Solvothermally Synthesized Sb<sub>2</sub>Te<sub>3</sub> Platelets Show Unexpected Optical Contrasts in Mid-Infrared Near-Field Scanning Microscopy

Hauer, Benedikt; Saltzmann, Tobias; Simon, Ulrich; Taubner, Thomas

doi:10.1021/nl503697c

Cited by 26 publications

(44 citation statements)

References 48 publications

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“…It is worth emphasizing that these patterns differ from the optical contrast in Sb 2 Te 3 platelets reported in previous studies. [27] There, the pattern is closely related to the spiral growth, with a topographically rough surface with screw dislocations, whereas in our system, the surface is flat, with no association of a screw dislocation with the formation of the optical patterns.…”

Section: Introductionmentioning

confidence: 49%

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Nanoimaging of Electronic Heterogeneity in Bi₂Se₃ and Sb₂Te₃ Nanocrystals

Khatib

et al. 2017

Adv Elect Materials

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featuring metallic surface states surrounding an insulating bulk. The associated unique electronic structure of the helical Dirac surface states results in many exotic physical properties, such as the topological magneto-electric effect, [6] Majorana fermions, [7] and the quantum anomalous Hall effect. [8] However, because of the low formation energy of intrinsic defects, [9] the resulting bulk conductivity often obscures or even suppresses the desired TI behavior. [10][11][12] The realization of these novel topological phases requires high-quality TI thin films with sufficiently low defect concentration, typically obtained by molecular beam epitaxy growth. [13] Chemical vapor deposition (CVD) and polyol methods, which offer facile and cost-effective synthetic routes promising for large-scale device applications, have also received interest with successful demonstrations of the ambipolar field effect, [14] Aharonov-Bohm, [15,16] and Shubnikov-de Hass [17] oscillations in (Bi x Sb 1−x ) 2 Te 3 nano plates, as well as in Bi 2 Se 3 and Be 2 Te 3 nanoribbons. Nevertheless, the quantum Hall effect as a hallmark of Dirac surface states [18] has not yet been realized in these TI nanostructures. One possible reason might be the appreciable bulk conduction associated with Topological insulators (TIs) are quantum materials with topologically protected surface states surrounding an insulating bulk. However, defectinduced bulk conduction often dominates transport properties in most TI materials, obscuring the Dirac surface states. In order to realize intrinsic topological insulating properties, it is thus of great significance to identify the spatial distribution of defects, understand their formation mechanism, and finally control or eliminate their influence. Here, the electronic heterogeneity in polyol-synthesized Bi 2 Se 3 and chemical vapor deposition-grown Sb 2 Te 3 nanocrystals is systematically investigated by multimodal atomicto-mesoscale resolution imaging. In particular, by combining the Drude response sensitivity of infrared scattering-type scanning near-field optical microscopy with the work-function specificity of mirror electron microscopy, characteristic mesoscopic patterns are identified, which are related to carrier concentration modulation originating from the formation of defects during the crystal growth process. This correlative imaging and modeling approach thus provides the desired guidance for optimization of growth parameters, crucial for preparing TI nanomaterials to display their intrinsic exotic Dirac properties.Topological Insulators

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Section: Introductionmentioning

confidence: 49%

“…[27,33,34] Considering that IR s-SNOM is sensitive to low-energy intra-and interband transitions, Drude conductivity, and related surface excitations, we performed broadband spectroscopic nanoimaging using synchrotron near-field infrared nanospectroscopy (SINS) [35] from 750 to 2000 cm −1 . (Figure 1d).…”

Section: Resultsmentioning

confidence: 99%

Nanoimaging of Electronic Heterogeneity in Bi₂Se₃ and Sb₂Te₃ Nanocrystals

Khatib

et al. 2017

Adv Elect Materials

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“…The region of largest near‐field phase contrast extends to the left of the TD, and exhibits a corresponding change in contrast in both the ECCI and SE images, but with no observable corresponding topographic feature identified in the AFM topography image. Previous s‐SNOM investigations have shown that variations in strain,27b charge‐carrier concentration,25a and polytype27a can induce such effects in the near‐field contrasts. In ECCI however, such a bright‐line charge contrast as is highlighted in Figure a is known to be due to subsurface strain, most likely caused by the nucleation point of the TD inducing the carrot defect.…”

