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This study reports on the synthesis of tellurium-based glasses that have a wide transmission far beyond the second atmospheric window. Several far-infrared(IR) transmitting glass systems including Ge-In-Te, Ge-Ga-Te, as well as some compositions containing alkali halides (KI, CsI) or metal halides (PbI2, CuI, AgI, CdI2 or ZnI2) are reported. Their glass-forming ability, thermal stability, and IR transmitting property are investigated. The results show that the broad absorption peak in the 15-20 μm disappear in the Fourier-transform infrared (spectrometer) spectra when gallium is replaced by indium. Te-based chalcogenide glasses containing metal-halides show superior glass-forming ability and better thermal stability than those containing alkali halides. Among these glasses, the ΔT of glass composition 65GeTe4-17In2Te6-18AgI can be as great as 115 °C. In ternary system, the glass composition Ge16Te69(AgI)15 (ΔT = 120 °C) is stable enough toward crystallization in combination with broad transmission region and good chemical durability to be drawn into optical fibers. [ABSTRACT FROM AUTHOR]

The glass‐ceramics of AgI‐based electroconductive chalcogenide system was realized using an appropriate heat treatment at a fairly high temperature (Tg + 40°C) and different times ranging from 4 to 20 hours. The crystallization behavior and electroconductive properties of the heat‐treated samples were studied in detail. Transmission study was performed, and the results show that the cut‐off edge of the short wavelength is red‐shifted at prolonged annealing time but remains an excellent transmittance in the mid‐infrared (IR) region. XRD and scanning electron microscopy results indicated that the precipitated crystalline phases are mainly β‐/γ‐AgI. Moreover, a small amount of α‐AgI, which rarely existed at room temperature, is precipitated in the AgI‐rich chalcogenide glass‐ceramics. The ionic conductivity of all glass‐ceramics was enhanced by heat treatment in contrast to that of base glass. Raman analysis exhibited the structure variation in the glass sample after heat treatments. This study provided an observation of crystallization in chalcogenide glass containing large amounts of AgI and be of good guidance to fabricate novel AgI‐based chalcogenide glass‐ceramics that can be candidates in infrared optics and solid electrolyte applications. [ABSTRACT FROM AUTHOR]

Diagram of the phase transformation behavior of GeS2- Ga2 S3- CsI glasses is realized in this article and the structure-property dependence of the chalcogenide glasses is elucidated using differential scanning calorimetry and Raman spectroscopy. We observe the compositional threshold of crystallization behavior locates at x = 6-7 mol% in (100− x)(0.8 GeS2-0.2 Ga2 S3)- x CsI glasses, which is confirmed by the thermodynamic studies. Structural motifs are derived from the Raman result that [ Ge( Ga) S4], [ S2 GeI2], [ S3 GaI], and [ S3 Ga- GaS3] were identified to exist in this glass network. Combined with the information of structural threshold, local arrangement of these structural motifs is proposed to explain all the experimental observations, which provides a new way to understand the correlation between crystallization behavior and network structure in chalcogenide glasses. [ABSTRACT FROM AUTHOR]

Abstract: Transparent glass ceramics based on Bi2O3–B2O3–TiO2 ternary glass system were prepared by controlled one-step heat treatment method. X-ray diffraction measurement confirms the formation of Bi2O3 phase crystals in glass network. Z-scan measurements at a wavelength of 750nm were employed to investigate the third-order optical nonlinearities of these transparent glass ceramics. The results show that the nonlinear properties were significantly enhanced after crystallization process. [ABSTRACT FROM AUTHOR]

