Non-oxide Chalcogenide Glasses Research Articles

Structure-terahertz property relationship and femtosecond laser irradiation effects in chalcogenide glasses

We report structure-terahertz (THz) property relationship for various non-oxide chalcogenide glasses including unary (vitreous selenium (Se)), binary (arsenic sulfide (As-S), arsenic selenide (As-Se), and germanium selenide (Ge-Se)), and ternary (germanium arsenic selenide (Ge-As-Se)), systems along with commercially available AMTIR-1, IRG 22, and IRG 24 Ge-As-Se glasses. This comprehensive study is the first of its kind to combine Raman spectroscopy to examine structural units, connectivity, and glass network and terahertz time-domain spectroscopy (THz-TDS) to record the THz refractive index, n(THz), across a broad THz bandwidth. THz-TDS was carried out at Alfred University (AU) and National Institute of Standards and Technology (NIST), ultimately providing confidence in n(THz) values measured at AU. Vitreous Se, <r> = 2.0, record the minimum THz refractive index value of all Se-containing glasses. As-S and As-Se binary glasses have the highest measurable THz refractive index value at <r> = 2.4. Ge-Se binary glasses measure increased THz refractive index as <r> increases, with the maximum at <r> = 2.8. Ternary Ge-As-Se glasses record the maximum THz refractive index value at <r> = 2.5 for Ge10As30Se60. Low-repetition rate femtosecond laser irradiation (≈1 KHz, ≈40 fs, and ≈70 mW) was used to modify As-S and As-Se glass systems, where Raman and THz-TDS were used to observe minimal structural and THz refractive index values changes, respectively. Long-wave infrared (LWIR) (e.g., 10 μm)-THz (e.g., 1.0 THz) refractive index correlation is presented for all binary and ternary studied chalcogenide glasses. Such a correlation is valuable for predicting and designing chalcogenide glasses for integrated optical applications across THz and IR regions.

Signature Of stiffness transition in electrical behaviour of Se-Te-Sn-Ge glassy alloys

ABSTRACT In the family of amorphous semiconductors, non-oxide chalcogenide glasses (ChGs) are in the spotlight because of their widespread applications in various scientific and industrial fields. In this paper, we have studied thermally activated A.C. conduction in multi-component Se-Te-Sn-Ge (STSG) glassy alloys in bulk form at different audio frequencies. The activation energy of A.C. conductivity and other electrical parameters have also been calculated to explore the material’s conduction mechanism. The A.C. conductivity σac is found proportional to ωs where ω is the angular frequency. The frequency exponent s is found to decrease with increasing temperature, which is in agreement with the correlation barrier hopping (CBH) model. The variation of the A.C. conduction with temperature and frequency of the glasses has been studied. Their microstructure has also been studied using the XRD characterisation technique to explore their electrical transport properties. XRD patterns confirm the glassy nature of the as-prepared samples. The change in behaviour of various electrical parameters after 2 atomic weight percentages of Ge indicates the occurrence of a stiffness transition followed by a self-organisation of the corner-sharing and the edge-sharing arrangements of the GeSe4 phase.

Investigation of the short range order structures in sodium thioborosilicate mixed glass former glasses

The very first detailed structural examination of glasses in the sodium thioborosilicate (NTBS) mixed glass former (MGF) system is reported. As in our previous studies of MGF systems, we have fixed the ratio of the modifier, Na2S, to the total glass former (GF), BS3/2 + SiS2, and varied the ratio of the two base GFs, the pure sodium thiosilicate (NTS) and sodium thioborate (NTB) end member binary glass systems. We have found that the 0.6Na2S + 0.4[xBS3/2 + (1-x)SiS2] series with its relatively high Na2S content is continuously glass forming for all x, 0 ≤ x ≤ 1, in large ~2 mm thick samples with only modest quenching was observed. Other higher and lower Na2S content glass series were investigated, but were found to be very poor glass formers and for this reason not further studied. Further, and advantageously, but not reported on here, this high Na2S content is also associated with glasses of the highest Na+ ion conductivities in either NTS or NTB binary glasses. Infrared, Raman, and 11B and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopies were used to examine the short-range order (SRO) structures present in these glasses as a function of x. As expected from this high modifier content, the predominate finding is that these glasses are comprised mostly of depolymerized SRO units that possess one or at most two bridging sulfurs (BSs). Indeed, the main SRO structures observed in these glasses are the Si0, B0, and Si1 SRO units which contain no BSs and one BS, respectively. The Si1 and B0 SRO units are those expected from the composition of the binary series of glasses studied here, namely 3Na/Si for x = 0 and 3 Na/B for x = 1, respectively. However, the Raman spectra shows clear evidence of the disproportionate sharing of the Na+ towards the Si SRO units. This creates significant fractions of Si0 units for intermediate compositions. Likewise, a very close inspection and deconvolution of the NMR spectra and careful attention to charge balance shows that, as seen in other MGF systems, other SRO units with more BS structures, such as B1, B2, and B4 SRO units are formed from the transfer of the Na2S from the NTB subsystem to the NTS subsystem. The E1Si2 unit appears to be a common SRO unit in NTS (and other alkali) glasses and consists of two Si possessing two non-bridging sulfurs (NBSs) but linked together by two BSs in an edge-sharing motif. Due to the presence of the E1Si2 units (50 mol% Na2S) in a compositional series that is nominally 60 mol% Na2S, we find that the lack of sufficient Si0 SRO units to account for the extra Na2S necessarily produces a small amount of free, unreacted Na2S, <10 mol% of the total sodium sulfide in the system. Interestingly, the concentration of this “free” Na2S appears to increase with increasing NTB, x, content. Finally, as in nearly all non-oxide chalcogenide glasses, we do find a small amount of contaminant oxygen, always less than ~5 mol%, as a fraction of the total O + S, O/(O + S), in all of the glasses that increases in proportion to the amount of BS3/2 in the glass. This result is consistent with our experience that the starting material BS3/2 always contains more impurity O than the SiS2 starting material.

