Antimony Telluride Thin Films Research Articles

Self-aligned shadow masking for antimony telluride growth: Novel advancements in single-leg thermoelectric array design

In the present study, a fabrication technique using self-aligned shadow masking was employed to create a state-of-art thermoelectric single-leg array of Antimony telluride (Sb2Te3) thin film via thermal evaporation technique. The thermoelectric (TE) performance of the array was evaluated using an in-house developed measurement setup. The TE characteristics of the developed p-type Sb2Te3 based TEGs with single-leg configurations, having 5-TE legs, exhibits a highest Power factor (PF) of ∼5173 μW/mK2 at RT along with thermoelectric voltage generation of 70 mV. As compared to planar configuration these segmented single-leg array-based TEG of Sb2Te3 exhibit higher efficiency (∼10 %) under a near-ambient temperature gradient. Also, the 3ω-method is utilized to assess the thermal conductivity of fabricated thin films of Sb2Te3, yielding a value of 0.41 Wm⁻1K⁻1. Furthermore, these thermoelectric generators (TEGs) showcase their versatility across various applications, efficiently harnessing near-room temperature waste heat from a range of sources such as tea coasters, the human body, and gas cookstoves into useable energy near room temperature.

Fabrication of Bi2Te3 and Sb2Te3 Thermoelectric Thin Films using Radio Frequency Magnetron Sputtering Technique.

Through various studies on thermoelectric (TE) materials, thin film configuration gives superior advantages over conventional bulk TEs, including adaptability to curved and flexible substrates. Several different thin film deposition methods have been explored, yet magnetron sputtering is still favorable due to its high deposition efficiency and scalability. Therefore, this study aims to fabricate a bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin film via the radio frequency (RF) magnetron sputtering method. The thin films were deposited on soda lime glass substrates at ambient temperature. The substrates were first washed using water and soap, ultrasonically cleaned with methanol, acetone, ethanol, and deionized water for 10 min, dried with nitrogen gas and hot plate, and finally treated under UV ozone for 10 min to remove residues before the coating process. A sputter target of Bi2Te3 and Sb2Te3 with Argon gas was used, and pre-sputtering was done to clean the target's surface. Then, a few clean substrates were loaded into the sputtering chamber, and the chamber was vacuumed until the pressure reached 2 x 10-5 Torr. The thin films were deposited for 60 min with Argon flow of 4 sccm and RF power at 75 W and 30 W for Bi2Te3 and Sb2Te3, respectively. This method resulted in highly uniform n-type Bi2Te3 and p-type Sb2Te3 thin films.

Structural, optical, and electrical analysis of tailoring Bi2-xSbxTe3 thin films

Bismuth antimony telluride (Bi2-xSbxTe3) thin films were synthesized using chemical bath deposition (CBD) with various amounts of antimony. The structural, morphological, and optical properties of Bi2-xSbxTe3 thin films have been scrutinized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), UV-Vis spectrophotometry. A higher amount of Sb contents can be observed the Sb0.405Te0.595, BiTe, and Bi4Te3 phases consisted in the pattern. Meanwhile, the energy band gaps are tuned in the range of 2.95 to 3.30 eV. Finally, measurement of resistance with various temperatures for activation energy (EAC) estimation was performed. The highest EAC value was equal to 0.654 eV for 0.8 g SbCl3 as a precursor of Sb atom incorporated in the Bi2Te3 lattice.

Low resistance large area terahertz detector based on antimony telluride thin film

Terahertz technology has great potential for various applications in fields like biomedicine, astronomy, communications, and security inspection. Therefore, terahertz detectors that can operate at room temperature with fast response times, high sensitivity, wide detection bandwidth, and can be seamlessly integrated. To achieve this, a metal–semiconductor-metal structure with a subwavelength gap is used, which creates an electromagnetic induced potential well within the semiconductor by utilizing the antisymmetric electric field of terahertz radiation. This structure allows for the injection and retention of electrons from the metal, enhancing electrical conductivity. Experimental results have shown that reducing the spacing between the forked finger electrodes improves the detection performance of the device. At room temperature, with a bias voltage of 1 V and 0.28 THz radiation, the device achieves an equivalent noise power of 9.76 × 10−13 W/Hz/2 and a detection rate of 2.41 × 1011cm Hz1/2W−1. Additionally, the device's simple structure and large effective detection area make it suitable for producing low-resistance and large-area terahertz detectors.

Low-Temperature ALD of SbOx /Sb2 Te3 Multilayers with Boosted Thermoelectric Performance.

