过，它们狭窄且只适用特定材料的光谱响应范围——也就是剩余射线带——大地限制了其技术应用。在此，在α-V2O5范德华半导体中嵌入钠原子，能增宽其剩余射线带，并因此让受激声子化子展现出低的损耗率（寿命为4± 1皮秒），这个数值已经与其在非插层晶体（寿命为6± 1皮秒）中的表现相近。作者预计这种嵌入方法也能被应用于其他范德华晶体，从而提供一种新的利用声子化子增宽中红外区域频谱的方法。
10. 中国科学技术大学 Xinzhong Chen
Moiré engineering of electronic phenomena in correlated oxides. Nat. Phys..
Figure 3. a,b, Infrared near-field image of a curved moiré pattern (a) and the corresponding simulation (b). The simulation is generated by multiplying two periodic striped patterns representing MSs and DSs. The white and black dashed lines in b indicate the MS and DS orientations, respectively. c, Line profiles from the blue dashed lines in a and b, exhibiting high consistency between the experimental and the simulated contrast. a.u., arbitrary units. d,e, Infrared near-field image and corresponding AFM image, respectively, showing alternating moiré and non-moiré regions across the LAO twin boundaries (indicated by red dashed lines). The white solid line in e is the AFM height profile. f, Line profile of the nano-infrared contrast along the blue dashed line in d. The different signal levels are marked ‘C’, ‘D’ and ‘M’, which represent constructively strained, destructively strained and mixed strained regions, respectively. g, Simulation of the image in d with the moiré pattern only visible on the right-hand side. Note that the MSs (orientation indicated by white dashed lines) change orientation across the LAO twin boundary (red dashed line), while the DSs (orientation indicated by black dashed lines) are consistently along the LAO [100] direction. The simulation details are shown in Extended Data Fig. 8c.
摘要：近段时间，摩尔纹工程被视为控制凝聚态系统中量子现象的有效途径。在范德华异质结构中，莫尔纹可以通过相邻原子层之间的晶格错位形成，并因此产生长程电子有序的结构。到目前为止，摩尔工程只在堆叠范德华多层结构上有所应用。而在本文中，作者描述了一种在LaAlO3基底上外延生长的原型性磁阻氧化物薄膜La0.67Sr0.33MnO3中产生的电子摩尔纹。通过扫描探针纳米成像，作者观察到了薄膜中应变调制的两种不同的非公度纹的共存和互相影响所产生的微观摩尔纹。其净效应表现为La0.67Sr0.33MnO3的电子电导率和铁磁性直到细观尺度都会受周期性摩尔纹的调制。我该研究工作为在应力外延材料中获得定制的电子纹理的空间图样开辟了一条潜在的道路。
11. 纳米中心 Xiangdong Guo
Efficient All-Optical Plasmonic Modulators with Atomically Thin Van Der Waals Heterostructures. Adv. Mater..
Figure 2. The all-optical graphene plasmon waveguide modulation with a thickness of only several atomic layers. a) Schematic diagram of band alignment and the physical mechanism of photocarrier transfer in the hole-doped graphene/MoS2heterostructure under visible light irradiation. b,c) Near-field images of a graphene/MoS2heterostructure on SiO2substrate in the b) absence and c) presence of 633 nm laser irradiation (6 mW cm−2). Dashed lines indicate the graphene edge. d) The plasmon signals extracted from the cut-lines (red and blue lines) in (b) and (c), respectively.
摘要：全光调制器正越来越受瞩目，这主要是因为它高速度，低损耗，与高带宽的本征特性，使其在未来的信息通讯技术中可以很好地为对应的电气元件做更新换代。但是，其较大的能量消耗与尺寸使得其光子间相互作用较弱，从而阻碍了其在非线性光学上的广泛应用。在本文中，作者通过在石墨烯中掺杂含有光生载流子的单层MoS2生成了原子薄度石墨烯-MoS2异质结构，形成了一种高效全光中红外等离子体波导和自由空间调制器。44 cm-1等离子的调制也通过LED得以呈现，其光强度可以低达0.15 mWcm-1,这一数值比通用的石墨烯非线性全光调制器要低4个数量（≈103 mWcm-2）。异质结构中光生载流子的超高速迁移以及复合的速率使得石墨烯等离子体的超高速调制成为了可能。作者认为，基于范德华异质结构的带有芯片可集成性和深亚波长光场限制性的高效全光中红外等离子体调制器的开发或许向片上全光器件应用的实现迈出了重要的一步。
12. 华中科技大学 Peining Li等人
Nanoscale Guiding of Infrared Light with Hyperbolic Volume and Surface Polaritons in van der Waals Material Ribbons. Adv. Mater..
