1. 中國科學(xué)院 重慶綠色智能技術(shù)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：太赫茲生物成像因其能以無標記、無創(chuàng)傷和非電離的方式獲取樣品的物理化學(xué)信息而頗受矚目。但是，低介電常數(shù)生物分子的反射率問題，使得單分子精度的太赫茲成像仍是一個挑戰(zhàn)。針對于此，作者開發(fā)了一種方法，利用石墨烯介導(dǎo)的太赫茲頻率散射型掃描近場光學(xué)顯微鏡，對單個蛋白分子直接成像。此項研究發(fā)現(xiàn)，擁有較高太赫茲反射率和原子平整度的石墨烯基底可以為蛋白分子提供較高的太赫茲對比度。另外，我們還發(fā)現(xiàn)對鉑探針的軸長優(yōu)化能增強太赫茲散射近場信號中的振幅信號強度?；谶@兩個效應(yīng)，作者同時獲得了尺寸只有數(shù)納米的免疫球蛋白G（IgG）和鐵蛋白分子的形貌以及太赫茲散射圖像。本文中所用的方法為單生物分子的太赫茲成像提供了新思路。
2. 華中科技大學(xué) 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?qū)倩锵嘧儾牧希≒CMs）在太赫茲（THz）頻率下會發(fā)生光學(xué)聲子共振現(xiàn)象，這個效應(yīng)可被用于研究相變的基本特性，并產(chǎn)生很強的介電對比度，使其可被用于太赫茲的光子學(xué)應(yīng)用。在本文中，我們證明可以通過頻率可調(diào)的太赫茲散射型掃描近場光學(xué)顯微鏡（s-SNOM）研究PCM的聲子。其具體方法為對包含非晶相和結(jié)晶相的PCM樣品進行太赫茲納米光譜成像。我們觀察到材料的聲子特征使其產(chǎn)生了很強的s-SNOM信號，以及重要的是，非晶態(tài)和結(jié)晶態(tài)PCM的光譜之間存在明顯的差異，這使我們可以在納米尺度上高信度地區(qū)分PCM的不同相。我們還發(fā)現(xiàn)可以通過增加針尖的半徑來增強以信號強度和頻譜對比度為標志的光譜特征。綜上所述，我們用太赫茲s-SNOM成功構(gòu)建了基于局部聲子光譜的納米結(jié)構(gòu)以及化學(xué)組成的圖譜。
3. 中國地質(zhì)大學(xué)-武漢 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：高度受限和低損耗的化子在石墨烯和六方氮化硼上是沿平面各向同性傳播的，這使得對光的控制被限制在了有限的自由度內(nèi)。而以α-MoO3and V2O5為代表的新興雙軸范德華材料則展現(xiàn)出了特的化傳播特性，它們的輔助光軸是在平面上的。利用這種強平面各向異性，作者通過空間納米成像觀測到了α-MoO3納米腔的圖樣內(nèi)有著受邊界導(dǎo)向的雙曲化子。并且發(fā)現(xiàn)邊界的夾角和結(jié)晶方向?qū)ζ涔鈱W(xué)響應(yīng)信號有著舉足輕重的影響，這對調(diào)整化圖樣的參數(shù)是至關(guān)重要的?；诖?，通過調(diào)整α-MoO3納米腔的幾何構(gòu)型，我們觀測到了雙曲化子會延邊界傳播并且會調(diào)整自身傳播方向的特性以及與之對應(yīng)的化子繞行禁區(qū)。而這種雙曲化子的壽命和性能指數(shù)則受到納米腔邊界寬高比的限制。
