Urbach Energy Eu Research Articles

NIR emissions from Nd3+-activated phosphate-based glass system for cost-effective, tunable, and miniaturised laser devices

This work represents a phosphate-based glass system of composition (40-x) P2O5 − 30 B2O3 − 30 ZnSO4 - x Nd2O3, ( × = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) to determine the optical absorption and emission spectral characteristics. Moreover, Judd-Ofelt (J-O) intensity and radiative parameters were computed. Samples were prepared using melt-quenching method and characterized using Archimedes measurement, Ultraviolet–Visible-Near Infrared Spectroscopy and Photoluminescence Spectroscopy. The density values of these samples were reduced as the Nd2O3 concentration increased. The absorption spectra revealed 11 peaks corresponded to Nd3+ transitions from the lowest electronic energy level (4I9/2) to various excited levels. The optical energy band gap was found to be reduced with Nd3+ doping. The refractive indices (n) increased as the Nd3+ increase. The improving tendency of n was clarified in terms of the enhancing trend of samples molar volume (obtained from density), indicating a structural-optical correlation in the proposed glass system. The obtained values of Urbach energy (Eu) have an increasing trend in the range of ∼ 0.318–0.711 eV. Tow significant NIR emission peaks were assigned to the 4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions of Nd3+. Values of J-O intensity parameters Ω2, Ω4 and Ω6 were found in the range of (1.63–2.25)× 10−19 cm2, (2.57–2.94)× 10−19 cm2 and (1.53–1.82)× 10−19 cm2, respectively. The obtained stimulated emission cross-section for the NIR transitions from Nd3+ ((23.83–26.64)× 10−20 cm2 for 4F5/2 → 4I9/2, and (10.93–17.91)× 10−20 cm2 for 4F3/2 → 4I9/2 obviously revealed the lasing effectiveness of the titled glass system.

Suppressed Trap Density Leads to Versatile p‐i‐n Heterojunction Photodiode with Enhanced Photovoltaic/Photodetection Dual‐Function

AbstractMultifunctional integration of optoelectronic devices within a single photodiode is in high demand for next‐generation on‐chip multifunctional integration and Internet of Things applications. Owing to the rapidity of nucleation‐crystallization that is associated with the solution method, large trap state densities (Nt), and consequently, severe dark current densities, as well as recombination losses are generally induced, which are detrimental to the detectivity (D*) of organic photodetectors (OPDs) and to the open‐circuit voltage (VOC) of organic photovoltaics (OPVs). Herein, a versatile p‐i‐n heterojunction organic photodiode with optimized vertical phase distribution and rational solid‐state packing is fabricated via a layer‐by‐layer (LBL) deposition procedure entailing the introduction of a rylene‐fullerene hybrid as a morphological modulator. This precisely controlled photodiode displayed suppressed Nt (2.5 × 1016 cm−3), low‐lying Urbach energy Eu (23.2 meV), as well as synergistically reduced series resistance, dark current, and sub‐bandgap radiative/non‐radiative recombination losses. Consequently, this ternary‐pseudo‐bilayer‐type photodiode exhibits excellent dual‐function performance with an outstanding D* of 9.48 × 1011 Jones in self‐powered OPD mode and a surprisingly suppressed energy loss of 0.538 eV in OPV mode. This study provides important insights into the mechanism and effects of trap density and energy disorder suppression in solution‐processed multifunctional integrated photoelectric conversion diodes.

