Short-wavelength Absorption Edge Research Articles

Synthesis and study of single crystals and optical ceramics based on the AgCl0.25Br0.75 – AgI system

To obtain non-toxic, non-hygroscopic materials used in IR fiber optics and optoelectronics, a comprehensive study of the AgCl0.25Br0.75 – AgI system was carried out. The study of the AgCl0.25Br0.75 – AgI system's phase diagram showed the presence of a homogeneity region with a content 0–16 mol.% AgI in AgCl0.25Br0.75 and heterogeneity region 16–98 mol.% AgI in AgCl0.25Br0.75. The phases in the homogeneous region have a cubic structure of the Fm3m type. The phases in the heterogeneous region are a mixture of cubic Fm3m and hexagonal P63mc phases. Within each of the regions, single-crystals samples with compositions of 4, 8, 16, and 20 mol.% AgI in AgCl0.25Br0.75 and optical ceramics ones of composition 20 and 33 mol.% AgI in AgCl0.25Br0.75 were synthesized. For a sample of 20 mol.% AgI in AgCl0.25Br0.75, different synthesis modes were used, as a result it was possible to obtain both a single-crystal and ceramics. The materials' band gap and the optical transmission range are determined. The band gap decreases from 2.5195 to 2.3724 with a rise in the fraction of AgI in AgCl0.25Br0.75. The materials are transparent in the range of 0.492 - 54 μm. Single-crystals are characterized by a stepwise increase in transmission up to 50–57% at the short-wavelength absorption edge. For optical ceramics, the transmission initially reaches 1% stepwise and then increases until reaching a maximum value in the IR of 15–20 μm. It is associated with scattering by grains of different phases. A uniform shift of the transmission spectrum to longer wavelengths from 492 to 525 nm in the visible and from 47 to 54 μm in the far IR with a rise in the proportion of AgI in AgCl0.25Br0.75 is shown. The single-crystals' and optical ceramics' highest transmission level reaches 75–78% in the wavelength range from 10 to 40 µm.

Optical ceramics based on TlCl0.74Br0.26 – AgI system transparent from visible to far IR region

The article is devoted to the study of the TlCl0.74Br0.26 – AgI solid solution system's phase diagram and the synthesis of optical materials based on it. The phase diagram showed the possibility of synthesizing crystals with a content 0–4 mol. % AgI in TlCl0.74Br0.26 and obtaining optical ceramics with content AgI in TlCl0.74Br0.26 from 4 to 34 mol. %. Were synthesized optical ceramics with a composition of 7, 14, 20, 27 mol. % AgI in TlCl0.74Br0.26, from which plane-parallel plates were made. The optical transmission of ceramic plates covers the region from 0.4 to 50.0 μm without absorption windows. The material refractive index varies depending on the composition from 2.348 to 2.419 at the short-wavelength absorption edge and from 2.179 to 2.236 at a wavelength of 10.6 μm. The optical properties of ceramics showed the efficiency of doping TlCl0.74Br0.26 with silver iodide, since this made it possible to expand the transmission range without absorption windows in the far IR region up to 50 μm.

Material-specific high-resolution table-top extreme ultraviolet microscopy

Microscopy with extreme ultraviolet (EUV) radiation holds promise for high-resolution imaging with excellent material contrast, due to the short wavelength and numerous element-specific absorption edges available in this spectral range. At the same time, EUV radiation has significantly larger penetration depths than electrons. It thus enables a nano-scale view into complex three-dimensional structures that are important for material science, semiconductor metrology, and next-generation nano-devices. Here, we present high-resolution and material-specific microscopy at 13.5 nm wavelength. We combine a highly stable, high photon-flux, table-top EUV source with an interferometrically stabilized ptychography setup. By utilizing structured EUV illumination, we overcome the limitations of conventional EUV focusing optics and demonstrate high-resolution microscopy at a half-pitch lateral resolution of 16 nm. Moreover, we propose mixed-state orthogonal probe relaxation ptychography, enabling robust phase-contrast imaging over wide fields of view and long acquisition times. In this way, the complex transmission of an integrated circuit is precisely reconstructed, allowing for the classification of the material composition of mesoscopic semiconductor systems.

