Glass Ge Research Articles

Impact of non-bridging oxygens on the thermal, electrical and optical properties of germanate glasses and exploration of the germanate anomaly

In this study, we successfully prepared quaternary germanate glasses (Bax/3Srx/3Cax/3)Ge(1-x)O3 (x = 0.1–0.5) using a containerless solidification method. The structure of the germanate amorphous materials was characterized using techniques such as XRD, SEM, TEM and Raman. We evaluated the thermodynamic properties of the amorphous materials using differential scanning calorimetry and investigated their crystallization activation energies. In terms of application performance, we measured electrical conductivity and impedance spectra for the electrical properties, while the optical properties were assessed through the refractive index and transmittance. The results revealed that the (Ba0.2/3Sr0.2/3Ca0.2/3)Ge0.8O3 system represented the germanium anomaly point. Due to the highest number of ternary rings and the most compact structure within this system, the values of density, glass transition temperature, refractive index, and bandgap all reached their maximum. As the content of alkaline earth oxides increased, the glass network structure gradually fractured, leading to an increase in non-bridging oxygens and corresponding changes in properties.

Structure of Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> glasses studied by high-resolution X-ray photoelectron spectroscopy and Raman scattering

In this paper, the structures of chalcogenide glasses Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> (<i>x</i> = 24%, 26.67%, 29.6%, 32% and 36%) at a fixed Ga atomic content of 8% are studied by high-resolution X-ray photoelectron spectroscopy and Raman scattering spectra. In order to quantify the evolutions of the different structural units in Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> glasses, the number of double peaks in the Ge 3d, Ga 3d and S 2p spectra are determined by iterative fitting method, the binding energy and the full width at half maximum of each peak, and the relative ratio of the integral area of each decomposed peak to that of the whole area of the X-ray photoelectron spectroscopy are thus achieved. On the other hand, the Raman scattering spectra of Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> glass are decomposed into multiple Gaussians based on the structural units. We use the iterative method to simulate the position of peak center, full width at half maximum, and height of each Raman peak. By analyzing the evolution of each unit structure in the glasses, it is found that the network structure of glass network is mainly formed by S atom bridging the tetrahedral structure of GeS<sub>4</sub> and GaS<sub>4</sub>. The S chains or rings structural units are formed in Ge<sub>24</sub>Ga<sub>8</sub>S<sub>68</sub> glass, indicating that S atoms are in excess in the chemical composition of the glass, so there are enough S atoms around Ge and Ga atoms, forming heteropolar Ge—S and Ga—S bonds. With the gradual increase of Ge content, S chains or rings structure units rapidly disappear in Ge<sub>26.67</sub>Ga<sub>8</sub>S<sub>65.33</sub> glass. The Ge—Ge homopolar bonds in the ethane-like structure S<sub>3</sub>Ge—GeS<sub>3</sub> and the <i>M</i>—<i>M</i> (Ge—Ge, Ga—Ga or Ge—Ga) homopolar bonds in the S<sub>3</sub>Ge/Ga—Ga/GeS<sub>3</sub> structure simultaneous appear in the Ge<sub>29.6</sub>Ga<sub>8</sub>S<sub>62.4</sub> glass, and the number of structures increases gradually with the increase of Ge content. This is mainly due to the insufficient number of S atoms in the Ge-Ga-S glass. Once S atoms are lacking, the excess Ge and Ga atoms can only combine with themselves to form the homopolar bond <i>M</i>—<i>M</i>. It can be concluded below. Firstly, Ge and Ga atoms appear mainly in the form of 4-coordination, while S atoms occur mainly in the form of 2-coordination in the chalcogenide glasses of Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub>. Secondly, the existence of <i>M</i>—<i>M</i> bond leads the nanophase to separate, and the ordering degree of glass network structure to decrease .

Na–Bi–Ge Glass Anode as a High‐Performance Network: Studies on Structure, High Rate Capability, and Long Cycle Stability

Herein, the influence of nanosized amorphous intermediate domains such as Na3Bi and NaGe on the electrochemical characteristics of the new Na2O–Bi2O3 glass anode network mixed with “GeO2” nanocrystals is highlighted. High‐resolution transmission electron microscopy pictures are evident of Bi2O3 and GeO2 crystals in the amorphous plain bright Na–Bi glass phase which is also justified in the X‐ray diffraction studies. The initial (1st) and final (500th) charge and discharge capacities are recorded to be 1097/783 and 621/614, respectively. The columbic efficiency ranged between 71% and 98.8% as the current rate varies from 0.1 to 5 C. The ionic conductivity achieved is quite high even for the 500th cycle. This is due to the lowest value of R ct in the electro impedance spectroscopy spectra, which indicates a rise in electronic conductivity. The appreciable results obtained in this investigation create potential interest in designing and developing various glass and glass–ceramic anodes for large‐scale energy storage applications.