This study reports on the synthesis of tellurium-based chalcogenide films that have high thermal stability for phase change memory application. Several Te-based chalcogenide alloys of In-Bi-Te, Ag-Bi-Te, In-Sb-Te, Sn-Sb-Te, Zn-Ge-Te, and Ga-Ge-Te are reported. Their thermal, optical, and electrical properties are investigated. The results show that Bi-Te-based films have a higher crystallization temperature and greater activation energy compared with the other Sb-Te-based and Ge-Te-based films. Especially, In2.8Bi36.6Te60.6 film exhibits high crystallization temperature (252 °C) and great activation energy (5.16 eV), showing much improved amorphous thermal stability. A relatively wider optical band gap (0.674 eV) of thermal annealed In2.8Bi36.6Te60.6 film is obtained. In addition, it also has a higher amorphous/crystalline resistance ratio of about 105, implying that current consumption could be low in the phase-change memory operation. [ABSTRACT FROM AUTHOR]

The superior performance of Zn-doped Sb7Te3 films might be favorable for the application in phase change memory. It was found that Zn dopants were able to suppress phase separation and form single stable Sb2Te crystal grain, diminish the grain size, and enhance the amorphous thermal stability of Sb7Te3 film. Especially, Zn30.19(Sb7Te3)69.81 film has higher crystallization temperature (∼258 °C), larger crystallization activation energy (∼4.15 eV), better data retention (∼170.6 °C for 10 yr), wider band gap (∼0.73 eV), and higher crystalline resistance. The minimum times for crystallization of Zn30.19(Sb7Te3)69.81 were revealed to be as short as ∼10 ns at a given proper laser power of 70 mW. [ABSTRACT FROM AUTHOR]

Zn-doped Sb2Te films are proposed to present the feasibility for phase-change memory application. Zn atoms are found to significantly increase crystallization temperature of Znx(Sb2Te)1-x films and be almost linearly with the wide range of Zn-doping concentration from x = 0 to 29.67 at.%. Crystalline resistances are enhanced by Zn-doping, while keeping the large amorphous/crystalline resistance ratio almost constant at ∼105. Especially, the Zn26.07(Sb2Te)73.93 and Zn29.67(Sb2Te)70.33 films exhibit a larger resistance change, faster crystallization speed, and better thermal stability due to the formation of amorphous Zn-Sb and Zn-Te phases as well as uniform distribution of Sb2Te crystalline grains. [ABSTRACT FROM AUTHOR]

Abstract: Dy3+ doped 40GeSe2–25Ga2Se3–35CsI (GGC) glass was synthesized, and optical spectrum, such as infrared transmission and Vis-Nir absorption was measured. Base on the Judd–Ofelt theory, the three Judd–Ofelt parameters Ω t (t =2, 4, 6) were calculated and the results were compared with other chalcogenide glasses. The small Ω 2 in GGC glass is ascribed to the weak covalency of Se–Dy bond. The theory of crystallization kinetics under non-isothermal condition was developed, and was applied to analyze this Dy3+ doped GGC glass. From the heating-rate dependence of crystallization temperature, the activation energy for crystallization E =148kJ/mol is obtained, and this value is much smaller than that of the undoped glass host, indicating the introduction of Dy3+ ions into the GGC glass will get the host crystallized easily. [Copyright &y& Elsevier]

Abstract: GeSe2–Ga2Se3–CsI chalcohalide glasses had been prepared by the melt-quenching technique. With the addition of CsI, the short wavelength cut-off edge of the glasses shifts to the short wavelength gradually, while the long wavelength cut-off edge located at ∼16μm is nearly unchanged. Thermal properties were measured by Differential Thermal Analysis (DTA). From the heating rate dependence of crystallization temperature, the activation energy for crystallization (E) and the order parameter (n) were calculated by the Kissinger equation. The results show that the activation energy of crystallization decreases dramatically with increasing of CsI content, and the most probable crystallization mechanism is volume controlled one-dimensional growth. [Copyright &y& Elsevier]

The confinement of CsPbX 3 (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr 3− x I x NCs with arbitrary I/Br ratio among an elaborately designed GeS 2 –Sb 2 S 3 -based chalcogenide glass matrix. Spherical CsPbBr 3− x I x NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr 3− x I x NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX 3 NCs into glassy matrices, facilitating their future applications in photoelectronic fields. [ABSTRACT FROM AUTHOR]

