Confinement Theory Research Articles

Quantum confinement theory of the heat capacity of thin films

Quantum confinement theory of the heat capacity of thin films

Nanotechnology and Its Impact on Physical Sciences

Purpose: The main objective of this study was to explore nanotechnology and its impact on physical sciences.
 Methodology: The study adopted a desktop research methodology. Desk research refers to secondary data or that which can be collected without fieldwork. Desk research is basically involved in collecting data from existing resources hence it is often considered a low cost technique as compared to field research, as the main cost is involved in executive’s time, telephone charges and directories. Thus, the study relied on already published studies, reports and statistics. This secondary data was easily accessed through the online journals and library.
 Findings: The findings revealed that there exists a contextual and methodological gap relating to nanotechnology and its impact on physical sciences. Preliminary empirical review revealed that nanotechnology has significantly transformed physical sciences, particularly in physics, chemistry, materials science, and condensed matter physics. It has facilitated the development of novel materials and devices, enabling advancements in quantum technologies and nanoelectronics. Interdisciplinary collaboration is key, emphasizing the need for researchers from diverse scientific backgrounds to work together to harness nanotechnology's full potential. Additionally, the study underscores the importance of ongoing research to address ethical, safety, and environmental concerns associated with nanotechnology, ensuring its sustainable integration into physical sciences.
 Unique Contribution to Theory, Practice and Policy: The Quantum Confinement Theory, Materials Science and Nanomaterials Theory and the Interdisciplinary Collaboration Theory may be used to anchor future studies on nanotechnology. The recommendations stemming from the study advocated for fostering interdisciplinary collaboration among researchers, investing in nanoscience education, promoting ethical and responsible research practices, and supporting long-term environmental assessments. These suggestions aim to facilitate the seamless integration of nanotechnology into the physical sciences, ensuring that it leads to innovative breakthroughs while addressing ethical, safety, and environmental considerations.

Control of Plasma Potential in GOL-NB Axisymmetric Multiple-Mirror Trap

The results on applying the technique of vortex plasma confinement in the GOL-NB facility are presented. The first experiments on optimizing the biasing the in-chamber electrodes demonstrated an improvement in the dynamics of trapping the injected fast hydrogen atoms, as well as a decrease in the fluctuations of local plasma parameters in the central trap and an increase in the plasma decay time. The geometry of in-chamber electrodes arrangement, as well as the polarity and magnitude of the supplied potentials, correspond to the theory of vortex confinement and to those in similar studies at other open traps.

Experimental study on performance of spring damping support structure system for large deformation tunnel in soft rock

According to the convergence confinement theory, it is an effective measure to control the large deformation of high ground stress in fractured soft rock tunnels by using yielding support. The yielding support can be classified as either radial or circumferential yielding support. Circumferential yielding support is achieved by transforming radial displacement into circumferential tangential closure without compromising the support capacity of the primary lining support structure. Based on this, and inspired by the design principle of dampers, a yielding support structure system with spring damping elements as its core was developed, based on the connection characteristics of steel arches in highway tunnel, which can provide increasing support resistance in the yielding deformation section. Then the mechanical properties of spring damping elements were obtained through indoor axial pressure and flexural tests. In addition, according to these results with numerical calculations, the yielding support structure system with embedded spring damping elements can reduce the internal force of the support structure by approximately 10% and increase the area of the plastic zone of the surrounding rock by 11.23%, which can fully utilize the self-bearing capacity of surrounding rock and verify the effectiveness of circumferential yielding support. Finally, the spring damping support structure system was designed with reference to the construction process of the tunnel excavated by drilling and blasting method, and the transformation of the spring damping element to spring damping support structure was achieved. Based on field test results, surrounding ground pressure for the yielding support optimization scheme was reduced by 40% and more evenly distributed, resulting in the successful application and a reduction in the construction cost of large deformation tunnels in soft rock.

Azimuthal confinement: the missing ingredient in understanding confinement loss in antiresonant, hollow-core fibers

