Hall Systems Research Articles

Crystallization behavior and structural characteristics of Cr-doped Sb70Se30 thin films for phase change memory

In this study, we prepare Cr-doped Sb70Se30 (SS) thin films via the magnetron sputtering. The influence of Cr doping on the crystallization behavior and structure characteristics of the SS thin films is systematically studied using a combination of experimental analyzes and theoretical calculations. The results reveal that compared with SS thin films, Cr-doped SS thin films exhibit higher crystallization temperature, better data retention capability, larger crystallization activation energy, and reduced resistance drift coefficient. In addition, the incorporation of Cr effectively suppresses grain growth in the SS thin films and refines the grain size. The electrical transport properties of the Cr-doped SS thin films are analyzed using a Hall system. Both X-ray photoelectron spectroscopy and first-principles calculations indicate that Cr is more prone to occupy Sb atoms and form stronger Cr–Se bonds, consequently enhancing the stability of the SS thin films. Raman spectroscopy confirms that the introduction of Cr leads to a decrease in bond length and an increase in bond energy. Moreover, the Cr-doped SS thin film exhibits minimal volume fluctuations and a smoother surface morphology, resulting in enhanced interface performance and reliability. Taken together, these results indicate that the introduction of Cr is an effective strategy for optimizing the properties and modifying the structures of SS phase-change materials.

Emerging pathways in thermoelectric: Chemical bath deposition of magnesium selenide thin films for sustainable energy harvesting

In this study, magnesium Selenide (MgSe) thin films were synthesized on glass substrate using the chemical bath deposition (CBD) method for thermoelectric power generation. After cleaning of glass substrate, selenium powder was dissolved in nitric acid to produce SeO2 and magnesium chloride was then introduced as the source of magnesium. Both SeO2 and MgCl2 were dissolved in 100 ml of dI water and later, these solutions were unified gradually. After that, the cleaned glass substrates were placed in the solution, while keeping the reaction temperature constant at 50o C for the deposition durations of 24, 48, 72, and 96 h. A number of characterization techniques, namely X-ray Diffraction (XRD), Raman spectroscopy and Scanning Electron Microscopy (SEM) were performed for structural and surface analysis of grown thin films. The effect of deposition time duration on the thermoelectric properties was investigated in depth using the Seebeck and Hall systems. It was found that the values of the Seebeck coefficient and power factor obey the increasing trend with maximum values 196.93 μV/K and 21.5 × 10−8 W/mK2 respectively. These observed values are seems to be the highest values for magnesium selenide thin film ever reported in the literature according to the best of our knowledge. Therefore, we have concluded that MgSe thin films supposed to be emerging material for thermoelectric power generation applications.

Construction of Teaching Content of Introduction to Energy Conservation Management Based on Grounded Theory

Energy saving and carbon reduction has attracted the attention of the whole society, and the Introduction to Energy Saving Management can be developed into a general elective course. In order to enrich and improve the curriculum system of energy conservation management, this paper sums up, summarizes and codes 23 original materials obtained from existing teaching records and interviews by taking root in the theoretical method, and conducts a qualitative analysis of the content system of energy conservation management curriculum in combination with Hall's system engineering methodology, and constructs a spatial model consisting of three dimensions of energy conservation management stage, energy conservation management mechanism and energy conservation management knowledge, The intersection in this space constitutes the teaching content system of energy-saving management course. In terms of time, the content can be roughly divided into four stages: decision-making, design, implementation, operation and maintenance; In terms of mechanism, it can be divided into four categories: market, government compulsion, voluntary negotiation and energy contract management; The knowledge field can be divided into five aspects: regulations and policies, energy consumption assessment, information software, planning management and cleaner production. It provides a clear logical framework and a solid theoretical basis for the course.

Topological BF Description of 2D Accelerated Chiral Edge Modes

In this paper, we consider the topological abelian BF theory with radial boundary on a generic 3D manifold, as we were motivated by the recently discovered accelerated edge modes on certain Hall systems. Our aim was to research if, where, and how the boundary keeps the memory of the details of the background metrics. We discovered that some features were topologically protected and did not depend on the bulk metric. The outcome was that these edge excitations were accelerated, as a direct consequence of the non-flat nature of the bulk spacetime. We found three possibilities for the motion of the edge quasiparticles: same directions, opposite directions, and a single-moving mode. However, requiring that the Hamiltonian of the 2D theory is bounded by below, the case of the edge modes moving in the same direction was ruled out. Systems involving parallel Hall currents (for instance, a fractional quantum Hall effect with ν=2/5) cannot be described by a BF theory with the boundary, independently from the geometry of the bulk spacetime, because of positive energy considerations. Thus, we were left with physical situations characterized by edge excitations moving with opposite velocities (for example, the fractional quantum Hall effect with ν=1−1/n, with the n positive integer, and the helical Luttinger liquids phenomena) or a single-moving mode (quantum anomalous Hall). A strong restriction was obtained by requiring time reversal symmetry, which uniquely identifies modes with equal and opposite velocities, and we know that this is the case of topological insulators. The novelty, with respect to the flat bulk background, is that the modes have local velocities, which correspond to topological insulators with accelerated edge modes.