Growth parameters and investigations on the structural, optical, mechanical, thermal and electrical properties of an l-proline guanidine carbonate single crystal

Single crystal of l-proline guanidine carbonate (LPGC) was grown by adapting most important method of slow evaporation technique by using double distilled water as a solvent at room temperature. Single crystal X-ray diffraction determined that the crystal structure of LPGC as orthorhombic non-centro symmetric system with the P212121 space group and the lattice parameters are confirmed to be a = 8.3580(4) Å, b = 10.3479(4) Å, c = 15.1833(5) Å, α = β = γ = 90°, Volume V = 1313.17(9) A3. The diffraction pattern of powder X-ray diffraction describes the factors of the crystallinity nature and the purity of the LPGC crystal. The optical absorption spectrum of LPGC crystal has been recorded and the linear optical constants such as the absorption coefficient (α), Energy band gap (Eg), extinction coefficient (K), refractive index (n) and Urbach energy (Eu) have been calculated. The active functional groups of the grown crystal were identified and confirmed by Fourier transform infrared spectroscopic study (FTIR) and Fourier transform Raman spectroscopy (FT-RAMAN). The thermal behavior and the thermal stability of the crystal were investigated by the thermogravimetric-differential thermal analysis (TG-DTA). Vickers micro hardness test was carried out to determine the mechanical stability and the hardness parameters of the crystals such as stiffness constant (C11), yield strength (σy), hardness number (Hv) and work hardening coefficient (n). The luminescence activity of the grown crystal was determined by the photoluminescence (PL) spectroscopy. The dielectric properties of the LPGC crystal were analyzed at various temperature and frequency. The presence of active chemical compounds in LPGC crystal was confirmed by energy dispersive analysis (EDAX). The Z-scan analysis of the grown crystal determines the Q-switching behavior of the grown LPGC crystal.

Impacts of praseodymium (III, IV) oxide on physical, optical, and gamma-ray shielding properties of boro-silicate glasses

The present work aims to study the influence of Pr3+ ions on the structural, optical, and gamma-ray shielding properties of borosilicate glasses. Therefore, a new series of boro-silicate glass reinforced by small concentrations of praseodymium oxide varied between 0 and 1 mol.%. The XRD was utilized to emphasize the amorphous phase of the fabricated glasses. Moreover, UV–Vis Spectroscopy is used to detect the absorbance which is used to evaluate the energy band gap (Eg, eV) and Urbach energy (Eu, eV). The optical results showed that the energy band gap for direct transition decreased from 3.508 eV to 3.086 eV and decreased for the indirect transition from 3.086 eV to 2.879 eV with raising the Pr6O11 concentration in the fabricated glasses. The Monte Carlo simulation method was applied to simulate the average track length of γ-photons inside the fabricated boro-silicate. The linear attenuation coefficient for the fabricated boro-silicate glasses was enhanced by factors of 2.56 times (at 26 keV), 2.68 (at 103 keV), and 1.05 times (at 511 keV) with raising the Pr6O11 concentration between 0 and 1 mol.%. The result depicts no considerable change in the γ-ray shielding properties observed at γ energy ≥511 keV.

Influence of Annealing on Gas-Sensing Properties of TiOx Coatings Prepared by Gas Impulse Magnetron Sputtering with Various O2 Content

TiOx films were prepared by gas impulse magnetron sputtering under oxygen-deficient (ODC) and oxygen-rich conditions (ORC) and annealing at 100–800 °C was used. The O2 content had an effect on their transparency level (Tλ). The films from the ORC mode had ca. Tλ = 60%, which decreased slightly in the VIS range after annealing. The film from the ODC mode had lower transmission (ca. <10%), which increased in the NIR range after annealing by up to ca. 60%. Differences in optical band gap (Egopt) and Urbach energy (Eu) were also observed. The deposition parameters had an influence on the microstructure of TiOx coatings. The ORC and ODC modes resulted in columnar and grainy structures, respectively. Directly after deposition, both coatings were amorphous according to the GIXRD results. In the case of TiOxORC films, this state was retained even after annealing, while for TiOxODC, the crystalline forms of Ti and TiO2-anatase were revealed with increasing temperature. Sensor studies have shown that the response to H2 in the coating deposited under oxygen-rich conditions was characteristic of n-type conductivity, while oxygen-deficient conditions led to a p-type response. The highest sensor responses were achieved for TiOxODC annealed at 300 °C and 400 °C.

