Infrared Transmission Spectra Research Articles

Improving the crystal quality and optoelectronic property of GaSb with Al doping

GaSb and Ga1-xAlxSb crystals were prepared with the vertical Bridgman (VB) method. The effects of aluminum atoms (Al) doping on the structure and photoelectric properties of GaSb crystal were investigated. The results show that the GaAlSb crystal maintains the zinc blende crystal structure of the GaSb crystal, and the crystal quality gradually improves with the increase of Al doping concentration, and the effective segregation coefficient keff of Al decreases from 3.69 to 2.83. Furthermore, Al doping significantly inhibits the formation of dislocations, of which density decreases from 3.634 × 103 cm−2 to 1.256 × 103 cm−2. As an element with the same equivalent electrons as Ga, Al doping makes GaSb crystal become into an n-type semiconductor with the free electrons as the main carriers, from a p-type semiconductor with the holes as the main carriers (8.867 × 1017 cm−3). And the carrier concentration, i.e., the free electrons concentration, increases with the doped Al concentration increase, up to the maximum of 1.929 × 1018 cm−3. And the mobility of electron carriers increases with the increase of Al concentration, up to 2.140 × 103 cm2/(V•s), far greater than that of the hole carriers 1.358 × 103 cm2/(V•s). And the resistivity decreases from 7.649 × 10−3 Ω•cm to 1.416 × 10−3 Ω•cm. Moreover, the infrared transmittance spectrum also shows a significant improvement of the crystal quality.

Transfer learning in near infrared spectroscopy for stingless bee honey quality prediction across different months

Near infrared spectroscopy (NIRS) coupled with machine learning has demonstrated its capability as an efficient secondary measurement method in various applications. However, a NIRS predictive model might be unable to maintain its accuracy when it is applied to samples that were acquired from different periods. Particularly, the qualities of stingless bee honey are affected by various uncontrolled factors, e.g. ecosystem, origins, and weather. Since it is unrealistic to have a NIRS dataset that can represent unforeseen future changes, an algorithm that can adapt existing data for new samples is worth to be investigated. Thus, this study aims to evaluate the feasibility of homogenous transfer learning approaches to overcome data constraints in developing NIRS predictive models of stingless bee honey qualities across different months. First, the near infrared transmittance spectra were acquired across honey samples prior to their respective conventional quality measurements in four different analysis months. Then, data from different analysis months were used as source and target datasets. Next, joint distribution adaptation based partial least square (JDA-PLS) and transfer component analysis based PLS (TCA-PLS) were implemented to establish NIRS predictive models of moisture, hydroxymethylfurfural (HMF), and glucose quality. Results show that the proposed TCA-PLS outperformed JDA-PLS and PLS by achieving the lowest RMSEP of 3.401 % and 0.804 mg/kg in predicting the moisture and glucose of stingless bee honey, respectively, across different months. Lastly, finding shows that both JDA and TCA were inefficacy when the label distributions of the calibration and validation datasets were similar.

Ce-doped MgO films on AZ31 alloy substrate for biomedical applications: preparation, characterization and testing

Magnesium ions, MgO nanoparticles and thin films, magnesium alloys and cerium compounds are materials intensively studied due to their corrosion protection, antibacterial and pharmacological properties. In this work, we have designed, prepared and investigated, novel thin films of MgO doped with cerium, deposited on Mg alloy (AZ31) for temporary implants, in order to enhance their life time. More precisely, we report on microstructure and corrosion behavior of MgO pure and doped with 0.1 at % Ce films, fabricated by sol–gel route coupled with spin-coating technique, on AZ31 alloy substrate. A modified sol–gel method that start from magnesium acetylacetonate, cerium nitrate and 2–methoxyethanol (as a stabilizer for the sol) was been used successfully for cerium doped MgO sol precursor preparation. The structure and morphology of the surface of the coatings, before and after immersion for 7–30 d in Hank’s solution at 37 °C, were characterized by x-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscope, x-ray photoelectron spectroscopy and Fourier infrared transmittance spectrum (FT–IR). A comparison between the corrosion protection of undoped MgO and MgO doped with 0.1 at % Ce coatings on the AZ31 alloy substrate is performed by electrochemical tests and immersion tests using open circuit potential and electrochemical impedance spectroscopy in Hank’s solution, at 37 °C. The electrochemical results showed that the protection of the AZ31 alloy substrate against corrosion was better with the doped with 0.1 at % Ce MgO film deposited than with pure MgO coting. The investigations of the films after immersion in Hank’s solution, at 37 °C, for 7, 21 and 30 d indicated that the grown layer on the film is bone like apatite that suggests a good bioactivity of 0.1 at % Ce–doped MgO coating. Our work demonstrates that the performance corrosion protection of the biodegradable magnesium alloys used for orthopedic applications, in simulated physiological environments (Hank and Ringer) can be enhanced through coating with Ce3+ doped MgO sol–gel thin film.