4. 國防科學(xué)技術(shù)大學(xué) 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：晶體結(jié)構(gòu)對相關(guān)材料的物理性質(zhì)有著深刻的影響。因此，即使化學(xué)組成相同（比如石墨烯和金剛石），我們也可以通過生成具有特定對稱性的晶體，來很大范圍內(nèi)調(diào)整它們的特性。而當(dāng)晶體的結(jié)構(gòu)相可以通過外部刺激動態(tài)改變時，更多有意思的可能性出現(xiàn)在了我們面前。這樣的材料特性雖不常見，但卻能引發(fā)很多喜人的現(xiàn)象，例如相變記憶效應(yīng)。具體到三層石墨烯，它有兩種常見的堆疊結(jié)構(gòu)（ABA和ABC），二者都具有特的電子能帶結(jié)構(gòu)，并展現(xiàn)出了與眾不同的特性。而這兩種堆疊結(jié)構(gòu)的三層石墨烯里的疇壁，則展現(xiàn)出了新的迷人的物理效應(yīng)，比如說量子谷霍爾效應(yīng)。科研工作者在三層石墨烯的相工程上投入了大量的精力。不過，操縱疇壁以實現(xiàn)對材料局部結(jié)構(gòu)和特性的調(diào)控仍然是一個難題。本文通過實驗表明，通過激光照射可以實現(xiàn)結(jié)構(gòu)相之間的轉(zhuǎn)換，并在三層石墨烯中構(gòu)建各種形狀的疇壁。這種能夠控制疇壁位置和方向的能力，使得我們能夠更好地調(diào)整石墨烯的局部結(jié)構(gòu)相和特性，并為可定制原子結(jié)構(gòu)，電子以及光學(xué)特性的人造二維材料的生成提供了一種簡潔且有效的路徑。
5. 華中科技大學(xué) 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：通過光子耦合激發(fā)和偶物質(zhì)激發(fā)所產(chǎn)生的化子可以沿具有雙曲線色散或橢圓色散的各向異性超表面?zhèn)鞑?。而在雙曲線色散與橢圓色散之間的轉(zhuǎn)換過程中（對應(yīng)拓撲結(jié)構(gòu)的轉(zhuǎn)換），有各種有趣的現(xiàn)象被觀測到，比如光子態(tài)密度的增強、化子的溝道效應(yīng)和超透鏡效應(yīng)。在本文中，作者從理論角度和實驗角度分別研究了這種拓撲結(jié)構(gòu)的轉(zhuǎn)換，單軸紅外聲子超表面中的化耦合和其強烈的非局域響應(yīng)信號，以及六方氮化硼 (hBN) 納米帶的光柵。 通過超高分辨紅外10納米成像，研究者觀察到了六方氮化硼中余輝帶里合成的橫向光學(xué)聲子的共振（即納米帶強烈的集體性近場耦合），這觸發(fā)了從雙曲線色散向橢圓色散的拓撲轉(zhuǎn)換。作者還表征并可視化了躍遷頻率附近深亞波長通道模式的空間演化，該模式作為一種準直化子為超透鏡和無衍射傳播打下了基礎(chǔ)。
6. 山西大學(xué) 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：選擇性地將二氧化碳(CO2)還原為燃料和化學(xué)品是通過碳中和發(fā)展可持續(xù)性能源經(jīng)濟的重點所在。而其中CO2的活化則是重中之重。考慮到電子遷移是這一過程的決速步驟，通過調(diào)節(jié)CO2還原催化劑的電子結(jié)構(gòu)來增強其活性則顯得更為關(guān)鍵。不過，人們對催化劑的電子特性與活性的內(nèi)在關(guān)系的理解還不是很深入，這也限制了高效CO2還原催化劑的有理論支撐的設(shè)計。本文中，作者設(shè)計了一種以鋁作為電子供體的催化劑-絕緣體-金屬系統(tǒng)，并以此來調(diào)節(jié)氧化鈷(Co3O4)催化劑的電子結(jié)構(gòu)。這樣，鋁中的電子便可以高效地通過一種超薄且自主形成的Al2O3絕緣層穿入Co3O4。實驗和理論結(jié)果毫無疑問確證了Co3O4的高電子密度有利于CO2的吸收和活化，并同時降低了COOH的生成能壘，尤其是CO*中間體的解吸能壘，這大大加速了CO2到CO的光還原反應(yīng)的動力學(xué)進程。相比Co3O4，Co3O4/Al2O3-Al中的Co的周轉(zhuǎn)頻率要高出很多。