Nanoscale superlattice (SL) structures have proven to be effective in enhancing the thermoelectric (TE) properties of thin films. Herein, the main phase of antimony telluride (Sb2 Te3 ) thin film with sub-nanometer layers of antimony oxide (SbOx ) is synthesized via atomic layer deposition (ALD) at a low temperature of 80 °C. The SL structure is tailored by varying the cycle numbers of Sb2 Te3 and SbOx . A remarkable power factor of 520.8 µW m-1 K-2 is attained at room temperature when the cycle ratio of SbOx and Sb2 Te3 is set at 1:1000 (i.e., SO:ST = 1:1000), corresponding to the highest electrical conductivity of 339.8 S cm-1 . The results indicate that at the largest thickness, corresponding to ten ALD cycles, the SbOx layers act as a potential barrier that filters out the low-energy charge carriers from contributing to the overall electrical conductivity. In addition to enhancing the scattering of the mid-to-long-wavelength at the SbOx /Sb2 Te3 interface, the presence of the SbOx sub-layer induces the confinement effect and strain forces in the Sb2 Te3 thin film, thereby effectively enhancing the Seebeck coefficient and reducing the thermal conductivity. These findings provide a new perspective on the design of SL-structured TE materials and devices.

Enhanced pseudo-atomic layer deposition of antimony telluride thin films by co-injecting NH3 gas with both precursors

This work proposed an enhanced deposition method of antimony telluride (Sb2Te3) thin films, which allowed facile growth at high temperatures (> 150 °C).

Wafer-Scale Growth of Sb2Te3 Films via Low-Temperature Atomic Layer Deposition for Self-Powered Photodetectors.

In this work, we demonstrate the performance of a silicon-compatible, high-performance, and self-powered photodetector. A wide detection range from visible (405 nm) to near-infrared (1550 nm) light was enabled by the vertical p-n heterojunction between the p-type antimony telluride (Sb2Te3) thin film and the n-type silicon (Si) substrates. A Sb2Te3 film with a good crystal quality, low density of extended defects, proper stoichiometry, p-type nature, and excellent uniformity across a 4 in. wafer was achieved by atomic layer deposition at 80 °C using (Et3Si)2Te and SbCl3 as precursors. The processed photodetectors have a low dark current (∼20 pA), a high responsivity of (∼4.3 A/W at 405 nm and ∼150 mA/W at 1550 nm), a peak detectivity of ∼1.65 × 1014 Jones, and a quick rise time of ∼98 μs under zero bias voltage. Density functional theory calculations reveal a narrow, near-direct, type-II band gap at the heterointerface that supports a strong built-in electric field leading to efficient separation of the photogenerated carriers. The devices have long-term air stability and efficient switching behavior even at elevated temperatures. These high-performance and self-powered p-Sb2Te3/n-Si heterojunction photodetectors have immense potential to become reliable technological building blocks for a plethora of innovative applications in next-generation optoelectronics, silicon-photonics, chip-level sensing, and detection.

Comparative study on the influence of transparent glass substrates for antimony telluride thin films via structural and optical properties

Antimony telluride (Sb 2 Te 3 ) thin films were deposited on to non-and conductive-glass substrates ‒ borosilicate (BRS), indium-doped tin oxide (ITO), and fluorine-doped tin oxide (FTO) using the doctor-blading technique as a white slurry precipitated from the solution during a chemical bath reaction. The study examines the influences of glass substrates on the structural and surface morphology of Sb 2 Te 3 thin films. The calculated structural parameters indicated that different glass substrates impacted the properties of Sb 2 Te 3 thin films. All optical parameters were investigated based on transmittance ( T ( λ )) and reflectance ( R ( λ )) spectra in the wavelength range of 300–1100 nm. The average energy band gap ( E g ) was calculated from the indirect ( E g i n d ) and direct ( E g d i ) energy band gaps and was estimated to be 1.44, 1.68, and 1.53 eV for BRS/Sb 2 Te 3 , ITO/Sb 2 Te 3 , and FTO/Sb 2 Te 3 , respectively. Importantly, the highest values for the χ (1) , χ (3) , and n 2 approximately of 0.0322, 1.92 × 10 −16 esu., and 5.91 × 10 −15 esu. respectively were achieved in the energy range from 2.0 to 3.5 eV for BRS/Sb 2 Te 3 . The highest β c of 86.31 cm/GW was obtained in the energy range from 1.23 to 1.65 eV. These results suggest the strong possibility of using the Sb 2 Te 3 thin film on BRS glass in nonlinear optical devices for the UV-visible region, such as optical quantum electronics, optical limiting, fast optical switching, and high-speed communication devices. This demonstration will open a new strategy and novel approach for the design and experimental fabrication of this kind of material. • Non-and conductive glass substrates were studied for the impacts of Sb 2 Te 3 thin films. • Lowest E g value correlated with the growth of Sb 2 Te 3 nanograins on borosilicate glass. • Influences of glass substrates on linear/nonlinear optical parameters were investigated. • Higher values of nonlinear optical parameters for borosilicate glass/Sb 2 Te 3 were revealed.

