Defective Crystals Research Articles

Optimization of the quality factor and sensitivity of one-dimensional photonic crystal methane sensor with cryptophane A cavity

In this work, we introduce a sensor for measuring different methane concentration levels. The model is based on a defective one-dimensional photonic crystal composed of alternating layers of air and Silicon with a cryptophane A cavity. We assume that the refractive index of silicon depends on temperature. The transmittance spectrum was calculated using the transfer matrix method. This work also assessed the effects of temperature and methane concentration on the wavelength shift of a localized mode within the photonic band gap. The results show the shift of this localized mode toward longer wavelengths as temperature increases, with the quality factor reaching its maximum value at around 8994.35. When maintaining a constant temperature, we observed a blue-shift when the methane concentration is in a range of 0.0–3.5%, and the quality factor decreases to 6358.26, with a maximum sensitivity of 144.485 nm by RIU. Due to its excellent performance to store energy within the cavity, this sensor can be used to detect different gas concentrations.

Sensor with enhanced performance based on photonic crystal with a defect layer

We propose an improved structure of an optical biosensor based on a photonic crystal with a defect layer, which can detect the concentration of organic contaminants in water by defect mode shift. We investigated 4 types of defective photonic crystals with different arrangements of layers inside the perfect photonic crystals and their impact on the performance of the sensor. The sensitivity and amplitude of defect mode were examined as a function of defect layer thickness. Also, the peculiarities of edge modes in the presence of defect layer were investigated. Finally, we obtained a characteristic equation to determine the wavelengths of defect modes for an arbitrary 1D photonic crystal with an isotropic defect inside.

XFEL Microcrystallography of Self-Assembling Silver n-Alkanethiolates.

New synthetic hybrid materials and their increasing complexity have placed growing demands on crystal growth for single-crystal X-ray diffraction analysis. Unfortunately, not all chemical systems are conducive to the isolation of single crystals for traditional characterization. Here, small-molecule serial femtosecond crystallography (smSFX) at atomic resolution (0.833 Å) is employed to characterize microcrystalline silver n-alkanethiolates with various alkyl chain lengths at X-ray free electron laser facilities, resolving long-standing controversies regarding the atomic connectivity and odd-even effects of layer stacking. smSFX provides high-quality crystal structures directly from the powder of the true unknowns, a capability that is particularly useful for systems having notoriously small or defective crystals. We present crystal structures of silver n-butanethiolate (C4), silver n-hexanethiolate (C6), and silver n-nonanethiolate (C9). We show that an odd-even effect originates from the orientation of the terminal methyl group and its role in packing efficiency. We also propose a secondary odd-even effect involving multiple mosaic blocks in the crystals containing even-numbered chains, identified by selected-area electron diffraction measurements. We conclude with a discussion of the merits of the synthetic preparation for the preparation of microdiffraction specimens and compare the long-range order in these crystals to that of self-assembled monolayers.

Monitoring and simulation of the fuel irradiation behavior in nuclear reactors based on phononic crystal structure

We have presented in the current work a novel idea for simulating the irradiation behaviors of the nuclear fuel pellets in nuclear reactors by using a one-dimensional defective phononic crystal (1D-DPnC) design was presented. The transmission spectra of the incident mechanical waves were considered basic data for expressing the characteristics of different nuclear fuel-pellets. Herein, the density, sound speed, and Young’s modulus of the fuel-pellets represent the key parameters that are influenced by the irradiation behaviors of these pallets. Mixed plutonium–uranium oxide (MOX) nuclear fuel is considered the main fuel in the present study. In addition, a comparison is performed for this fuel with other types of nuclear fuels. Moreover, the mechanical properties of these MOX-pellets are dependent on the porosity, the ratio of oxygen-to-metal (O/M), and the plutonium (Pu-content). The theoretical treatments depend on the transfers matrix method to compute the transmission spectra through the 1D-DPnC. The numerical findings provided that the MOX-pellet has the highest performance compared to other fuel pellets and with sensitivity equal to 59.388 × 103 Hz s/m. It was also reported that the effects of the percentage of the O/M and Pu- content in MOX had a minor effect in a comparison with the impact of porosity. The theoretical simulation agreed extremely with the experimental data reported for these nuclear fuels. Because of the close relationship between sound speed and density, this sensor can be utilized to monitor the porosity, O/M, Pu-content, and density of fuel-pellets as a quick and non-destructive evaluation technique in a nuclear fuel fabrication laboratory. This article has proven theoretically that MOX fuel produced from nuclear waste of uranium dioxide and plutonium dioxide gives excellent results compared to other types of nuclear fuels, and this agrees with experimental researches. Thus, it may contribute in preserving the environment from nuclear waste, and this can be considered a novel kind of purification of environmental pollution treatment.