Effects of Eu2+ doping on the structure and luminescence properties of strontium borosilicate glasses

Eu2+-doped SiO2-SrO-B2O3 glasses (abbreviated as GE) were successfully prepared and the structure and luminescence properties were detailed investigated. The results show that the GE glass with 0.4 mol% Eu2+ has the most compact structure owing to its low molar volume, high density. The GE glasses exhibit broad luminescence band centered at approximately 469 nm and 0.4 mol% Eu2+ is the optimum doping concentration. The absorption and emission spectra show redshift as increasing Eu2+ concentration. The optical band gap decreases from 2.86 to 2.68 eV and the Urbach energy decreases from 0.2241 to 0.1737 eV. The 5d-4f transition of Eu2+ is an indirect electronic transition. Concentration quenching occurs with the increase of Eu2+ content and the mechanism is belong to the type of electric dipole-dipole interaction. The luminescence intensity decreases with increasing temperature and the thermal quenching activation energy is 0.26 eV. The chromaticity shift is lower than Eu2+-doped commercial phosphors.

Na–Ge glass anode network mixed with bismuth oxide nanocrystallites: A high capacity anode material for use in advanced sodium-ion battery design

Exploring the growing phenomenon of amorphous intermediate domains at nanoscale and its application as flexible active centres in a glass anode network is decisively significant to enhance sodium-ion battery performance. The outstanding stability of nanosized h-Na3Bi and NaGe domains in the glass anode network makes it more electrochemically efficient and increases its ionic conductivity. Subsequently, improved cycle stability and rate capability of glass anode half-cell have been achieved due to optimum void space between domains and open glass network. It also exhibits enhanced ability to withstand extensive volume variations during the repetitive sodiation/de-sodiation process. The size of the amorphous intermediate domains, structure, and lattice planes separation has been estimated based on the HRTEM and SAED images. The advantages gained by the growth of amorphous domains in the sodium-germanate glass network highlights its potential application as high-performance anode components for the advancement of Na-ion battery (NIB) efficiency.

New approach for preparation of high-purity sulfide-germanium glasses doped with praseodymium

It has been established that rare earth elements (REE), as alloying additives, are a significant source of hydrogen and oxygen impurity in glasses of Ge – S and Ge – As – S systems. A method has been developed that includes loading germanium in the form of monosulfide and high-temperature annealing of REE and their compounds in sulfur vapor, reducing content of absorbing impurities in sulfide-germanium glasses. Samples of especially pure glasses of Ge42.5S57.5 and Ge35As10S55 composition doped with praseodymium up to 1450 ppm(at) were prepared. The impurity content of hydrogen and oxygen in the form of SH-groups and Ge–O in the best glass samples was 0.02–0.06 ppm(wt) and <0.1– 0.2 ppm(wt), respectively. The absorption coefficients and the absorption cross section were determined for various energy states of the Pr3+ ion in Ge35As10S55 glass. The luminescence intensity of Pr3+ ions in the spectral ranges 2.0–2.8 and 3.5–5.8 µm in Ge42.5S57.5 glasses is by 3 orders of magnitude higher than in Ge35As10S55 glasses.

