Te Films Research Articles

Design of a self-powered 2D Te/PtSe2 heterojunction for room-temperature NIR detection

Narrow bandgap Te films were obtained and used as the basis for the fabrication of Te/PtSe2 heterojunction infrared detectors with self-driven operation under zero bias and excellent infrared detection performance.

The microstructure and electrical and optical properties of Ge–Cu–Te phase-change thin films

The grain orientation of Ge–Cu–Te films evolves from the {111} texture with favorable carrier mobility into a random distribution with improved optical reflectivity as the annealing temperature increases.

Facile Fabrication of Flexible and High-Performing Thermoelectrics by Direct Laser Printing on Plastic Foil.

The emerging fields of wearables and the Internet of Things introduce the need for electronics and power sources with unconventional form factors: large area, customizable shape, and flexibility. Thermoelectric (TE) generators can power those systems by converting abundant waste heat into electricity, whereas the versatility of additive manufacturing suits heterogeneous form factors. Here, additive manufacturing of high-performing flexible TEs is proposed. Maskless and large-area patterning of Bi2Te3-based films is performed by laser powder bed fusion directly on plastic foil. Mechanical interlocking allows simultaneous patterning, sintering, and attachment of the films to the substrate without using organic binders that jeopardize the final performance. Material waste could be minimized by recycling the unexposed powder. The particular microstructure of the laser-printed material renders the-otherwise brittle-Bi2Te3 films highly flexible despite their high thickness. The films survive 500 extreme-bending cycles to a 0.76mm radius. Power factors above 1500 µW m-1K-2 and a record-low sheet resistance for flexible TEs of 0.4 Ω sq-1 are achieved, leading to unprecedented potential for power generation. This versatile fabrication route enables innovative implementations, such as cuttable arrays adapting to specific applications inself-powered sensing, and energy harvesting from unusual scenarios like human skin and curved hot surfaces.

Reassembled phase diagram for Fe y Se x Te1−x superconducting films grown by pulsed laser deposition

Fe y Se x Te targets with different Fe contents have been prepared by the solid state reaction method followed by the hot-pressed sintering, and corresponding single-phase Fe y Se x Te films with high quality have been deposited at different substrate temperatures by the pulsed laser deposition. The evolution of the structure, superconductivity and pinning mechanism of the Fe y Se x Te superconductors with the Fe content has been investigated in detail. It can be found that the excess Fe can form the residual Fe impurities scattered in the polycrystalline bulks when the Fe content in the nominal composition exceeds 1.36. More importantly, a reassembled phase diagram for Fe y Se x Te superconducting films based on the change of both Fe and Se contents is constructed for the first time. It can be clearly seen that both the Fe and Se contents can greatly affect the superconductivity of Fe y Se x Te films within a wide range of Fe content (). The Fe vacancies caused by the Fe deficiency is beneficial to the improvement of both critical temperature and activation energy, while with the increase of the Fe content, the superconductivity degrades because of the introduction of the interstitial Fe and the planar defects. The optimal Fe content at constant Se content shifts to the higher value with the increase of Se content. Our results facilitate the rational regulation of the superconducting properties, as well as the study of the underlying superconducting mechanism of FeSeTe superconductors.

Synthesis, Properties, and Application of Ultrathin and Flexible Tellurium Nanorope Films: Beyond Conventional 2D Materials.