Tuning of fermi level in antimony telluride thin films by low-energy Fe−-ion implantation

Tuning of fermi level in antimony telluride thin films by low-energy Fe−-ion implantation

Spin‐Charge Conversion in Fe/Au/Sb2Te3 Heterostructures as Probed By Spin Pumping Ferromagnetic Resonance

AbstractLarge‐area antimony telluride (Sb2Te3) thin films are grown by a metal organic chemical vapor deposition technique on 4” Si(111) substrates, and their topological character probed by magnetoconductance measurements. When interfaced with Fe thin films, broadband ferromagnetic resonance spectroscopy (BFMR) shows a clear increase of the damping parameter in Fe/Sb2Te3 when compared to a reference Fe layer, which may suggest the occurrence of spin pumping (SP) into Sb2Te3. Simultaneously, X‐ray reflectivity and conversion electron Mossbauer spectroscopy evidence the development of a chemically and magnetically pure Fe/Sb2Te3 interface. However, by conducting SP‐FMR, it is shown that no spin‐to‐charge conversion (S2C) occurs in Fe/Sb2Te3, while a clear SP signal develops by introducing a 5 nm Au interlayer between Fe and Sb2Te3, with a measured inverse Edelstein effect conversion efficiency of λIEE = 0.27 nm. The results shed some light on the correlation among the chemical‐structural‐magnetic properties of the Fe/Sb2Te3 interface, the broadening of the magnetic damping parameter as detected by BFMR, and the occurrence of S2C, as probed by SP‐FMR.

Fabrication of PEDOT: PSS-PVP Nanofiber-Embedded Sb2Te3 Thermoelectric Films by Multi-Step Coating and Their Improved Thermoelectric Properties.

Antimony telluride thin films display intrinsic thermoelectric properties at room temperature, although their Seebeck coefficients and electrical conductivities may be unsatisfactory. To address these issues, we designed composite films containing upper and lower Sb2Te3 layers encasing conductive poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)- polyvinylpyrrolidone(PVP) nanowires. Thermoelectric Sb2Te3/PEDOT:PSS-PVP/Sb2Te3(ED) (STPPST) hybrid composite films were prepared by a multi-step coating process involving sputtering, electrospinning, and electrodeposition stages. The STPPST hybrid composites were characterized by field-emission scanning electron microscopy, X-ray diffraction, ultraviolet photoelectron spectroscopy, and infrared spectroscopy. The thermoelectric performance of the prepared STPPST hybrid composites, evaluated in terms of the power factor, electrical conductivity and Seebeck coefficient, demonstrated enhanced thermoelectric efficiency over a reference Sb2Te3 film. The performance of the composite Sb2Te3/PEDOT:PSS-PVP/Sb2Te3 film was greatly enhanced, with σ = 365 S/cm, S = 124 μV/K, and a power factor 563 μW/mK.

Optimizing the Structural, Electrical and Thermoelectric Properties of Antimony Telluride Thin Films Deposited on Aluminum Nitride-coated Stainless Steel Foil

In this study, we examined the thermoelectric (TE) properties of co-evaporated p-type antimony telluride (Sb2Te3) thin films on aluminum nitride (AlN)-coated stainless steel foil substrates. We investigated the influence of composition and substrate temperature on the thin-film microstructure and transport properties, by varying the tellurium (Te) concentration in the thin films as well as the substrate temperature during deposition (room temperature (RT) and 300 °C). Thin films prepared with an RT substrate were further annealed at 264 °C to obtain crystallized thin films with high phase purity. Columnar thin films with large grains and a standard multi-oriented crystal structure were obtained when thin films were deposited on substrates heated to 300 °C. Thin films deposited at RT and subsequently annealed at 264 °C had a dense, layered microstructure, with a preferential c-axis or (00 l) texture as the compositions approached phase stoichiometry. The temperature dependence of the thermoelectric properties was measured, and variations were interpreted in terms of the deviation from stoichiometry and the obtained microstructure. A maximum power factor (PF) of 0.87 mW/m ∙ K2 was obtained for off-stoichiometric 65.0 at% Te thin film, which was the highest among the samples deposited at high substrate temperatures. A higher PF of 1.0 mW/m ∙ K2 was found for off-stoichiometric thin films with 64.5 at% Te, which was deposited at RT and subsequently annealed. The improvement of thermoelectric power in films containing excess Te could be related to energy dependent carrier scattering at the Sb2Te3/Te interface.