Enhanced Goos-Hänchen shift in a defective Pell quasiperiodic photonic crystal with monolayer MoS2.

Monolayer M o S 2 has attracted wide attention because of its finite bandgap, and it has become a potential candidate for the investigation of the Goos-Hänchen (GH) shift. However, the magnitude of the GH shift in free-standing monolayer M o S 2 is small, which greatly hinders its possible applications in the photoelectric sensors and detectors. We have theoretically designed a defective quasiperiodic photonic crystal and investigated its GH shift, where monolayer M o S 2 is sandwiched between two quasiperiodic photonic crystals arranged by the Pell sequence. By optimizing the thicknesses of all the components and the period number of the Pell quasiperiodic photonic crystal, we find that the GH shift of the designed structure is significantly enhanced at the specific working wavelength. In addition, we discuss the influence of the thicknesses of the dielectric components on the GH shift. Our work confirms that the quasiperiodic photonic crystal structure has the ability to enhance the GH shift of monolayer transition metal dichalcogenides, which provides a new platform for the GH investigations and greatly promotes the applications of this defective structure in optoelectric devices.

An Investigation of High-Performance Pressure Sensor Employing a Polymer-Defect-Based 1D Annular Photonic Crystal

This study aims to theoretically address the design and analysis of an efficient pressure sensor designed using a polymer-based defective 1D annular photonic crystal (APC). The 1D APC comprises an alternate arrangement of Si and SiO2 in a cylindrical fashion, incorporating a central defect layer. The investigation of the reflectance characteristics of the proposed structure is conducted by separately considering the polystyrene (PS) and the polymethyl methacrylate (PMMA) polymer materials as the defect layer. The pressure-sensitive refractive index of the polymers and the constituent materials of the APC play a vital role in envisaging the pressure-sensing application. The cornerstone of this study is represented by the shift analysis regarding the wavelength of the defect mode inside the band gap using different applied pressures, employing the modified transfer matrix method (MTMM). Various geometrical parameters like the defect polymer layer’s thickness and the APC period were carefully optimized to achieve an improved sensing performance. The proposed design demonstrated a remarkable pressure sensitivity and FoM of 51.29 nm/GPa and 301.7 GPa−1, respectively, which is considerably high in the current research scenario. It is believed that the proposed structure can be an apt candidate for an innovative high-performance pressure sensor, and could play a key role in photonic integrated circuits.

Impact of truncation on absorption spectra in a graphene-based random photonic crystal

The present study investigates the influence of randomness on achieving multimode broadband and narrowband absorption of graphene-embedded photonic structures. In the first proposed photonic configuration, with a change in randomness parameter, it is possible to achieve single-mode and multimode broadband absorption up to 0.8. This value is further enhanced up to 0.99 by varying the Fermi level to −0.9 eV. The position of absorption peaks can be tuned by varying the thickness of the silicon carbide layer. Further, an investigation is carried out on the influence of adding a defective periodic photonic crystal to the first photonic configuration, which provides a multimode narrowband absorption with a value of up to 0.99, and the strength and location of absorption peaks can be altered to the desired value by changing the graphene Fermi level and the thickness of the silicon carbide layer. Finally, the authors also survey the influence of a magnetic field B on the absorption behaviour of left-handed circularly polarised (LCP) and right-handed circularly polarised (RCP) waves. The results indicate that the full width at half-maximum of absorption peaks expands with the application of a positive magnetic field for LCP waves, whereas it shrinks for RCP waves. This has applications in the design of tunable broadband and narrowband absorbers and sensors.