Nanomaterials that can be easily processed into thin films are highly desirable for their wide range of applicability in electrical and optical devices. Currently, Te-based 2D materials are of interest because of their superior electrical properties compared to transition metal dichalcogenide materials. However, the large-scale manufacturing of these materials is challenging, impeding their commercialization. This paper reports on ultrathin, large-scale, and highly flexible Te and Te-metal nanorope films grown via low-power radiofrequency sputtering for a short period at 25°C. Additionally, the feasibility of such films as transistor channels and flexible transparent conductive electrodes is discussed. A 20 nm thick Te-Ni-nanorope-channel-based transistor exhibits a high mobility (≈450 cm2 V-1 s-1 ) and on/off ratio (105 ), while 7 nm thick Te-W nanorope electrodes exhibit an extremely low haze (1.7%) and sheet resistance (30 Ω sq-1 ), and high transmittance (86.4%), work function (≈4.9eV), and flexibility. Blue organic light-emitting diodes with 7 nm Te-W anodes exhibit significantly higher external quantum efficiencies (15.7%), lower turn-on voltages (3.2V), and higher and more uniform viewing angles than indium-tin-oxide-based devices. The excellent mechanical flexibility and easy coating capability offered by Te nanoropes demonstrate their superiority over conventional nanomaterials and provide an effective outlet for multifunctional devices.

Significantly improved thermoelectric performance of Ag-doped Bi0.5Sb1.5Te3 films deriving from high-efficient carrier filtering effect

Selective carrier energy filtering effect is an important strategy to promote the power factor of a thermoelectrical materials, which requires an appropriate potential barrier and coherent interfaces between the secondary phase and the host matrix. Although the energy filtering effect has been realized in various bulk systems, its efficiency in promoting their thermoelectric performance is limited. Herein, simultaneously increased electrical conductivity and Seebeck coefficient are investigated in Ag-doped Bi0.5Sb1.5Te3 films, leading to an increasement of the power factor up to 700%. Microstructure analysis reveals that the thin films prepared from magnetron sputtering consist of highly uniform nanocrystal domains, which construct coherent interfaces somewhere. Moreover, the local Ag doping might depress the Fermi level, providing the possibility to form a suitable potential barrier between the adjacent nanograins. This study suggests a facile method to significantly enhance the thermoelectric performance via energy filtering effect in high quality thin films.

A High-Performance Thin-Film Sensor in 6G for Remote Sensing of the Sea Surface

Functional devices in the THz band will provide a highly important technical guarantee for the promotion and application of 6G technology. We sought to design a high-performance sensor with a large area, high responsiveness, and low equivalent noise power, which is stable at room temperature for long periods and still usable under high humidity; it is suitable for the environment of marine remote sensing technology and has the potential for mass production. We prepared a Te film with high stability and studied its crystallization method by comparing the sensing and detection effects of THz waves at different annealing temperatures. It is proposed that the best crystallization and detection effect is achieved by annealing at 100 °C for 60 min, with a sensitivity of up to 19.8 A/W and an equivalent noise power (NEP) of 2.8 pW Hz−1/2. The effective detection area of the detector can reach the centimeter level, and this level is maintained for more than 2 months in a humid environment at 30 °C with 70–80% humidity and without encapsulation. Considering its advantages of stability, detection performance, large effective area, and easy mass preparation, our Te thin film is an ideal sensor for 6G ocean remote sensing technology.

Controlling the shape of hexagonal structure by growth condition improves the thermoelectric properties of p-type Bi-Te films

Improving the thermoelectric (TE) properties of typical p-type Bi0.5Sb1.5Te3 film is crucial for power generation in film-based thermoelectric devices. The shape of the hexagonal structure in the Bi0.5Sb1.5Te3 film can be controlled by adjusting the magnetron sputtering parameters. The results indicate that a high nucleation rate under high sputtering power promotes island growth with a preferred orientation of (015). Thermal energy influences the growth in the in-plane direction along the (00 l) orientation and induces the c-axis orientation in the out-of-plane direction. Consequently, a dense layered hexagonal structure with a high grain boundary density is formed, leading to increased defect density, carrier concentration, and phonon scattering. In this case, the power factor reaches 3149.01 μW·m-1·K-2 at 480 K and the ZT value is 1.14 at 480 K. These results indicate that the film with a dense layered hexagonal structure enhances the TE properties.

