Search

NiTe

Iron chalcogenides have been widely studied due to their intriguing superconducting and magnetic properties. We investigate the intrinsic defects existing in single-crystal FeTe via scanning tunneling microscopy (STM). The cleavage surfaces of FeTe show that Te vacancies exist primarily at the top or bottom Te sites. It is known that FeTe presents charge ordering with 2a periodicity (a = lattice constant), as driven by the bicollinear antiferromagnetic (AFM) order at the Fe layer. Numerous studies confirmed that the Neel temperature of FeTe varies from TN = 60–70 K. Interestingly, we find that the STM topography images exhibit local charge orderings with 2a periodicity at 79 K, which is slightly above the TN. This result suggests that the AFM phase might still survive locally with fluctuations up to temperatures slightly above TN without macroscopic ordering. Our work provides important information that captures the moment of phase transition between AFM and paramagnetic ordering in the FeTe system.

Tin selenide (SnSe) is considered a robust candidate for thermoelectric applications due to its very high thermoelectric figure of merit, ZT, with values of 2.6 in p-type and 2.8 in n-type single crystals. Sn has been replaced with various lower group dopants to achieve successful p-type doping in SnSe with high ZT values. A known, facile, and powerful alternative way to introduce a hole carrier is to use a natural single Sn vacancy, VSn. Through transport and scanning tunneling microscopy studies, we discovered that VSn are dominant in high-quality (slow cooling rate) SnSe single crystals, while multiple vacancies, Vmulti, are dominant in low-quality (high cooling rate) single crystals. Surprisingly, both VSn and Vmulti help to increase the power factors of SnSe, whereas samples with dominant VSn have superior thermoelectric properties in SnSe single crystals. Additionally, the observation that Vmulti are good p-type sources observed in relatively low-quality single crystals is useful in thermoelectric applications because polycrystalline SnSe can be used due to its mechanical strength; this substance is usually fabricated at very high cooling speeds.

Interesting lattice dynamics were recently reported in 1T′ structure of bilayer VSe2 attributed to the vibration of Se atoms, but it was limited to topographic observation using scanning tunneling microscopy (STM). We conduct further systematic STM study to understand the origin of lattice dynamics in bilayer VSe2. Time spectroscopy of tunneling current is measured with the feedback loop disabled, while holding the position of the STM tip over a single Se atom. The time spectroscopy indeed shows random telegraph signals that tunneling current fluctuates between high and low currents. Such fluctuations of current reflect the vibrational motion of the Se atom. Statistical analysis described by the Markov process provides average residence time (τ) for high and low current states, and transition rate (R = 1/τ). Interestingly, the transition rate as a function of tunneling current (I) follows a power law of R = IN (N = constant), and the N value is close to 1. This linearity of transition rate indicates that the lattice dynamics are mostly induced by tunneling current. Our result confirms the role of tunneling current that drives the observed lattice dynamics in the bilayer VSe2.

Author(s): Pham, AT; Vu, TH; Cheng, C; Trinh, TL; Lee, JE; Ryu, H; Hwang, C; Mo, SK; Kim, J; Zhao, LD; Duong, AT; Cho, S | Abstract: High-quality SnSe2 single crystals were successfully synthesized using a temperature gradient method. N-type characteristics and strong anisotropic transport properties of SnSe2 single crystals were exhibited between the ab plane and the c-axis. At 673 K, the power factor (PF) value along the ab plane is 3.43 μW cm-1 K-2, while it is 0.92 μW cm-1 K-2 along the c-axis. The ratio between thermal conductivities along the ab plane (κab) and c-axis (κc) is on the order of 7.6 at 300 K, while this value is about 5.6 at 673 K. The thermoelectric figure of merit (ZT) in the c-axis (0.15) is higher than that (0.1) along the ab plane, according to the ultralow out-of-plane thermal conductivity. The electronic band structure results, which were examined by angle-resolved photoemission spectroscopy (ARPES) predicted the potential of improving the thermoelectric performance of SnSe2 single crystals by electron doping.