Scaling behavior of the quantum phase transition from a quantum-anomalous-Hall insulator to an axion insulator

The phase transitions from one plateau to the next plateau or to an insulator in quantum Hall and quantum anomalous Hall (QAH) systems have revealed universal scaling behaviors. A magnetic-field-driven quantum phase transition from a QAH insulator to an axion insulator was recently demonstrated in magnetic topological insulator sandwich samples. Here, we show that the temperature dependence of the derivative of the longitudinal resistance on magnetic field at the transition point follows a characteristic power-law that indicates a universal scaling behavior for the QAH to axion insulator phase transition. Similar to the quantum Hall plateau to plateau transition, the QAH to axion insulator transition can also be understood by the Chalker–Coddington network model. We extract a critical exponent κ ~ 0.38 ± 0.02 in agreement with recent high-precision numerical results on the correlation length exponent of the Chalker–Coddington model at ν ~ 2.6, rather than the generally-accepted value of 2.33.

Structure of uniform and high-quality Al-doped ZnO films by magnetron sputter deposition at low temperatures

Spatial distribution of highly energetic negative ions inherent in magnetron sputtering of oxides has long made low temperature deposition unsuitable for high quality films uniform over relatively large areas. Here we examine the distributions of structure as well as physical properties of magnetron sputtered Al-doped ZnO (AZO) films deposited at low temperatures (≤393 K) in which the bombardment from the negative oxygen ions was systematically studied by changing the discharge voltage (i.e., ion energy) and the substrate position (i.e., ion flux). The film structure was characterized by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy; and the electrical and optical properties were obtained by a Hall system and Spectroscopic Ellipsometry. We found (i) that uniform yet high crystallite quality films can be obtained only when the energy of the negative ions was set below a threshold; (ii) that the ion flux exerted an ever-decreasing effect on modifying the film structure as the ion energy was reduced; and (iii) that a set of structural criteria, incorporating crystallite quality (orientations, size, lattice spacing) and point defects, were derived for low resistivity AZO films. The benefit of lowering the ion energy is then explained in terms of the favorable competition between radiation-induced defect generation and the subsequent dynamic annealing. These findings may pave a way for large-area coating of high quality AZO films at low temperatures.

Integrated Pound\u2212Drever\u2212Hall laser stabilization system in silicon

Low noise stable lasers have far-reaching applications in spectroscopy, communication, metrology and basic science. The Pound−Drever−Hall laser stabilization technique is widely used to stabilize different types of lasers in these areas. Here we report the demonstration of an integrated Pound−Drever−Hall system that can stabilize a low-cost laser to realize a compact inexpensive light source, which can ultimately impact many fields of science and engineering. We present an integrated architecture utilizing an electronically reconfigurable Mach−Zehnder interferometer as the frequency reference to reduce the frequency noise of semiconductor lasers by more than 25 dB and the relative Allan deviation by more than 12 times at 200 μs averaging time. Compared to the bench-top implementations, the integrated Pound−Drever−Hall system has significantly lower power consumption, less sensitivity to the environmental fluctuations and occupies an area of only 2.38 mm2. The photonic and electronic devices are integrated on a standard 180 nm complementary metal-oxide semiconductor silicon-on-insulator process.

Effect of copper concentration on the physical properties of copper doped NiO thin films deposited by spray pyrolysis

The spray pyrolysis (SP) technique is an important and powerful method for the preparation of nickel oxide (NiO) and copper-doped nickel oxide thin films. The best films were obtained when the substrate temperature, Ts = 450 °C on glass substrates. Copper (Cu) concentrations in the films were varied from 0 to 8%. The effect of Cu concentration on the structural, morphological, spectral, optical, and electrical properties of the thin films were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), UV–vis–NIR spectrophotometer, Hot probe and Hall system. The X-ray diffraction result shows the polycrystalline cubic structure of sprayed films with (200) preferred orientation. The variations of the structural parameters such as lattice parameters and grain sizes were investigated. The SEM image displays the surface morphology of the NiO and Cu:NiO thin films. The FTIR of the as-deposited films were associated with chemical identification. The optical transmittance and absorbance spectra of the films were measured by UV–vis–NIR spectrophotometer. The absorption coefficient and band gaps of the films were calculated using the optical method. All the NiO and Cu:NiO films were p-type. The resistivity of the above films decreases with the increase in copper concentration and so the conductivity of the films depend on the precursor concentration.

