Structural characterization of thermally evaporated Bi2Te3 thin films

Ramakrishnan, S.; Dheepa, J.

doi:10.1016/j.jpcs.2006.09.014

Cited by 45 publications

(16 citation statements)

References 24 publications

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“…We use the value n = 2.4 reported for lattice sites in Bi 2 Te 3 (20). The hyperfine coupling, which is a local probe of the electronic wavefunctions in the vicinity of implanted 8 Li + ions, is mediated by the strong SOC between the nuclei and the p-band carriers (11,16,21,22).…”

Section: Resultsmentioning

confidence: 99%

Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators

Koumoulis

Morris

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Considerable evidence suggests that variations in the properties of topological insulators (TIs) at the nanoscale and at interfaces can strongly affect the physics of topological materials. Therefore, a detailed understanding of surface states and interface coupling is crucial to the search for and applications of new topological phases of matter. Currently, no methods can provide depth profiling near surfaces or at interfaces of topologically inequivalent materials. Such a method could advance the study of interactions. Herein, we present a noninvasive depth-profiling technique based on β-detected NMR (β-NMR) spectroscopy of radioactive 8 Li + ions that can provide "one-dimensional imaging" in films of fixed thickness and generates nanoscale views of the electronic wavefunctions and magnetic order at topological surfaces and interfaces. By mapping the 8 Li nuclear resonance near the surface and 10-nm deep into the bulk of pure and Cr-doped bismuth antimony telluride films, we provide signatures related to the TI properties and their topological nontrivial characteristics that affect the electronnuclear hyperfine field, the metallic shift, and magnetic order. These nanoscale variations in β-NMR parameters reflect the unconventional properties of the topological materials under study, and understanding the role of heterogeneities is expected to lead to the discovery of novel phenomena involving quantum materials.topological insulator | nuclear magnetic resonance | depth profiling | condensed matter physics | nanoscale physics T opological insulators (TIs) are narrow-gap semiconductor materials that are insulating in the bulk and conductive on their surface. The constituent atoms are typically heavy elements with large spin-orbit coupling (SOC). In time-reversal-invariant materials, the electronic structure of TIs is characterized by band inversions from strong SOC at an odd number of time-reversalinvariant momenta in the bulk Brillouin zone. Unlike metals or ordinary insulators (OIs), charge carriers in TIs evolve from metallic to insulating as a function of depth from the surface. The surface-state electrons are characterized by a suppression of backscattering and an intrinsic chirality of spin-momentum locking, making them of interest in spintronics. A number of theoretical predictions of experimental observations have been made including Majorana fermions, condensed-matter axions, and quantized Hall conductance (1, 2). Heterostructure engineering, where a crystal is formed consisting of a sequence of different building blocks (for example, alternating TI and OI layers), can trigger new physical phenomena such as TIs with enhanced bulk band gaps (3) or Weyl semimetals (4).Because topological materials are characterized by sharp changes in electronic properties at their surfaces and at interfaces with other materials, sensitive techniques are required to probe electronic and magnetic properties in a spatially resolved manner down to the atomic length scale. It has become clear that TI properties are spatially de...

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Section: Resultsmentioning

confidence: 99%

Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators

Koumoulis

Morris

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…where D is the crystallite size, λ is the wavelength, β 2 is full width half maximum (FWHM) and θ is the angle [19]. Figure 2 (b) shows the calculation result of peak related to (231) plane and (112) plane, and it can be gained that the crystallite size is almost invariable with the size of ~25 nm for (231) and ~ 17 nm for (112).…”

Section: Resultsmentioning

confidence: 97%

“…In our early report, the crystallite size of the un-doped ZnSb thin film is 20 nm for (231) [18], suggesting that the grain size expands after Ti doped. The dislocation density is estimated using the relation [19]  where  is microstrain which defines as equation [19]   It can be calculated that the largest  is the 5.7 10 -15 cm -2 of sample S4 which is lower than the pure ZnSb thin film [18]. In fact, the thin films with lower dislocation density will lead to better mechanical property and electrical property.…”

Section: Resultsmentioning

confidence: 99%

Enhancement of power factor in zinc antimonide thermoelectric thin film doped with titanium

Zheng

Luo

et al. 2017

Materials Letters

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Titanium doped zinc antimonide thin films were prepared on flexible substrates by multi-step co-sputtering method, which can assure that the Ti is homogeneous distribution in the thin film.The influence of Ti content on the microstructure and thermoelectric properties of the ZnSb based thin films was systematically investigated. The high-resolution transmission electron microscopy and X-ray diffraction exhibit that the sample has nano-sized crystallite, which will lead to better thermoelectric properties. The electrical conductivity of the Ti-doped ZnSb thin films is stable at the temperature ranging from room-temperature to 200 °C and then it has a significant increase when the temperature continues increasing. As expected, the power factor of the thin film has almost 80 % enhancement after Ti doped.

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“…No impurity peaks could be observed from the patterns of these thin films, thereby indicating that all samples comprised a single CoSb 3 phase and were well-crystallized. Crystallite size D was calculated from XRD data using the Debye-Sherrer Equation: D = κ·λ/β 2θ ·cosθ, where λ represents the wavelength, β 2θ refers to the full width at half maximum, and θ is the angle [25]. Figure 2c shows the calculation results of the peak related to the (013) plane.…”

Section: Resultsmentioning

confidence: 99%

Improvement of Power Factor of CoSb3 Thermoelectric Thin Films via Microstructure Optimization

Zheng

Wei

et al. 2017

Coatings

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Skutterudite CoSb 3 has emerged as one of the most studied candidate materials for thermoelectric applications. In this work, CoSb 3 thin films were prepared by radio frequency sputtering, and their microstructure was investigated with emphasis on the effect of target composition and deposition temperature. The goal was to enhance the thermoelectric properties of CoSb 3 thin films via microstructure optimization. Results showed that the Sb content of films gradually decreased with increasing deposition temperature. Although the thin films prepared by the target with a Co and Sb element ratio of 1:3.5 approached the ideal stoichiometric ratio, they showed poor thermoelectric properties due to the formation of an additional Sb phase. By contrast, the thin films obtained with insufficient Sb showed a single CoSb 3 phase and good thermoelectric properties. The mechanism behind this difference was studied accordingly. The power factor of the thin films was enhanced due to their dense structure and good crystallization.

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Structural characterization of thermally evaporated Bi2Te3 thin films

Cited by 45 publications

References 24 publications

Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators

Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators

Enhancement of power factor in zinc antimonide thermoelectric thin film doped with titanium

Improvement of Power Factor of CoSb3 Thermoelectric Thin Films via Microstructure Optimization

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