Structural principles in non-oxide chalcogenide glasses. Site speciation in the system PAsSe as investigated by high-speed 31P MAS-NMR

The locals structure of phosphorousarsenicselenium glasses of composition ( P 1− x As x ) 1− y Se y was investigated by high-speed magic-angle spinning (MAS) 31P NMR. At sufficiently high spinning speeds, PSe 3 2 and Se= PSe 3 2 units yield well-separated resonance lines, whose integrals provide that detailed phosphorous speciation in these glasses as a function of composition. The microstructure of PSe glasses is retained upon successive substitution of P by As up to substitution levels of x = 0.5. This substitution enhances the tendency of P to be four-coordinate, and indicates, that the site speciations of P and As differ. The results are quantitatively explained in terms of a liquid equilibrium reaction between different short-range-order environments according to: RSe 3 2 + [ Se n] 1 n √ Se= RSe 3 2 ( R = P, As) , assuming that arsenic substitutes exclusively for three-coordinate P atoms. In the range 0 ⩽ x ⩽ 0.5, this process is characterized by a universal equilibrium constant of 0.80 (mole fraction) −1 reflecting the thermodynamic equivalence of AsSe 3 2 and PSe 3 2 groups. Thus, the inability of As to form four-coordinate species is compensated by a higher degree of conversion of the P atoms, such that the resulting glass contains an approximately constant fraction of four-coordinated species.

Structural tailoring of silicon chalcogenide glasses: Compositional control of edge-sharing units as monitored by high-resolution29Si solid state NMR

29Si MAS-NMR data provide strong evidence for the presence of edgesharing tetrahedra in non-oxide chalcogenide glasses derived from SiS2 and SiSe2. The spectra show three distinct peaks which have been assigned on the basis of suitable model compound studies. It is further shown that the fraction of edge-sharing can be controlled by compositional parameters. In glassy SiSe2 both the presence of excess selenium and additional network formers such as phosphorus selenide are shown to diminish the degree of edge-sharing due to the formation of Si-Se-Se or Si-Se-P bonds. In glassy SiS2 a similar effect can be accomplished by a network modifier such as Li2S. In the latter case, the creation of nonbridging chalcogen atoms is accompanied by a concomitant decrease of edge-sharing tetrahedra.

Structural transformation of non-oxide chalcogenide glasses. The short-range order of lithium sulfide (Li2S)-phosphorus pentasulfide (P2S5) glasses studied by quantitative phosphorus-31, lithium-6, and lithium-7 high-resolution solid-state NMR

Structural transformation of non-oxide chalcogenide glasses. The short-range order of lithium sulfide (Li2S)-phosphorus pentasulfide (P2S5) glasses studied by quantitative phosphorus-31, lithium-6, and lithium-7 high-resolution solid-state NMR

Chemical disorder in non-oxide chalcogenide glasses. Site speciation in the system phosphorus-selenium by magic angle spinning NMR at very high spinning speeds

Chemical disorder in non-oxide chalcogenide glasses. Site speciation in the system phosphorus-selenium by magic angle spinning NMR at very high spinning speeds

Competitive network modification in non-oxide chalcogenide glasses structural and motional properties of glasses in the system Li2S-P2S5-B2S3 studied by multinuclear NMR techniques