Section: Resultsmentioning

confidence: 96%

“…To extract the spectral response, the sample can be probed at multiple discrete incident frequencies of the focused laser in succession to plot the frequency‐dependent s‐SNOM amplitude and/or phase, providing a map of the spatial variation in the s‐SNOM response at each frequency 22b. Thus, s‐SNOM provides obvious benefits for high resolution defect imaging when monitored at mid‐IR frequencies as it provides the potential to i) investigate the impact of defects upon the free‐carrier density or polaritonic behaviors, ii) provide information regarding crystalline structure and polytype, and iii) determine the role such defects play in the performance of nanophotonic devices such as polaritonic antennas, waveguides, and metasurfaces . While s‐SNOM should not be expected to replace the previously mentioned spectroscopic and microscopic methods, it instead provides a noninvasive technique offering complementary IR spectroscopic information about the defect(s) and surrounding regions of interest, while simultaneously imaging the topography of the sample.…”

Section: Introductionmentioning

confidence: 99%

Exploiting Phonon‐Resonant Near‐Field Interaction for the Nanoscale Investigation of Extended Defects

Hauer

Marvinney

Lewin

et al. 2020

Adv Funct Materials

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The evolution of wide bandgap semiconductor materials has led to dramatic improvements for electronic applications at high powers and temperatures. However, the propensity of extended defects provides significant challenges for implementing these materials in commercial electronic and optical applications. While a range of spectroscopic and microscopic tools have been developed for identifying and characterizing these defects, such techniques typically offer either technique exclusively, and/or may be destructive. Scattering‐type scanning near‐field optical microscopy (s‐SNOM) is a nondestructive method capable of simultaneously collecting topographic and spectroscopic information with frequency‐independent nanoscale spatial precision (≈20 nm). Here, how extended defects within 4H‐SiC manifest in the infrared phonon response using s‐SNOM is investigated and the response with UV‐photoluminescence, secondary electron and electron channeling contrast imaging, and transmission electron microscopy is correlated. The s‐SNOM technique identifies evidence of step‐bunching, recombination‐induced stacking faults, and threading screw dislocations, and demonstrates interaction of surface phonon polaritons with extended defects. The results demonstrate that phonon‐enhanced infrared nanospectroscopy and spatial mapping via s‐SNOM provide a complementary, nondestructive technique offering significant insights into extended defects within emerging semiconductor materials and devices and thus serves as an important diagnostic tool to help advance material growth efforts for electronic, photonic, phononic, and quantum optical applications.

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“…[ 12,14–16 ] Because of the variability of their electrical properties (mainly resistance), PCMs have been widely used in nonvolatile electric fields, such as high‐density memories. [ 17–23 ] Because of the variability of their optical properties (mainly optical constants, [ 9,24,25 ] reflectivity, [ 26,27 ] transmission, [ 25,28,29 ] absorption, [ 30,31 ] and emissivity [ 32 ] ), PCMs been widely applied in nonvolatile photonic applications, such as all‐photonic memories, [ 26,33,34 ] active absorbers, [ 35 ] filters, [ 25 ] lenses, [ 34,36 ] sensors, [ 36 ] displays, etc. [ 26,27,37–39 ] Among the above optical applications, the PCM‐based solid‐state reflective display [ 27 ] is a revolutionary display technology.…”

Section: Introductionmentioning

confidence: 99%

Phase Change Materials for Nonvolatile, Solid‐State Reflective Displays: From New Structural Design Rules to Enhanced Color‐Changing Performance

