Electrical Transport Behavior Research Articles

Room‐Temperature Out‐of‐Plane Ferroelectricity and Resistance Switching Based on 2D Bi2O2Se

AbstractAlthough 2D Bi2O2Se plays an important role in the electronics and optoelectronics based on its in‐plane property, its out‐of‐plane electrical transport behavior remains unclear, especially in fabricating vertical devices with high integration density for novel functionality. Here, a solution‐processed method is developed to prepare 2D Bi2O2Se with mass production (e.g., hundreds of milliliter scale). The out‐of‐plane ferroelectric property of 2D Bi2O2Se is observed by piezoresponse force microscopy and the ferroelectric dipole map atom‐by‐atom at the Bi2O2Se surface, which shows an atomically resolved dipolar displacement of Se ions. The out‐of‐plane resistant switching property of 2D Bi2O2Se is revealed by conductive atomic force microscopy. Moreover, the electric field on the local polarization of Bi2O2Se is addressed by using ab initio simulations, which shows a broken inversion symmetry along the z‐axis of Bi2O2Se. The working mechanism of resistant switching behavior in Bi2O2Se is attributed to the diffusion and shuttle of Se ions. Besides, a controllable wet‐assembled method is developed to prepare Bi2O2Se thin film with centimeter scale and explores its application on photodetectors under 808 nm laser light. This work reveals the unique out‐of‐plane transport behavior of 2D Bi2O2Se, providing the basis for fabricating multifunctional devices with high integration based on this 2D material.

Enhancing thermoelectric performance with perpendicular anisotropic magnetic domain arrays

In recent years, the incorporation of magnetic nanoparticles into thermoelectric materials has been introduced to enhance their performance. However, understanding the impact of dispersed magnetic substances in the matrix on thermoelectric properties, considering different domain directions, is crucial for performance improvement. In this study, we have designed and fabricated high-quality epitaxial single crystal thin films consisting of FePt arrays with varying magnetic domain directions embedded in an Sb2Te3 matrix. Our findings reveal that the electrical transport behavior of the films responds differently to magnetic materials with distinct domain directions, especially in the case of discontinuous arrays. The FePt array oriented perpendicular to the carrier flow direction effectively regulates the direction of carrier movement and local low-energy carriers, functioning as an "energy supplier" to enhance material performance. Simultaneously, the quantum dots formed between the Sb2Te3 and the metal film play the role of carrier channels, further regulating the carrier concentration. Therefore, the perpendicular magnetic anisotropy array synergistically modulates the electrical transport behavior through carriers, resulting in a significant improvement in the thermoelectric power factor. By increasing the S value at the measurement temperature, we achieved a maximum power factor (PFmax) of 3.35 mWm-1K-2 and an average power factor (PFave) of 3.14 mWm-1K-2.

High wide-temperature-range thermoelectric performance in GeTe through hetero-nanostructuring

GeTe is emerging as promising medium-temperature thermoelectric material due to its highly competitive performance and good mechanical properties. Strong Rashba spin splitting was harnessed to markedly improve the Seebeck coefficient and power factor of Bi and Sn codoped GeTe at low-medium temperature. Moreover, it is found that Bi-Sn-Cu doping reduces the phase-transition temperature to extend better electrical transport behavior of cubic phase to low temperature. As a result, the electrical transport properties in low-medium temperature were overall enhanced. In the meanwhile, endotaxial hetero-nanostructures efficiently scatter phonons and play a dominant role on affecting phonon propagation. The lattice thermal conductivity was reduced to 0.2 W m−1K−1 at 673 K. Drive by strengthening Rashba effect and endotaxial hetero-nanostructures, a record-high average ZT (300–823 K) of 1.6 and a high ZT of 2.1 were obtained in lead-free GeTe-based compounds. The vast increase of ZT promotes GeTe as a promising candidate for a wide range of applications in waste heat recovery and power generation.

Bismuth Telluride Supported Sub-1 nm Polyoxometalate Cluster for High-Efficiency Thermoelectric Energy Conversion.

