Search Results (49)

This study investigates the dielectric relaxation and conduction mechanisms in $S{e}_{90}S{n}_{6}P{b}_4$ chalcogenide glassy material, which is of interest for applications in phase-change memory devices, optical memory, and thermoelectric sensors. Despite previous studies on chalcogenide glasses, the conduction mechanisms at varying temperatures and the role of correlated barrier hopping (CBH) remain unclear. Using impedance spectroscopy in the frequency range 1 Hz–1 MHz at temperatures from 288 K to 318 K, the real ($Z\prime$) and imaginary ($Z″$) parts of the complex impedance were recorded. The sample was also characterized by X-ray diffraction (XRD) to confirm its glassy nature, and X-ray photoelectron spectroscopy (XPS) to determine the surface chemical composition and oxidation states of the elements. Peaks in $Z″$ at each temperature were used to evaluate the relaxation time τ, revealing thermally activated processes with an activation energy of 0.62 eV. Nyquist plots showed semicircular behavior with decreasing radii at higher temperatures, indicating enhanced d.c. conductivity with an activation energy of 0.63 eV. A.C. conductivity analysis demonstrated frequency-dependent behavior consistent with the CBH model, with hopping energy calculated as 0.32 eV. The dielectric loss increased with temperature and decreased with frequency, stabilizing above 250 Hz at 318 K. These findings provide new insights into the dielectric and conduction properties of $S{e}_{90}S{n}_{6}P{b}_4$ glasses, supporting their optimization for practical electronic applications. Full article

The long-wave infrared band, which at room temperature covers the infrared radiation of humans and objects, has significant applications across various fields including wireless communication, national defense, military, biomedical, and advanced driver assistance systems. Metalens provides a pathway to lightweight, compact, and integrated solutions for infrared imaging and sensing systems, marking an inevitable trend in future development. This study presents a design for a high numerical aperture of 0.89 in a polarization-insensitive all-chalcogenide metalens operating at 10 µm, utilizing the commercially available chalcogenide glass material As₂Se₃ via a transmission phase approach. Building upon this, we have achieved, for the first time, a high numerical aperture of 0.84 for an all-chalcogenide broadband LWIR achromatic metalens operating in the 9.5–10.5 µm range, with significantly improved focusing performance through the application of particle swarm optimization algorithms. The superior performance of the all-chalcogenide LWIR metalens, combined with the advantages of chalcogenide glass over traditional LWIR materials such as Si or Ge—namely, lower cost, reduced optical loss, and a smaller thermo-optic coefficient—suggests it has significant potential for broader applications. Full article

Chalcogenide glasses are known as optical materials for the infrared spectral range. These compounds may also be of interest as materials for the low-frequency part of the terahertz range of electromagnetic waves, which is currently being intensively studied in connection with the numerous possible applications of terahertz radiation. However, the terahertz optical characteristics of chalcogenide glasses remain poorly studied. In this work, eight different compositions of GeAsSeSbSnTe chalcogenide glasses were investigated using terahertz time-domain spectroscopy. A number of compositions, in particular GeSeTe and AsSeSbSn, were studied in the terahertz spectral range for the first time. Spectra of the refractive index and extinction coefficient were obtained for studied materials in the spectral range of 0.1–2.2 THz. The experimental frequency dependence of the product of the terahertz power absorption coefficient and the refractive index for the entire set of studied glasses is approximated by a power function. It was established that the exponent of the approximating power functions varies from 1.68 to 2.34 depending on the composition of the chalcogenide glass. For the studied glasses, a correlation was found between the values of the average coordination number characterizing the chalcogenide glass structure, and the values of the exponent of the functions approximating the THz absorption spectra. Full article