Differences among primary care patients with different mechanical patterns of low back pain: a cross-sectional investigation

ObjectivesTo characterise and compare a persistent low back pain (LBP) population based on 4 clinical pain patterns.DesignCross-sectional analysis of patient-reported data.SettingPatients from 220 primary care practitioners in 3 cities in...

Topological Number from Entanglement

Recently, a new characterization of symmetry-protected topological phases has been proposed by combining quantum information with topology. The characterization has been successfully applied to two-dimensional quantum (spin) Hall systems.

Fractional quantum Hall effect revisited

The topology-based explanation of the fractional quantum Hall effect (FQHE) is summarized. The cyclotron braid subgroups crucial for this approach are introduced in order to identify the origin of the Laughlin correlations in 2D (two-dimensional) Hall systems. Flux-tubes and vortices for composite fermions in their standard constructions are explained in terms of cyclotron braids. The derivation of the hierarchy of the FQHE is proposed by mapping onto the integer effect within the topology-based approach. The experimental observations of the FQHE supporting the cyclotron braid picture are reviewed with a special attention paid to recent experiments with a suspended graphene. The triggering role of a carrier mobility for organization of the fractional state in Hall configuration is emphasized. The prerequisites for the FQHE are indicated including topological conditions substantially increasing the previously accepted set of physical necessities. The explanation of numerical studies by exact diagonalizations of the fractional Chern insulator states is formulated in terms of the topology condition applied to the Berry field flux quantization. Some new ideas withz regard to the synthetic fractional states in the optical lattices are also formulated.

Room-temperature thermoelectric properties of GaN thin films grown by metal organic chemical vapor deposition

The GaN thin films with different doping concentrations are grown by metal organic chemical vapor deposition. Carrier concentrations, mobilities and Seebeck coefficients of the GaN thin films are measured by Hall and Seebeck system at room temperature. The power factor and the thermoelectric figure of merit are calculated by experimental and theoretical data. The mobility and Seebeck coefficient of GaN thin film decrease with the increase of carrier concentration. The conductivity of GaN thin film increases with the increase of carrier concentration. The Seebeck coefficient of GaN thin film varies from 100 to 500 μV/K, depending on carrier concentration. The highest power factor is 4.72×10-4 W/mK2 when the carrier concentration is 1.60×1018 cm-3. The thermal conductivity of GaN thin film decreases with the increase of carrier concentration due to the increase of phonon scattering. The largest thermoelectric figure of merit of the GaN thin film at room temperature is 0.0025 when the carrier concentration is 1.60×1018 cm-3.