Plasma assisted pulsed laser deposition of WO3 films for thermochromism

Tungsten trioxide (WO3) is one of the extensively investigated transition metal oxides. Its excellent chromogenic properties make WO3 promising for a variety of scientific and technological applications. We report a new method for reactively depositing WO3 films by plasma assisted pulsed laser deposition that combines electron cyclotron resonance microwave discharge and pulsed laser ablation. The plasma formed during film deposition was spectroscopically characterized by optical emission measurement, revealing that the plasma contains high density of reactive gaseous oxygen and tungsten species which are essential for efficiently synthesizing WOx precursors and depositing WO3 films. The structure of the deposited films and the effect of post-deposition thermal annealing on the film structure were characterized by X-ray diffraction and Raman spectroscopy. The as-deposited WO3 film appears amorphous in nature. Annealing resulted in the growth of crystalline grains and the improvement in the crystallinity of monoclinic WO3. Optical properties of the prepared WO3 films were studied by measuring ultraviolet–visible–near infrared transmission spectra. With the increase of annealing temperature, the WO3 films show a continuous change in color, decline in transmittance, red shift in absorption edge, and narrowing in band gap, clearly manifesting the thermochromic features of the deposited WO3 films.

Parameters inversion of ZnS multi-phonon absorption model based on the transmissivities in variable temperature

In order to solve the difficulty of characterizing the optical constants of ZnS at high temperatures, the multi-phonon absorption dielectric function model which includes temperature parameters is constructed and modified in this paper. The multi-phonon absorption parameters of ZnS have been inverted based on variable temperature infrared transmittance spectra. The variable temperature infrared transmittance spectra of ZnS have been well fitted. The temperature dependence of the dissociation energy of ZnS materials is demonstrated, and the optical constants of the ZnS material have been obtained at 25 °C, 100 °C, 200 °C, 300 °C, and 400 °C.

Comparison the effect of co-precipitation and sol-gel techniques on the structural and magnetic attributes of ZnO and Zn(1-x)Fe0.05CoxO nanoparticles for attaining room temperature ferromagnetism (RTFM)

In current study, ZnO and Fe/Co co-doped ZnO (Zn1-x Fe0.05 Cox O where x = 0, 0.005) nanoparticles were prepared by using two different methodologies: sol gel method and coprecipitation method. The structural properties were determined by X-Ray diffraction technique which verifies the hexagonal wurtzite structure of prepared nanoparticles. Crystallite size varies from 18.68-37.43 nm for the samples synthesized by co-precipitation method and it varies from 19.97-38.45 nm for sol-gel method. Fourier transform infrared transmittance spectra were used to investigate the type of functional groups present in all the prepared nanoparticles. The UV-Visible absorption spectroscopy was employed to investigate the optical properties of ZnO and doping of Fe/Co in ZnO semiconducting host. The energy band gap varies from 3.03 - 3.68 eV for the samples synthesized by coprecipitation method and for sol-gel method, it ranges from 3.13 - 3.86 eV, by increasing dopant concentration. Vibrating sample magnetometer was used to inquire the magnetic behavior of synthesized nanoparticles which shows the weak ferromagnetic behavior of the doped nanoparticles prepared by both the techniques. Samples prepared by co-precipitation method showed higher values of saturation magnetization and coercivity as compared to the samples prepared by the sol-gel method. In comparison of two synthesis techniques, a slight change was observed in the particle size, energy band gap and magnetization values. The improved optical and magnetic behavior favors the co-precipitation method rather than sol gel method for obtaining room temperature ferromagnetism for practical applications in spintronics field.