Antiresonant, hollow-core optical fibers are currently challenging or even exceeding the loss performance of conventional solid-core fibers. Despite this progress, there are aspects of the guidance mechanism in these fibers that are still not understood. For example, a physical mechanism to explain why negative curvature of the core surround is correlated with low loss remains elusive. It is shown that the glass elements of the cladding structure with an approximately radial orientation play a crucial role in determining the confinement loss by strongly shaping the wave fields in the azimuthal coordinate. This shaping, described as azimuthal confinement, can result in an evanescent field in the radial direction through the cladding, and this leads to a confinement loss that is substantially lower than would be the case without azimuthal confinement. A comprehensive theory of azimuthal confinement is developed, yielding an expression for the confinement loss of any fiber structure with a single antiresonant glass layer between the core and the outer glass jacket. This is tested by comparison with large-scale numerical simulations on two types of cladding structure. It is shown that negative curvature of the core surround has little or no intrinsic role in reducing confinement loss in fibers with a nodeless cladding structure. The power of azimuthal confinement is demonstrated in model structures where the confinement loss drops by more than two orders of magnitude as the radial width of the cladding is increased. It is anticipated that the concept of azimuthal confinement will be valuable in interpreting confinement loss in a wide range of existing antiresonant, hollow-core fibers and in the design of novel, low loss cladding structures.

Macrobenthos of the Tortolì Lagoon: A Peculiar Case of High Benthic Biodiversity among Mediterranean Lagoons

Coastal lagoons and brackish ponds are extremely dynamic and temporary ecosystems that follow natural changes throughout their geological history. The correct management of the lagoons ensures their integrity and proper functioning. For this reason, their ecological status should be surveyed for assessing the most appropriate strategies of use. In the present study, historical datasets collected in 2003–2004 are used to investigate the spatiotemporal variation in the species composition and community structure of the macrobenthos of the Tortolì Lagoon (Sardinia, Italy) and to assess their relationship with key environmental variables. Owing to the presence of a riverine runoff at a site and confined areas at some distance from the sea inlet, we hypothesize the marked spatiotemporal changes of the macrobenthic community consistent with the high environmental variability typical of coastal lagoons. The results show a surprisingly high benthic biodiversity for a medium-sized lagoon (250 ha), with 101 species unevenly distributed across the lagoon. The environmental variables did not explain the zonation of the macrobenthic community as that typically found along a lagoonal gradient, due to a marked marine influence. The sampling sites were in fact discriminated by the species distribution according to their ecological affinity; in particular, the most distinctive characteristics of the Tortolì Lagoon emerged from the strictly marine species that represented the most abundant group, consistently with the high marinization of the lagoon. Our results show that the Tortolì Lagoon constitutes a peculiar ecosystem within Mediterranean lagoons, departing from the classic confinement theory.

A multiscale model for multiaxial inelastic behavior of elastomeric particulate composites

This article addresses the problem of the multiscale constitutive representation of the multiaxial inelastic behavior of elastomeric particulate composites. A fully three-dimensional model is proposed within a micromechanical treatment to describe the multiaxial inelastic response in relation to the reinforcement mechanisms. A network decomposition based on the tube confinement theory is used to consider the combined effects of multiaxiality and inelasticity. The near-field direct interactions between the particles and the rubber networks are physically described using the Eshelby inclusion theory. The capabilities of the microstructure-based model are evaluated for different modes of deformation over a wide range of filler concentrations. It is found being able to successfully reproduce the significant features of the multiaxial macro-response upon monotonic and cyclic loading sequences. Important insights about the effective role of the reinforcement mechanisms on the multiaxial dissipation are revealed.

Joint analysis of macrofaunal and meiofaunal assemblages improves the assessment of lagoonal environmental heterogeneity

Matching datasets of macrofaunal and meiofaunal assemblages were jointly analyzed for the first time in a coastal lagoon (Cabras Lagoon, Sardinia) in relation to the lagoonal environmental heterogeneity. Within the common faunal list, indicator species/taxa for different environmental conditions were found evenly for both assemblages, with the two faunal components responding distinctly to the putative environmental gradients according to their autecology. The relationship between the number of individuals and species/taxa richness of both assemblages showed an exponential increase at increasing salinity and DO concentrations in water as expected basing on the confinement theory. Along the trophic gradient, the two metrics of both macrofaunal and meiofaunal assemblages showed a similar belt-shaped curve in agreement with theoretical predictions and quantitative field studies, with a peak at intermediate OM values followed by a sharp decrease at OM above 12% at the most confined site. While not a causality measure, our results indicate that these simple benthic-OM relationships applied to both faunal components represent a valuable screening-level indicator for evaluating the likelihood of reduced sediment quality and associated bioeffects in eutrophic lagoons. The present study demonstrates that macrofaunal and meiofaunal assemblages in coastal lagoons, as commonly shown in marine waters, are coherent and distinct entities and that their joint use represents a more comprehensive and robust tool to assess the environmental heterogeneity and quality of these highly variable systems.