Structure- and excitation-dependent photoluminescence of As–S:Yb3+ films

In the article, we present and discuss the features of the structure and photoluminescence properties of Yb-doped As–S films synthesized by PECVD employing solid-state initial precursors. The doping was carried out during the deposition process. By controlling the temperature of the precursor sources and the composition of the low-temperature nonequilibrium plasma, we synthesized amorphous As–S:Yb films with Yb content ranging from 0.6 to 8.4 at. %. The change in the ratio of structural elements and surface morphology as a function of the elemental composition is shown. The increase of the Yb content leads to a redshift of the short-wavelength absorption edge. The dependence of the shape and intensity of 2F5/2 → 2F7/2 photoluminescence, observed in the range 930–1030 nm on the excitation wavelength (632.8 nm and 785 nm) and Yb concentration was evaluated. The relation between composition and atomic structure of the amorphous matrix of arsenic sulfide on the photoluminescent properties of Yb3+ ions is discussed.

A Lanthanum Ammonium Sulfate Double Salt with a Strong SHG Response and Wide Deep-UV Transparency.

The targeted synthesis of deep-ultraviolet (deep-UV) nonlinear optical (NLO) materials, especially those with non-π-conjugated sulfates, has experienced considerable difficulties due to the need to reconcile the oft-competing requirements for deep-UV transparency and strong second-harmonic generation (SHG). We report herein the designed synthesis of the first rare-earth metal-based deep-UV sulfate La(NH4 )(SO4 )2 by a double-salt strategy involving introduction of complementary cations, together with optical studies that reveal a short-wavelength deep-UV absorption edge (below 190 nm) and the strongest SHG response among deep-UV NLO sulfates (2.4×KDP). Theoretical calculations and crystal structure analysis suggest that the excellent balance between SHG response and deep-UV transparency can be attributed to a synergistic interaction of the hetero-cations La3+ and [NH4 ]+ , which optimize alignment of the [SO4 ] tetrahedra and highly polarizable [LaO8 ] polyhedra.

Photo-induced solid-state reaction on the interface of As2S3–Ge30Se70 thin films

The laser-induced solid-state reaction in double-layer As2S3 and Ge30Se70 thin films evaporated on each other on substrates was studied. The extent of the solid-state reaction on the interface of two films was evaluated as a shift of the short-wavelength absorption edge, which was significantly higher for the illuminated/annealed double-layer in comparison with the sum of shifts of the individual virgin films. The presence of a newly created intermix layer was proved by FTIR, AFM and ellipsometry.

Influence of small additives of germanium on the physical properties of chalcogenide glasses based on composition As30.5S44.5I25

Advanced for the infrared region of the spectrum chalcogenide glass composition As30.5S44.5I25 with small germanium additives were investigated. The concentration dependences of some physical and chemical properties indicate an increase in the performance of glasses due to the modification of the glass network. The character of the change in the short-wavelength absorption edge with an increase in the content of germanium atoms had an exponential character, shifting from 597 to 582 nm. A non-monotonic dependences were also found for the values of density, refractive index, and glass transition temperature. A joint analysis of the results obtained and structural studies described in the literature for similar glass systems made it possible to propose possible structural groups of glass compositions under investigation.

Mid-infrared single-Mode As-S-Se glass fiber and its supercontinuum generation

Two kinds of single-mode (SMF) step-index(SIF) chalcogenide fibers based on S-rich and S-poor As-S-Se glass have been fabricated successfully by an isolated extrusion method. We experimentally explored the effects of S and Se weights on the IR light transmission in the infrared area of the waveguide medium. By exploring the infrared transmission. It is found that the As-S-Se system has a transmission varied range between full S-based (As2S3) and full Se-based (As2Se3) glasses. The results show that with the addition of selenium, the red-shift is observed in both the short-wavelength absorption edge and long-wave cut-off wavelength. This phenomenon can be sourced from the varying of optical band gaps and phonon energies. Simultaneously, single-mode fibers was employed to evaluate the attenuation and supercontinuum(SC). We found that S-rich fiber shows a lower optical loss of 0.67–1.5 dB/m in 4.1–5.9 μm region, with a minimum value of 0.67 dB/m at 4.6 μm than that of S-poor fiber does. Yet, the SC results of S-poor fiber shows a flatter and broader spectrum region than that of S-rich fiber does.