Enhancement in optical, thermal and electrical properties of Polyvinyl pyrrolidone/ polyethylene oxide matrix-based nanocomposites for advanced flexible optoelectronic technologies considering nanoceramic zinc oxide/titanium dioxide filler

Polyvinyl pyrrolidone (PVP) and polyethylene oxide (PEO) hybrid nanocomposites with varying zinc oxide (ZnO) and titanium dioxide (TiO2) concentrations were created using the solution casting process. The influence of ZnO/TiO2 nanoparticles on the optical, thermal, and electrical properties of the pure PVP/PEO composite was investigated and discussed. The results of the XRD analysis show that as ZnO/TiO2 NPs concentrations increases, the crystallinity of the nanocomposite films decreases. The interactions between the ZnO/TiO2 nanoparticles and the PVP/PEO polymeric chain is shown by FT-IR spectra. Peak positions and intensity variations in the FT-IR absorption spectra are observed when the concentration increases from 0.5 to 2 wt.% of ZnO/TiO2 NPs. The optical parameters including energy gap (Eg), refractive index (n), and Urbach energy (Eu) for PVP/PEO/ZnO/TiO2 nanohybrid samples were calculated using UV/Vis analytical spectroscopy. The energy gap narrows when ZnO/TiO2 nanohybrid concentration rises, as shown by the optical absorption spectra. The allowed indirect energy gap of the polymer matrix was reduced from 3.72 to 1.94 eV by the addition of 2 wt.% ZnO/TiO2 NPs. The TGA curve shows that the ZnO/TiO2 nanohybrid enhanced the thermal stability of the samples. As the concentration of metal oxides increased, the activation energy (Ea) decreased. AC conductivity showed that the PVP/PEO -(2 wt.%) ZnO/TiO2 NPs nanocomposites have higher electrical conductivity than PVP/PEO. For samples of -(2 wt.%) ZnO/TiO2, the σdcof nanocomposites reached 4.64×10−5Scm−1. Exponential factor (S) results show that in nanocomposite samples with non-Debye relaxation processes, the correlated barrier hopping mechanism (CBH) is dominant. High values of ε' at low-frequency in the dielectric characteristics demonstrated space charge polarization, whereas higher values of ε" in the composite samples could be associated with an increase in energy loss. These results illustrate the appropriateness of these nanocomposites for variety of uses, including flexible capacitors, battery separators, and energy storage devices.

Radiation Induced Changes in Makrofol PCVM Polycarbonate

Makrofol PCVM is a sort of Makrofol polycarbonate solid state nuclear track detector. It is worth mentioning that this paper is almost the first one that deals with the modification of the optical properties of this type of Makrofol under the effect of laser radiation. Samples from Makrofol PCVM were exposed to infrared pulsed laser with different fluences ranging from 15 to 125 J/cm2 . UV spectroscopic technique was used to obtain knowledge about the optical parameters that describe the samples under study. The changes of Urbach energy (Eu ), optical band gap (Eg ) and refractive index (n) with the laser fluence were investigated. Both Eu and n increased with increasing the fluence up to 125 J/cm2 , associated with a decrease of Eg values. These trends were assigned to the predominance of chain crosslinking that damaged the crystalline portion in the Makrofol polymer. Additionally, we used the CIE technique to calculate the color differences between the noncoloured pristine and the irradiated samples. The crosslinking created color centers that produced color difference between the exposed films and the uncolored pristine Makrofol film. The color difference was significant as the values of ΔE were greater than 5. This optimized the Makrofol polymer to be used in dosimetric applications.