Effect of composition and structure of In-Te alloy on evaporation property and film of Te

Te (tellurium) film used for semiconductors and photocathode is prepared by a resistive heating evaporation system in this paper. The evaporation property is assessed by comparing the evaporation rate of In-Te alloy with different compositions and structures. The morphology and structure of Te films prepared by In5Te95, In10Te90, and In15Te85 alloy are characterized. The result shows that the In-Te alloy consists of the Te phase and the In2Te5 phase with a hexagonal and monoclinic structure. The primary Te phase and eutectic Te phase are obtained in In5Te95 alloy, and the eutectic Te phase is displayed in In10Te90 and In15Te85 alloy only. The content of Te is 100% in the primary Te phase and eutectic Te phase. Alloying has reduced the evaporation of Te effectively, while the evaporation rate is affected by the distribution of the Te phase. The Te films prepared with three alloys are consisting of the needle-shape Te grain. The Te film deposited from the eutectic Te phase has smaller grain size and the film thickness is affected by the evaporation rate. The composition of Te is confirmed by XPS. The peak value of XPS spectra matches the Te3d5/2 and Te3d3/2.

Thermal Conductivity for p–(Bi, Sb)2Te3 Films of Topological Insulators

In this study, we investigated the temperature dependencies of the total, crystal lattice, and electronic thermal conductivities in films of topological insulators p–Bi0.5Sb1.5Te3 and p–Bi2Te3 formed by discrete and thermal evaporation methods. The largest decrease in the lattice thermal conductivity because of the scattering of long-wavelength phonons on the grain interfaces was observed in the films of the solid-solution p–Bi0.5Sb1.5Te3 deposited by discrete evaporation on the amorphous substrates of polyimide without thermal treatment. It was shown that in the p–Bi0.5Sb1.5Te3 films with low thermal conductivity, the energy dependence of the relaxation time is enhanced, which is specific to the topological insulators. The electronic thermal conductivity was determined by taking into account the effective scattering parameter in the relaxation time approximation versus energy in the Lorentz number calculations. A correlation was established between the thermal conductivity and the peculiarities of the morphology of the interlayer surface (0001) in the studied films. Additionally, the total κ and the lattice κL thermal conductivities decrease, while the number of grains and the roughness of the surface (0001) increase in unannealed films compared to annealed ones. It was demonstrated that increasing the thermoelectric figure of merit ZT in the p–Bi0.5Sb1.5Te3 films formed by discrete evaporation on a polyimide substrate is determined by an increase in the effective scattering parameter in topological insulators due to enhancement in the energy dependence of the relaxation time.

Prominently optimized thermoelectric performance via possibly magnified carrier energy filtering effect in sandwich-structured p-type Cu-doped Bi0.5Sb1.5Te3 films

Prominently optimized thermoelectric performance via possibly magnified carrier energy filtering effect in sandwich-structured p-type Cu-doped Bi0.5Sb1.5Te3 films

Carrier concentration and orientation optimization for high performance (Sb,Bi)2Te3 thermoelectric films via magnetron co-sputtering

High performance flexible thermoelectric thin films are desired for power generation of flexible thermoelectric device. Thermoelectric performance of (Sb,Bi)2Te3 films are determined by the Te content in the matrix as anti-site defect dominates the carrier concentration. By controlling the Te target co-sputtering power, annealing temperature and time, not only the film in-plane orientation is enhanced, the carrier concentration is also effectively controlled in this work. Through a systematically investigation of Te content dependence of the thermoelectric performance, the carrier concentration and orientation is optimized through tuning Te content, and a high power factor of ∼32 μW/cm-K2 for Sb2Te3 film, ∼36 μW/cm-K2 for Bi0.5Sb1.5Te3 film is realized in in-plane orientation. Besides, The thermal conductivity along in-plane direction is determined by photon-electro-thermal (TPET) technique, and the final zT values are ∼0.49 for Sb2Te3, and ∼0.58 for Bi0.5Sb1.5Te3 films at room temperature, respectively.