Primordial black holes from confinement

A mechanism for the formation of primordial black holes is proposed. Here, heavy quarks of a confining gauge theory produced by de Sitter fluctuations are pushed apart by inflation and get confined after horizon re-entry. The large amount of energy stored in the colour flux tubes connecting the quark pair leads to black-hole formation. These are much lighter and can be of higher spin than those produced by standard collapse of horizon-size inflationary overdensities. Other difficulties exhibited by such mechanisms are also avoided. Phenomenological features of the new mechanism are discussed as well as accounting for both the entirety of the dark matter and the supermassive black holes in the galactic centres. Under proper conditions, the mechanism can be realised in a generic confinement theory, including ordinary QCD. We discuss a possible string-theoretic realisation via $D$-branes. Interestingly, for conservative values of the string scale, the produced gravity waves are within the range of recent NANOGrav data. Simple generalisations of the mechanism allow for the existence of a significant scalar component of gravity waves with distinct observational signatures.

Drift kinetic theory of alpha transport by tokamak perturbations

Upcoming tokamak experiments fuelled with deuterium and tritium are expected to have large alpha particle populations. Such experiments motivate new attention to the theory of alpha particle confinement and transport. A key topic is the interaction of alpha particles with perturbations to the tokamak fields, including those from ripple and magnetohydrodynamic modes like Alfvén eigenmodes. These perturbations can transport alphas, leading to changed localization of alpha heating, loss of alpha power and damage to device walls. Alpha interaction with these perturbations is often studied with single-particle theory. In contrast, we derive a drift kinetic theory to calculate the alpha heat flux resulting from arbitrary perturbation frequency and periodicity (provided these can be studied drift kinetically). Novel features of the theory include the retention of a large effective collision frequency resulting from the resonant alpha collisional boundary layer, correlated interactions over many poloidal transits and finite orbit effects. Heat fluxes are considered for the example cases of ripple and the toroidal Alfvén eigenmode (TAE). The ripple heat flux is small. The TAE heat flux is significant and scales with the square of the perturbation amplitude, allowing the derivation of constraints on mode amplitude for avoidance of significant alpha depletion. A simple saturation condition suggests that TAEs in one upcoming experiment will not cause significant alpha transport via the mechanisms in this theory. However, saturation above the level suggested by the simple condition, but within numerical and experimental experience, which could be accompanied by the onset of stochasticity, could cause significant transport.

Optical study of electron and acoustic phonon confinement in ultrathin-body germanium-on-insulator nanolayers

Nanoelectronics require semiconductor nanomaterials with high electron mobility like Ge nanolayers. Phonon and electron states in nanolayers undergo size-dependent changes induced by confinement and surface effects. Confined electrons and acoustic phonons determine layer optical, electric and thermal properties. Despite scientific and practical significance, their experimental studies in individual nanolayers are still lacking. Thanks to recent progress in the fabrication of high-quality nanolayers, here, we report the thickness dependencies of Raman spectra of acoustic phonons and optical spectra of electrons confined in germanium-on-insulator (GeOI) nanolayers with thicknesses TGeOI = 1-20 nm. We show that for TGeOI > 5 nm, both GeOI acoustic phonon Raman spectra and the E1 electron energy gap display dependencies on TGeOI which are reasonably described by the corresponding phonon and electron confinement theories. Accordingly, TGeOI can be probed using acoustic phonon Raman spectra at TGeOI > 5 nm. However, both confinement theories fail to describe GeOI thickness dependencies at TGeOI < 5 nm. We attribute this discrepancy to an increased influence of the Ge-GeO2 interface disorder with TGeOI reduction. The acoustic phonon data suggest a decrease of Ge normal-to-the-layer longitudinal sound velocity. Generation of interface-disorder-induced dispersionless phonons might contribute to this. The change in GeOI phonon properties at TGeOI < 5 nm might influence E1(TGeOI) dependence via a change in the GeOI electron-phonon interaction. We demonstrate that the Al2O3 coating improves the agreement between experimental and confinement theories, probably, via reduction of disorder at the Ge-GeOx-Al2O3-interface. Our results are important for control of nanolayer-confined electrons and phonons with benefits for modern and future nanoelectronic devices.

The Origin of Quantum Effects in Low‐Dimensional Thermoelectric Materials

AbstractThermoelectric material, which directly converts waste heat to electricity, provides an ecofriendly power generator to reuse heat energy sources. New attempts have started for thermoelectricity of low‐dimensional materials since 1993 when the theory of confinement effect was presented by Hicks and Dresselhaus. Experimental works have been inspired by the theory of confinement to the use of low‐dimensional materials for improving thermoelectric efficiency for more than two decades. In this report, it is considered how recent theories and experiments have made progress on the quantum confinement effects. In particular, the reason is explained why the thermal de Broglie wavelength becomes a key parameter to enhance the power factor.