The wettability of variously treated As42Se58 thin films

Amorphous As42Se58 films were prepared by thermal evaporation from previously synthetized bulk glass. The influence of the physical ageing, annealing and illumination with white and UV light on the wettability of the thin films surface was studied. The changes in wettability (the equilibrium contact angle) of glycerol and formamide were correlated with the surface roughness, the structure disorder manifested itself by the change of parameter B1/2 (slope of the short wavelength absorption edge) or relevant FTIR band width/shape and surface oxidation/hydrolysis. The darkening of the thin films (the red shift of the optical band gap) was observed with the magnitude depending on the treatment.

Electron beam induced changes in optical properties of glassy As35S65 chalcogenide thin films studied by imaging ellipsometry

Spectroscopic imaging ellipsometry was used to study 50 μm × 50 μm squares recorded into glassy As35S65 thin film by electron beam with different exposure doses. Optical constants (refractive index n and extinction coefficient k) of electron exposed areas were determined from imaging ellipsometric data recorded over a spectral range 390–800 nm. Complex dielectric permittivity of each of electron exposed square (glassy As35S65 with different electron exposure dose) was parametrized by a Tauc-Lorentz oscillator. Gradient optical model with the refractive index changing linearly within the layer thickness was used.Evaluation of parameters of Tauc-Lorentz oscillator revealed decrease of energy bandgap, increase of the refractive index in whole recorded spectra (more pronounced at the top of the film) and increase of extinction coefficient in the part of spectra where the material absorbs with the increasing electron exposure dose used for exposure of the squares.The decrease in local disorder with increasing electron exposure dose is quantified from the short wavelength absorption edge onset using a Mott-Davis model. The dependence of the parameters of Wemple-DiDomenico model for the transparent part of the optical constants spectra on electron exposure dose is shown.Thin film with recorded image was subsequently etched in amine based solution in aprotic solvent. While native film was fully etched off the remaining height of the exposed areas is increasing with the increasing electron exposure dose used.Knowledge of the changes of optical properties and etching rates induced by electron beam of different exposure doses can be used for fabricating of optical elements by high resolution electron beam lithography.

Synthesis and characterization of a new beryllium-free deep-ultraviolet nonlinear optical material: Na2GdCO3F3

A new noncentrosymmetric (NCS) material, namely, Na2GdCO3F3 has been obtained using the hydrothermal method. Na2GdCO3F3 exhibits an intricate three-dimensional structure that is composed of NaO4F2, NaO2F4 and GdO3F6 distorted polyhedra and planar [CO3] triangles. Powder second-harmonic generation (SHG) using the Kurtz−Perry technique shows that Na2GdCO3F3 is type I phase-matchable, and the measured SHG coefficient was 2.0 times that of KH2PO4(KDP). The result from the UV–vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edge was below 200 nm, suggesting that Na2GdCO3F3 is a promising deep-UV nonlinear optical material.

An Ultraviolet Nonlinear Optic Borate with 13-Ring Channels Constructed from Different Building Units.

Under solvothermal conditions, a chair open-framework borate, Na2B9O15(H2O)(H3O) (1), has been synthesized. Compound 1 shows regular pores of zeolites as well as nonlinear optical (NLO) properties of borates. The large 13-ring channels of the boron oxide framework are constructed from different cluster units of B3O7 and B6O13 with three-ring units. The second harmonic generation (SHG) signal intensity of 1 is similar to that of KH2PO4 (KDP) and gradually increased with larger particle size. Compound 1 is a potential UV NLO material for its short wavelength absorption edge.