Tao

Wang

et al. 2020

Advanced Optical Materials

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can rapidly convert from amorphous to crystalline states under appropriate electrical/optical/thermal excitation. [1][2][3][4][5][6][7][8] During transformation from amorphous to crystalline states, the chemical bonds and degree of order of PCMs change significantly. [9][10][11][12][13] As a result, their electrical and optical properties also change drastically. [12,[14][15][16] Because of the variability of their electrical properties (mainly resistance), PCMs have been widely used in nonvolatile electric fields, such as highdensity memories. [17][18][19][20][21][22][23] Because of the variability of their optical properties (mainly optical constants, [9,24,25] reflectivity, [26,27] transmission, [25,28,29] absorption, [30,31] and emissivity [32] ), PCMs been widely applied in nonvolatile photonic applications, such as all-photonic memories, [26,33,34] active absorbers, [35] filters, [25] lenses, [34,36] sensors, [36] displays, etc. [26,27,[37][38][39] Among the above optical applications, the PCM-based solid-state reflective display [27] is a revolutionary display technology. It has many advantages, such as high resolution, rich colors, and fast color switching over traditional technologies, such as electrophoresis and electronic ink display. The PCM-based solid-state reflective display has become the most promising portable display technology.Current research on PCM-based nonvolatile coatings for displays mainly focuses on designing multilayer film structures and improving their color-changing properties. Specifically, the related research can be roughly summarized into three aspects. First, Hosseini et al. [26,27,40] pioneered the new concept of PCMbased "non-volatile displays" in 2014, and then designed and developed Ge 2 Sb 2 Te 5 -and Ag 3 In 4 Sb 76 Te 17 -based four-layer display coatings with a metal/transparent dielectric/PCM/transparent dielectric structure. These coatings have high resolution, color tunability, and broad color gamut, [10] and thus can be applied to various opaque/transparent and rigid/soft substrates. Second, Cheng et al., [41,42] and Liu, [43] et al. systematically studied the effect of the thicknesses of transparent dielectric layer and Ge 2 Sb 2 Te 5 layer on the color rendering performance of coatings. They extended the color gamut of the coatings by optimizing the thickness of each film. Besides, they developed a Ge 2 Sb 2 Te 5 -based three-layer film system, which could reduce With the arrival of omnimedia era, there has been an increasing demand for energy-saving, colorful, and portable displays. Traditional display technologies, such as electrophoresis and electronic ink display suffer from low color switching speed and poor color richness. Due to their high performances, phase change materials (PCMs)-based nonvolatile, solid-state reflective display coatings have become the most promising materials for new portable display technology. Existing researches mainly focus on improving the color-changing performance of coatings by optimizing film structural parameters, but ignore...

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Solvothermally Synthesized Sb₂Te₃ Platelets Show Unexpected Optical Contrasts in Mid-Infrared Near-Field Scanning Microscopy

Cited by 26 publications

References 48 publications

Nanoimaging of Electronic Heterogeneity in Bi₂Se₃ and Sb₂Te₃ Nanocrystals

Nanoimaging of Electronic Heterogeneity in Bi₂Se₃ and Sb₂Te₃ Nanocrystals

Exploiting Phonon‐Resonant Near‐Field Interaction for the Nanoscale Investigation of Extended Defects

Phase Change Materials for Nonvolatile, Solid‐State Reflective Displays: From New Structural Design Rules to Enhanced Color‐Changing Performance

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Solvothermally Synthesized Sb2Te3 Platelets Show Unexpected Optical Contrasts in Mid-Infrared Near-Field Scanning Microscopy

Cited by 26 publications

References 48 publications

Nanoimaging of Electronic Heterogeneity in Bi2Se3 and Sb2Te3 Nanocrystals

Nanoimaging of Electronic Heterogeneity in Bi2Se3 and Sb2Te3 Nanocrystals

Exploiting Phonon‐Resonant Near‐Field Interaction for the Nanoscale Investigation of Extended Defects

Phase Change Materials for Nonvolatile, Solid‐State Reflective Displays: From New Structural Design Rules to Enhanced Color‐Changing Performance

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Solvothermally Synthesized Sb₂Te₃ Platelets Show Unexpected Optical Contrasts in Mid-Infrared Near-Field Scanning Microscopy

Nanoimaging of Electronic Heterogeneity in Bi₂Se₃ and Sb₂Te₃ Nanocrystals

Nanoimaging of Electronic Heterogeneity in Bi₂Se₃ and Sb₂Te₃ Nanocrystals