Figure 4. Thickness dependence of h-BN waveguide modes. a) Schematics of the experiment. b) Near-field amplitude images s3of h-BN waveguides of same nominal width w = 1 µm and different thicknesses d at ω = 1430 cm−1. c) Wavevector of the waveguide modes as a function of thickness. Symbols indicate experimental wavevectors measured at the edge (triangles) and at the center (circles) of the waveguide. The solid and dashed lines show wavevectors obtained with the full-wave simulations. The dotted red line is a guide to the eye. The inset shows line profiles from 16 nm thick waveguide at edge (gray) and center (blue) as indicated by arrows in (b). d) Schematic comparison of dielectric and hyperbolic volume waveguide modes near cutoff, when the thickness of the waveguide is decreased.
摘要：范德华（vdW）材料因其所含有的各种化子，成为了新兴的纳米尺度光操纵用材料平台。凭借范德华材料的层状结构，这些化子在薄片当中呈双曲线色散和纳米体制御模式。另一方面，它们在薄片边缘则呈面制御模式。然而令人意想不到的是，这些模式在以典型的线性波导结构为代表的带状材料上的导向正全方位地亟待研究。作者就六方氮化硼带中双曲声子化子的传播方式的研究成果做了详细的报告。通过纳米红外成像，作者观测到了各种模式。尤其是展现出截止宽度的重要的体波导模式。并且有趣的是该截止宽度可以通过降低波导厚度来减小。除此之外，该团队还观察到了具有不同频率和波导宽度的面模式杂化以及演化。而重点是，作者发现对称杂化面模式并没有展现出任何截止宽度，这让任意窄带里的化子都呈线性波导。另外，研究者的实验数据也支持了相关的模拟结果，这为我们在未来的光子器件应用中担当重任的线性波导双曲化子的理解打下了坚实的基础。
13. 清华大学 Shuai Wu等
Super-Slippery Degraded Black Phosphorus/ Silicon Dioxide Interface. ACS Appl. Mater. Interfaces.
Figure 3. Chemical structure of the BP/SiO2interface. (a) AFM amplitude image and (b) phase image (scale bars: 2 μm) after the motion of the degraded BP flake on the SiO2substrate. (c) Normalized nano-FTIR phase (φ) spectroscopy plots of the degraded BP surface, residuals on the substrate, and fresh BP flake (exfoliated within 30 min) in the region of 900–1100 cm–1. (d) {1H-31P}1H double CP spectra of the BP/SiO2sample; the first contact time (tCP1) was set to 5 ms, and the variable second contact time (tCP2) is indicated on each spectrum.
摘要：二维（2D）材料与二氧化硅（SiO2）/硅（Si）基底之间的界面，通常被看做是固固机械接触。这在微系统和纳米工程的结构设计与性能优化时，常常会被特别强调。不过，如何理解基于2D材料的系统的界面结构与动力学仍然是一个悬而未决又无法绕过的问题。在本研究中，由于在常态降解时引入了羟基，一层在界面内可流动的水被插入了降解黑鳞（BP）薄片与SiO2/Si基底之间。因此，作者得到了一个滑度高的降解BP/SiO2界面。通过实验测定，其界面剪切应力（ISS）可低达0.029 ± 0.004 MPa，这一数值已可与非公度刚性晶体接触比肩。通过分析核磁共振波谱仪和原位X射线光电子能谱仪进行的结果，该团队发现界面内的液态水的存在是剪切应力低的超高滑度BP/SiO2界面的形成主因。这一发现证明了降解BP和水分子之间存在着强烈的互相影响，并表明纳米BP膜在生物基润滑领域有着广泛的应用潜力。
14. 北京理工大学 Tao Yan等人
Facile preparation and synergetic energy releasing of nano-Al@RDX@Viton hollow microspheres. Chem. Eng. J..
Figure 4. Topography (a) and near-field amplitude image of the microsphere at frequency ω = 923 cm−1(b), 1131 cm−1(c) and 1168 cm−1(d). Line profiles of infrared signal extracted at the position indicated by the red dashed line (e).
摘要：为了提高含能材料的反应速率，电喷雾技术被应用于双溶剂法集成纳米铝（nAl）和氟橡胶（Viton）的重结晶环三亚甲基三硝胺 (RDX)微球的开发。其形貌特征与化学异质性的测试结果表明电喷雾生成的微球是空心的，并有RDX均匀地分布在其中。而且RDX的纳米晶体是紧密地附着在nAl@Viton骨架的两侧的，这增大了不同组分之间的接触面积。另一方面，对微球的热分析则表明，通过减小微球分解的表观活化能，nAl颗粒能够加速能量的释放。实验结果表明电喷雾nAl@RDX@Viton，因其各组分的特征结构和协同作用，比物理混合物具有更短的激光点火延迟和更剧烈的燃烧火焰。
15. 上海光机所 Lulu Chen等人
Near-field imaging of the multi-resonant mode induced broadband tunable metamaterial Absorber. RSC Adv..