Size plays a crucial role in chemistry and material science. Subnanometer polyoxometalate (POM) clusters have gained attention in various fields, but their use in thermoelectrics is still limited. To address this issue, we propose the POM clusters as an effective second phase to enhance the thermoelectric properties of Bi0.4Sb1.6Te3. Thanks to their subnanometer size, POM clusters improve electrical transport behavior through the superposition of atomic orbitals and the interfacial scattering effect. Furthermore, their ultrasmall size strongly reduces thermal conductivity. Consequently, the introduction of a mere 0.1 mol % of POM into the Bi0.4Sb1.6Te3 matrix realizes a state-of-the-art zT value of 1.46 at 348 K, a 45% enhancement over Bi0.4Sb1.6Te3 (1.01), along with a maximum thermoelectric-conversion efficiency of the integrated module of 6.0%. The enhancement of carrier mobility and the suppression of thermal conduction achieved by introducing the subnanometer clusters hold promise for various applications, such as electronic devices and thermal management.

High‐Performance Bi2Te3‐Based Thermoelectrics Enabled by ≈1 nm Metal Chalcogenide Clusters with Size‐Dependent Electron and Phonon Structures

AbstractThe untapped potential of sub‐nanometric materials (SNMs) in constructing high‐performance thermoelectrics (TE) presents a promising yet unexplored avenue. This study investigates the utilization of supertetrahedral CdS clusters, representing SNMs, in conjunction with state‐of‐the‐art Bi2Te3‐based systems. The CdS cluster with size‐dependent electronic structure enables selective interface scattering of carriers, while its 1 nm size and size‐dependent phonon density of states (DOS) contribute to significant interfacial thermal resistance. Furthermore, interfacial dislocations and significant grain refinement induced by the incorporation of the CdS cluster boost the mechanical properties. Consequently, a remarkable peak figure of merit (ZT) value of 1.47 at 350 K and a record‐high Vickers hardness of 1.08 GPa is achieved in the Bi0.5Sb1.5Te3/0.1 wt% CdS cluster composite. The robust TE module achieves an excellent conversion efficiency of about 6.1% under a ΔT of 241 K. This work opens up exciting possibilities for utilizing 1 nm clusters in thermoelectrics and even inspires other fields involving size‐dependent electrical and thermal transport behaviors.

Artificial Q-Grader: Machine Learning-Enabled Intelligent Olfactory and Gustatory Sensing System.

Portable and personalized artificial intelligence (AI)-driven sensors mimicking human olfactory and gustatory systems have immense potential for the large-scale deployment and autonomous monitoring systems of Internet of Things (IoT) devices. In this study, an artificial Q-grader comprising surface-engineered zinc oxide (ZnO) thin films is developed as the artificial nose, tongue, and AI-based statistical data analysis as the artificial brain for identifying both aroma and flavor chemicals in coffee beans. A poly(vinylidene fluoride-co-hexafluoropropylene)/ZnO thin film transistor (TFT)-based liquid sensor is the artificial tongue, and an Au, Ag, or Pd nanoparticles/ZnO nanohybrid gas sensor is the artificial nose. In order to classify the flavor of coffee beans (acetic acid (sourness), ethyl butyrate and 2-furanmethanol (sweetness), caffeine (bitterness)) and the origin of coffee beans (Papua New Guinea, Brazil, Ethiopia, and Colombia-decaffeine), rational combination of TFT transfer and dynamic response curves capture the liquids and gases-dependent electrical transport behavior and principal component analysis (PCA)-assisted machine learning (ML) is implemented. A PCA-assisted ML model distinguished the four target flavors with >92% prediction accuracy. ML-based regression model predicts the flavor chemical concentrations with >99% accuracy. Also, the classification model successfully distinguished four different types of coffee-bean with 100% accuracy.

Unveiling the potential of vanadium-doped CVD-grown p-type MoS2 in vertical homojunction UV–Vis photodiodes

2D materials are a popular choice for the fabrication of p-n diodes for applications in integrated optoelectronics owing to their outstanding properties such as strong light-matter interactions, high mobility, and tunable band gap. The synthesis of monolayer and few-layer 2D materials with both p-type and n-type behavior is thus essential for the design and fabrication of such devices. However, the large-scale direct synthesis of p-type 2D materials is still a challenge as most of these materials are either n-type or ambipolar. Here, we report the successful synthesis of large-area, p-type MoS2 layers doped with vanadium on SiO2/Si substrates, achieving flake sizes >100 μm. By varying the concentration of the vanadium precursor, we precisely controlled the doping level, achieving vanadium atomic percentages ranging from 0.70 % to 1.57 %. Back gate field-effect transistors (FETs) were fabricated, enabling the tuning of device characteristics to exhibit ambipolar or p-type behavior. Moreover, a vertical p-n MoS2 homojunction was fabricated for rectification and optoelectronic applications, demonstrating a high responsivity of up to 978.1 A/W and a specific detectivity (D*) of 1.06 × 1012 Jones at λ = 365 nm with varied powers of the incident light source. This work demonstrates the role of vanadium as a dopant for tunable electrical transport behavior as well as for the fabrication of a photodiode, which can be used for high-performance optoelectronic devices in the future.