Spectroscopic ellipsometry characterization of spin-coated Ge25S75 chalcogenide thin films

Abstract Spectroscopic ellipsometry study on spin-coated non-toxic Ge25S75 thin films annealed at different temperatures were conducted. Multi sample analysis with two sets of samples spin-coated onto soda-lime glass and onto silicon wafers was utilized. Optical constants (refractive index n and extinction coefficient k) of these films were determined from ellipsometric data recorded over a wide spectral range (0.05–6 eV). Different parametrization of Ge25S75 complex dielectric permittivity which consists of a Tauc-Lorentz or Cody-Lorentz oscillator describing the short wavelength absorption edge, a Lorentz or Gauss oscillators describing phonon absorption or optically active absorption of alkyl ammonium germanium salts in the middle infrared part of spectra is discussed. Using a Mott-Davis model, the decrease in local disorder with increasing annealing temperature is quantified from the short wavelength absorption edge onset. Using the Wemple-DiDomenico single oscillator model for the transparent part of the optical constants spectra, a decrease in the centroid distance of the valence and conduction bands with increasing annealing temperature is shown and increase in intensity of the inter-band optical transition due to annealing temperature occurs. Intensity of absorption near 3000 cm−1 could be used as alternative method to evaluation of quality of prepared films.

Spectroscopic ellipsometry characterization of ZnO:Sn thin films with various Sn composition deposited by remote-plasma reactive sputtering

ZnO:Sn thin films were deposited onto thermally oxidized silicon substrates using a remote plasma reactive sputtering. Their optical constants (refractive index n and extinction coefficient k) were determined from ellipsometric data recorded over a wide spectral range (0.05–6eV). Parametrization of ZnO:Sn complex dielectric permittivity consists of a parameterized semiconductor oscillator function describing the short wavelength absorption edge, a Drude oscillator describing free carrier absorption in near-infrared part of spectra and a Lorentz oscillator describing the long wavelength absorption edge and intra-band absorption in the ultra-violet part of the spectra. Using a Mott-Davis model, the increase in local disorder with increasing Sn doping is quantified from the short wavelength absorption edge onset. Using the Wemple-DiDomenico single oscillator model for the transparent part of the optical constants spectra, an increase in the centroid distance of the valence and conduction bands with increasing Sn doping is shown and only slight increase in intensity of the inter-band optical transition due to Sn doping occurs. The Drude model applied in the near-infrared part of the spectra revealed the free carrier concentration and mobility of ZnO:Sn. Results show that the range of transparency of prepared ZnO:Sn layers is not dramatically affected by Sn doping whereas electrical conductivity could be controlled by Sn doping. Refractive index in the transparent part is comparable with amorphous Indium Gallium Zinc Oxide allowing utilization of prepared ZnO:Sn layers as an indium-free alternative.

The effects of germanium addition on properties of Ga-Sb-S chalcogenide glasses

Properties of the glasses are experimentally investigated when Ga is gradually substituted by Ge in Ga8Sb32S60 chalcogenide glass. The glass structure is also studied to elucidate the variations of the properties. While the substitution of Ga by Ge does not remarkably change the glass transition temperature Tg, the thermal stability against crystallization becomes optimum when half of the Ga atoms are replaced by Ge atoms. The short-wavelength absorption edge λS (or optical bandgap Eg) exhibits a remarkable decrease when a small amount of Ge is added, however, its value does not change significantly with further Ga substitution. As Ga is gradually replaced by Ge, the long-wavelength cut-off edge λL, the density ρ, the linear refractive index n, and the third-order nonlinear refractive index n2 decrease. It is shown that the property variations of the glasses could be explained by the evolution of the glass structure.

Deep‐Ultraviolet Nonlinear Optics in a Borate Framework with 21‐Ring Channels

A new borate LiBa3 (OH)[B9 O16 ][B(OH)4 ], which combines the uniform porosity of open-frameworks with the extraordinary NLO properties of borates, has been obtained under hydrothermal conditions by using mixed lithium and barium ions as templates. The framework displays an acs-type net with large 21-ring channels. The second harmonic generation (SHG) measurement shows that it is a type I phase-matchable material with a strong SHG signal intensity about 3.1 times that of KDP (KH2 PO4 ). UV/Vis-NIR diffuse reflectance analysis indicates that the compound has a wide transparency range with the short-wavelength absorption edge below 200 nm. These characteristics reveal that the compound is a promising deep-UV nonlinear optical material.