The growing need for real-time, accurate monitoring of hazardous gases in environmental, industrial, and healthcare settings has highlighted the limitations of traditional sensing methods. Photonic Integrated Circuits (PICs) have become a revolutionary platform due to their high sensitivity, accurate selectivity, compact size and cost-effectiveness. We present in this work a comprehensive overview of the best-reported PIC-based gas sensors. We discuss the basic concepts behind resonance-based and absorption-based sensing. A detailed overview of the various material platforms, from well-known silicon and silicon nitride to new polymers, chalcogenide glasses, and 2D materials, is presented. A comparison of key device topologies, such as waveguides, microring resonators, Mach–Zehnder interferometers, and metasurfaces, is conducted, with performance benchmarks indicating the limit of detection (LoD). The main limitations of PIC sensors are discussed in this review. We also discuss promising technologies, especially the game-changing potential of artificial intelligence to create fully autonomous devices. Full article

The creation of novel, effective materials with specific properties is necessary to advance technology. To do this, objective regularities between the material’s composition, structure, and properties must be found. A comparative analysis of glass-forming regions, arranged according to the systematic substitution of one element by its analog within a periodic system subgroup, provides a useful framework for discussing trends in glass formation in semiconductor alloys. In this review, the information on the glass formation in the chalcogenide systems GeSe₂–As₂Se₃–MeCh, where Me = Cu, Ag, Zn, Cd, Sn, Pb; Ch = Se, Te, was subjected to a thorough comparative analysis to establish objective patterns in the change in the glass-forming ability in these systems. The effect of MeCh on the formation of glass in the binary system GeSe₂–As₂Se₃ was traced. Full article

This paper is about the design and fabrication of infrared lenses, which are the core components of thermal imaging cameras to be mounted on vehicles. To produce an athermalized optical system, chalcogenide glass (As₄₀Se₆₀) with a lower thermo-optic coefficient (dn/dT) than germanium was adopted as a lens material, and each lens was designed so that defocus occurs in opposite directions depending on temperature. The designed lens was fabricated using a compression molding method, and the molded lenses showed less than 1.5 μm of form error (PV) using a mold iteration process. Through evaluations of MTF and thermal images obtained from the lens module, it was judged that this optical design process is obtainable. Full article

New bulk chalcogenides from the system (GeTe₆)_1−xCu_x, where x = 5, 10, 15 and 20 mol%, have been synthesized. The structure and composition of the materials were studied using X-ray powder diffraction (XRD) and energy-dispersive spectroscopy (EDS). Scanning electron microscopy (SEM) was applied to analyze the surface morphology of the samples. Some thermal characteristics such as the glass transition, crystallization and melting temperature and some physico-chemical properties such as the density, compactness and molar and free volumes were also determined. The XRD patterns show sharp diffraction peaks, indicating that the synthesized new bulk materials are crystalline. The following four crystal phases were determined: Te, Cu, CuTe and Cu₂GeTe₃. The results from the EDS confirmed the presence of Ge, Te and Cu in the bulk samples in concentrations in good correspondence with those theoretically determined. A layered thin-film material based on Ge₁₄Te₈₁Cu₅, which exhibits lower network compactness compared to the other synthesized new chalcogenides, and the azo polymer PAZO was fabricated, and the kinetics of the photoinduced birefringence at 444 nm was measured. The results indicated an increase in the maximal induced birefringence for the layered structure in comparison to the non-doped azo polymer film. Full article

The shortage of tellurium and toxicity of lead are major obstacles to scaling mid-temperature thermoelectric generators. We engineer quaternary lead chalcogenides with composition (Pb_0.8Ge_0.2Te)_0.95-x(PbSe)_0.05(PbS)_x (0 ≤ x ≤ 0.25), where Pb is lead, Ge is germanium, Te is tellurium, Se is selenium, S is sulfur, and x denotes the molar fraction of lead sulfide (PbS). The primary novelty lies in achieving ultra-low thermal conductivity through controlled phase segregation induced by systematic PbS incorporation. X-ray diffraction analysis reveals single-phase solid solutions up to x ≈ 0.10, with secondary PbS precipitates forming beyond this threshold. These PbS-rich phases create hierarchical microstructures that scatter phonons across multiple length scales, suppressing total thermal conductivity to 0.6 Wm⁻¹K⁻¹ at x = 0.15—approximately 84% lower than pristine lead telluride (PbTe) and approaching glass-like thermal conductivity values. Electrical transport measurements demonstrate sulfur’s role as an electron donor, enabling carrier-type control from p-type to n-type conduction. Despite moderate electrical power factors, the optimized composition (x = 0.20) achieves a peak dimensionless figure of merit ZT ≈ 0.34 at 650 K. This work demonstrates an effective strategy for tellurium-lean, lead-reduced thermoelectric materials through sulfur-induced phase segregation, providing practical design guidelines for sustainable waste heat recovery applications. Full article