A Reassessment of the National Three Hall System in the Late Northern Song

A Reassessment of the National Three Hall System in the Late Northern Song Yongguang Hu In recent years, a number of historians have reevaluated the reform policies of Cai Jing 蔡京 (1047–1126), the chief councilor of Emperor Huizong 徽宗 (r. 1100–1126), in the early twelfth century. Rather than accepting the traditional view of Cai as an avaricious, corrupted official weakening the empire’s fiscal foundation and bringing the Northern Song to a tragic end,1 their new perspective calls for a reexamination of Cai Jing’s reforms based on a neutral reading of sources “wherever possible.”2 Neutral reading allows scholars to identify potential Neo-Confucian biases in the narratives compiled in the Southern Song and Yuan and then present a more nuanced view of politics and society in that period.3 Scholars also started to study Cai Jing’s reforms [End Page 139] in a larger historical context, in which both Huizong and Cai Jing aimed to create magnificence and set a new hallmark of the empire by a number of policies, such as constructing a lavish imperial garden with exotic Jiangnan stones, sponsoring artistic creation in painting and calligraphy, revising palace music, erecting large size stone tablets throughout the empire, and offering a whole package of educational and social welfare programs. Both the conference volume edited by Patricia Ebrey and Maggie Bickford, Emperor Huizong and Late Northern Song China, and Ebrey’s new biography on Huizong view the above measures as displays of imperial authority.4 Many of these policies attempted to achieve goals never attained in history; in this way, Huizong and Cai Jing could demonstrate that they were taking the empire to a new level of universal prosperity.5 One example is the national Three Hall System (sanshefa 三舍法), an empire-wide government school network actively promoting Confucian education to male students.6 A vast system supporting as many as 200,000 students in 1116,7 it was conveniently ignored in traditional official histories because of Cai Jing’s reputation. Thanks to studies by Thomas H. C. Lee, John Chaffee, Yuan Zheng, and Kondo Kazunari, all of whom relied on court documents to present introductory information about the system, we now have a better understanding of this policy.8 Still, many questions are left unanswered. Did [End Page 140] the government build as many schools as it claimed? How could the state allocate adequate resources to support this system? Did the reformers use the Three Hall System to enforce their brand of political theory throughout the empire? What might be the reasons for its abolishment in 1121? This study utilizes a variety of sources, especially local gazetteers, tomb inscriptions, and scholarly works, to present a more thorough analysis of this institution with the above questions in mind. The main arguments are that the well-supported Three Hall System was a remarkable design which promoted education in the early twelfth century and that this government-controlled institution helped to create an increasingly diverse intellectual landscape in those decades. In the following sections, I will first provide a brief introduction, followed by a detailed study on school building and maintenance based on local gazetteers. After showing the scale and scope of this reform, I briefly discuss why it was ended in the early 1120s. The last section locates individual experiences within the Three Halls and reveals how school became a cultural field that opened opportunities to different interests groups. This might be the most important contribution of this reform to Song society, whether Cai Jing expected it or not. The Three Hall Policy In 1102, an imperial decree required every prefecture and county to establish its own school. This was not the first time that the government made school building compulsory, but unlike the cases in previous centuries, in which this type of orders was often ignored by local officials, the 1102 decree did establish a vast government educational network in the empire.9 Hundreds of [End Page 141] schools were built or renovated in the following years. According to the law, each school should have three halls: an outer hall (waishe 外舍), an inner hall (neishe 內舍), and an upper hall (shangshe 上舍), which functioned like grade levels in modern school...

Structures, electrical and optical properties of nickel oxide films by radio frequency magnetron sputtering

The NiO films were sputtered by radio frequency (rf) magnetron sputtering at different oxygen partial pressures. The structures, electrical and optical properties of the NiO films were investigated. The resulting films were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible spectrophotometer (UV). The electrical properties were measured by Hall system. The results show that the NiO films deposited at room temperature with the ratio of oxygen partial pressures varying from 0 to 80% develop only (200) preferred orientation and very high optical transmittances. The lowest resistivity of 2.368 Ω cm and highest carrier density of 2.235 × 1019 cm−3 could be obtained. Comparatively, the controllable electrical properties of the films can be achieved by the variation of crystal quality arises from the oxygen partial pressures.

The effect of the multi-period on the properties of deep-ultraviolet transparent conductive Ga2O3/ITO alternating multilayer films

Ga2O3/ITO alternating multilayer films were deposited on quartz glass substrates by magnetron sputtering. The effect of the multi-period on the structural, optical and electrical properties of Ga2O3/ITO alternating multilayer films was investigated by an X-ray diffractometer, a double beam spectrophotometer and the Hall system, respectively. A low sheet resistance of 225.5 Ω/□ and a high transmittance of more than 62.9% at a 300 nm wavelength were obtained for the two-period alternating multilayer film with a thickness of 72 nm.

Investigation of electrophysical and mechanical characteristics of porous copper-carbon composite materials prepared by spark plasma sintering

Copper-carbon composites are attractive materials for electrical applications, such as contact strips for pantographs and collector shoes in electric railways and brushes for motor technology. Because the copper-carbon composites combine the positive characteristics of both components, i.e. thermal and electrical conductivity from the copper and low thermal expansion coefficient and resistivity properties from the carbon. In this report the porous copper-carbon composite material with optimal ratio was prepared and electrophysical, mechanical characteristics were investigated. The specimens were sintered by spark plasma sintering technique which allowed preparing the specimens for short time. The copper-carbon composites samples were prepared with using additional sodium oleate and sodium chloride admixtures for making porous structure. The sintering pressure and temperature are one of the important parameter which influences the properties of the specimens. After sintering for making porous structure the prepared composite samples were treated in boiled deionized water where remained organic materials dissolved in liquid solution. It was shown that the physical, mechanical, electrical properties and porosity degree are directly depends from the initial size of the powders, and material composition. In particular, at different pressure, and applying the optimal copper-carbon ratio (Cu-C) was fabricated porous samples from copper-derived composites where used carbon source and electrolytic grade copper powder. The structural and composition parameters and the obtained composite samples fabricated by spark plasma sintering technique have been investigated by micro-hardness tester, hall system, density tester, optical microscope, XRD and FE-SEM