The glass-forming ability, crystallization behavior and physical properties of GeS 2 -Sb 2 S 3 -CsX (X = Cl, Br, I) glasses and glass-ceramics (GCs) are systematically studied by various characterization techniques. With the introduction of cesium halides, transparent chalcogenide GCs containing the single nanocrystals of CsX can be obtained in a controlled fashion. The crystallization behavior was investigated in the line of (100- x) (0.5GeS 2 -0.5Sb 2 S 3)- x CsX glasses. IR-transmitting chalcogenide GCs embedded with CsCl and CsBr nanocrystals of a large crystallinity have been fabricated successfully after thermal treatments, whereas surface crystallization of CsI is dominated in GeS 2 -Sb 2 S 3 –CsI glassy samples. Such distinct crystallization behaviors of CsX crystal phases are compared and discussed with microstructural results. We propose that the ionic diffusion ability of halogen in the GeS 2 -Sb 2 S 3 -CsX glassy network determines the nucleation and crystal growth of CsX. This finding is of guidance meaning for future design of chalcogenide GCs with novel optical functions and microstructures. [ABSTRACT FROM AUTHOR]

Abstract Germanium-Telluride has been widely studied as a phase-change material due to its fast crystallization speed. The understanding of the crystallization kinetics is important to evaluate the potential applications of the material, but this is limited by the conventional calorimetry with low heating rate and narrow temperature range. We here employed an ultrafast calorimetry method, named flash differential scanning calorimetry, to investigate the crystallization kinetics of Ge x Te 100-x in a wide compositional range (15 ≤ x ≤ 55). By means of the X-ray diffraction, we found the complicated competition between crystalline GeTe and Te (or Ge) phases in these binary alloys. The crystallization kinetics of first crystalline phase were estimated and it was found that, Ge x Te 100-x generally has intermediate crystal growth speed and fragility, which is ascribed to the border between covalent and metallic properties. Component dependences of maximum crystal growth rate (U max) and fragility were investigated, revealing the component in x = 20.4 has the lowest U max of 1.22 × 10−3 m s−1 with the smallest fragility of 42.2, and the component in x ≈ 50 possesses the largest U max of 3.5 m s−1. It confirms that, GeTe is the most suitable phase-change material for information storage and GeTe 4 is the best media for information transparency in Ge-Te binary. Moreover, a tri-counter pattern was carried out for obtaining the crystal growth rate directly in studied supercooled Ge x Te 100-x liquids (15 ≤ x ≤ 55). In addition, we first found a peculiar component Ge 22 Te 78 with terrible thermal properties, i.e., phase separation, low crystallization temperature, ultrahigh fragility and anomalous crystallization kinetics. More importantly, together with the crystallization kinetics parameters of other glass formers, it was found a specific relation between reduced glass temperature (T rg) and U max for which can be benefit to simplify material screenings and performance optimizations. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

We have reported the fabrication and characterization of Ge 23.5 Ga 11.5 Se 65 glasses and glass-ceramics with different Er 3+ concentrations. It was found that, the emission properties of the bulk glasses showed the fluorescence intensity and lifetime increased until they reached a maximum, and then decreased with increasing Er 3+ concentration. This is due to concentration quenching effect although the maximum dissolving concentration of Er 3+ can be up to ∼1 wt% of Er. A careful thermal process has led to the formation of ∼80 nm β-Ga 2 Se 3 crystalline particles in Ge 23.5 Ga 11.5 Se 65 glasses doped with 0.8 wt% of Er 3+ . By monitoring 4 I 13/2 → 4 I 15/2 Er 3+ transition, almost fourfold enhancement in the intensity and ∼0.57 ms prolongation in the lifetime of near-infrared fluorescence at 1.54 μm have been observed after crystallization. It was assigned to the decreasing phonon energy of the local environment of Er 3+ ions during the crystallization. [ABSTRACT FROM AUTHOR]