Unexpected versatile electrical transport behaviors of ferromagnetic nickel films

Perpendicular magnetic anisotropy (PMA) of magnets is paramount for electrically controlled spintronics due to their intrinsic potentials for higher memory density, scalability, thermal stability and endurance, surpassing an in-plane magnetic anisotropy (IMA). Nickel film is a long-lived fundamental element ferromagnet, yet its electrical transport behavior associated with magnetism has not been comprehensively studied, hindering corresponding spintronic applications exploiting nickel-based compounds. Here, we systematically investigate the highly versatile magnetism and corresponding transport behavior of nickel films. As the thickness reduces within the general thickness regime of a magnet layer for a memory device, the hardness of nickel films’ ferromagnetic loop of anomalous Hall effect increases and then decreases, reflecting the magnetic transitions from IMA to PMA and back to IMA. Additionally, the square ferromagnetic loop changes from a hard to a soft one at rising temperatures, indicating a shift from PMA to IMA. Furthermore, we observe a butterfly magnetoresistance resulting from the anisotropic magnetoresistance effect, which evolves in conjunction with the thickness and temperature-dependent magnetic transformations as a complementary support. Our findings unveil the rich magnetic dynamics and most importantly settle down the most useful guiding information for current-driven spintronic applications based on nickel film: The hysteresis loop is squarest for the ∼8 nm-thick nickel film, of highest hardness with Rxy r /Rxy s ∼ 1 and minimum Hs −Hc , up to 125 K; otherwise, extra care should be taken for a different thickness or at a higher temperature.

Pressure-induced superconductivity in SnSb2Te4

Owing to their unique compositional and structural characteristics, layered van der Waals solids in binary and ternary chalcogenide families provide a fertile testbed for exploring novel exotic structures and states, e.g., topological insulators and superconductors. Herein, a comprehensive study on the structural variations and correlated electrical transport behavior of SnSb2Te4, a ternary member, has been carried out considering elevated pressures. Under 45.6 GPa, three distinct structural phase transitions have been observed, with strong evidence from the variations of high-pressure X-ray diffraction patterns. The onsets of phase II (monoclinic, C2/m ) at 6.3 GPa, phase III (monoclinic, C2/c ) at 15.5 GPa, and phase IV (body-centered cubic with substitutional disorder, Im-3m ) at 17.2 GPa have been observed owing to the emergence of new diffractions. Based on electrical measurements at low temperature and high pressure conditions, two pressure-induced superconducting states have been distinguished in SnSb2Te4. The first state occurs in the range of 12.3-17.1 GPa. The positive pressure dependence on Tc indicates that the aforementioned state is related to the monoclinic C2/m phase. At > 17.1 GPa, the second superconducting state emerges, with the negative pressure dependence on Tc . It relates to the body-centered cubic solid solution phase, which is characteristic of a substitutional disordered crystal structure. The discovery that the pressure-induced superconductivity in SnSb2Te4 is affected by structural phase transitions under pressure may help understand the universal relationship between the ambient condition topological insulating state and derived superconductivity. Ab initio theoretical calculations reveal that an electronic topological transition takes place at approximately 2.0 GPa, which is featured by the obvious changes in the distribution of electronic density of states near the Fermi level.