其表觀量子產(chǎn)率在420納米處能高達3.8%，這一數(shù)字超越了絕大部分文獻中對催化劑的記述。另外，Co3O4中電子密度的提高也有效地抑制了析氫競相反應(yīng)。同時對CO的篩選性也從Co3O4的57.9%提高到了Co3O4/Al2O3-Al的82.4%。值得注意的是，通過控制Al的含量和粒徑我們還可以合理調(diào)節(jié)催化劑的催化效率。綜上，該項研究建立了催化劑的電子結(jié)構(gòu)與其對 CO2還原反應(yīng)的催化活性之間的聯(lián)系。并且，作者提出的這種Al2O3-Al結(jié)構(gòu)，還有潛力成為其他非均相催化劑電子效應(yīng)研究的全新平臺。
7. 中山大學(xué) 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：特定的幾何形貌與改進過的晶體特性對微納米尺度材料的開發(fā)來說是舉足輕重的。不過，對于高熔點鉬來說，想高質(zhì)量地生成同時具有單晶特性和預(yù)設(shè)形貌的結(jié)構(gòu)是很困難的。在本文中，作者通過一種熱蒸發(fā)技術(shù)和與之對應(yīng)的實驗調(diào)控，生成了金字塔形的單晶結(jié)構(gòu)鉬。而之后細致的材料表征工作則表明其生長機理遵循的是一個包括MoO2分解、Mo 沉積、島狀單晶形成、層狀成核和競爭性生長在內(nèi)的連續(xù)性過程。此外，經(jīng)測量還發(fā)現(xiàn)這種生成物有著非常的物理性能。比如通過機械性能的測量，發(fā)現(xiàn)納米結(jié)構(gòu)的鉬展現(xiàn)出了遠高于其塊體材料的納米壓痕硬度、彈性模量和拉伸強度。而在電子特性的測量中，這種材料的單體結(jié)構(gòu)則展現(xiàn)出了非常的電傳輸特性，其電導(dǎo)能達到約0.16 S。所制備的0.02平方厘米的膜材料展現(xiàn)出了大電流電子發(fā)射特性，其大電流達到了33.6毫安，其電流密度則達到了1.68安每平方厘米。同時，通過光學(xué)特性的測量，該團隊發(fā)現(xiàn)這種結(jié)構(gòu)展現(xiàn)了明顯的電磁場定位和增強效應(yīng)，這使其作為基底材料，非常適合應(yīng)用于表面增強拉曼散射（SERS）。作者還進一步討論了對應(yīng)的結(jié)構(gòu)與響應(yīng)信號之間的關(guān)系。文章中提到的，包括微納米尺度，每個晶粒中所蘊含的單晶特性，以及材料的金字塔尖形貌在內(nèi)的，這些納米結(jié)構(gòu)鉬的基礎(chǔ)特性，都對其物理特性有著正面的影響。
8. 香港理工大學(xué) 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：由二維過渡金屬二硫?qū)倩镏瞥傻耐負涞依税虢饘?TMDCs)，因其電子傳輸特性，在電子和光電設(shè)備領(lǐng)域的應(yīng)用得到了廣泛的關(guān)注。作為具有強層間相互作用的范德華材料，這種半金屬被期望可以用于支持尚未被實驗證明的層相關(guān)等離子體化激元的存在。在本研究中，作者利用近場納米成像展示了II型鉑碲狄拉克半金屬（PtTe-2）納米帶和納米薄片中的中紅外等離子體波的延遲和衰減。從近場駐波圖像中總結(jié)出的PtTe-2納米帶（厚度為15到25納米）的等離子體模式衰減色散關(guān)系被應(yīng)用于MIR區(qū)的PtTe-2介電常數(shù)擬合，其結(jié)果表明自由載流子和狄拉克費米子都參與了中紅外光和物質(zhì)的相互作用。而對超?。ㄐ∮?0納米）PtTe-2等離子體模式的湮滅的觀察和分析使作者發(fā)現(xiàn)是PtTe-2與本征層相關(guān)的光電特性導(dǎo)致了其無近場共振圖像的現(xiàn)象。以上結(jié)果為應(yīng)用TMDC進行MIR區(qū)的光電探測和調(diào)制鋪展了道路。