The thermal stability and crystallization characteristics of W-doped Sb 3 Te films have been studied systematically. It was found that W atoms presented in the form of amorphous content, which increased the crystallization temperature and crystalline resistance, sustained uniform single crystalline structure and refined their grain size of Sb 3 Te films. The optimized W 20.1 (Sb 3 Te) 79.9 film exhibits higher crystallization temperature (∼204 °C), larger crystalline activation energy (∼3.13 eV) and better data retention ability (∼123 °C for 10 yr) as well as a single stable Sb 2 Te phase for phase change memory application. [ABSTRACT FROM AUTHOR]

The Zn-doped Sb 2 Te 3 films have been investigated systematically during the phase transformation process. It was found that, the increase of crystallization temperature in the Zn-doped Sb 2 Te 3 films leads to its enhanced amorphous stability, and Zn incorporation can increase electrical resistance, widen optical band gap and refine crystalline grain size. The crystallization mechanism can be tuned into nucleation-dominated from growth-dominated type. Moreover, Sb 2 Te 3 film with high Zn-doping concentration such as Zn 38.8 (Sb 2 Te 3 ) 61.2 film was found to exhibit a higher crystallization temperature (233 °C), better data retention ability (keeping the amorphous state at 146.5 °C for ten years), and wider band gap (0.839 eV). A lower threshold of crystallization (~ 25 ns) can be realized in the Zn 38.8 (Sb 2 Te 3 ) 61.2 film irradiated at the laser power of 70 mW in comparison with that in the conventional Ge 2 Sb 2 Te 5 film. We confirm that the Zn doping is responsible for a fast switching and the Zn 38.8 (Sb 2 Te 3 ) 61.2 compound is stable against segregation with cycling. [ABSTRACT FROM AUTHOR]

Abstract: Mg-doped Ge2Sb2Te5 (GST) films with different Mg doping concentrations have been prepared, and their crystallization behavior, structure and electrical properties have been systematically investigated for phase-change memory applications. The results show that the addition of Mg into GST films could result in an enhancement in crystallization temperature, activation energy and electrical resistance compared with the conventional GST films, indicating that a good amorphous thermal stability. On the other hand, the proper Mg concentration ranging from 13.6 to 31.1at.% can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase and suppress the formation of the hexagonal close-packed (hcp) crystalline phase. X-ray photoelectron spectra (XPS) further confirm that the formation of covalent Mgcontribute to the enhanced thermal stability in Mg-doped GST films. [Copyright &y& Elsevier]

Abstract: The thermal and electrical properties of Zn1.25Sb2Te3 film have been investigated for phase change memory (PCM) applications. Compared with the conventional Ge2Sb2Te5, Zn1.25Sb2Te3 film exhibits a higher crystallization temperature (∼200°C), greater activation energy (2.71eV), and better data retention of 10 years at 105°C. In addition, higher crystalline resistance and better resistance contrast are helpful to reduce RESET current and achieve a higher On/OFF ratio of PCM, respectively. Raman spectra of crystalline thin films suggests that the local bonding arrangement around Sb atoms changes; Sb2Te3 component is thus mainly responsible for the phase transition in Zn1.25Sb2Te3 alloys. [Copyright &y& Elsevier]

Abstract: A systematic series of (Ge20Se15Te65)1− x –(SnI2) x (x =0, 0.05, 0.1, 0.15) chalcogenide glasses have been prepared. The amorphous nature can be confirmed by XRD and SEM. With the SnI2 content increasing, the indirect optical band gaps are decreased from 0.662 to 0.622eV according to Tauc laws. The introduction of SnI2 makes the glasses much easier to prepare and more stable against crystallization, making them drawable as optical fibers. The highest ΔT (130°C) value for (Ge20Se15Te65)0.9–(SnI2)0.1 glass composition can be obtained. A slight red-shifting of the long-wavelength cutting-off edge from 18.4 to 19.4μm was shown and it seems that SnI2 in these glasses offers the improvement in the far-infrared properties. [Copyright &y& Elsevier]