A charge density wave (CDW), an ordered modulation of electron distribution and lattice distortion, is one of the intriguing phenomena observed in transition metal dichalcogenides. Recent STM studies reported a new CDW phase with √3 × 2 and √3 × √7 periodicities in monolayer (ML) VSe2 grown on graphene, which is totally different from the 4 x 4 x 3 CDW periodicity in bulk. Although the emergence of new CDW phase is of great research interest, the origin of the new modulation in ML VSe2 has not been clearly investigated. In this report, we conduct a systematic study to understand the nature of the √3 × 2 and √3 × √7 CDW in ML VSe2 using scanning tunneling microscopy (STM). Bias dependent topography and differential conductance (dI/dV) mapping indicate that the √3 × 2 and √3 × √7 modulations are mostly driven by strong lattice distortions of the Se atoms rather than by charge orderings. In addition, STM topography reveals that the v3 × 2 modulation corresponds to a gap feature, and the v3 × v7 modulation corresponds to an isolated Se atom in the distorted lattice structures. Our work provides prerequisite information to understand the emergence of √3, × 2 and √3, × √7 CDW in ML VSe2.

Cu2O has been investigated for decades to understand the complex nature of oxidation and to utilize its high catalytic activity and intrinsic p-type character. However, the structures and intrinsic...

Polymorphisms allowing multiple structural phases are among the most fascinating properties of transition metal dichalcogenides (TMDs). Herein, the polymorphic 1T' phase and its lattice dynamics for bilayer VSe2 grown on epitaxial bilayer graphene are investigated via low temperature scanning tunneling microscopy (STM). The 1T' structure, mostly observed in group-6 TMDs, is unexpected in VSe2, which is a group-5 TMD. Emergence of the 1T' structure in bilayer VSe2 suggests the important roles of interface and layer configurations, providing new possibilities regarding the polymorphism of TMDs. Detailed topographical analysis elucidates the microscopic nature of the 1T' structure, confirming that Se-like and V-like surfaces can be resolved depending on the polarity of the sample bias. In addition, bilayer VSe2 can transit from a static state of the 1T' phase to a dynamic state consisting of lattice vibrations, triggered by tunneling current from the STM tip. Topography also shows hysteretic behavior during the static-dynamic transition, which is attributed to latent energy existing between the two states. The observed lattice dynamics involve vibrational motion of the Se atoms and the middle V atoms. Our observations will provide important information to establish in-depth understanding of the microscopic nature of 1T' structures and the polymorphism of two-dimensional TMDs.

Oxidation can deteriorate the properties of copper that are critical for its use, particularly in the semiconductor industry and electro-optics applications1–7. This has prompted numerous studies exploring copper oxidation and possible passivation strategies8. In situ observations have, for example, shown that oxidation involves stepped surfaces: Cu2O growth occurs on flat surfaces as a result of Cu adatoms detaching from steps and diffusing across terraces9–11. But even though this mechanism explains why single-crystalline copper is more resistant to oxidation than polycrystalline copper, the fact that flat copper surfaces can be free of oxidation has not been explored further. Here we report the fabrication of copper thin films that are semi-permanently oxidation resistant because they consist of flat surfaces with only occasional mono-atomic steps. First-principles calculations confirm that mono-atomic step edges are as impervious to oxygen as flat surfaces and that surface adsorption of O atoms is suppressed once an oxygen face-centred cubic (fcc) surface site coverage of 50% has been reached. These combined effects explain the exceptional oxidation resistance of ultraflat Cu surfaces.

A combined study of scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) is conducted to understand the multiple charge density wave (CDW) phases of monolayer (ML) VSe

Using Indium $\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ on Si(111) as an atomically thin superconductor platform, and by systematically controlling the density of nanohole defects (nanometer size voids), we reveal the impacts of defect density and defect geometric arrangements on superconductivity at macroscopic and microscopic length scales. When nanohole defects are uniformly dispersed in the atomic layer, the superfluid density monotonically decreases as a function of defect density (from 0.7% to 5% of the surface area) with minor change in the transition temperature ${T}_{C}$, measured both microscopically and macroscopically. With a slight increase in the defect density from 5% to 6%, these point defects are organized into defect chains that enclose individual two-dimensional patches. This new geometric arrangement of defects dramatically impacts the superconductivity, leading to the total disappearance of macroscopic superfluid density and the collapse of the microscopic superconducting gap. This study sheds new light on the understanding of how local defects and their geometric arrangements impact superconductivity in the two-dimensional limit.