Chalcogenide glasses (ChGs) are a class of amorphous materials presenting remarkable mechanical, optical, and electrical properties, making them promising candidates for advanced photonic and optoelectronic applications. With the increasing integration of artificial intelligence in modern materials design, we are able to systematically select, prepare, and optimize appropriate compositions for desired applications in a manner that was unachievable before. This study employs various machine learning models to reliably predict the refractive index at 20 °C using a small dataset of 541 samples extracted from the SciGlass database. The input for the algorithms consists of a selected set of physico-chemical features computed for the chemical composition of each entry. Additionally, these algorithms served as inner models for an ensemble logistic regression estimator that achieved a superior ${\mathrm{R}}^2$ value of 0.8985. SHAP feature analysis of the second-best model, CatBoostRegressor (${\mathrm{R}}^2$ = 0.8920), revealed the importance of elemental density, atomic weight, ground state atomic gap, and fraction of p valence electrons in tuning the value of the refractive index of a chalcogenide compound. Full article

Zinc sulfide (ZnS) is extensively utilized in various applications due to its exceptional optical transmittance across numerous spectral bands. To achieve ultra-high surface quality ZnS optical components, shear thickening polishing (STP) is employed to reduce roughness. A comparison between traditional fixed abrasive polishing (FAP) and STP for ZnS glass showed that FAP results in poor surface quality due to its low removal efficiency and uneven abrasive exposure, while STP provides better surface quality due to its flexible removal process, proving its feasibility and advancement. The Taguchi method was used to study the impact of three key polishing parameters on surface roughness (Ra) and the material removal rate (MRR), finding that polishing angle most influenced roughness and speed most influenced MRR. With optimal parameters, ZnS glass surface roughness was reduced from 110 ± 15 nm to 8.85 ± 0.5 nm, with an MRR of 32.5 nm/min. Scanning electron microscope (SEM) images further confirmed STP’s effectiveness in removing microdefects and smoothing the ZnS glass surface, offering a new method for the efficient, high-quality polishing of chalcogenide glasses without surface damage. Full article

Being a type of carbonaceous material, glassy carbon possesses thermomechanical properties akin to ceramics, offering both mechanical and chemical stability at high temperatures; therefore, it can be applied in electrochemistry and high-temperature manufacturing. However, the direct pyrolysis of a bulk precursor leads to internal pores and cracks, usually resulting in fracture. Our characterization results show that at temperatures below 400 °C, large pores do not form, and pre-carbonized glassy carbon (PGC) formed at 350 °C has a dense microstructure without cracks. It exhibits a high compressive strength of ~370 MPa and flexural strength of ~190 MPa, making it suitable for load-bearing applications. Additionally, the PGC-350 material shows small mass loss (~5%) and reasonably low thermal expansion (2.5 × 10⁻⁶/°C) when heated to 350 °C again. These properties suggest the potential of PGC for high-temperature applications. As a demonstration, PGC formed at 350 °C was employed to fabricate molds to press chalcogenide glass blanks, which exhibited favorable molding results for various surface morphologies. Full article