Blending of Poly(methyl methacrylate) with Poly(1,3-diphenyl-1H-pyrazol-5-yl methacrylate): Investigation of its Optical Properties

In present study, a new blend polymer consisting of a pyrazole-derived polymer poly(1,3-diphenyl-1H-pyrazol-5-yl methacrylate) and poly(methyl methacrylate) was prepared solution mixing method. The blend polymer was spectrally characterized with FTIR and 1H-NMR techniques. TGA analysis showed that the blend polymer was stable up to 275.4 °C. A thin film of blend polymer was prepared by using spin coating technique. The UV measurements were obtained as a function of wavelength (300 – 700 nm). The optical and dispersion parameters were reported in detail. Transmittance was increased depending on the increasing wavelength whereas the reflectance decreased. The Transmittance value at 700 nm was measured as 97.55%, meaning the blend polymer was transparent. The refractive index at 700 nm was 1.37. The Urbach energy (Eu) and the optical band gap constant (Eg) were calculated to be 0.831 eV and 3.737 eV, respectively. The type of electronic transitions for polymer was determined as indirect allowed transition.

Investigation of structural, optical and magnetic properties of Y3-xCexFe5-yEryO12 compound

Herein, we have studied the structural, optical and magnetic properties of Y3-xCexFe5-yEryO12 (0.00 ≤ x ≤ 0.02), (0.00 ≤ y ≤ 0.06) compound synthesized via sol gel process. Structural characterization by X-ray diffraction (XRD) confirmed the YIG single phase formation, belong to the Ia3‾d cubic centrosymmetric crystal structure. The lattice constant, lattice strain, dislocation density and average crystallite size variations were calculated and discussed in terms of the rare earth's dopant concentrations. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed redshift for the Fe–O stretching modes as the dopant content increase, testifying the crystal lattice expansion. Raman spectra inspection corroborated the YIG single phase formation and shifts in the vibrational modes confirmed the Ce3+ and Er3+ rare earths inclusion in the sites occupied by Y3+ and Fe3+ cations, respectively. The coral-like of YIG nanoparticles were confirmed by scanning (SEM) and transmission (TEM) microscopies, whereas the existence of the elements Y, Fe, O, Ce and Er, were verified by Energy Dispersive Spectroscopy analysis (EDS). The optical band gap (Eg) decreases, while Urbach energy (Eu) increases varying the Er content. The result confirms the effect of Ce3+ and Er3+ addition on the optical properties of YIG, contributing to localized oxygen vacancy defects formation. Using a phenomenological model, it was shown that, the highest probability of Er3+ cations occupation corresponds to octahedral sites. For the Y2.98Ce0.02Fe5-yEryO12 (0.00 ≤ y ≤ 0.06) compound, the theoretical saturation magnetization (Ms) was calculated from the cation distribution obtained by the phenomenological model, resulting a slight increase with the Er content. The result agrees with the experimental Ms measurements, although for y = 0.06 a discrepancy was detected, which can be attributed to the breaking of collinear array of magnetic moments due to high lattice distortions.

The synthesis and the effect of Cu on optoelectronic qualities of β-In2S3 as a window layer for CIGS thin film solar cells

In this paper, the vacuum thermal evaporation technique was used to investigate β-In2S3 doped with copper (Cu) as window layer thin film for solar cells. The amount of the Cu source was used to be 0–8 % atomic weight compared with In2S3 source. For various Cu doping levels, the characteristics of the thin films were studied utilizing structural, morphological, and optical characterization techniques, as well as dielectric testing. The research included X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS), Infrared analysis (FTIR), XPS, Ellipsometry and UV-NIR spectroscopy. The measurements demonstrated that the real and imaginary isolation constants were over the wavelength range and successfully estimated the Urbach energy (Eu) and band gap energy. The Urbach energy varied from 1.88 to 2.21 eV. The band gap energy decreases from 2.10 to 1.93 eV for direct transitions. Moreover, based on the measured optical constants (n and k), employing the Wemple-Didomenico model helped uncover the Cauchy coefficients’, the refractive index, the dispersion and the oscillation energies. Therefore, the results presented in this paper show that the use of Cu-In2S3 for perovskite cells offers a high-efficiency alternative in the solar energy field.