Enhanced electrical conduction and c-axis orientation in copper-rich Cu1+δCrO2 (δ = 0-0.10) ceramics

Copper-rich Cu1+δCrO2 (δ = 0–0.12) ceramics with highly c-axis orientation were synthesized by solid-state reaction in the air. The effects of copper-rich on grain alignment and electrical transport properties have been systematically investigated. While δ = 0–0.10, the ceramics are in a single phase delafossite structure, and grains grow up more than 10 times along the ab-plane, which the c-axis orientation Lotgering factors F(00l) increase from 0.17 to 0.87 and the densities increase. All the ceramics exhibit thermal activation semiconducting electrical transport behavior. Their thermal activation energy decreased from 0.303 eV to 0.209 eV, and the resistivity decreased by more than 2 orders of magnitude at room temperature. The Seebeck coefficient decreased. When δ = 0.12, the impurity CuO reduces the electrical conduction and c-axis preferred orientation. X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS) results confirm that the acceptor Cu(Cr)2+ anti-site defects are generated by the substitution of excessive Cu ion on the Cr site, which significantly increases the hole carriers concentration. Copper-rich is observed to be efficient in enhancing the c-axis preferred orientation leading to dominant electrical transport along the ab-plane and weakened defect scattering, resulting in enhanced electrical conduction in CuCrO2 ceramic.

Lattice dynamics and thermoelectric properties of diamondoid materials

AbstractThe diamondoid compounds are a large family of important semiconductors, which possess various unique transport properties and had been widely investigated in the fields of photoelectricity and nonlinear optics. For a significantly long period of time, diamondoid materials were not given much attention in the field of thermoelectricity. However, this changed when a series of diamondoid compounds showed a thermoelectric figure of merit (ZT) greater than 1.0. This discovery sparked considerable interest in further exploring the thermoelectric properties of diamondoid materials. This review aims to provide a comprehensive view of our current understanding of thermal and electronic transport in diamondoid materials and stimulate their development in thermoelectric applications. We present a collection of recent discoveries concerning the lattice dynamics and electronic structure of diamondoid materials. We review the underlying physics responsible for their unique electrical and phonon transport behaviors. Moreover, we provide insights into the advancements made in the field of thermoelectricity for diamondoid materials and the corresponding strategies employed to optimize their performance. Lastly, we emphasize the challenges that lie ahead and outline potential avenues for future research in the domain of diamondoid thermoelectric materials.

Towards graphene-based asymmetric diodes: a density functional tight-binding study.

Self-consistent charge density functional tight-binding (DFTB) calculations have been performed to investigate the electrical properties and transport behavior of asymmetric graphene devices (AGDs). Three different nanodevices constructed of different necks of 8 nm, 6 nm and 4 nm, named Graphene-N8, Graphene-N6 and Graphene-N4, respectively, have been proposed. All devices have been tested under two conditions of zero gate voltage and an applied gate voltage of +20 V using a dielectric medium of 3.9 epsilon interposed between the graphene and the metallic gate. As expected, the results of AGD diodes exhibited strong asymmetric I(V) characteristic curves in good agreement with the available experimental data. Our predictions implied that Graphene-N4 would achieve great asymmetry (A) of 1.40 at |VDS| = 0.2 V with maximum transmittance (T) of 6.72 in the energy range 1.30 eV. More importantly, while the A of Graphene-N4 was slightly changed by applying the gate voltage, Graphene-N6/Graphene-N8 showed a significant effect with their A increased from 1.20/1.03 under no gate voltage (NGV) to 1.30/1.16 under gate voltage (WGV) conditions. Our results open up unprecedented numerical prospects for designing tailored geometric diodes.

Electrical transport mechanism of manganite-based trilayer heterostructures in the Cusp and insulating regions

In the present study, efforts are made to study the temperature dependent resistivity (ρ-T) variations of manganites (La0.7Sr0.3MnO3 (LSMO) single layer) and manganites-based systems ((LSMO/γ-Fe2O3/LSMO) trilayer heterostructures) in two distinct regions (Cusp region and Insulating region). Cusp region is an intermediate region between Metallic region and Insulating region. The resistivity-temperature curves are studied and analysed by various resistive models and fitting equations. The co-existence of ferromagnetic clusters and polarons manifests in the Cusp region. The Insulating region is explored and fitted under two regimes: Low Temperature Insulating region and High Temperature Insulating region. Various mathematical models viz. Thermal Activation model, Small Polaron Hopping model and Variable Range Hopping model were employed to study the ρ-T variations under various temperature ranges for LSMO (60 nm) single layer system and LSMO/γ-Fe2O3/LSMO (150 nm) trilayer heterostructures. In Insulating region, the deviations in the fitted curves from the experimental data is due to intrinsic disorder at the R/A site in case of LSMO single layer system while in case of trilayer system disorder exists at both R/A and B sites. The study is crucial to understand the microscopic picture of electrical transport behavior in both the systems near and above Metal-Insulator Transition.