Atomically thin vanadium diselenide (VSe2 ) is a two-dimensional transition metal dichalcogenide exhibiting attractive properties due to its metallic 1T-phase. With the recent development of methods to manufacture high-quality monolayer VSe 2 on van der Waals materials, the outstanding properties of VSe2 -based heterostructures have been widely studied for diverse applications. Dimensional reduction and interlayer coupling with a van der Waals substrate lead to its distinguishable characteristics from its bulk counterparts. However, only a few fundamental studies have investigated the interlayer coupling effects and hot electron transfer dynamics in VSe2 heterostructures. In this work, we reveal ultrafast and efficient interlayer hot electron transfer and interlayer coupling effects in VSe2 /graphene heterostructures. Femtosecond time-resolved reflectivity measurements showed that hot electrons in VSe 2 were transferred to graphene within a 100-fs timescale with high efficiency. Besides, coherent acoustic phonon dynamics indicated interlayer coupling in VSe2 /graphene heterostructures and efficient thermal energy transfer to three-dimensional substrates. Our results provide valuable insights into the intriguing properties of metallic transition metal dichalcogenide heterostructures and motivate designing optoelectronic and photonic devices with tailored properties., Comment: 30 pages, 5 figures, supplementary information(7 pages, 5 figures)

Interlayer coupling in van der Waals heterostructures exhibits unique physical properties and presents a new pathway for diverse applications in materials science and photonics. Interestingly, photo-responsivity of graphene with semiconducting transition metal dichalcogenide (TMD) can be enhanced in the UV-visible range by interlayer charge/energy transfer. However, such an effect has been studied only for semiconducting materials. In this work, we will discuss ultrafast hot-electron transfer in atomically thin metallic-layer VSe2/graphene heterostructures investigated by time-resolved pump-probe spectroscopy. Our experimental finding extends the concepts of conventional two-dimensional heterostructures to metallic-layer and can provide a new degree of freedom for designing novel functionalized materials and devices.

We investigated the ultrafast carrier dynamics in metallic monolayer 1T-VSe2 and efficient interlayer hot electron transfer in VSe2/graphene van der Waals heterostructures by employing ultrafast pump-probe spectroscopy.

SnSe is a 2D semiconductor with an indirect energy gap of 0.86 - 1 eV; it is widely used in solar cell, optoelectronics, and electronic device applications. Recently, SnSe has been considered as a robust candidate for energy conversion applications due to its high thermoelectric performance (ZT = 2.6 in p-type and 2.2 in n-type), which is assigned mainly to its anhamornic bonding leading to an ultralow thermal conductivity. In this review, we first discuss the crystalline and electronic structures of SnSe and the source of its p-type characteristic. Then, some typical single crystal and polycrystal growth techniques, as well as an epitaxial thin film growth technique, are outlined. The reported thermoelectric properties of SnSe grown by using each technique are also reviewed. Finally, we will describe some remaining issues concerning the use of SnSe for thermoelectric applications.

Accurate atomistic models for metal/oxide interfaces play a pivotal role in determining copper-based interfacial processes, ranging from electronic circuitry wirings to chemical catalysis. The “29” and “44” surfaces represent two of the most classical embryonic oxides on Cu(111). Although many attempts have been made to offer detailed atomistic models of these surface oxides, their atomic structures remain elusive. Here, we address this open question via ab initio STM simulations, where the functionalized-metal tips are explicitly included, and they are corroborated by STM experiments. We find that the fine structures of STM images of the “29” and “44” surfaces are correctly captured with STM theories going beyond the Tersoff-Hamann approximation only. Furthermore, we elucidate a complete atomistic model for the larger “44” surface, completing the picture of early oxidation on copper.