Biophotonic sensor for swift detection of malignant brain tissues by using nanocomposite YBa2Cu3O7/dielectric material as a 1D defective photonic crystal

In the present research work we have theoretically examined the biosensing capabilities of proposed one dimensional defective photonic crystal for swift detection of malignant brain tissues. The transfer matrix formulation and MATLAB computational tool have been used to examine the transmission properties of proposed structure. The identical buffer layers of nanocomposite superconducting material have been used either side of cavity region to enhance the interaction between incident light and different brain tissue samples poured into the cavity region. All the investigations have been carried out under normal incidence to suppress the experimental liabilities involved. We have investigated the biosensing performance of the proposed design by changing the values of two internal parameters (1) the cavity layer thickness (d4) and (2) volume fraction (η) of nanocomposite buffer layers one by one to get the optimum biosensing performance from the structure. It has been found that the sensitivity of the proposed design becomes 1.42607 μm/RIU when the cavity region of thickness 15dd is loaded with lymphoma brain tissue. This value of sensitivity can be further increased to 2.66136 μm/RIU with η = 0.8. The findings of this work are very beneficial for designing of various bio-sensing structures composed of nanocomposite materials of diversified biomedical applications.

Deep-learning-based framework for inverse design of a defective phononic crystal for narrowband filtering

This paper proposes a deep-learning-based inverse design framework for a one-dimensional, defective phononic crystal (PnC) as a narrow bandpass filter under longitudinal elastic waves. The purpose of the design-optimization problem is to maximize the transmittance at the defect-band frequency, which is equal to the target frequency. The framework comprises three steps: (i) inverse design generation and filtering, (ii) forward analysis of frequencies and filtering, and (iii) forward analysis of transmittance and near-optimal design selection. Four deep-learning models are considered in the inverse model: a deep neural network, a tandem neural network, a conditional variation autoencoder, and a conditional generative adversarial network. The frameworks developed with each deep-learning model are evaluated using a test dataset and an arbitrarily defined defect-band frequency and phononic band-gap range. The results show that the frameworks proposed using the conditional variation autoencoder and the conditional generative adversarial network effectively present the best performance by solving the nonunique response-to-design mapping problem through probabilistic approaches. The deep-learning-based framework reduces the need for manual intervention and simplifies the inverse design process, making it a promising approach for finding the near-optimal design solution for the use of defective PnCs as narrow bandpass filters.

Bistable Switch Based on Tunable Fano Resonance in Coupled Resonator-Cavity Structure

We report a side-coupled resonator-cavity configuration with a tunable Fano-type interference effect for a novel subwavelength switch. A defective microstrip photonic crystal (PC) structure is designed to provide a continuum state, while a split ring resonator (SRR) is introduced to offer a narrow discrete resonance. The SRR is conductively side-coupled with the microstrip PC cavity in a subwavelength volume. Interactions between them result in Fano-type transmitting spectra with a sharp and asymmetric spectral line profile. A varactor diode serving as the nonlinear medium inclusion is integrated into the slit of the SRR for active control of the sharp Fano resonance. The strongly localized field produced by Fano resonance plays a role in improving the nonlinear properties of the microstrip PC cavity. It is found that a significant blue shift of 94 MHz on the Fano resonance frequency can be achieved by increasing the input power levels from −25 dBm to 8 dBm. We also found that the maximum transmission contrast exceeding 15.9 dB can take place between two bistable states existing at 3.05 dBm and 4.32 dBm for a bidirectional sweep of input power under a monochromatic signal frequency of 1.27 GHz. The findings may benefit the exploitation of metamaterials-assisted active photonic nanocircuits.

Nonlinear extension of the Kolosov-Muskhelishvili stress function formalism.

The method of stress function in elasticity theory is a powerful analytical tool with applications to a wide range of physical systems, including defective crystals, fluctuating membranes, and more. A complex coordinates formulation of stress function, known as the Kolosov-Muskhelishvili formalism, enabled the analysis of elastic problems with singular domains, particularly cracks, forming the basis for fracture mechanics. A shortcoming of this method is its limitation to linear elasticity, which assumes Hookean energy and linear strain measure. Under finite loads, the linearized strain fails to describe the deformation field adequately, reflecting the onset of geometric nonlinearity. The latter is common in materials experiencing large rotations, such as regions close to the crack tip or elastic metamaterials. While a nonlinear stress function formalism exists, the Kolosov-Muskhelishvili complex representation had not been generalized and remained limited to linear elasticity. This paper develops a Kolosov-Muskhelishvili formalism for the nonlinear stress function. Our formalism allows us to port methods from complex analysis to nonlinear elasticity and to solve nonlinear problems in singular domains. Upon implementing the method to the crack problem, we discover that nonlinear solutions strongly depend on the applied remote loads, excluding a universal form of the solution close to the crack tip and questioning the validity of previous studies of nonlinear crack analysis.