Growth and temperature-tuned band gap characteristics of LiGd(MoO4)2 single crystals for optoelectronic applications

LiGd(MoO4)2 has been investigated due to its optoelectronic applications, especially for development of light-emitting diodes. In the present paper, LiGd(MoO4)2 single crystals grown by Czochralski method was studied in terms of structural and temperature dependent optical properties. X-ray diffraction analysis showed that the crystal crystallizes in a single phase tetragonal structure. Raman spectrum exhibited six distinguishable peaks around 207, 319, 397, 706, 756 and 890 cm−1. These peaks correspond to vibrational modes of free rotation, symmetrical stretching, symmetric bending, antisymmetric stretching and antisymmetric bending of (MoO4)2− tetrahedron. Infrared transmittance spectrum had eight minima around 2114, 2350, 2451, 2854, 2929, 2960, 3545 and 3578 cm−1 which are due to multiphonon absorptions. Spectral change of transmittance curves at various temperature between 10 and 300 K was utilized to elucidate temperature effect on absorption characteristics. Optical band gap of the material was found using Tauc and spectral derivative methods. The band gap value was obtained as 3.09 eV at room temperature and this value increased to 3.22 eV with decreasing temperature down to 10 K. The detailed analysis on the temperature dependency of the band gap was applied by Varshni model. The band gap at 0 K and change of rate of the band gap were estimated as 3.23 eV and −1.45 × 10−3 eV/K, respectively. Room temperature photoluminescence spectrum of the crystal presented a peak around 709 nm which corresponds to red light emission. LiGd(MoO4)2 is a potential candidate for optoelectronic devices emitting red light.

Comparative study on infrared properties of PLD-grown DLC film and SiC film

Diamond-like carbon and silicon carbide coatings were grown by pulsed laser deposition under different laser fluences, and their infrared transmission spectra were compared with each other. Raman spectroscopies and their deconvolutions for the silicon carbide films prepared by different laser fluences exhibited no changes nearly in micro-structure, and the infrared spectra showed these layers had high infrared transmission. On the other hand, the obvious changes in micro-structure of the diamond-like carbon films grown by the different laser fluences, which indicated laser fluence played an important role in the growth process of the diamond-like carbon films. A relatively higher laser fluence could grow the diamond-like carbon film with higher sp3 bond content, increasing the infrared property, while a lower one increased the absorption of the layer, reducing its infrared transmission seriously. Nano-scratch test showed that silicon carbide layer can be used as the buffer layer for the multilayer diamond-like carbon film enhancing the adhesive performance of the whole coating on the substrate with the protective and anti-reflective properties.

Structural & thermal study of Sb14Se(86-x)Sn(x) chalcogenide glassy system

The structural and thermal analyses of Sb14Se(86-x)Sn(x) (x = 3 and × = 6) glassy system generated by the usual melt-quenching approach are presented in this study. Using the differential scanning calorimeter (DSC) technology, the crystallisation mechanism of the produced glass samples were investigated. With increasing Sn content there is increase in glass transition temperature Tg. The less difference in melting temperature and crystallisation temperature makes prepared glasses suitable for memory switching devices. At room temperature the infrared transmission spectra of Sb14Se(86-x)Sn(x) (x = 0, 3, 6, 9, 12 and 15) chalchogenide glasses were acquired in the 2000–2500 cm−1 spectral range. With Sn addition, far IR spectra are shifted towards the high frequency side and some new bonds appear. Because it was evident that Se atoms were being replaced by Sn atoms, a corresponding rise in the production of Sn-Sn bonds and a subsequent fall in Se-Se bonds were seen. The glasses produced in this manner exhibit improved glass forming capability and strong thermal stability. There was good agreement between experimental data and theoretical estimations of bond energy, relative likelihood of bond formation, and wave number. [copyright information to be updated in production process]

Влияние химического состава пористой матрицы и атмосферы спекания на люминесцентные свойства висмутсодержащих композиционных материалов

The spectral-optical and luminescence properties of bismuth-containing composite materials based on matrices of high-silica porous glasses are investigated. Luminescence spectra, luminescence excitation spectra, infrared transmission spectra (8000–4000 cm-1) depending on the composition of different types of matrices and sintering atmosphere (nitrogen, argon) of bismuth-containing composite materials were examined. It was found that the samples of bismuth-containing composite materials are characterized by UV (λem = 350 nm), blue-green (λem = 410–550 nm) and orange-red (λem = 600–725 nm) luminescence due to the presence of various bismuth active centers. The analysis of the spectra obtained by near-infrared spectroscopy demonstrates the formation of Bi2+ dimers of bismuth and bismuth active centers associated with silicon.