The roller-to-plate (R2P) hot-embossing process is an effective, low-cost method for producing high-quality micro-/nano-optical components. In the field of night vision applications, the fabrication of chalcogenide glass microstructures is emerging as a promising alternative to traditional infrared glass. This trend is driven by the potential of chalcogenide glass to surpass conventional materials in terms of performance. However, the development of R2P hot embossing faces challenges, such as the high cost of curved mold manufacturing, the reliance on roll-to-roll processes for nano hot embossing, the limitations of plastic materials, and the unclear viscoelastic properties of infrared glass. In this study, a novel R2P hot-embossing process was developed to fabricate flat chalcogenide glass structures. The key parameters, such as roller temperature, speed, and embossing pressure, were investigated to understand their impact on the glass-filling performance. The deformation mechanism of the glass microstructures was also analyzed. The experimental results show that the R2P hot-embossing method offers excellent reproducibility, achieving a maximum filling rate of 96% and an average roughness deviation of 8.36 nm. The increase in the roller temperature and embossing force increased the filling height of the glass microstructure arrays, while an increase in the roller speed decreased the filling height. Different embossing methods, including variations in speed, temperature, and force, are summarized to analyze the structural changes during embossing. This study provides a foundation and a basis for future research on the roller-to-plate hot embossing process. Full article

High-conductivity tellurium-based glasses were anticipated to be the attractive candidates in chalcogenide glass systems on account of their distinctive characteristics and extensive application prospects. In this paper, the high-density (>96%) Sn₈[(Ga₂Te₃)₃₄(SnTe)₆₆]₉₂ bulk glass with the density of 5.5917 g/cm³ was successfully prepared by spark plasma sintering (SPS) technology at 460 K, using a 5 min dwell time and 450 MPa pressure. The room-temperature thermal conductivity of Sn8 bulk materials significantly decreased from 1.476 W m⁻¹∙K⁻¹ in the crystalline sample to 0.179 W m⁻¹∙K⁻¹ in the glass, and the Seebeck coefficient obviously increased from 35 μV∙K⁻¹ in to 286 μV∙K⁻¹, indicating that the glass transition of tellurium-based semiconductors could optimize the thermal conductivity and Seebeck coefficient of the materials. Compared to the conventional tellurium-based glassy systems, the fabricated Sn8 bulk glass presented a high room-temperature conductivity (σ = 6.2 S∙m⁻¹) and a large glass transition temperature (T_g = 488 K), which was expected to be a promising thermoelectric material. Full article

Chalcogenide glasses have broad applications in the mid-infrared optoelectronics field and as phase-change materials (PCMs) due to their unique properties. Chalcogenide glasses can have crystalline and amorphous phases, making them suitable as PCMs for reversible optical or electrical recording. This study provides an in-depth analysis of the evaporation kinetics of indium-doped chalcogenides, GeTe₄ and GeTe₅, using the physical vapor deposition technique on glass substrates. Our approach involved a detailed examination of the evaporation process under controlled temperature conditions, allowing precise measurement of rate changes and energy dynamics. This study revealed a significant and exponential increase in the evaporation rate of GeTe₄ and GeTe₅ with the introduction of indium, which was particularly noticeable at higher temperatures. This increase in evaporation rate with indium doping suggests a more complex interplay of materials at the molecular level than previously understood. Furthermore, our findings indicate that the addition of indium affects the evaporation rate and elevates the energy requirements for the evaporation process, providing new insights into the thermal dynamics of these materials. This study’s outcomes contribute significantly to understanding deposition processes, paving the way for optimized manufacturing techniques that could lead to more efficient and higher-performing optoelectronic devices and memory storage solutions. Full article

The disadvantage of chalcogenide glasses containing rare earth ions as luminescent materials for the IR optical range is the strong concentration quenching of luminescence due to the non-uniform distribution of rare earth ions in the glass matrix. This study investigates the effect of grinding chalcogenide glass containing Pr³⁺ ions in a planetary ball mill on its luminescent properties in the near-IR range, as well as its optical properties and structure. The results indicate that milling, under certain conditions, leads to a decrease in the concentration quenching of the luminescence of Pr³⁺ ions. This finding suggests that milling can be used in the development of glassy materials with the increased efficiency of luminescence of rare earth ions. However, it is essential to consider that high-energy milling may result in the formation of areas with increased pressure in the obtained material, leading to structural changes in the glass. Full article