Biophotonic sensor design for the detection of reproductive hormones in females by using a 1D defective annular photonic crystal

Abstract In this research work, we have proposed a one-dimensional (1D) defective annular photonic crystal (DAPC) (AB)5 CDC(AB)5 to identify the presence of reproductive progesterone and estradiol hormones in women. The periodicity of the proposed biosensing design made up of 1D annular photonic crystal (APC) has been broken by introducing a cylindrical cavity D of porous gallium nitride (GaN) material. The inner and outer faces of cylindrical cavity D are surrounded by concentric cylindrical buffer layers of magnesium fluoride (MgF2) material. We have used a modified transfer matrix method with the help of MATLAB software to carry out investigations pertaining to the proposed theoretical work. The two distinct categories of blood samples containing reproductive hormones of different concentrations have been used in this work. The sensitivity of proposed 1D DAPC varies between 159.673 nm nmol−1 L−1 to 170.1525 nm nmol−1 L−1 when a cavity is infiltrated with a blood sample having progesterone hormone whose concentration varies between 0 and 200 nmol L−1. Moreover, the sensitivity of the structure varies between 158.7816 nm nmol−1 L−1 to 170 nm nmol−1 L−1 under the influence of blood samples having estradiol hormones of different concentrations. In order to evaluate the performance of the proposed biosensor in the true sense we have also computed quality factor (Q) and figure of merit (FoM) values of the biosensor corresponding to both categories of blood samples of different concentrations. Our study shows that biosensors made up of 1D annular photonic structures are more efficient in comparison to the biosensors made up of planar 1D photonic crystals. Apart from detecting the reproductive hormones in females such kind of APC-based specialized biosensing devices may be very useful in the field of medical engineering and technology.

Employing metamaterial and Ti3C2Tx (MXene) material for cancer cells detection using defective 1D photonic crystal

Employing metamaterial and Ti3C2Tx (MXene) material for cancer cells detection using defective 1D photonic crystal

Initial Response of Pentaerythritol Tetranitrate (PETN) under the Coupling Effect of Preheating, Shock and Defect via the Molecular Dynamics Simulations with the Multiscale Shock Technique Method.

The initial response of PETN under the coupling of preheating, impact and defects was simulated by Multiscale Shock Technique (MSST) method and molecular dynamics. The temperature change of PETN during impact compression can be divided into three stages: (1) the elastoplastic change of the system caused by initial compression; (2) part of PETN decomposes and releases energy to raise temperature; (3) a secondary chemical reaction occurs, resulting in rapid temperature rise. Under the given conditions, a higher initial preheating temperature will lead to faster decomposition of PETN; The existence of defects will accelerate the decomposition of PETN molecules; Coupling the highest preheating temperature with defects will lead to the fastest decomposition of PETN molecules, while in the defect-free PETN system with a preheating temperature of 300 K, the decomposition of PETN molecules is the slowest. For the case of Us = 8 km·s-1, the effect of defects on the initial PETN reaction is greater than the initial preheating temperature; When the impact velocity is greater than 9 km·s-1, the impact velocity is an important factor affecting the decomposition of PETN molecules. For Us = 10 km·s-1, NO2 is the main initial product in the defective PETN crystal, while in the perfect PETN crystal, it is the combination of NO2 and HONO. The chemical reaction kinetics analysis shows that the preheating temperature and defects will accelerate the decomposition of PETN. The higher the preheating temperature, the faster the decomposition of PETN. For the case of Us = 7 km·s-1, 8 km·s-1 and 9 km·s-1, the existence of defects will increase the decomposition rate by more than 50% regardless of the initial preheating temperature. In the case of Us = 10 km·s-1, the improvement of decomposition rate by defects is not as significant as the initial preheating temperature.