Critical behavior in the epitaxial growth of two-dimensional tellurium films on SrTiO3 (001) substrates

Materials’ properties may differ in the thin-film form, especially for epitaxial ultra-thin films, where the substrates play an important role in their deviation from the bulk quality. Here by molecular beam epitaxy (MBE) and scanning tunneling microscopy/spectroscopy, we investigate the growth kinetics of ultra-thin tellurium (Te) films on SrTiO3 (STO) (001). The MBE growth of Te films usually exhibits Volmer–Weber (VW) island growth mode and no a-few-monolayer film with full coverage has been reported. The absence of wetting-layer formation in the VW growth mode of Te on STO (001) is resulted from its low diffusion barriers as well as its relatively higher surface energy compared with those of the substrate and the interface. Here we circumvent these limiting factors and achieve the growth of ultra-thin β-Te films with near-complete coverages by driving the growth kinetics to the extreme condition. There is a critical thickness (3 monolayer) above which the two-dimensional Te films can form on the STO (001) substrate. In addition, the scanning tunneling spectra on the ultra-thin Te film grown on STO exhibits an enormously large forbidden gap compared with that grown on the graphene substrate. Our work establishes the necessary conditions for the growth of ultra-thin materials with similar kinetics and thermodynamics.

Critical behavior in the epitaxial growth of two-dimensional tellurium films on SrTiO3 (001) substrates

Materials’ properties may differ in the thin-film form, especially for epitaxial ultra-thin films, where the substrates play an important role in their deviation from the bulk quality. Here by molecular beam epitaxy (MBE) and scanning tunneling microscopy/spectroscopy, we investigate the growth kinetics of ultra-thin tellurium (Te) films on SrTiO3 (STO) (001). The MBE growth of Te films usually exhibits Volmer–Weber (VW) island growth mode and no a-few-monolayer film with full coverage has been reported. The absence of wetting-layer formation in the VW growth mode of Te on STO (001) is resulted from its low diffusion barriers as well as its relatively higher surface energy compared with those of the substrate and the interface. Here we circumvent these limiting factors and achieve the growth of ultra-thin β-Te films with near-complete coverages by driving the growth kinetics to the extreme condition. There is a critical thickness (3 monolayer) above which the two-dimensional Te films can form on the STO (001) substrate. In addition, the scanning tunneling spectra on the ultra-thin Te film grown on STO exhibits an enormously large forbidden gap compared with that grown on the graphene substrate. Our work establishes the necessary conditions for the growth of ultra-thin materials with similar kinetics and thermodynamics.

The crystallization of thin Sb2Te films with vacuum annealing and an electron beam

Thin Sb2Te films with a thickness gradient were studied via transmission electron microscopy. The processes of forced crystallization were examined with thermal annealing and an electron beam. The crystallization’s general tendencies, including competitive nucleation and growth crystallization, were revealed. As the thickness of the sample increases, the size of the crystals growing in the film enlarges. As the temperature increases, the number of crystals in the film grows. Crystallization under the action of an electron beam occurs mainly by nucleation mechanism.

Low‐Cost and Biodegradable Thermoelectric Devices Based on van der Waals Semiconductors on Paper Substrates

We present a method to fabricate handcrafted thermoelectric devices on standard office paper substrates. The devices are based on thin films of WS2, Te, and BP (P‐type semiconductors) and TiS3 and TiS2 (N‐type semiconductors), deposited by simply rubbing powder of these materials against paper. The thermoelectric properties of these semiconducting films revealed maximum Seebeck coefficients of (+1.32 ± 0.27) mV K−1 and (−0.82 ± 0.15) mV K−1 for WS2 and TiS3, respectively. Additionally, Peltier elements were fabricated by interconnecting the P‐ and N‐type films with graphite electrodes. A thermopower value up to 6.11 mV K−1 was obtained when the Peltier element were constructed with three junctions. The findings of this work show proof‐of‐concept devices to illustrate the potential application of semiconducting van der Waals materials in future thermoelectric power generation as well as temperature sensing for low‐cost disposable electronic devices.