EFFECT OF ALTERNATE LAYERS OF Bi2Te3 - Sb2Te3 THIN FILMS ON STRUCTURAL, OPTICAL AND THERMOELECTRIC PROPERTIES

There is an increasing demand for the development of new thermoelectric materials with high figure of merit. This is due to the fact that convectional energy generating methods causes many environmental problems. Thermoelectric materials have capacity to harvest waste energy as they convert directly any type of waste heat into electricity. Telluride based materials are known as best thermoelectric materials as they have high figure of merit. Present work is based on multilayered structure of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin films. In this work thin film of single layered Bi2Te3, Sb2Te3, their bilayers (Bi2Te3-Sb2Te3), 5 layers and 10 layers have been deposited on clean glass substrate by e-beam evaporation method. X- Ray diffraction (XRD) has been done for the characterization of these thin films. In this paper, studies of electrical properties are also reported which have been carried out by Hall and I-V measurements while optical properties have been studied by employing by UV – Vis spectrometer. Thermoelectric characteristics have been measured by laboratory thermoelectric measurement setup.

Epitaxial and large area Sb2Te3 thin films on silicon by MOCVD.

Antimony telluride (Sb2Te3) thin films were prepared by a room temperature Metal–Organic Chemical Vapor Deposition (MOCVD) process using antimony chloride (SbCl3) and bis(trimethylsilyl)telluride (Te(SiMe3)2) as precursors. Pre-growth and post-growth treatments were found to be pivotal in favoring out-of-plane and in-plane alignment of the crystallites composing the films. A comprehensive suite of characterization techniques were used to evaluate their composition, surface roughness, as well as to assess their morphology, crystallinity, and structural features, revealing that a quick post-growth annealing triggers the formation of epitaxial-quality Sb2Te3 films on Si(111).

Surface Deformation Study of the Electrodeposited Nanostructured Bi2Te3 and Sb2Te3 Thin Films by Double‐Exposure Digital Holographic Interferometry

Bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin films are successfully deposited on stainless steel (SS) substrate by the potentiostatic mode of electrodeposition. Herein, the focus is on surface deformation during the electrodeposition process under the effect of deposition time. This study is carried out using double‐exposure digital holographic interferometry (DEDHI) technique and the prepared optimized films are characterized for their physico‐chemical properties. The deposition potential is found out by cyclic voltammetry; it is −170 and −260 mV for Bi2Te3 and Sb2Te3, respectively. The hologram fringes are recorded during the electrodeposition of films and the variations in the number of fringes, deposited mass, thickness of film, and stress to surface with respect to deposition time are studied.

Silver content dependent thermal conductivity and thermoelectric properties of electrodeposited antimony telluride thin films

While electrodeposited antimony telluride thin films with silver contents demonstrated promising thermoelectric properties, their thermal conductivity and the silver content dependence remain unknown. Here, we report the thermal conductivities of Ag3.9Sb33.6Te62.5 and AgSbTe2 thin films with controlled annealing and temperature conditions and demonstrate the impact of silver content on thermal transport. After annealing at 160 °C, the room-temperature thermal conductivity of Ag3.9Sb33.6Te62.5 and AgSbTe2 thin films increases from 0.24 to 1.59 Wm−1 K−1 and from 0.17 to 0.56 Wm−1 K−1, respectively. Using phonon transport models and X-ray diffraction measurements, we attribute the thermal conductivity increases to the crystal growth and explain the thermal conductivity variations with the degree of crystallization. Unlike electrical properties reported in previous studies, the presence of silver contents has little impact on the thermal conductivity of Ag3.9Sb33.6Te62.5 and leads to a strong reduction in the thermal conductivity of AgSbTe2 thin films. By performing transient thermal conductivity measurements at 94 °C, we find the crystallization activation energy of Ag3.9Sb33.6Te62.5 and AgSbTe2 films as 1.14 eV and 1.16 eV, respectively. Their differences reveal the role of silver in inhibiting the nucleation and growth of Sb2Te3 crystals and impeding thermal transport. These findings provide guidance for optimizing doping and annealing conditions of antimony tellurides for near-room-temperature thermoelectric applications.