Polymorphisms allowing multiple structural phases are among the most fascinating properties of transition metal dichalcogenides (TMDs). Herein, the polymorphic 1T' phase and its lattice dynamics for bilayer VSe

This review is designed to initiate a discussion we believe is necessary for the biomedical community, because of some recent evidences for existing of a new body anatomical system, or the primo vascular system (PVS), which could be the missing link in the scientific explanation of the unknown mechanism of action of acupuncture. Some important questions for the medical society, (eg, "What is the main source of the mistrust of Western medicine toward traditional Oriental medicine and could it be overcome?" or "Is the PVS a real one and what is its distribution, formation, and function?" or "Are there scientific proofs for intimate relationships of the PVS with meridian system and whether the PVS would be the physical basis of meridians?") are deeply studied and appropriately answered. Various pieces of knowledge are now combined to achieve a better understanding and to provide an acceptable explanation about the functions of such new system and to explain the functional path used by traditional Eastern medicine to cure diseases. Some possibilities to use this PVS for development of some innovative therapies to treat some diseases are also discussed (eg, pharmacopuncture as a new innovative drug delivery method that combines acupuncture therapy with medication by injecting pharmacological substances into target acupoints).

A combined study of scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) is conducted to understand the multiple charge density wave (CDW) phases of monolayer (ML) VSe2films manifested by graphene substrates. Submonolayer (∼0.8 ML) VSe2films are prepared on two different substrates of single-layer graphene (SLG) and bi-layer graphene (BLG) on a 6H-SiC(0001). We find that ML VSe2films are less coupled to the SLG substrate compared to that of ML VSe2/BLG. Then, ML VSe2grown on SLG and BLG substrates reveals a very different topography in STM. While ML VSe2/BLG shows one unidirectional modulation of √3 × 2 and √3 × √7 CDW in topography, ML VSe2/SLG presents a clear modulation of 4 × 1 CDW interfering with √3 × 2 and √3 × √7 CDW which has not been previously observed. We explicitly show that the reciprocal vector of 4 × 1 CDW fits perfectly into the long parallel sections of cigar-shaped Fermi surfaces near the M point in ML VSe2, satisfying Fermi surface nesting. Since bulk VSe2is also well-known for the 4 × 4 × 3 CDW formed by Fermi surface nesting, the 4 × 1 CDW in ML VSe2/SLG is attributed to the planar projection of 4 × 4 × 3 CDW in bulk. Our result clarifies the nature of the 4 × 1 CDW in ML VSe2system and is a good example demonstrating the essential role of substrates in two-dimensional transition metal dichalcogenides.

We report on the effects of Se/Sn flux ratio to the growth and thermoelectric properties of SnSe thin films on MgO (100) substrate. All films were epitaxially grown at 300 °C with various Se/Sn flux ratios of 0.8, 0.9, 1, 3, 5, and 7. The crystal structure of the obtained SnSe thin films was orthorhombic (Pnma space group) with a-axis (h00) orientation. XRD Φ-scan studies showed an existence of orthorhombic domains, whose rotation can be modulated by the Se/Sn flux ratio. A structure consisting of 0° and 90° rotated domains was observed in all samples, while additional 45° rotated domains were simultaneously observed in the samples with higher Se/Sn ratio of 5 and 7. Especially, 135° rotated domains were observed in sample Se/Sn = 7. Interestingly, the best crystalline film was obtained at the Se/Sn = 1. We found that Seebeck coefficients were positive at room temperature, decreased with temperature and became negative for the sample Se/Sn = 1, indicating bipolar transport in the samples. A maximum PF value of 3.74 μWc m −1 K −2 was obtained at 550 K for sample Se/Sn = 0.8 .

Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe2 on graphene substrates. Angle-resolved photoemission spectroscopy (ARPES) uncovers that Fermi-surface nesting becomes perfect in ML VSe2. Renormalization group analysis confirms that imperfect nesting in three dimensions universally flows into perfect nesting in two dimensions. As a result, the charge density wave transition temperature is dramatically enhanced to a value of 350 K compared to the 105 K in bulk VSe2. More interestingly, ARPES and scanning tunneling microscopy measurements confirm an unexpected metal-insulator transition at 135 K, driven by lattice distortions. The heterointerface plays an important role in driving this novel metal-insulator transition in the family of monolayered transition metal dichalcogenides., Comment: 21 pages, 4 figures

Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe

Reducing the thickness of three-dimensional samples on appropriate substrates is a promising way to control electron-electron interactions, responsible for so called electronic reconstruction phenomena. Although the electronic reconstruction has been investigated both extensively and intensively in oxide heterostructure interfaces, this paradigm is not well established in the van der Waals heterointerface system. In the present study, we examine the nature of a charge ordering transition in monolayer vanadium diselenide $({\text{VSe}}_{2})$. This two-dimensional phase transition would be distinguished from that of ${\text{VSe}}_{2}$ bulk samples, driven by more enhanced electron-electron correlations. We recall that ${\text{VSe}}_{2}$ bulk samples show a charge-density-wave (CDW) transition around ${T}_{\text{CDW}}\ensuremath{\sim}105\phantom{\rule{4pt}{0ex}}\text{K}$. This bulk phase transition results from Fermi-surface nesting properties, where the low-temperature CDW state coexists with itinerant electrons of residual Fermi surfaces. Recently, angle-resolved photoemission spectroscopy measurements [Nano Lett. 18, 5432 (2018)] uncovered that the Fermi-surface nesting becomes perfect, where the dynamics of hot electrons is dispersionless along the orthogonal direction of the nesting wave vector. In addition, scanning tunneling microscopy measurements [Nano Lett. 18, 5432 (2018)] confirmed that the resulting CDW state shows essentially the same modulation pattern as the three-dimensional system of ${\text{VSe}}_{2}$. Here, we perform the renormalization group analysis based on an effective-field theory in terms of critical CDW fluctuations and hot electrons of imperfect Fermi-surface nesting. As a result, we reveal that the imperfect nesting universally flows into perfect nesting in two dimensions, where the Fermi velocity along the orthogonal direction of the nesting vector vanishes generically. We argue that this electronic reconstruction is responsible for the observation [Nano Lett. 18, 5432 (2018).] that the CDW transition temperature is much more enhanced to be around ${T}_{\text{CDW}}\ensuremath{\sim}350\phantom{\rule{4pt}{0ex}}\text{K}$ than that of the bulk sample.

In this research, a smart mechanism to automatically configure the relative locations of clustered intelligent nodes arranged in a grid pattern is introduced. If an intelligent node knows the relative location of more than one neighboring node, its location can be recognized. By studying the feature of the grid structure and the short-range infrared signal communication method between the adjacent nodes, the location of an intelligent node and the location map construction of the whole system are configured automatically at each node. The algorithms in this study are tested by a cross-module image or video display task with modularized and reconfigurable digital surface, a modular Cyber-Physical System platform which has stacked `smart modules' each of which has smart sensing and multimedia node with infra-red transceivers at four corners. Exemplary applications demonstrate the feasibility of the system in its scalability and practicality as well as performance by being applied to various spatially reconfigurable multimedia platforms.

The thickness dependence of Au–Pb alloy formation on Pb quantum films is studied via in-situ low-temperature scanning tunneling microscopy/spectroscopy (STM/S). 2D islands with moire pattern are observed on top of Pb films when sub-monolayer Au is deposited onto Pb films at a substrate temperature of 90 K. After annealing at up to 250 K, various types of 2D islands, including Au–Pb alloys, are formed and show very different electronic structures. A detailed STS study suggests that the formation of these islands is directly related to the quantum well states (QWS) of Pb films, indicating quantum size effects (QSE) on the formation of Au–Pb alloys.