Quantum confinement and size resolved modeling of electronic and optical properties of small soot particles

Electronic and optical properties of flame-generated carbon nanoparticles were modeled based on quantum confinement and amorphous semiconductor theory of monodispersed particles. The ionization energies and optical band gaps of polydispersed particles 4–23 nm in volume median diameter (Liu et al., Proc. Natl. Acad. Sci. U.S.A. 116 (2019) 12692–12697) were re-analyzed by deconvolution to obtain particle-size specific properties. The complex refractive index was derived from optical absorption and the Kramers–Krönig relations over the wavelength range of 185–1400 nm. Dependence of the refractive index on the primary particle size is shown for the first time. The real component of the refractive index is weakly dependent on the particle size, but the imaginary component is found to be particularly sensitive to the particle size. The refractive indices of relatively large soot particles are found to be in close agreement with literature values in the visible spectrum; those of smaller particles (〈 ∼ 15 nm in diameter) show a significant difference from the literature values. The current result highlights the need for accounting for the size effect in the refractive index in laser diagnostics of soot in flames. It also suggests that some of the earlier extinction and scattering measurements of flame soot may have to be re-evaluated, especially for lightly sooting flames and during the early stage of soot growth.

Measurements of axial energy loss from magnetic mirror trap

The work represents a next step in studies of longitudinal energy losses from linear magnetic plasma confinement devices. The paper describes the experimental technique that has been developed and used to measure the absolute values of longitudinal particle and energy density fluxes from an open magnetic mirror trap. Using this technique, it was possible to measure and account for the secondary electron emission coefficient from plasma-facing end plate, and perform a comparison with the existing theory of energy confinement in open traps. It is shown that the average energy transported by an ion-electron pair leaving the trap is close to theoretically predicted minimum value of 6–8 electron temperatures. As confirmed by the measured dependencies, this conclusion is valid in a broad range of parameters and the threshold value of the magnetic expansion ratio does not exceed its theoretically predicted minimum of .

Confinement of Fermions in Tachyon Matter

In this paper, we develop a phenomenological model inspired by QCD that mimics the QCD theory. We use the gauge theory in color dielectric medium (Gϕ) coupled with fermion fields to produce scalar and vector confinements in the chromoelectric flux tube scenario. The Abelian theory will be used to approximate the non-Abelian QCD theory in a consistent manner. We will calculate vector and scalar glueballs and compare the result to the existing simulation and experimental results and projections. The QCD-like vacuum associated with the model will be calculated and its behavior studied relative to changing quark masses. We will also comment on the relationship between tachyon condensation, dual Higgs mechanism, QCD monopole condensation, and their association with confinement. The behavior of the QCD string tension obtained from the vector potential of the model will be studied to establish vector dominance in confinement theories.

The Role of Pressure Anisotropy in Cosmic-Ray Hydrodynamics

Abstract The mean free path of cosmic rays in diffuse interstellar and intracluster gas is determined primarily by pitch angle scattering from hydromagnetic waves with wavelength of order the cosmic-ray gyroradius. In the theory of cosmic-ray self confinement, the waves are generated by instabilities driven by the cosmic rays themselves. The dominant instability is due to bulk motion, or streaming, of the cosmic rays, parallel to the background magnetic field , and transfers cosmic-ray momentum and energy to the thermal gas as well as confining the cosmic rays. Classical arguments and recent numerical simulations show that self confinement due to the streaming instability breaks down unless the cosmic-ray pressure and thermal gas density gradients parallel to are aligned, a condition that is unlikely to always be satisfied We investigate an alternative mechanism for cosmic-ray self confinement and heating of thermal gas based on pressure anisotropy instability. Although pressure anisotropy is demonstrably less effective than streaming instability as a self-confinement and heating mechanism on global scales, it may be important on mesoscales, particularly near sites of cosmic-ray injection.