High thermopower in (00l)-Oriented nanocrystalline Bi-Sb-Te thin films produced by one-step thermal evaporation process

In the present study, we have studied the low temperature power factors of (00l) oriented nanocrystalline bismuth antimony telluride thin films that were deposited by one step thermal evaporation. Structural features of the films were probed using X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM). XRD analysis revealed that the films were oriented along (00l) direction, in contrast to the films deposited at room temperature conditions. Films showed a promising seebeck coefficient (S) of −167.4 μV/K and electrical conductivity (σ) of 6.19 × 103 S/m which led to a power factor (S2σ) of 173.5 μW/mK2 at room temperature. FESEM analysis depicted that the film was composed of ‘flake’ like grains. Crystallite size corresponding to the most intense peak in XRD turned out to be 22.7 nm. Thickness of the films was found to be 135 nm from the cross sectional FESEM of the film. Elemental composition of the films was probed using Energy Dispersive X-ray spectroscopy. The electrical properties of the film were also checked at regular time interval which showed that films had a stable electrical performance.

Multifold improvement of thermoelectric power factor by tuning bismuth and antimony in nanostructured n-type bismuth antimony telluride thin films

Bismuth telluride (Bi2Te3) based alloys are preferred thermoelectric materials for room temperature thermoelectric applications. Electrical transport and thermopower properties of n-type nanostructured BixSb2-xTe3 films were tuned by post-growth heat treatment. We report that annealing of sputter-deposited nanostructured Bi0.7Sb1.3Te3 films lead to several-fold increases in thermoelectric power factor α2σ, where σ is electronic conductivity and α is Seebeck coefficient. Annealing at Tanneal = 200 °C nearly quadruples the power factor to α2σ = 3.1 μW cm−1 K−2. Spectroscopy and microscopy analyses indicate that the power factor increase is attributable to ~50% decrease in the Bi/Sb ratio, and grain growth, which increase the charge carrier concentration and mobility. The observed Bi depletion is contrary to annealing-induced Te depletion reported in p-type films. For Tanneal > 200 °C, although continued Bi depletion increases σ, a precipitous decrease in α sharply lowers the power factor, yielding tenfold lower α2σ for Tanneal = 400 °C than the as-deposited films. Our findings indicate that post-deposition annealing is a potent way to tune the thermoelectric properties of n-type Bi2Te3-based alloy films to fabricate devices for high-efficiency solid-state refrigeration and power harvesting from waste heat.

Passively Q-Switched Pulse Erbium Doped Fiber Laser Using Antimony (III) Telluride (Sb2Te3) thin Film as Saturable Absorber

This paper demonstrates on an antimony telluride (Sb2Te3) thin film sandwiched between two fiber ferrule as saturable absorber for Q-switched pulsed Erbium doped fiber (EDF) laser. The saturable absorber is fabricated by dissolving Antimony (III) Telluride powder into PVA solution and dry in the ambient temperature for 48 hours. Then, 1 mm2 x 1 mm2 Sb2Te3-PVA film based saturable absorber is sandwiched in between FC/PC ferrule for Q-switched laser generation. The modulation depth of the Sb2Te3 is measured as 28.01% with input intensity 0.02 MW/cm2. The developed passive saturable absorber integrated in EDF laser in ring cavity and the characterised pulse is with repetition rates of 30.21 kHz, shortest pulse width of 3.26 µs and signal-noise-ratio (SNR) of 42 dB. The maximum output pulse energy is achieved at pump power 69.5 mW with 29.5 nJ and the output power 0.89 mW.

Sb2Te3 thin film for the passive Q-switching of a Tm:GdVO4 laser

We report on the first application of an antimony telluride (Sb2Te3) thin film as a saturable absorber (SA) in a microchip laser. The 3–15 nm-thick Sb2Te3 films were deposited on glass substrates by pulsed magnetron sputtering and they were studied by SEM, X-ray diffraction, Raman and optical spectroscopy. The saturable absorption of the Sb2Te3 film was confirmed at 1.56 μm for ns-long pulses revealing low saturation intensity of 0.17 MW/cm2. The microchip laser was based on a Tm:GdVO4 crystal diode-pumped at ~802 nm. In the continuous-wave regime, this laser generated 3.54 W at 1905–1921 nm with a slope efficiency of 37%. The Q-switched laser generated a maximum average output power of 0.70 W at 1913 nm. The highest pulse energy of 3.5 µJ and the shortest pulse duration of 223 ns were obtained at the 200 kHz repetition rate.