Figure 5. (a) Experimental absorptivity of the GST absorber between two states. The black line and red line are for the a-GST and c-GST sample. (b) The simulated spectra for the total and each layer of the c-GST absorber. Inset: the magnetic field distribution at the resonance wavelength. (c–f) Experimental and simulated near-field amplitude |Ez| and phase φzimages mapped at the spectral positions C and C1.
摘要：具有可调性的超材料吸收器在中红外吸收的应用领域具有广阔的前景。虽然研究者们提出了各种控制吸收的方法，如何深入分析和呈现吸收机制的物理图像仍是值得期待且有意义的。在本文中，作者利用近场光学显微镜展示了多谐振模式诱导下的带宽可调超材料吸收器的实验空间近场分布。该吸收器由双倍尺寸的单元结构与金属镜片构成，二者由Ge2Sb2Te5(GST)薄垫片加以分割。为了获得清晰的物理图像，作者利用由四个方形谐振器组成的混合单元结构，在 7.8 μm 和 8.3 μm 处产生两个吸收峰。当GST薄膜从非晶态转变为晶态时，共振的中心波长呈现红移趋势。而无论GST处于那种相态，我们都分别在其吸收频率下观察到了吸收器产生的近场振幅和相位的光学信号。综上，本研究为光学可调吸收的控制打下了科学理论的基础，并展现了其潜在的应用前景。
16. 中国科学技术大学 Wenhao Zhang and Yuhang Chen
Visibility of subsurface nanostructures in scattering-type scanning near-field optical microscopy imaging. Opt. Expr..
Figure 1. (a) Schematic illustration of the experimental s-SNOM setup for investigating the visibility of buried structures in a multilayered architecture. The underneath structures are patterned on a metal film and they are covered with a thin polymer layer. A pseudoheterodyne detection method is employed to obtain background-free near-field optical signal. (b) Schematic illustration of the dipole model for a simple theoretical analysis.
Figure 7. Subsurface nano-imaging by s-SNOM. The sample is a patterned silicon substrate covered by the glue from a double-side tape. (a) Topography. (b) The third harmonic s-SNOM amplitude. The inset is a zoomed view of the area sketched by the dashed rectangle. (c) Sectional profiles of the topography and amplitude images. The two profiles are taken from the same position as guided by the dashed line in topography.
摘要：以纳米分辨率探测被膜材料覆盖的结构有着很高的重要性。在本研究中，作者用散射型扫描近场光学显微镜（s-SNOM）探索了影响面下材料对比度和结构可见度的因素。作者生成了一种包含不同掩埋结构的多层结构参考样品，用来做s-SNOM成像。还研究了近场光学对比度对结构几何形状、尺寸和覆盖层厚度的影响。结果表明区分掩埋狭缝图样比具有相同临界尺寸的圆孔更容易。s-SNOM能够在100多纳米厚的聚甲基丙烯酸甲酯层下感知材料之间的差异，其面下空间分辨率可以好过100纳米。
17. 华中科技大学 Dong Wei等人
Optical modulator based on the coupling effect of different surface plasmon modes excited on the metasurface. Opt. Mater. Expr..
Figure 6. SEM, AFM and near-field lightwave intensity distribution of the NRANC metasurface. (a) SEM images of a metasurface sample, (b) near-field lightwave intensity distribution on the sample, (c) near-field lightwave intensity distribution along red dashed line. The white dashed lines are the outlines of the nano-apertures. The red dotted line is the trendline of the electric intensity distribution curve. (d) AFM image of the metasurface sample.
摘要：作者设计并生成了一种由带中央纳米柱的纳米脊孔阵列(NRANC)构成的超表面光学调制器。研究者还细致地研究了，分布在纳米脊孔的每个纳米顶点和中央纳米圆柱外缘上的局域表面等离子体（LSPs），与在周期性超表面上生成的表面等离子体激元(SPPs)，这二者之间的耦合效应。这种锥形结构可用于入射能量的集中与局部光场的增强。而在其上的感应电偶子则可以调节反射或透射特性。这种在NRANC 上形成的LSPs的耦合效应将增强表面感应电偶子，并进一步调节NRANC的光学特性。通过改变超表面的几何参数，可以调整LSPs模式的谐振频率，并观察到透射峰的平移，以及让增强因数达到1.4×103。另一方面，LSPs和SPPs之间的耦合则会激发法诺共振。在可见光和红外范围内调整照射激光的入射角则能调节SPPs的激发，并因此引起相对较大的透射光谱变化。于是通过进行近场光学测量，可以观察到包括表面感应电荷信息在内的近场光学特性，以及在45°入射的633纳米TM激光照射下的一个小（x方向上，约96纳米）且亮的热点。综上，作者研究中构建的NRANC超表面突出了其在类似彩色滤光片、反射镜、表面增强拉曼等方面的潜在应用前景。
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