Photoluminescence of crystalline and glassy lead thiogermanate

Purpose: The interest to glasses Ge–Pb–S system is due to the opening possibilities of using them as a three-dimensional optical coating for active devices of integrated optics and multifunctional devices of semiconductor photonics, as well as electrophoto-graphic layers characterized by small value of the limit charging potentials and fast kinetics of dark half-decay. Methods: This paper presents the comparative study results of radiative recombination and photoluminescence excitation (PLE) spectra, temperature dependence of photoluminescence, lux-brightness characteristics (LBC) of crystalline ( c- ) and glassy ( g -) PbGeS 3 in the temperature range 77–300 K. Results: The PL spectra of ordered and disordered phases are qualitatively similar; they contain one intense broad radiation band, the energy position of its maximum at T = 77 K is hv max = 1.04 eV for the crystal and it lies within 1.13–1.18 eV for the glass. The luminescence excitation spectrum is a bell-shaped curve with a maximum at the photon energy of 2.7 eV for the crystal and 2.26 eV for the glass, which are close to the band gap of ordered and disordered phases, it indicates on the band-type excitation character. The Stokse shift W S = E PLE – E PL for the crystal phase W Sс = 1.65 eV is much larger than for the glassy phase W Sg = 1.07 eV. Lux-brightness characteristics (LBC) have the linear character for both PbGeS 3 phases. Only slight shift of the maximum in PL spectra into the high energy region is observed with the intensity excitation increasing. Linear LBCs along with the exponential decay of PL indicate to the monomolecular character of recombination in both phases. The similarity of PL and luminescence excitation spectra of c - and g -PbGeS 3 as well as their comparison to the known results for c - and g -GeS 2 (GeSе 2 ) allow to conclude that the radiative processes in lead thiogermanate are determined primarily by the chemical nature of luminescence centers and poorly depend on the presence of long-range order, while the nonradiative processes are very sensitive to the structure disordering. Conclusion: For the first time, in the photoluminescence spectra of both PbGeS 3 phases, a wide band with a Gaussian-shaped contour was detected, with the emission band for glassy samples shifted by ~0.1 eV towards higher energies. The relatively large half-widths and the absence of the oscillatory structure of the luminescence bands indicate that in both phases a high heat release occurs, and the energy position of the band maxima in the emission spectra indicates the impurity nature of the luminescence and high stokes losses.

Compressibility, Electrical Conductivity, and Crystallization of Glassy Selenium at a High Pressure

The volume and the electrical resistivity of glassy selenium (g-Se) are precisely measured at a high hydrostatic pressure up to 9 GPa. The bulk modulus at normal pressure (B = 9.05 ± 0.15 GPa) and its baric derivative ( $$B_{P}^{'}$$ = 6.4 ± 0.2) fall on the general concentration dependence of the properties of Se–Ge glasses. The bulk modulus is found to behave substantially nonlinearly in the pressure range P < 3 GPa, and this behavior is not related to glass density relaxation (which is absent in this pressure range). The electrical resistivity of g-Se decreases almost exponentially with increasing pressure and reaches 20 Ω cm at 8.75 GPa. The inelastic behavior and weak volume relaxation in g-Se begin at a pressure above 3.5 GPa. Both the volume and the logarithm of electrical resistivity exhibit noticeable (logarithmic in time) relaxation at above 8 GPa. The detected volume hysteresis (1%) and significant (two orders of magnitude) electrical resistivity hysteresis are associated with the pressure-induced structural changes in the glass. They cannot be explained by partial glass crystallization, since no crystalline phase impurity was detected right after experiments. A noticeable (about 1.5%) crystalline phase impurity appears in a sample only after long-term (1 day) storage at a pressure above 8 GPa. Moreover, the crystallization kinetics of g-Se is studied under normal conditions after the action of a high pressure.

Surface defect analysis on formed chalcogenide glass Ge22Se58As20 lenses after the molding process.

Chalcogenide glass (ChG) is increasingly used in infrared optical systems owing to its excellent infrared optical properties and scalable production using precision glass molding (PGM). However, surface scratches affected by the molding temperature and microdimples on the lens surface caused by gas release seriously impair the quality of the formed lens. To reduce these surface defects when molding Ge22Se58As20 ChG, the temperature effect must be studied, and the gas generation must be minimized, while the gas escape must be maximized. In this work, we studied the effect of temperature on the surface defects. Additionally, we studied the influences of the roughness and curvature of the contact surfaces, as well as the pressing force on the formation of the microdimples. It was found that the molding temperature should be approximately 30°C higher than the softening temperature (Ts) to avoid surface scratches. The gas generation could be inhibited by increasing the pressing force and decreasing the roughness of the mold surface, and finally, increasing the curvature difference between the mold and glass preform surfaces improved the gas escape.

Correlating Structure with Threshold Behavior of Chalcogenide Glasses Within Ge–Sn–Se Ternary System

A systematic investigation of the optical and structural properties of chalcogenide glasses in Ge–Sn–Se ternary system is presented. We have found a threshold behavior of optical property, namely, existence of transitional composition of the Ge–Sn–Se glasses, with progressive replacement of Se by Sn. Calculation of mean coordination number indicates that the transition‐like feature of optical property is associated with the evolution of chemical ordering of the Ge–Sn–Se network. Analysis of Raman spectra of the glasses explains that the interaction between Se–Se bonds, Sn(Se1/2)4 tetrahedra, and Sn–Sn homopolar bonds is the origination of such optical phenomenon.