Electrical transport behavior of the oxygen vacancies-rich LaAlO3/SrTiO3 heterogeneous interface at high temperature

Oxygen vacancy is one of the original mechanisms of the two-dimensional electron gas (2DEG) at the LaAlO3 (LAO) and SrTiO3 (STO) heterogeneous interface, and it has an important impact on the electrical properties of LAO/STO heterojunction. In this work, the LAO thin films were grown on the STO substrates by pulsed laser deposition, and the electrical transport behavior of the LAO/STO interface at high temperature and high vacuum were systematically studied. It was found that at high temperature and high vacuum, the oxygen vacancies-rich LAO/STO heterojunction would undergo a metal–insulator transition, and return to metal conductivity when the temperature is further increased. At this time, the conduction mechanism of the sample is drift mode and the thermal activation energy is 0.87 eV. While during the temperature decreasing, the conduction mechanism would transfer to hopping conduction with the thermal activation energy of 0.014 eV and the resistance would increase dramatically and present a completely insulated state. However, when the oxygen vacancies-rich sample is exposed to air, the resistance would gradually decrease and recover.

Investigation of manganese doped BaSe for energy harvesting and spintronics devices

Abstract The incorporation of magnetism to a solid material may drastically alter its electrical transport behavior, providing a way to modify the magneto-optoelectronic and thermoelectric features that have recently drawn a lot of scientific attention. In this regard, we utilized density function theory (DFT) based full potential linearized augmented plane wave (FP-LAPW) approach to study doping effect of Mn on physical characteristics of barium selenide (BaSe). Pristine BaSe is nonmagnetic semiconductor with indirect bandgap of 2.11 eV. Concentration dependent Mn doping in BaSe introduces spin polarized intermediate bands in the vicinity of Fermi level primarily composed of Mn-3d orbitals. Asymmetric band profiles indicate the ferromagnetic semiconductor nature of of Mn doped BaSe compounds. Total magnetic moment value of 5.0 μ B, 10.0 μ B, and 20.0 μ B are obtained for corresponding Ba1−xMnxSe (x = 6.25%, 12.5%, 25%) systems. Furthermore, the analysis of optical and thermoelectric characteristics reveals the importance of studied alloy for application in advanced technologies including low energy light absorbers and thermoelectric generators.

Carrier and morphologically tailored thermoelectric properties of MBi2O4 (M=Cu, Ni, and Zn) kusachiites

In this article, we first report the newly evolved MBi2O4 (M = Cu, Ni and Zn) kusachiite's thermoelectric properties in the mid-temperature range. The material's structure and surface morphology are tailored to influence the thermoelectric properties. CuBi2O4, NiBi2O4, and ZnBi2O4 kusachiite compounds were synthesized via an efficient solvothermal method. MBi2O4 shows variation in thermoelectric transport behavior with different transition metals at the ‘M’ site. CuBi2O4 and NiBi2O4 show p-type transport properties at 303 K. Whereas ZnBi2O4 shows n-type transport properties at 303 K and with rising temperature transitions from n-type to p-type due to stochiometric deviation of cations. MBi2O4 has increased electrical conductivity at the end of the examined temperature, where ions dominate the conduction. The presence of Cu+ and Ni3+ uplifts the electrical transport behavior of CuBi2O4 and NiBi2O4 than ZnBi2O4. The thermal conductivity of NiBi2O4 falls below 1 Wm−1K−1 in the entire measured temperature and that of ZnBi2O4 decreases with the increasing temperature. The porous surface of NiBi2O4 act as phonon scattering centers. Further, NiBi2O4 structure and porosity were found to be efficient for thermoelectric applications due to the influence of Ni.