Magnetic frustration driven by conduction carrier blocking in Nd2Co0.85Si2.88

The intermetallic compound ${\mathrm{Nd}}_{2}{\mathrm{Co}}_{0.85}{\mathrm{Si}}_{2.88}$ having a triangular lattice could be synthesized in single phase only with defect crystal structure. Investigation through different experimental techniques indicate the presence of two magnetic transitions in the system. As verified experimentally and theoretically, the high-temperature transition ${T}_{\mathrm{H}}\ensuremath{\sim}$ 140 K is associated with the development of ferromagnetic interaction between itinerant Co moments, whereas the low-temperature transition at ${T}_{\mathrm{L}}\ensuremath{\sim}$ 6.5 K is due to the coupling among $\text{Nd}\text{\ensuremath{-}}4f$ and $\mathrm{Co}\text{\ensuremath{-}}3d$ moments, which is antiferromagnetic in nature. Detailed studies of temperature-dependent dc magnetic susceptibility, field dependence of isothermal magnetization, nonequilibrium dynamical behavior, viz., magnetic relaxation, aging effect, magnetic-memory effect, and temperature dependence of heat capacity, along with density functional theory (DFT) calculations, suggest that the ground state is magnetically frustrated spin glass in nature, having competing magnetic interactions of equivalent energies. DFT results further reveal that the $3d/5d$-conduction carriers are blocked in the system and act as a barrier for the $4f\text{\ensuremath{-}}4f$ RKKY interactions, resulting in spin frustration. Presence of vacancy defects in the crystal are also conducive to the spin frustration. This is an unique mechanism of magnetic frustration, not emphasized so far in any of the ternary ${R}_{2}T{X}_{3}$ ($R$ = rare earth, $T$ = transition elements, and $X$ = Si, Ge, In) type compounds. Due to the competing character of the itinerant $3d$ and localized $4f$ moments, the compound exhibits anomalous field dependence of magnetic coercivity. The system also exhibits a considerable magnetic entropy change of $\ensuremath{-}\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{M}}\ensuremath{\sim}$ 13.3 J/kg K with a relative cooling power (RCP) of 220 J/kg and adiabatic temperature change $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{ad}}$ of 6 K for magnetic field change of 70 kOe.

Molecular rotations trigger a glass-to-plastic fcc heterogeneous crystallization in high-pressure water.

We report a molecular dynamics study of the heterogeneous crystallization of high-pressure glassy water using (plastic) ice VII as a substrate. We focus on the thermodynamic conditions P ∈ [6-8] GPa and T ∈ [100-500] K, at which (plastic) ice VII and glassy water are supposed to coexist in several (exo)planets and icy moons. We find that (plastic) ice VII undergoes a martensitic phase transition to a (plastic) fcc crystal. Depending on the molecular rotational lifetime τ, we identify three rotational regimes: for τ > 20 ps, crystallization does not occur; for τ ∼ 15 ps, we observe a very sluggish crystallization and the formation of a considerable amount of icosahedral environments trapped in a highly defective crystal or in the residual glassy matrix; and for τ < 10 ps, crystallization takes place smoothly, resulting in an almost defect-free plastic fcc solid. The presence of icosahedral environments at intermediate τ is of particular interest as it shows that such a geometry, otherwise ephemeral at lower pressures, is, indeed, present in water. We justify the presence of icosahedral structures based on geometrical arguments. Our results represent the first study of heterogeneous crystallization occurring at thermodynamic conditions of relevance for planetary science and unveil the role of molecular rotations in achieving it. Our findings (i) show that the stability of plastic ice VII, widely reported in the literature, should be reconsidered in favor of plastic fcc, (ii) provide a rationale for the role of molecular rotations in achieving heterogeneous crystallization, and (iii) represent the first evidence of long-living icosahedral structures in water. Therefore, our work pushes forward our understanding of the properties of water.