Radiation optical effects in commercial SiO2:Ge fibers

Present work is dedicated to investigation of radiation optical properties of SiO2:Ge glass fibers produced by Fujikura and Corning Glass. Distribution of Ge dopant characteristics in core and cladding of quartz fibers have been determined. Ge dopant rings shaped luminescence in optical fibers has been observed. New method of determination the Ge dopant distribution in core and cladding cross sectional profile of silica glass fibers is presented. The thermoluminescence and light storage processes in fibers affected by x-ray radiation have been investigated. The photoluminescence investigations shows that there are two bands of luminescence with 400 nm and 550 nm maxima, which appear in different temperature stimulation conditions. Obtained results are discussed.

Glass formation and physical properties of chalcogenide glasses in Ge–S–Pb system

Chalcogenide glasses based on Ge–S–Pb system were prepared, and the compositional dependence of their physic-chemical properties and glass structure were investigated. Up to 23mol% Pb can be dissolved in this glass system and the glass-formation region like a small isolated island was found. The effect of the introduction of Pb on the glass structure is discussed by employing Raman spectra. It is shown that the substitution of Pb for Ge decreases the number of [GeS4] and [S3Ge–GeS3] units, leading to the variation of properties, such as Tg, H′, and Hv. The knowledge of this structure–properties relationship of Ge–S–Pb glasses would be of significance to select or to design suitable host glass for optoelectronic applications.

Structural properties of glassy Ge2Se3from first-principles molecular dynamics

The structural properties of glassy Ge${}_{2}$Se${}_{3}$ were studied in the framework of first-principles molecular dynamics by using the Becke-Lee-Yang-Parr scheme for the treatment of the exchange-correlation functional in density functional theory. Our results for the total neutron structure factor and the total pair distribution function are in very good agreement with the experimental results. When compared to the structural description obtained for liquid Ge${}_{2}$Se${}_{3}$, glassy Ge${}_{2}$Se${}_{3}$ is found to be characterized by a larger percentage of fourfold coordinated Ge atoms and a lower number of miscoordinations. However, Ge$\ensuremath{-}$Ge homopolar bonds inevitably occur due to the lack of Se atoms available, at this concentration, to form GeSe${}_{4}$ tetrahedra. Focusing on the family of glasses Ge${}_{x}$Se${}_{1\ensuremath{-}x}$, the present results allow a comparison to be carried out in reciprocal and real space among three prototypical glassy structures. The first was obtained at the stoichiometric composition (glassy GeSe${}_{2}$), the second at a Se-rich composition (glassy GeSe${}_{4}$) and the third at a Ge-rich composition (glassy Ge${}_{2}$Se${}_{3}$). All networks are consistent with the ``$8\ensuremath{-}N$'' rule, in particular, glassy GeSe${}_{4}$, which exhibits the highest degree of chemical order. The electronic structure of glassy Ge${}_{2}$Se${}_{3}$ has been characterized by using the Wannier localized orbital formalism. The analysis of the Ge environment shows the presence of dangling, ionocovalent Ge$\ensuremath{-}$Se, and covalent bonds, the latter related to Ge$\ensuremath{-}$Ge connections.

Photonic crystal nanocavities fabricated from chalcogenide glass fully embedded in an index-matched cladding with a high Q-factor (&gt;750,000)

We have designed and fabricated a 2-D photonic crystal hetero-structure cavity in the chalcogenide glass Ge(11.5)As(24)Se(64.5) that is fully embedded in a cladding with refractive index of 1.44. The low index contrast of this structure (≈1.21) means that high-Q resonances cannot be obtained using standard hetero-structure cavity designs based on W1 waveguides. We show that reducing the waveguide width can substantially improve light confinement, leading to high-Q resonances in a hetero-structure cavity. Numerical simulations indicate intrinsic Q(v) > 10(7) are possible with this approach. Experimentally, an optical cavity with a high intrinsic Q(v)>7.6 x 10(5) was achieved in a structure with a theoretical Q(v) = 1.7 x 10(6).

NQR study of chalcogenide glasses Ge‐As‐Se

A three-component Ge-As-Se system is studied by the nuclear quadrupole resonance (NQR) method on (75)As nuclei and by the nutation NQR spectroscopy. The NQR (75)As spectra of the glasses Ge(0.021) As(0.375) Se(0.604), Ge(0.043) As(0.348) Se(0.609) and Ge(0.068) As(0.318) Se(0.614) reveal broad lines with two peaks assigned to the main structural unit of As(2)Se(3). With increasing average coordination number ( ̅r), the spectrum signals are shifted towards higher frequencies. At ̅r > 2.54, the spectrum becomes complex, which is a consequence of formation of more complex molecular structures in the glasses of high content of germanium. At fixed frequencies the asymmetry parameter η of the samples studied is determined.