Confinement Effect in Thermoelectric Properties of Two–Dimensional Materials

ABSTRACT:Thermoelectric (TE) materials, or materials that can generate an electrical energy from temperature gradient, are promising for renewable energy technology. One fundamental aspect in the TE research is the demand to maximize the TE power-factor, PF = S2 σ, by having as large Seebeck coefficient (S) and electrical conductivity (σ) as possible. In the early 90s, Hicks and Dresselhaus proposed the PF enhancement by using low-dimensional materials, in which electrons are confined in certain directions and they move freely in the other directions. This quantum effect is known as the confinement length (L) effect, in which L is the thickness or diameter of the two-dimensional (2D) or one-dimensional materials, respectively. However, a key challenge is to understand the critical value of L, at which the PF can be significantly enhanced. Recently, we reevaluated the confinement theory of the low-dimensional materials to solve this issue. We showed that electrons are fully confined only when L is smaller than an intrinsic length Λ, the so-called thermal de Broglie wavelength, which depends on the materials and can be experimentally measured. Monolayer 2D materials naturally satisfy the condition of L &lt; Λ since their confinement length is ∼ 1 nm, while their thermal de Broglie wavelength is ∼ 5-10 nm. Therefore, they could be a good candidate for TE materials. In this review article, we first review the TE materials with low dimensions. Then, we show the basic concept of the confinement effect and the consequence of such an effect. Finally, based on this effect, we turn our attention to the progress achieved recently in the TE properties of the 2D materials such as monolayer InSe, GaN electron gas, and SrTiO3 superlattices.

High-performance UV-B detectors based on MnxZn1-xS thin films modified by bandgap engineering

The high-speed performance ultraviolet (UV) detectors were successfully fabricated based on the ternary MnxZn1-xS (0.2 ≤ x ≤ 0.4) thin films deposited by a simple spray pyrolysis method. The optoelectrical properties of the samples were modified by introducing the Mn impurities at high content to enhance the performance of UV detectors. Microstructural characteristics confirmed the well-incorporation of Mn2+ ions into the ZnS lattice having nanocrystalline nature with homogeneous surface and strong adherence to the substrates. The optical measurements revealed that at the higher Mn2+ concentration, the optical transmittance increased over 95 % in the visible to near-infrared regions. Compared to the pure ZnS, the values of bandgap energy were found to blue-shift about 0.14 eV due to both quantum confinement and Burstein-Moss theories. Meanwhile, the Urbach energy decreased dramatically, leading to a considerable reduction of the electron-phonon interaction. The photoluminescence (PL) spectra revealed that the PL emission intensity was enhanced by introducing excess charge carriers through increasing the Mn2+ concentration, which can improve the generation of electron-hole pairs in the alloys. The photoresponse characterization featured a tremendous photosensing and photoswitching for the fabricated UV detectors, in which an excellent UV-B responsivity and high visible rejection were observed for the devices. For the UV detector based on the Mn0.4Zn0.6S thin film, the current gain greatly improved over 4.5 times compared to the pure ZnS one. Likewise, the photoresponse speed of the samples was found to enhance over 5 times, considerably.

Comprehensive study on the concept of spectral-domain reflection and refraction

Space-time duality and time-to-frequency mapping bring a lot of analogies. We apply the concept of optical reflection and refraction, for the first time, to the spectral domain. The optical reflection and refraction phenomena are addressed in the spectral domain across a dispersion discontinuity boundary, where a weak probe pulse is co-propagating with a strong perpendicularly polarized parabolic pulse. The total internal reflection behavior in the spectral domain is analytically determined. Our results can complete the theory of the optical wave confinement in the spatial, temporal and spectral domains, which can be a guide for spectrum engineering and characterization.

Structural and Optical Characteristics of Nanoscale Semiconductor Lasers for Telecommunication and Biomedical Applications: A Review

This paper presents the structural and optical characteristics of nanoscale semiconductor lasers for telecommunication and biomedical applications. Improved fabrication techniques, new materials and nano-scale heterostructures have led to improvement in the device performance. The material selection and their bandgap have an important role in the heterostructure to generate a lasing wavelength for particular applications. The bandgap modification can be done by the use of alloy semiconductor, quantum well structure, and strain layer epitaxy without changing the material itself. Semiconductor multilayers on the substrate are generally grown by using the metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) process. Many researchers have provided different designs of heterostructures for the lasers. Generally, lasers are manufactured by using different semiconductor layers grown on GaAs, InP or GaSb substrate at the nanoscale. But controlling the thickness of the layer grown on the substrate at the nanoscale is the major problem in the fabrication. In a study, it has been found that for the proper functioning of semiconductor lasers it is beneficial to have light conduction and valence band masses. By using band structure engineering theory of quantum confinement and incorporation of strain on the active layer, this problem can be resolved. Red lasers are currently used in biomedical applications for treatment of superficial skin diseases like psoriasis, vitiligo etc. The manufacturing of red laser was earlier done by using nitrides material but they are harmful to skin and are expensive as well. An alternative for designing of red laser is manufacturing red lasers by using phosphides. The red laser is manufactured by using GaInP and AlGaInP ternary and quaternary compounds are widely used in the biomedical industry currently. This paper is the outcomes of the papers presented by many researchers in the field of optoelectronics.