Effect of substrate temperature on the properties of deep ultraviolet transparent conductive ITO/Ga2O3 films

ITO/Ga2O3 bi-layer films were deposited on quartz glass substrates by magnetron sputtering. The effect of substrate temperature on the structure, surface morphology, optical and electrical properties of ITO/Ga2O3 films was investigated by an X-ray diffractometer, a scanning electron microscope, a double beam spectrophotometer and the Hall system, respectively. The structural characteristics showed a dependence on substrate temperature. The resistivity of the films varied from 6.71 × 10−3 to 1.91 × 10−3 Ω·cm as the substrate temperature increased from 100 to 350 °C. ITO (22 nm)/Ga2O3 (50 nm) films deposited at 300 °C exhibited a low sheet resistance of 373.3 Ω/□ and high deep ultraviolet transmittance of 78.97% at the wavelength of 300 nm.

Structures and properties of the Al-doped ZnO thin films prepared by radio frequency magnetron sputtering

Al-doped ZnO thin films were deposited by radio frequency magnetron sputtering using a ZnO target with 2wt.% Al2O3. The structures and properties of the films were characterized by the thin film X-ray diffraction, high resolution transmission electron microscopy, Hall system and ultraviolet/visible/near-infrared spectrophotometer. The Al-doped ZnO film with high crystalline quality and good properties was obtained at the sputtering power of 100W, working pressure of 0.3Pa and substrate temperature of 250°C. The results of further structure analysis show that the interplanar spacings d are enlarged in other directions besides the direction perpendicular to the substrate. Apart from the film stress, the doping concentration and the doping site of Al play an important role in the variation of lattice parameters. When the doping concentration of Al is more than 1.5wt.%, part of Al atoms are incorporated in the interstitial site, which leads to the increase of lattice parameters. This viewpoint is also proved by the first principle calculations.

Optical and electrical properties of Sn-doped CdO thin films obtained by pulse laser deposition

Transparent tin-doped cadmium oxide (Sn–CdO) thin films with different Sn concentration were deposited on quartz glass substrates by pulse laser deposition (PLD) at 400 °C. The film’s crystallographic structure, optical and electrical properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV–VIS spectrophotometer and Hall system. Results show that doping of Sn enhances the film’s [111] preferred orientation and causes slight shift in the (200) Bragg angle towards higher value. The optical band gaps ( E g) of the Sn-doped films were found to increase with the increase of Sn doping concentration. In addition, proper doping of Sn evidently improves the electrical properties of CdO, such as the resistivity of the CdO film with 2.9 at% Sn doping is about one-twelfth of that of the CdO film, while the carrier concentration is about 13 times of that of the undoped. The improvements both in optical and electrical properties endow that the Sn–CdO thin films have potential application as TCO material for different optoelectronic device applications.

Impurities and heterogeneity in pyrite: Influences on electrical properties and oxidation products

Macroscopic pyrite crystals originating from a variety of geologic settings were made into thick sections. Electrical properties were measured with a Hall system, and minor element composition was analyzed with laser ablation inductively coupled plasma mass spectroscopy (LA-ICPMS). Selected thick sections were oxidized in a moist air environment inside a glove chamber. The relative metal content of surface products formed during oxidation was analyzed by LA-ICP-MS. Natural pyrite exhibits a range of electrical properties corresponding to the content of the common minor elements Co, As and Ni. These properties are similar to those of synthetic pyrite doped with single elements. Pyrite enriched in Co is an n-type semiconductor with low resistivity and high carrier mobility, while arsenian pyrite tends to be p-type and have higher resistivity. The effect of Ni is weaker and tends to be obscured by Co and As in samples of mixed composition. Cobalt demonstrates the strongest effect on electrical properties. Enrichment of Co at oxidized pyrite surfaces is inversely correlated with its concentration in the underlying pyrite. Cobalt enrichment in oxidation products is also more pronounced along crystal defects such as fractures, and in crystals with heterogeneous distribution of trace elements. These observations might be explained by differences in the electronic structure of pyrite arising from the presence of impurities, and by the distribution of domains with different impurity compositions, facilitating electron transfer.