9. 上海微系統(tǒng)所&長春光機所 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：性范德華晶體中的聲子化子——一種光與晶格振動的耦合——是有在納米尺度上控制能量流動的有力候選者，因為它們有著很強的限制場、各向異性的傳播方式和皮秒的超長壽命。不過，它們狹窄且只適用特定材料的光譜響應(yīng)范圍——也就是剩余射線帶——大地限制了其技術(shù)應(yīng)用。在此，在α-V2O5范德華半導(dǎo)體中嵌入鈉原子，能增寬其剩余射線帶，并因此讓受激聲子化子展現(xiàn)出低的損耗率（壽命為4±?1皮秒），這個數(shù)值已經(jīng)與其在非插層晶體（壽命為6±?1皮秒）中的表現(xiàn)相近。作者預(yù)計這種嵌入方法也能被應(yīng)用于其他范德華晶體，從而提供一種新的利用聲子化子增寬中紅外區(qū)域頻譜的方法。
10. 中國科學(xué)技術(shù)大學(xué) 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：近段時間，摩爾紋工程被視為控制凝聚態(tài)系統(tǒng)中量子現(xiàn)象的有效途徑。在范德華異質(zhì)結(jié)構(gòu)中，莫爾紋可以通過相鄰原子層之間的晶格錯位形成，并因此產(chǎn)生長程電子有序的結(jié)構(gòu)。到目前為止，摩爾工程只在堆疊范德華多層結(jié)構(gòu)上有所應(yīng)用。而在本文中，作者描述了一種在LaAlO3基底上外延生長的原型性磁阻氧化物薄膜La0.67Sr0.33MnO3中產(chǎn)生的電子摩爾紋。通過掃描探針納米成像，作者觀察到了薄膜中應(yīng)變調(diào)制的兩種不同的非公度紋的共存和互相影響所產(chǎn)生的微觀摩爾紋。其凈效應(yīng)表現(xiàn)為La0.67Sr0.33MnO3的電子電導(dǎo)率和鐵磁性直到細觀尺度都會受周期性摩爾紋的調(diào)制。我該研究工作為在應(yīng)力外延材料中獲得定制的電子紋理的空間圖樣開辟了一條潛在的道路。
11. 納米中心 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：全光調(diào)制器正越來越受矚目，這主要是因為它高速度，低損耗，與高帶寬的本征特性，使其在未來的信息通訊技術(shù)中可以很好地為對應(yīng)的電氣元件做更新?lián)Q代。但是，其較大的能量消耗與尺寸使得其光子間相互作用較弱，從而阻礙了其在非線性光學(xué)上的廣泛應(yīng)用。在本文中，作者通過在石墨烯中摻雜含有光生載流子的單層MoS2生成了原子薄度石墨烯-MoS2異質(zhì)結(jié)構(gòu)，形成了一種高效全光中紅外等離子體波導(dǎo)和自由空間調(diào)制器。44 cm-1等離子的調(diào)制也通過LED得以呈現(xiàn)，其光強度可以低達0.15 mWcm-1,這一數(shù)值比通用的石墨烯非線性全光調(diào)制器要低4個數(shù)量（≈103 mWcm-2）。異質(zhì)結(jié)構(gòu)中光生載流子的超高速遷移以及復(fù)合的速率使得石墨烯等離子體的超高速調(diào)制成為了可能。作者認為，基于范德華異質(zhì)結(jié)構(gòu)的帶有芯片可集成性和深亞波長光場限制性的高效全光中紅外等離子體調(diào)制器的開發(fā)或許向片上全光器件應(yīng)用的實現(xiàn)邁出了重要的一步。