Effect of water vapor pressure on positive and negative tone electron-beam patterning of poly(methyl methacrylate)

Variable-pressure electron-beam lithography (VP-EBL) employs an ambient gas at subatmospheric pressures to reduce charging during electron-beam lithography. VP-EBL has been previously shown to eliminate pattern distortion and provide improved resolution when patterning poly(methyl methacrylate) (PMMA) on insulating substrates. However, it remains unknown how water vapor affects the contrast and clearing dose nor has the effect of water vapor on the negative-tone behavior of PMMA been studied. In addition, water vapor has recently been shown to alter the radiation chemistry of the VP-EBL process for Teflon AF. Such changes in radiation chemistry have not been explored for PMMA. In this work, VP-EBL was conducted on conductive substrates to study the effect of water vapor on PMMA patterning separately from the effects of charge dissipation. In addition, both positive and negative-tone processes were studied to determine the effect of water vapor on both chain scission and cross-linking. The contrast of PMMA was found to improve significantly with increasing water vapor pressure for both positive and negative-tone patterning. The clearing dose for positive-tone patterning increases moderately with vapor pressure as would be expected for electron scattering in a gas. However, the onset set dose for negative-tone patterning increased dramatically with pressure revealing a more significant change in the exposure mechanism. X-ray photoelectron spectra and infrared transmission spectra indicate that water vapor only slightly alters the composition of exposed PMMA. Also, electron scattering in water vapor yielded a much larger clear region around negative-tone patterns. This effect could be useful for increasing the range of the developed region around cross-linked PMMA beyond the backscattered electron range. Thus, VP-EBL for PMMA introduces a new means of tuning clearing/onset dose and contrast, while allowing additional control over the size of the cleared region around negative-tone patterns.

Influence of the chemical composition of the porous matrix and sintering atmosphere on the luminescent properties of bismuth-containing composites

The spectral-optical and luminescence properties of bismuth-containing composite materials based on matrices of high-silica porous glasses are investigated. Luminescence spectra, luminescence excitation spectra, infrared transmission spectra (8000-4000 cm-1) depending on the composition of different types of matrices and sintering atmosphere (nitrogen, argon) of bismuth-containing composite materials were examined. It was found that the samples of bismuth-containing composite materials are characterized by UV (λem=350 nm), blue-green (λem=410-550 nm) and orange-red (λem=600-725 nm) luminescence due to the presence of various bismuth active centers. The analysis of the spectra obtained by near-infrared spectroscopy demonstrates the formation of Bi2+ dimers of bismuth and bismuth active centers associated with silicon. Keywords: Bismuth-containing composite materials, high-silica porous glass, near-infrared spectroscopy, luminescence, bismuth active centers.

Изменение вероятности оптических переходов в ионе Yb-=SUP=-3+-=/SUP=- при магнитных фазовых переходах в мультиферроике Cu-=SUB=-3-=/SUB=-Yb(SeO-=SUB=-3-=/SUB=-)-=SUB=-2-=/SUB=-O-=SUB=-2-=/SUB=-Cl

The infrared transmission spectra of Cu3Yb(SeO3)2O2Cl, an ytterbium analogue of the natural mineral francisite, have been studied in a wide temperature range. Two phase transitions (at TN = 35 K and TR = 9 K) were registered by studying the splittings of Yb3+ Kramers doublets. It is shown that the low-temperature transition is spin-reorientational one. An analysis within the framework of the mean field theory allows us to conclude that the single-ion magnetic anisotropy of ytterbium does not coincide with the anisotropy of the copper magnetic subsystem. An estimate of the energy required for the reorientation of the copper magnetic subsystem has been obtained, it is 864 Jmol-1. It was found that the probability of a 0-0 transition in the Yb3+ ion changes in the temperature range of both phase transitions, presumably due to spontaneous magnetostriction.