Transition from weak antilocalization to linear magnetoresistance by tuning structure geometry and chemical potential in nanostructured Bi2Se3 films

We report the electrical and magnetic transport behavior in vertical Cu-doped Bi2Se3 nanoplate films prepared by the chemical vapor deposition method. In vertical Cu-doped Bi2Se3 nanoplate films, the topological surface states are tuned by both the large surface-to-bulk ratio and the Cu doping. Due to their high specific surface area, the magnetoresistance of the vertical undoped Bi2Se3 nanoplate film exhibits a weak antilocalization effect, and it indicates that the topological surface state properties are greatly enhanced. In vertical Cu-doped Bi2Se3 nanoplate films, the electron doping is inhibited, and the carrier type is changed from n-type to p-type. The observed linear magnetoresistance is attributed to have a quantum origin from the topological surface states. When the Cu concentration reaches 1.73 at.% in vertical Bi2Se3 nanoplate film, the linear magnetoresistance can be maintained up to 100 K. Meanwhile, these vertical nanoplate films exhibit the 3D magnetotransport property. Thus, using the same material system with a broad range of carrier density and type, our work shows the transition from a weak-antilocalization to linear magnetoresistance in nanostructured topological insulator Bi2Se3 films with an unusual morphology where the nanoplates are vertically aligned to increase the surface area.

Emergent weak antilocalization and wide-temperature-range electronic phase diagram in epitaxial RuO2 thin film

Binary ruthenium dioxide (RuO2) has gradually attracted much attention in condensed matter physics and material sciences due to its various intriguing physical properties, such as strain-induced superconductivity, anomalous Hall effect, collinear anti-ferromagnetism, etc. However, its complex emergent electronic states and the corresponding phase diagram over a wide temperature range remain unexplored, which is critically important to understanding the underlying physics and exploring its final physical properties and functionalities. Here, through optimizing the growth conditions by using versatile pulsed laser deposition, high-quality epitaxial RuO2 thin films with clear lattice structure are obtained, upon which the electronic transport is investigated, and emergent electronic states and the relevant physical properties are unveiled. Firstly, at a high-temperature range, it is the Bloch–Grüneisen state, instead of the common Fermi liquid metallic state, that dominates the electrical transport behavior. Moreover, the recently reported anomalous Hall effect is also revealed, which confirms the presence of the Berry phase in the energy band structure. More excitingly, we find that above the superconductivity transition temperature, a new positive magnetic resistance quantum coherent state with an unusual dip as well as an angel-dependent critical magnetic field emerges, which can be attributed to the weak antilocalization effect. Lastly, the complex phase diagram with multiple intriguing emergent electronic states over a wide temperature range is mapped. The results greatly promote the fundamental physics understanding of the binary oxide RuO2 and provide guidelines for its practical applications and functionalities.

Pressure-induced ionic–polaronic–ionic transition in LaAlO3

Combining alternate-current impedance spectrum measurement and first-principle calculations, we thoroughly analyzed the electrical transport behavior of LaAlO3 under high pressure. A pressure-induced ionic–polaronic–ionic transition has been discovered through impedance spectroscopy measurements. Through first-principle calculations, we have elucidated the physical origin of the emergence of polaronic conduction, which results from the distortion of electron density background around Al and O atoms. Furthermore, the discontinuous changes in the starting frequency of ion migration fW, relaxation frequency fb, and ionic resistance Ri have been found at around 13.2 GPa, which can be ascribed to the phase transition of LaAlO3 from rhombohedral to cubic phase. Pressure can enhance the migration of O2− ions, causing an increase in the ionic conductivity of LaAlO3. This research will deepen our comprehension on the ion migration in solid electrolytes.

Synergy of grain size and texture effect for high-performance Mg3Sb2-based thermoelectric materials

High-performance n-type Mg3Sb2-based thermoelectric materials have attracted much attention due to the six-fold degenerate carrier pockets in the conduction band. This study uncovers the electrical and thermal transport behaviors in different directions with respect to the spark plasma sintering (SPS) pressure that is rarely investigated. Results indicate that the grain size in the ⊥P direction (perpendicular to the SPS pressure direction) is slightly larger than that in the ∥P direction. In addition, a moderate texture is observed, reflecting a preferential orientation of the (001)-plane in the ⊥P direction. The synergy of both grain size and the texture leads to an improved electrical conductivity for Mg3.24Sb1.5Bi0.49Te0.01 compounds with lamellar crystal structures. Consequently, the highest thermoelectric figure of merit ZTpeak ∼1.71 and ZTavg ∼1.12 (almost the best ZT values ever reported for Te-doped Mg3Sb2-based materials) are achieved in the ⊥P direction compared to the ∥P direction.