12. 華中科技大學(xué) 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：范德華（vdW）材料因其所含有的各種化子，成為了新興的納米尺度光操縱用材料平臺。憑借范德華材料的層狀結(jié)構(gòu)，這些化子在薄片當(dāng)中呈雙曲線色散和納米體制御模式。另一方面，它們在薄片邊緣則呈面制御模式。然而令人意想不到的是，這些模式在以典型的線性波導(dǎo)結(jié)構(gòu)為代表的帶狀材料上的導(dǎo)向正全方位地亟待研究。作者就六方氮化硼帶中雙曲聲子化子的傳播方式的研究成果做了詳細的報告。通過納米紅外成像，作者觀測到了各種模式。尤其是展現(xiàn)出截止寬度的重要的體波導(dǎo)模式。并且有趣的是該截止寬度可以通過降低波導(dǎo)厚度來減小。除此之外，該團隊還觀察到了具有不同頻率和波導(dǎo)寬度的面模式雜化以及演化。而重點是，作者發(fā)現(xiàn)對稱雜化面模式并沒有展現(xiàn)出任何截止寬度，這讓任意窄帶里的化子都呈線性波導(dǎo)。另外，研究者的實驗數(shù)據(jù)也支持了相關(guān)的模擬結(jié)果，這為我們在未來的光子器件應(yīng)用中擔(dān)當(dāng)重任的線性波導(dǎo)雙曲化子的理解打下了堅實的基礎(chǔ)。
13. 清華大學(xué) 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：二維（2D）材料與二氧化硅（SiO2）/硅（Si）基底之間的界面，通常被看做是固固機械接觸。這在微系統(tǒng)和納米工程的結(jié)構(gòu)設(shè)計與性能優(yōu)化時，常常會被特別強調(diào)。不過，如何理解基于2D材料的系統(tǒng)的界面結(jié)構(gòu)與動力學(xué)仍然是一個懸而未決又無法繞過的問題。在本研究中，由于在常態(tài)降解時引入了羥基，一層在界面內(nèi)可流動的水被插入了降解黑鱗（BP）薄片與SiO2/Si基底之間。因此，作者得到了一個滑度高的降解BP/SiO2界面。通過實驗測定，其界面剪切應(yīng)力（ISS）可低達0.029 ± 0.004 MPa，這一數(shù)值已可與非公度剛性晶體接觸比肩。通過分析核磁共振波譜儀和原位X射線光電子能譜儀進行的結(jié)果，該團隊發(fā)現(xiàn)界面內(nèi)的液態(tài)水的存在是剪切應(yīng)力低的超高滑度BP/SiO2界面的形成主因。這一發(fā)現(xiàn)證明了降解BP和水分子之間存在著強烈的互相影響，并表明納米BP膜在生物基潤滑領(lǐng)域有著廣泛的應(yīng)用潛力。
14. 北京理工大學(xué) 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：為了提高含能材料的反應(yīng)速率，電噴霧技術(shù)被應(yīng)用于雙溶劑法集成納米鋁（nAl）和氟橡膠（Viton）的重結(jié)晶環(huán)三亞甲基三硝胺 (RDX)微球的開發(fā)。其形貌特征與化學(xué)異質(zhì)性的測試結(jié)果表明電噴霧生成的微球是空心的，并有RDX均勻地分布在其中。而且RDX的納米晶體是緊密地附著在nAl@Viton骨架的兩側(cè)的，這增大了不同組分之間的接觸面積。另一方面，對微球的熱分析則表明，通過減小微球分解的表觀活化能，nAl顆粒能夠加速能量的釋放。實驗結(jié)果表明電噴霧nAl@RDX@Viton，因其各組分的特征結(jié)構(gòu)和協(xié)同作用，比物理混合物具有更短的激光點火延遲和更劇烈的燃燒火焰。