Combinatorial study to the physical properties of Cd1-xZnxTe thin films as budding absorber for solar cell applications

Cadmium telluride (CdTe) has long been recognized as promising absorber for single-junction solar cells, yet it suffers from snag of apposite contact. CdZnTe provides band gap tunability and can be used as absorber layer in tandem devices concerned. The impact of Zn content on physical properties of Cd1-xZnxTe thin films is indubitable and hence, present work demonstrates concentration evolution to physical properties of Cd1-xZnxTe thin films. Structural characterization depicted zinc blende cubic phased (220) plane as dominant reflection. The optical energy band gap (Eg) of films is attained within range 1.70–1.92 eV and electrical properties portrayed Ohmic character of films. Photoluminescence spectra showed single peak and topographical analysis demonstrated hill like-topographies. Field emission scanning electron microscopy (FESEM) maps exposed compact morphologies and compositional studies validated presence of constituent elements. The present study unveiled that maximum grain size, apt optical energy band gap and higher conductivity of Cd0.9Zn0.1Te films make these as budding absorbers for solar cell applications.

Quantum anomalous Hall interferometer

Electronic interferometries in integer and fractional quantum Hall regimes have unfolded the coherence, correlation, and statistical properties of interfering constituents. This is addressed by investigating the roles played by the Aharonov–Bohm effect and Coulomb interactions on the oscillations of transmission/reflection. Here, we construct magnetic interferometers using Cr-doped (Bi,Sb)2Te3 films and demonstrate the electronic interferometry using chiral edge states in the quantum anomalous Hall regime. By controlling the extent of edge coupling and the amount of threading magnetic flux, distinct interfering patterns were observed, which highlight the interplay between the Coulomb interactions and Aharonov–Bohm interference by edge states. The observed interference is likely to exhibit a long-range coherence and robustness against thermal smearing probably owing to the long-range magnetic order. Our interferometer establishes a platform for (quasi)particle interference and topological qubits.

Fabrication of Meter‐Long Class Fe(Se,Te)‐Coated Conductors with High Superconducting Performance

Previous research results have demonstrated that Fe(Se,Te) films with high critical current density Jc can be realized on flexible metal substrates and are promising for high field applications at 4.2 K. For practical applications, the length of the coated conductor is a key factor. Regarding the fabrication of long Fe(Se,Te)‐coated conductor tapes, the biggest difficulty is how to achieve a breakthrough from static coating to continuous dynamic coating process. Herein, it is demonstrated that Fe(Se,Te)‐coated conductor with high superconducting performance can be continuously fabricated. 1 m‐long Fe(Se,Te)‐coated conductors have been successfully fabricated by multiturn pulsed laser deposition on CeO2‐buffered ion beam‐assisted deposition MgO tape. The Fe(Se,Te)‐coated conductors have high critical temperature of 17.5 K and Jc over 2 MA cm−2 at 4.2 K and self‐field. The end‐to‐end critical current of 1 m‐long Fe(Se,Te)‐coated conductor is as high as 108 A cm−1‐width at 4.2 K and self‐field, and the corresponding Jc is 1.54 MA cm−2, which is above the threshold for industrial applications. The upper critical field at 0 K is deduced to be about 53 T. To the best of knowledge, this is the first demonstration of continuous fabrication of long Fe(Se,Te)‐coated conductors with high performance.

Enhancement of the Surface Morphology of (Bi0.4Sb0.6)2Te3 Thin Films by In Situ Thermal Annealing.

The study of the exotic properties of the surface states of topological insulators requires defect-free and smooth surfaces. This work aims to study the enhancement of the surface morphology of optimally doped, high-crystalline (Bi0.4Sb0.6)2Te3 films deposited by molecular beam epitaxy on Al2O3 (001) substrates. Atomic force microscopy shows that by employing an in situ thermal post anneal, the surface roughness is reduced significantly, and transmission electron microscopy reveals that structural defects are diminished substantially. Thence, these films provide a great platform for the research on the thickness-dependent properties of topological insulators.