Growth and characterization of NaBi(Mo0.5W0.5O4)2 single crystal: A promising material for optoelectronic applications

The structural and optical characteristics of NaBi(Mo0.5W0.5O4)2 single crystals grown by Czochralski method were investigated. X-ray diffraction (XRD) pattern exhibited four well-defined peaks related to tetragonal crystalline structure with a space group I41/a. Raman and infrared transmittance spectra were recorded to investigate vibrational properties of the compound. Room temperature transmission spectrum was measured to reveal band gap energy of the crystal. The derivative spectral and absorption coefficient analyses resulted in direct band gap energy of 3.19 and 3.18 eV, respectively. Urbach energy of the crystal was also determined as 0.17 eV from photon energy dependency of absorption coefficient. The structural and optical parameters obtained for NaBi(Mo0.5W0.5O4)2 were compared with the parameters of the NaBi(XO4)2 (X: Mo,W) compounds to understand the effect of the composition on the studied properties. The reported characteristics of NaBi(Mo0.5W0.5O4)2 point out that the compound has significant potential to be used in optoelectronic devices.

Crosspolarization with imperfect infrared polarizers

The analysis of vibrational bands is a core application of infrared (IR) spectroscopy. Polarization-dependent measurements enable the study of anisotropic materials. However, imperfect IR polarizers exhibit polarizer leakage, which causes pronounced bandshape and baseline distortions for samples with weak optical anisotropy. Based on the 4 × 4 Mueller-matrix formalism, we propose a polarimetric measurement scheme for handling imperfect polarizers and source prepolarization that delivers correct co- and crosspolarized transmission and reflection IR spectra. The scheme is applied to a weakly anisotropic polypropylene sheet, resolving crosspolarized signatures as small as 5⋅10−5. We determine the polymer’s direction-dependent complex refractive index in the vibrational fingerprint range.

Infrared transmittance spectra of polar stratospheric clouds

Polar stratospheric clouds (PSCs) are responsible for polar ozone depletion. Infrared transmittance spectra of PSCs recorded by the Fourier transform spectrometer (FTS) on the Atmospheric Chemistry Experiment (ACE) satellite were used to determine the composition and properties of PSCs. These unique broad band infrared spectra identify PSCs as nitric acid trihydrate (NAT), supercooled ternary solutions (STS) of nitric and sulfuric acid, and ice, as expected. Quantitative modeling of these PSC spectra shows that supercooled nitric acid (SNA) is also common, i.e., “STS” with no observable sulfuric acid in their infrared spectra. ACE-FTS observations therefore classify PSCs into 4 basic spectral types, NAT, STS, SNA and ice, as well as their mixtures. As an example, this classification scheme was applied to the Antarctic for July to September 2019. The composition and particularly the phase of PSCs are critical to the understanding and detailed chemical modeling of polar stratospheric ozone depletion.

Subwavelength Quasi-Periodic Array for Infrared Antireflection.

Infrared antireflection of a zinc sulfide (ZnS) surface is important to improve performance of infrared detector systems. In this paper, double-pulse femtosecond laser micro-machining is proposed to fabricate a subwavelength quasi-periodic array (SQA) on ZnS substrate for infrared antireflection. The SQA consisting of approximately 30 million holes within a 2 × 2 cm2 area is uniformly formed in a short time. The double-pulse beam can effectively suppress the surface plasma shielding effect, resulting in obtaining a larger array depth. Further, the SQA depth is tunable by changing pulse energy and pulse delay, and can be used to readily regulate the infrared transmittance spectra as well as hydrophobicity. Additionally, the optical field intensity distributions of the SQA simulated by the rigorous coupled-wave analysis method indicate the modulation effect by the array depth. Finally, the infrared imaging quality captured through an infrared window embedded SQA is evaluated by a self-built infrared detection system.