Profundity study on structural and optical properties of heavy oil fly ash (HOFA) doped calcium carbonate (CaCO3) nanostructures and thin films for optoelectronic applications

The present study was concerned with the synthesis of thin films and nano samples from heavy oil fly ash (HOFA) doped-calcium carbonate (CaCO3) with different contents (x = 0, 1, 2, 3, 4, and 5 wt%.). The motivation of this study was to benefit from fly ash resulting from heavy oil combustion in power plants in optoelectronic applications rather than as an environmental problem with repercussions including global warming, etc. The nano- and thin-film samples with a thickness of 200 nm were controlled and tuned by the monitor device and were prepared by the spin coating method on pre-clean glass substrates. The structural analysis was carried out using XRD and SEM techniques. Both techniques were proven on the crystallinity of the studied samples, and the structural parameters were calculated, such as grain size, which was affected by the increase in calcium carbonate. Furthermore, SEM images of thin-film surfaces revealed a more packed structure with a lower number of pores in the thin film containing nano-CaCO3. According to the optical spectra (transmittance T, reflectance, R), the optical absorption coefficient was calculated. Then, the related optical parameters (Tauc energy Eg, Urbach energy Eu), optical constants (an extinction coefficient kex., a reflective index n), and dispersion parameters (a single oscillator energy Eo, a dispersion energy Ed) were determined. It was clear that these layers have the great potential to be used as a window layer in solar cells and other optoelectronic applications due to the high energy range of the optical bandgap. In addition, all-optical properties were affected and improved by increasing the calcium carbonate content. This improvement in the optical properties along with the improvement of the structural properties makes the thin films and the nanoscaled samples very suitable for various applications.

Study of radiation effect and bismuth content on the physical properties of some chalcogenides based on selenium

A series of Ge18BixSe82−x (x = 0.5, 2, 4, 6 & 8) thin films were prepared using thermal evaporation on glass substrates. The structural, optical and electrical properties of the prepared samples were investigated. The samples were exposed to γ-ray of 60Co source with gradually increased doses up to (150 kGy). The changes of the properties of the irradiated samples have been studied. Single oscillator and Drude models were used to describe the dispersion region. The changes of the optical parameters such as optical energy gap (Eop), Urbach energy (Eu), and the plasma frequency due to gamma irradiation were studied. The results obtained were explained in terms of the interaction of radiation with matter. The electrical conductivity was studied for both the as-prepared and irradiated films revealing negative differential conductance behavior.

Evaluation of hydrogen evolution reaction on chemical bath deposited Cu2O thin films: Effect of copper source and triethanolamine content

The chemical bath deposition method was used to deposit thin films of cuprous oxide. The effect of copper source and triethanolamine content on the optical, morphological, structural, electrochemical and photoelectrochemical properties of the thin films for the development of photocathodes for hydrogen production was investigated. Triethanolamine promotes the complexing of Cu+ ions independent of the copper source used, its increase promotes thicker films due to better growth control and reduction of rapid Cu2O precipitation in the bulk solution. The increase in thickness promoted a change in preferential orientation from (111) plane to (200) plane, which also influenced and reduced the conductivity because there is a decrease in disorder (Urbach energy EU). The thickness also varied due to copper source used, reaching the thickest films with copper nitrate while the thinnest films with copper acetate, this tendency is in agreement with their solubility in water. The lower solubility reduces the complexing of Cu + ions which promotes the Cu2O precipitation in the bulk solution, limiting the growth of the film. Also, electrical properties varied (measured as disorder EU) with copper source. The most conductive being the thin films deposited with copper acetate and nitrate while the most resistive being the films deposited with copper sulphate. Very little variation in optical properties was observed, estimating the band gap in the range of 2.62–2.66 eV, while high absorption coefficient (>105 cm−1) was calculated below the absorption edge (460–470 nm). All thin films showed p-type semiconducting behavior with a flat band potential in the range of −0.10 to 0.18 V (Ag/AgCl sat electrode), which confirms their ability to work as photocathodes for hydrogen production. The best photoelectrochemical performance was observed with the thinnest films, which also are the most conductive and present the highest values of absorption coefficient.