Tunable Fano resonance in coupled topological one-dimensional photonic crystal heterostructure and defective photonic crystal

In this paper, we theoretically investigate the transmission properties of a structure composed of a topological one-dimensional photonic crystal (1D PhC) heterostructure and a conventional 1D PhC containing indium-antimonide (InSb) as a defect layer using the transfer matrix method. The phenomenon of Fano resonance can be achieved by coupling the defect mode with the topological edge state mode, which is supported by the topological PhC. The numerical results show that a narrow Fano resonance is observed in the transmission spectrum of the structure in the presence of the external magnetic field applied to the InSb defect layer. The optical properties of the InSb defect layer, and, therefore, the Fano resonance, can be dynamically controlled by changing the applied external magnetic field. The results obtained with the proposed structure reveal that the magnetic field has the greatest influence on controlling the optical properties of the Fano resonance. These findings could be beneficial for optical devices such as optical filters, sensors, and optical switches.

Temperature Sensing Based on Defect Mode of One-Dimensional Superconductor-Semiconductor Photonic Crystals

Based on the transfer-matrix method, we theoretically explore the transmission and reflection properties of light waves in a one-dimensional defective photonic crystal composed of superconductor (HgBa2Ca2Cu3O8+δ) and semiconductor (GaAs) layers. The whole system is centrosymmetric and can generate a defect transmission peak in the photonic band gap. We study the effect of the temperature on the defect mode. Results obtained show that the defect mode shifts to the lower frequency regions as the value of the environmental temperature increases, and the resonance of the defect mode can be strengthened further as the number of periods increases. In addition, our findings reveal that the central wavelength of the defect mode increases with the increase in the environmental temperature and it presents a nearly linear relationship between the central wavelength of the defect mode and the temperature in cryogenic environments. Therefore, we can use the temperature response of the defect mode to detect the temperature. It is hoped that this study has potential applications for the development of cryogenic sensors with high sensitivity.

Influence of H2 treatment on the surface morphology of SiC with different wafer orientation and doping

H2 treatment is becoming a valuable method for the in-situ surface preparation of SiC wafer. Then clean interfacial layer can be attained in manufacturing SiC-based devices. However, surface morphology of SiC depends on wafer orientation and doping. Herein, H2-etched SiC wafers comprising various crystal planes were analyzed in detail. Formation of faceted etch pits occurs on C- and Si-faces of on-axis substrates. Meanwhile, Si-face of 4° off-cut substrate and the epitaxial layer boasts obvious terrace step after 1650 °C H2 treatment, indicating the increment of surface roughness. As our study revealed, H2 treatment is beneficial for achieving smoother surface morphology of C-face than Si-face wafers, as well as realizing ∼15 % to ∼51 % decrement in average roughness in C-face 4° off-cut substrate. Furthermore, defective graphitic structure and SiC crystal are identified after high temperature Ar treatment. The use of these results is expected to gain insights into the decomposition behavior of SiC with different wafer orientation and surface doping. Also, it is meaningful to realize the surface preparation process in power- and nano- electronic device fabrications.

Heavy metals biosensor based on defective one-dimensional phononic crystals

In recent years, the detection of water pollution with low levels of heavy metals has attracted the great attention of many researchers as a result of the imminent danger of this type of pollution to all mankind. Meanwhile, we introduce a theoretical approach based on the one-dimensional phononic crystals (1D-PnCs) with a central defect layer as a novel platform for the highly sensitive detection of heavy metal pollution in freshwater. Therefore, the creation of a resonant peak in the transmittance spectrum related to this defect layer is highly conceivable. In this regard, the detection of cadmium chloride (CdCl2) as a dangerous, toxic, and extremely hazardous heavy metal could be investigated based on the small displacement in the position of this resonant peak with the changes in the CdCl2 concentration. Notably, any change in CdCl2 concentration has a direct impact on its acoustic properties. The theoretical framework of our research study is essentially based on the 2 × 2 transfer matrix method and the acoustic properties of the constituent materials as well. The optimization of all sensor parameters represents the mainstay of this study to get the best sensor performance. In this regard, the proposed sensor has a remarkably high sensitivity (S = 1904.25 Hz/ppm) over a concentration range of 0 – 10000 ppm. In addition, the sensor has a high quality factor (QF), and figure of merit of 1771.318, and 73529410−5 (ppm−1), respectively. Finally, we believe this sensor could be a key component of a feasible platform for detecting low concentrations of different heavy metal ions in freshwater.