A discrimination model for dead cocoons using near-infrared transmission spectra analyses

Silk from cocoons is widely used as a functional raw material for alleviating skin diseases, improving memory, preventing diabetes, and as antioxidants. Dead cocoons are screened to utilize silk, resulting in poor marketability and cross-contamination of other cocoons. Considering that the screening of cocoons is performed manually to date, there is a high demand for automating this process. Spectroscopic analyses are actively used for non-destructive analysis methods. In this study, a discrimination model was developed to determine whether a cocoon is dead or alive using the near-infrared transmission spectra. A total of 367 normal cocoons and 152 dead cocoons were used in our experiment, and the cocoons were cut to determine whether they were dead or alive. The near-infrared transmission spectra were obtained for each cocoon for the wavelength band 900–1700 nm. Nine pre-processing methods were applied to eliminate spectral noise; pre-processing related to normalization demonstrated significant difference compared to other pre-processing methods. Furthermore, principal component analysis (PCA) was used to visualize the distribution of spectra, and discrimination models were developed using the wavelength range of the highest transmittance intensity and partial least squares-discriminant analysis (PLS-DA). PCA successfully discriminated between normal and dead cocoons. The discrimination model according to the wavelength range of the highest transmittance intensity demonstrated a discriminant accuracy of 94.80 %. Using PLS-DA with range normalization pre-processing spectra, the discriminant accuracies were 94.56 % and 94.64 % for calibration and validation, respectively. Thus, the proposed method can help discriminate between normal and dead cocoons non-destructively using the near infrared transmission spectra. • A discrimination model is developed to discriminate live and dead cocoons. • The model is based on near-infrared transmission spectra. • Transmission spectra at 904–1707 nm were acquired and analyzed. • A discriminant accuracy of 94.80 % was demonstrated by the model. • This method can help discriminate between dead and live cocoons non-destructively.

Miniature quartz tuning fork-based broad spectral coverage and high detectivity infrared spectroscopy

This paper reports a type of detector based on the thermoelastic effect of a miniature quartz tuning fork (mQTF) for infrared spectroscopy applications. Instead of using a pyroelectric infrared detector, a mQTF with a resonant frequency of ∼45 kHz was adopted as a detector for infrared light signal collection. To explore the capabilities of this technique, measurement of infrared absorption spectra of samples was conducted, and the effect of scattered light on the sensitivity was investigated. The experimental results indicate that the mQTF detector is sensitive to infrared radiation within a wide range of wavelengths, and packaging the mQTF could increase the sensitivity and signal-to-noise ratio (SNR) by 2.54, and 2.87 times, respectively. The infrared transmission spectrum of polystyrene (PS), polyethylene (PE) have been measured by the mQTF detector, and the experimental data show that the infrared characteristic absorption peaks appears in the same position as commercial pyroelectric detector. Finally, mid-infrared spectroscopy of acetone gas was measured by the mQTF with highprecision. It is worth noting that this is the first study of using the mQTF-based photodetector for gas phase infrared spectroscopy, the mQTF exhibits its cost-effectiveness, sensitivity, and broadband optical response advantages, could be used for qualitative analysis of components by the infrared spectrum.

Silver-Neodymium Codoped Lithium Aluminum Metaphosphate Glasses for Radio-Photoluminescence Dosimeter.

Commercial radio-photoluminescence (RPL) glass dosimeters generally use Ag single-doped phosphate glass as a single-wavelength sensor. Now, a novel type of Ag–Nd-codoped phosphate glass has been developed, which can be applied to dual-wavelength or multi-wavelength RPL sensors, and can thus improve the accuracy and stability of RPL dosimeters. An anhydrous 99.5 (0.7LiPO3–0.3Al (PO3)3) −0.25Ag2O–0.25Nd2O3 glass was prepared and irradiated at different doses, and then the absorption, fluorescence, infrared transmission spectra, as well as fluorescence lifetimes were tested and analyzed. The results show that there is an energy transfer between the Ag defect center and Nd3+ ions, and the transfer efficiency using 380 nm excitation is greater than that using 310 nm excitation. Aside from the 650 nm fluorescence of the Ag defect center, strong 882 nm and 1054 nm fluorescences of Nd ions are exhibited. It is possible that these fluorescences would allow the developed Ag–Nd-codoped phosphate glass to be applied to new RPL glass sensors and dosimeters.