Thermal Stability, Optical Properties, and Gamma Shielding Properties of Tellurite Glass Modified with Potassium Chloride.

The synthesized glass system with a composition of (80-x) TeO2-10P2O5-10Nb2O5-xKCl mol% (where x = 5, 10, 15, 20, and 25) was successfully fabricated. The density (ρ) and molar volume (Vm) have been calculated. The investigated glasses were characterized using different analysis methods (differential thermal analysis (DTA) and UV-VIS-NIR spectroscopy). The radiation shielding effectiveness of the synthesized glass system was evaluated using different shielding parameters, such as mass and linear attenuation coefficients (MAC, LAC), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), and effective electron number (Neff). The results showed that with the increasing potassium chloride (KCl) concentration and decreasing tellurium oxide (TeO2) concentration, the density, refractive index, Urbach energy (Eu), and glass transition temperature (Tg) decreased, while the optical energy gap (Eopt) and thermal stability increased. As the KCl concentration increases, the values of MAC, LAC, and Zeff increase in the following order: TPNK5 % > TPNK10 % > TPNK15 % > TPNK20 % > TPNK25 %. Additionally, the shielding effectiveness of TPNK glass system showed good performance compared with some standard materials. The synthesized glass with a minimum KCl content has both good shielding effectiveness and good optical properties, in addition to reasonable thermal stability, which makes it suitable for shielding and optical applications.

Structural and optical properties of transparent conducting oxide Cd1-xCrxO thin films prepared by the sol-gel dip-coating method

Evenly Cr-doped CdO thin films have been prepared with different percentages (0, 5, 10, 15, 20, and 30%) by the sol-gel method on glass substrates. The crystal structures of the prepared films were found to be polycrystalline nature as characterized by the X-ray diffraction (XRD) pattern. Micro-structural parameters such as lattice constant (a), average particle size (Davg), lattice strain (ε), and dislocation density (δ) were evaluated. The domains formed by the aggregation of the nano-crystallites were characterized by the field emission scanning electron microscope (FE-SEM). According to the results, the increase in surface roughness is attributed to the well spread of the crystal structure of the examined films with nanoparticles over the surface without any cracks. The optical band gap Eg increases with increasing Cr ratio from 2.49 to 2.82 eV, and Urbach energy EU decreases with increasing Cr ratio. The oscillator energy (E0), the dispersion energy (Ed) the refractive index (n), the real part (ε') and imaginary part (ε'') of the dielectric constants, and the electronic polarizability (αp) were calculated. The electrical resistivity ρRT, sheet resistance Rs decreased from 10 to 1.23 Ω m−1 with increasing the ratio of Cr.

Refinement of optical/structural features and neutron/gamma-ray protecting capability of P2O5–Li2O–BaO phosphate glass system by adding Bi2O3