15. 上海光機所 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：具有可調(diào)性的超材料吸收器在中紅外吸收的應(yīng)用領(lǐng)域具有廣闊的前景。雖然研究者們提出了各種控制吸收的方法，如何深入分析和呈現(xiàn)吸收機制的物理圖像仍是值得期待且有意義的。在本文中，作者利用近場光學(xué)顯微鏡展示了多諧振模式誘導(dǎo)下的帶寬可調(diào)超材料吸收器的實驗空間近場分布。該吸收器由雙倍尺寸的單元結(jié)構(gòu)與金屬鏡片構(gòu)成，二者由Ge2Sb2Te5(GST)薄墊片加以分割。為了獲得清晰的物理圖像，作者利用由四個方形諧振器組成的混合單元結(jié)構(gòu)，在 7.8 μm 和 8.3 μm 處產(chǎn)生兩個吸收峰。當(dāng)GST薄膜從非晶態(tài)轉(zhuǎn)變?yōu)榫B(tài)時，共振的中心波長呈現(xiàn)紅移趨勢。而無論GST處于那種相態(tài)，我們都分別在其吸收頻率下觀察到了吸收器產(chǎn)生的近場振幅和相位的光學(xué)信號。綜上，本研究為光學(xué)可調(diào)吸收的控制打下了科學(xué)理論的基礎(chǔ)，并展現(xiàn)了其潛在的應(yīng)用前景。
16. 中國科學(xué)技術(shù)大學(xué) 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：以納米分辨率探測被膜材料覆蓋的結(jié)構(gòu)有著很高的重要性。在本研究中，作者用散射型掃描近場光學(xué)顯微鏡（s-SNOM）探索了影響面下材料對比度和結(jié)構(gòu)可見度的因素。作者生成了一種包含不同掩埋結(jié)構(gòu)的多層結(jié)構(gòu)參考樣品，用來做s-SNOM成像。還研究了近場光學(xué)對比度對結(jié)構(gòu)幾何形狀、尺寸和覆蓋層厚度的影響。結(jié)果表明區(qū)分掩埋狹縫圖樣比具有相同臨界尺寸的圓孔更容易。s-SNOM能夠在100多納米厚的聚甲基丙烯酸甲酯層下感知材料之間的差異，其面下空間分辨率可以好過100納米。
17. 華中科技大學(xué) 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：作者設(shè)計并生成了一種由帶中央納米柱的納米脊孔陣列(NRANC)構(gòu)成的超表面光學(xué)調(diào)制器。研究者還細致地研究了，分布在納米脊孔的每個納米頂點和中央納米圓柱外緣上的局域表面等離子體（LSPs），與在周期性超表面上生成的表面等離子體激元(SPPs)，這二者之間的耦合效應(yīng)。這種錐形結(jié)構(gòu)可用于入射能量的集中與局部光場的增強。而在其上的感應(yīng)電偶子則可以調(diào)節(jié)反射或透射特性。這種在NRANC 上形成的LSPs的耦合效應(yīng)將增強表面感應(yīng)電偶子，并進一步調(diào)節(jié)NRANC的光學(xué)特性。通過改變超表面的幾何參數(shù)，可以調(diào)整LSPs模式的諧振頻率，并觀察到透射峰的平移，以及讓增強因數(shù)達到1.4×103。另一方面，LSPs和SPPs之間的耦合則會激發(fā)法諾共振。在可見光和紅外范圍內(nèi)調(diào)整照射激光的入射角則能調(diào)節(jié)SPPs的激發(fā)，并因此引起相對較大的透射光譜變化。于是通過進行近場光學(xué)測量，可以觀察到包括表面感應(yīng)電荷信息在內(nèi)的近場光學(xué)特性，以及在45°入射的633納米TM激光照射下的一個?。▁方向上，約96納米）且亮的熱點。綜上，作者研究中構(gòu)建的NRANC超表面突出了其在類似彩色濾光片、反射鏡、表面增強拉曼等方面的潛在應(yīng)用前景。
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