A Deep-Ultraviolet Nonlinear Optical Crystal: Strontium Beryllium Borate Fluoride with Planar Be(O/F)3 Groups

A new strontium beryllium borate fluoride, Sr3[(BexB1–x)3B3O10][Be(O1–xFx)3] x = 0.30 (SBBOF), designed to be used in the deep-UV nonlinear optical (NLO) application, was grown by the spontaneous crystallization of a molten flux of SrO–B2O3–LiF. It crystallizes in the space group R3m (No. 160) with the following unit cell dimensions: a = 10.3179(11) A, c = 8.3958(13) A, V = 774.1(2) A3, and Z = 3. SBBOF consists of [(BexB1–x)3B3O10] anionic groups and isolated [Be(O1–xFx)3] planar groups. Importantly, a new strategy to improve the birefringence was introduced by changing the local configuration of isolated structural units from trigonal pyramids to planar triangles. UV–vis diffuse reflectance spectroscopy indicates that the short-wavelength absorption edge of SBBOF is below 200 nm. The band structure and refractive index were calculated. Second harmonic generation (SHG) was measured using the Kurtz and Perry technique, which showed that SBBOF is a phase-matchable material in both visible and UV regions, a...

Structure and properties of spin-coated Ge_25S_75 chalcogenide thin films

Amorphous chalcogenide thin films of Ge25S75 composition have been deposited by spin-coating technique. Optical properties of thin films were investigated by spectroscopic ellipsometry in UV-MIR spectral range. Obtained results prove increase of thin films refractive index in the transparent region and decrease of their thickness with increasing annealing temperature implying densification of the glass structure. Short wavelength absorption edge is shifting to lower energies (red shift) with increasing annealing temperature. Decreasing organic molecules content with increasing temperature of annealing was observed in MIR part of extinction coefficient and verified by Raman spectroscopy and EDS. Raman spectra also gave evidence of thermo-induced structural polymerization and decomposition of organic salts molecules yielding thin films with structure similar to the structure of the source bulk glass.

K2Pb3(CO3)3F2 and KCdCO3F: Novel Fluoride Carbonates with Layered and 3D Framework Structures.

Two new mixed metal fluoride carbonates, KCdCO3F and K2Pb3(CO3)3F2, have been synthesized by solvothermal and solid-state techniques. KCdCO3F crystallizes in the acentric nonpolar space group P6̅m2, and its structure features a three-dimensional anionic framework in which the CdCO3 layers are further interconnected by bridging F(-) anions with the negative charge balanced by K(+) cations. K2Pb3(CO3)3F2 crystallizes in the centrosymmetric space group P63/mmc, and its structure exhibits a layered anionic skeleton featuring corner-shared PbO6F and PbO6F2 polyhedra. UV-vis diffuse reflectance spectroscopy studies show that the short-wavelength absorption edges of KCdCO3F and K2Pb3(CO3)3F2 are 227 and 287 nm, respectively. The second harmonic generation (SHG) measurement reveals that KCdCO3F is a phase-matchable material for generation of doubled-frequency light at both 532 and 266 nm, with a large SHG response of approximately 5.2 times that of KH2PO4 (KDP) at 532 nm and a moderate SHG response of approximately 0.75 times that of β-BaB2O4 (BBO) at 266 nm. Therefore, it is a promising UV material for fourth harmonic generation on a 1064 nm Q-switched Nd:YAG laser.

Syntheses, characterization and nonlinear optical properties of sodium–scandium carbonate Na5Sc(CO3)4·2H2O

A novel nonlinear optical (NLO) material Na5Sc(CO3)4·2H2O has been synthesized under a subcritical hydrothermal condition. The structure is determined by single-crystal X-ray diffraction and further characterized by TG analyses and UV–vis–NIR diffuse reflectance spectrum. It crystallizes in the tetragonal space group P-421c, with a = b = 7.4622(6) Å, C = 11.5928(15) Å. The Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that Na5Sc(CO3)4·2H2O was a phase-matchable material, and its measured SHG coefficient was about 1.8 times as large as that of d36 (KDP). The results from the UV–vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges of Na5Sc(CO3)4·2H2O is about 220 nm, suggesting that this crystal is a promising UV nonlinear optical (NLO) materials.