In this work, a new phosphate glass system with the nominal compositions 65P2O5 +10Li2O +(25-x)BaO + xBi2O3 was fabricated by using the conventional solid-state technique. Phosphate glasses were evaluated for their suitability in optical and radiation shielding applications. The amorphous nature of manufactured glasses was proved by utilizing an X-ray diffraction pattern. The density of glass samples was enhanced with rising Bi2O3 substitution ratio. UV–Vis absorption spectra were measured based on the concentration of Bi2O3 in PLBB glasses, optical energy band gap Eg for indirect and direct transitions were decreased from 3.43, 4.25 to 3.15, 3.95 eV with enhancing Bi2O3 substitution ratio respectively while urbach energy Eu was increased from 0.632 to 0.661 eV. The single oscillator energy (Eo) was found to decrease with increasing Bi2O3 however the average oscillator wavelength (λo) was increased. The Gamma-ray attenuation features of PLBB glasses were obtained via EpiXS program and MCNPX simulation codes. Mass attenuation coefficients (MAC) for PLBB0 and PLBB25 glasses were determined in the range of 14.995–0.0247 cm2/g and 43.912–0.0335 cm2/g, respectively. Outcomes obtained from MAC values and other photon shielding parameters such as MFP, HVL, Zeff, Nel, and EBF revealed that the replacement of Bi2O3 with BaO improves the capacity of PLBB glasses to reduce the intensity of gamma-rays. Furthermore, the macroscopic neutron cross section of PLBB25 glass with 25% Bi2O3 substitution is 0.133 cm−1 while it is 0.113 cm−1 for PLBB0 glass. The increase of Bi2O3 addition to the new phosphate glass system has remarkably improved both optical and nuclear radiation protecting properties.

Effect of GZO cap-layer thickness and post-annealing treatment on GZO/HGZO bi-layer films

Hydrogen and Ga-codoped ZnO (HGZO) films caped with different thickness of Ga-doped ZnO (GZO) films (0–80 nm) were prepared by RF magnetron sputtering at room temperature, and the influences of GZO layer thickness and post-annealing treatment on structural, electrical and optical properties of the GZO/HGZO bi-layer films were investigated. The results show that increasing GZO layer thickness weakens the (002) preferred orientation, decreases the crystallize size and increases compressive stress of the films. The electrically conductive properties of the films first enhance and then degrade with increase of GZO layer thickness, and the best conductive properties can be obtained at GZO layer thickness of 20 nm. As GZO layer thickness increases, transmittance in visible range (TVis) and bandgap (Eg) of the films show a decreased trend, but their Urbach energy (Eu) increases. The crystallite size of the films first greatly and then slightly increases with increasing annealing temperatures to 400 °C, and annealing atmosphere (air or vacuum) and time (10 min or 2 h) have little effect on the crystallite size at the same annealing temperature. With increasing annealing temperature, compressive stress greatly decreases firstly and then slightly decreases under vacuum annealing or converts to tensile stress under air annealing. The conductive properties of the films degrade after vacuum annealing for 2 h, but they degrade significantly even after air annealing for 10 min. Increasing GZO layer thickness can retard the decline of conductive properties of the films under vacuum annealing of 200–400 °C for 2 h or air annealing of 200–300 °C for 10 min. With increasing annealing temperature, the TVis of the films basically shows a trend of first increase and then decrease, and the Eg and Eu of the films basically decrease. After annealing at 400 °C, the decreased Eg and Eu values of films under air annealing are close for different annealing time, but they are larger than those under vacuum annealing. Basically, thicker GZO layer is more likely to restrain the decrease of Eg, but leads to obvious decrease of Eu. In addition, effect of hydrogen doping and out-diffusion, crystallize growth and stress relaxation mechanism under annealing, and carrier transport and Eg shift mechanisms are also discussed.

White light upconversion in NdOHCO3 to Nd2O3 nanocrystals: Structural and optical transition

In a previous report, some morphological, structural, and optical properties of NdOHCO3 to Nd2O3 transition were presented. This paper continues investigating this interesting inorganic nanomaterial, proposing the creation of the coordination complex [Nd(NH3)6]3+ ion during crystalline growth as a crucial step for the growth of NdOHCO3 nanocrystals. A concise experimental-theoretical model is detailed in order to understand the spherical-like crystalline growth observed. The orthorhombic and cubic phases for NdOHCO3 and Nd2O3 nanocrystal samples were identified from the X-Ray diffraction results. In addition, the average grain size was estimated for each sample: NdOHCO3 ~15.31–18.82 nm and Nd2O3 ~45.10–59.01 nm. Other optical parameters like absorbance, transmittance, and reflectance are examined. The Urbach energy (Eu) model allows us to investigate the degree of absorption. The Maxwell-Boltzmann statistical (MBS) model results fit well with the experimental photoluminescence (PL) spectroscopy data registered, implying that native intrinsic crystalline defects behave as free particles and the emission bands overlap 4f4s2→4f4s2 electronic intra-transitions. The PL spectra show two emission bands: Yellow ~3.10–1.55 eV and Red > 1.99 eV. Finally, the trap densities of NdOHCO3 (~1.08 × 1014 cm−3) and Nd2O3 (~9.64 × 1013 cm−3) were estimated.