ENHANCING EMISSION PROPERTIES OF RARE EARTH IONS IN CHALCOGENIDE GLASS VIA MINUTE COMPOSITIONAL ADJUSTMENTS

The significant role of the chemical environments of rare earths ions in controlling their radiative and nonradiative processes are exemplified in this study: The emission properties of rare earth ions ( Dy3+ or Tm3+ ) embedded in the strong covalent chalcogenide glass ( Ge and/or As containing sulphide glass) are dramatically enhanced upon the addition of very small amount of the Group III elements ( Ga or In ) and alkali halides ( CsBr or RbBr ). These compositional adjustments alter only the local structural environments of rare earth ions, while thermal stability of the modified glass is kept unaltered.

High‐Conductivity Tellurium‐Based Infrared Transmitting Glasses and their Suitability for Bio‐Optical Detection

Many biological molecules carry a net surface charge and have the potential to be monitored in drinking water by electrodepositing them on an optical sensing element and measuring their spectroscopic fingerprints in the infrared (IR) spectral region. In this detection scheme, glasses with high conductivity and excellent IR transmitting property are essential. Therefore, it is necessary to develop suitable materials that combine these properties. In this paper, a series of high‐conductivity IR transmitting glasses in Ge–As–Te and Ge–As–Te–Cu systems are reported. The conductivity, thermal stability, IR transmitting property, as well as chemical durability are studied. Their suitability for bio‐optical detection applications is also evaluated. Some glasses in these two systems have relatively high conductivities (near 10−4 (Ω·cm)−1), and exhibit superior thermal stability, excellent IR transmitting property, as well as good chemical durability. The electro‐deposition and spectroscopic tests of protein molecules indicate that these glasses are promising materials for bio‐optical detection applications.

Large and dynamical tuning of a chalcogenide Fabry-Perot cavity mode by temperature modulation

Te-enriched chalcogenide glass Ge(15)As(25)Se(15)Te(45) (GAST) is synthesized, thermo-optically characterized and used to fabricate a one dimensional photonic crystal cavity mode that is dynamically and reversibly tuned by temperature modulation. The optical cavity mode is designed using GAST and As(2)S(3) glasses after fully determining their temperature dependence of the complex refractive indices in the visible and near infrared spectrum using spectroscopic ellipsometry. By making use of the very large thermo-optic coefficient (dn/dT = 4 x 10(-4)/ degrees C) of GAST glass at 1.2 mum, the cavity mode of the multilayer was tuned reversibly more than 16 nm, which is, to the best of our knowledge, an order of magnitude larger for this kind of cavity modulation. Wide and dynamical spectral tuning of low bandgap chalcogenide glasses via temperature modulation can be utilized in photonic crystal based integrated optics, quantum dot resonance matching, solid state and gas laser components, and infrared photonic crystal fibers.

The investigation of the glasses Ge&lt;sub&gt;x&lt;/sub&gt;As&lt;sub&gt;y&lt;/sub&gt;Se&lt;sub&gt;100-x-y&lt;/sub&gt; by differential scanning calorimetry method

Досліджено кінетику склування стекол системи Ge-As-Se методом диференціальної скануючої калориметрії. На основі зміщення характеристичних температурних точок ендотермічного процесу в області розм’якшення на кривих ДСК при зміні швидкості сканування, були визначені числові значення енергії активації в’язкої течії. Показано, що вони суттєво залежать від середнього координаційного числа стекол. Проаналізовані особливості та механізми теплових ефектів у досліджених матеріалах.

Effect of tellurium addition on the optical and physical properties of germanium selenide glassy semiconductors

Thin films of the glasses Ge 10 Se 90− x Te x (0 ≤ x ≥ 40) have been prepared by melt quenching technique; thin films were evaporated at a pressure of ≈10 −4 Pa. The optical absorption behavior of these thin films was studied from the reflection and transmission spectrum in the spectral range 200–1200 nm. The optical constants i.e optical band gap ( E opt), absorption coefficient, refractive index ( n) are calculated. The optical band gap has been estimated using Tauc extrapolation and found to decrease with Te content. The Dispersion of refractive index has been studied in terms of Wemple – Di Domenico model. The value of static refraction index has been found to increase with Te content. The distribution of the possible chemical bonds has been calculated. The obtained results were correlated with the character of the chemical bond for the prepared compositions through a study of parameters such as average heat of atomization (Hs), the cohesive energies of the bonds (CE), The mean bond energy < E> and average coordination number ( m).