Non-oxide chalcogenide glasses based on more than one network former species have certain advantages for applications as solid electrolytes in batteries. To elucidate the influence of competitive glass-formation on the structural and motional properties of ionically conductive chalcogenide glasses, the system (Li2S)0.67[(B2S3)1−y (P2S5) y ]0.33 has been characterized comprehensively by DSC, electrical conductivity and6Li,7Li,31P, and11B solid state NMR techniques. The data obtained provide the first systematic characterization of the coformer effect in a chalcogenide glass system. Homogeneous glassy samples are formed fory=0.3 and 0.9≦y≦1.0, and microphase separated glasses for 0≦y≦0.2. The presence of a coformer leads to an increase in the electrical conductivity and a decrease of the activation energy, as compared to either binary system (Li2S-B2S3 or Li2S-P2S5), but only if homogeneous glasses are formed. The NMR data, in conjunction with systematic DSC and NMR studies of the binary systems (Li2S)x(B2S3)1−x (0.50≦x≦0.75) and (Li2S) x (P2S5)1−x (0.50≦x≦0.70), lead to the following conclusions: 1)11B MAS-NMR is well-suited to quantitate the amounts of three- and four coordinated boron atoms; in the binary glasses, the fraction of four-fold boron (N4) increases with decreasing Li2S/B2S3 ratio; in the ternary glasses N4 increases with increasingy. 2)31P MAS-NMR spectra of the binary glasses discriminate between three different phosphorus microenvironments, assigned to sulfide-analogs of metaphosphate, pyrophosphate, and orthophosphate species, respectively. These results suggest the applicability of network modification models originally developed for oxide glasses. For the ternary glasses, the DSC and NMR data of glasses with low phosphorus contents are consistent with a phase separation model involving a Li-rich thioborate glass that contains all of the phosphorus component and a glass phase less rich in lithium containing the four-fold boron atoms. In addition to the structural studies, the7Li spin-spin relaxation times (T 2) are used to characterize the mobility of the Li atoms. The activation energy of Li motion, determined from temperature dependentT 2 measurements and analyzed by using BPP theory differs from that determined from conductivity measurements by a factor of 2–3, possibly reflecting the inapplicability of this theory to the lithium diffusion process.

Structural models for non-oxide chalcogenide glasses. Atomic distribution and local order in the system phosphorus-selenium studied by phosphorus-31 dipolar NMR spectroscopy

Structural models for non-oxide chalcogenide glasses. Atomic distribution and local order in the system phosphorus-selenium studied by phosphorus-31 dipolar NMR spectroscopy

Structural characterization of non‐oxide Chalcogenide Glasses using solid state NMR

AbstractIn spite of the long‐standing importance of non‐oxide chalcogenide glasses in infrared optics and semiconductor technology, concepts describing the structural principles governing glass formation in these systems are just emerging. Most recently, modern quantitative solid state NMR techniques have offered new unique insights into the structural organization of these systems. In this review, we discuss the basic principles of various experimental approaches and their application to boron‐silicon,‐ and phosphorus chalcogenide glasses.

NMR studies of chalcogenide glasses: The system phosphorus-selenium

The feasibility of modern pulsed high-field high resolution solid state NMR techniques in non-oxide chalcogenide glasses is demonstrated for the system phosphorus-selenium. Isotropic and anisotropic chemical shieldings as well as 31P-31P dipolar couplings from 31P MAS and spin-echo NMR are reported on the glasses (10 to 50 mole% P), and the crystalline model compounds P4Se3 and P4Se4. Measurement of spin-echo decays show a monotonic increase of 31P-31P homonuclear dipole-dipole couplings with increasing phosphorus contents. The latter result suggests that the structure is more random than implied by the cluster model previously suggested.

Solid State NMR Studies of Ionically Conductive Non-Oxide Chalcogenide Glasses

AbstractThe utility of 29Si, 31 p, and 6.7 Li MAS-NMR at 7.05 T to provide structural information in non-oxide chalcogenide glasses is discussed in connection with experimental results obtained on the systems Li2 S-SiS2, Li2 S-SiS2 -P2S5, and Li2 S-P2 S5-B2 S329Si MAS-NMR data indicate that the principles governing glass formation in these systems are fundamentally different from those applicable to stoichiometry-analog oxide glasses. 31p MAS-NMR can be used to identify microphase-separation in glasses containing two network former constituents. The use of the rare isotope 6 Li instead of 7 Li offers the advantage of significantly improved spectroscopic resolution, enabling the presentation of the first comprehensive lithium NMR chemical shift scale in the solid state.

Infrared Transmitting Glasses

The basic principles used to design infrared transmitting glasses are briefly explained. The composition and properties of oxide, halide, and nonoxide chalcogenide glasses show the utility and limitations of these materials for infrared applications. In general, glass systems with an infrared absorption edge at longer wavelengths have smaller compositional areas of glass formation, and the glasses have poorer physical and chemical properties.

On the preparation and properties of some nonoxide chalcogenide glasses

Six nonoxide chalcogenide glasses were made and studied for optical transmission in the range 0.6–20 μm. Four of these materials, AgAsS 2, TlAsSe 2, TlAsSe 3 and Hg 3Tl 4As 8Sb 2S 20, appeared to have useful transmission within this range, but absorption bands were seen which were ascribed to oxide impurities. The other two materials, AgTlS and TlAsS 2, were opaque in the thicknesses of several millimeters used in the study.

Nonoxide Chalcogenide Glasses as Infrared Optical Materials

In recent years, glassy systems based on the group VI A elements S, Se, or Te in combination with group IV A and group V A elements or V A elements alone, have been investigated as potential sources for new iroptical materials. The results obtained in the qualitative evaluation of glasses from many systems reported in the literature are given. Several specific compositions from different glass systems have been prepared in amounts large enough to allow quantitative evaluation of optical and related physical properties. The magnitudes of the parameters that describe the properties of chalcogenide glasses are discussed and compared to those of other ir optical materials. The methods currently used to compound the glass compositions are given and problems associated with fabrication are briefly discussed. Three potential sources of limited quantities of chalcogenide glasses are given.