Skin depth, optical density, electron-phonon interaction, steepness parameter, band tail width, carriers transitions and dissipation factors in Cu-Co bilayer films

This work aims to study Cu films, and Cu-Co bilayer deposited using DC Magnetron sputtering system on silicon substrates. It can be seen that as the thicknesses of films were increased, the grain size becomes larger which was in good agreement with the presented SEM and AFM images. The high-intensity peak for FCC materials was generally (111) reflection, which is observed in the films when the Co-doping ratio was increased, the (111) peak became stronger. The PL spectra have shown that the Cu films with 70 nm Cu have a maximum value of the oxygen defect density however Cu-Co bilayer with 70 nm Co have a minimum value of the oxygen defect density. We found that the Cu-Co bilayer with 70 nm Co was more disordered and the disordering energy EU in these bilayers was in a bout of 0.681 eV. The Cu-Co bilayers with 40 nm Co have maximum values of the energy gap about of 3.75 eV. The Cu-Co bilayers with 40 nm Co have maximum values of the electron-phonon interaction Ee-ph in about 0.0180 eV. The maximum value of the steepness parameter has occurred in Cu films with 70 nm Co and was 51.55 eV. It can be seen that the surface and volume dissipation factors in the Cu-Co bilayers with 60 nm Co have the maximum value. The maximum value of skin depth of films has occurred in Cu films with 60 nm Cu and it has a peak maximum about of 280 nm. The Cu-Co bilayers with 70 nm have maximum values of the average crystallite size about of 29.1 nm. Also, it is found that the Cu-Co bilayers with 70 nm have minimum values of micro strain ε. It can be observed that the relation between the optical band gap energy Eg and the Urbach energy Eu by Eg = 0.71 ‒ 0.5Eu were studied.

Effect of MWCNT addition on the optical band gap of PVA/CS transient biocomposites

In recent years, as a result of increasing environmental concerns, biodegradable materials have gained great attention. With the rapid development of electronic technology, the importance of innovation and development of low-cost, sustainable, transient bioelectronics materials is increasing. In this research, the preparation of Poly(Vinyl Alcohol) (PVA), Chitosan (CS), and Multi-Walled Carbon nanotube (MWCNT) biocomposite films have been described. The solution mixing, ultrasonic mixing, and spin coating techniques were used to prepare the PVA/CS/MWCNT biocomposite thin films. UV–Vis absorption spectroscopy and two-point probe resistivity measurement techniques were used to study the optical and electrical properties of the biocomposite thin films. Optical band gap energies ( Eg) of PVA/CS/MWCNT biocomposites were obtained using the Tauc and Absorbance Spectrum Fitting (ASF) methods. Results obtained with both methods were found to be exactly the same. Experimental results have shown that with increasing MWCNT concentration, electrical conductivity (σ) increases from 1.75x10−16 S to 2.94x10−3 S, and Eg decreases significantly. At the same time, the fundamental optical parameters such as band tail (Urbach) energy ( Eu), refractive index ( n), absorption ( α), and extinction ( k) coefficient of the PVA/CS/MWCNT biocomposites were investigated in the UV-VIS range. The improvement observed in the optical and electrical properties of PVA/CS/MWCNT biocomposite films shows that these composites could be used as bioelectronics materials.