Having modernized imaging tools for precise positioning of acupuncture points over the human body where the traditional therapeutic method is applied is essential. For that reason, we suggest a more systematic positioning method that uses X-ray computer tomographic images to precisely position acupoints. Digital Korean human data were obtained to construct three-dimensional head-skin and skull surface models of six individuals. Depending on the method used to pinpoint the positions of the acupoints, every acupoint was classified into one of three types: anatomical points, proportional points, and morphological points. A computational algorithm and procedure were developed for partial automation of the positioning. The anatomical points were selected by using the structural characteristics of the skin surface and skull. The proportional points were calculated from the positions of the anatomical points. The morphological points were also calculated by using some control points related to the connections between the source and the target models. All the acupoints on the heads of the six individual were displayed on three-dimensional computer graphical image models. This method may be helpful for developing more accurate experimental designs and for providing more quantitative volumetric methods for performing analyses in acupuncture-related research.

Recently, layered chalcogenide alloys (LCAs) have been extensively investigated for use in various practical applications by selectively controlling the amount of foreign components. However, the alloying behavior of layered chalcogenides has been rarely explored at the atomistic level. Here, we study the microstructural evolution of SnSe

Recently, layered chalcogenide alloys (LCAs) have been extensively investigated for use in various practical applications by selectively controlling the amount of foreign components. However, the alloying behavior of layered chalcogenides has been rarely explored at the atomistic level. Here, we study the microstructural evolution of SnSe1−xSx alloys on the atomic scale by combining scanning tunneling microscopy (STM) measurements with first-principles density functional theory (DFT) calculations. STM topographic images suggest that S atoms substituted in SnSe1−xSx are not randomly distributed, but tend to form local SnS clusters. The degree of S atom alloying was quantitatively estimated to be about 60% from STM images, indicating that homo-atoms (S–S) are a preferred arrangement over hetero-atoms (S–Se). Our DFT calculations further confirmed that the mixing energy of random SnSe1−xSx alloys showed positive behavior over the whole S composition range considered. This result suggests that SnSe1−xSx has a tendency toward local phase segregation into SnSe and SnS rather than random alloys. We expect our atomistic study on the alloying behavior to provide important insight for fabricating optimal SnSe1−xSx alloys with high thermoelectric properties.

In order to study Sa-Ahm's underlying thoughts on the basis of Yin-Yang and the five-element theory, the 12 acupuncture meridian systems and eight extra meridian systems were investigated in detail. The clinical acupuncture points for Sa-Ahm's four-needle acupuncture technique were also reviewed. The forms of the combinations using the five Shu acupuncture points, which are based on the promotion and control cycles with tonification and sedation, were shown to connect to the acupuncture points, which represent the meridian system itself. However, not all of Sa-Ahm's clinical cases were fully explained by this doctrine, so the five correlations among the meridian systems and the acupuncture points that affect the clinical treatment and the occurrence of disease were determined. The mutual efficacies for Sa-Ahm's clinical cases can be analyzed and explained with correlativity diagrams that include five interrelations.

It is very well known that spinal meninges are composed of three layers, dura, arachnoid and pia mater, and that the main components of pia mater are collagen and reticular fibers. However, the distribution of those fibers has not been extensively investigated but just described as a mesh of fibers. In this study, we detected novel structures, which are composed of unidirectionally arranged fibers, in a rat spinal pia mater by using a polarized light microscope. They were seen as three parallel lines, one of which ran along a posterior spinal vein and the rest two of which ran along a pair of posterior spinal arteries. Histological analysis including Masson's trichrome, picrosirius-red staining, Gordon & Sweet's staining and immunohistochemistry with anti-collagen type 1 and 3 antibodies uncovered that they are mainly composed of collagen fibers and some reticular fibers. In addition, a putative primo vessel was detected in the novel fibrous tissue, which was proven out to be different from a blood vessel. In conclusion, we report a newly detected fibrous structure in the spinal pia mater, which may contribute to provide tensile force to the spinal meninges and to harbor the primo vascular system inside.

Traditional Eastern medicine has had a successful existence for a long time and has provided functional paths for curing disease. However, some scientists do not accept acupuncture, primarily because the meridian system lacks a physical anatomical basis. To date, scientific theories have not been able to explain the functional paths used by traditional Eastern medicine to cure disease. According to Western medicine, no known anatomical foundation exists for the meridians and unknown nervous, circulatory, endocrine, and immune mechanisms mediate the effects of acupuncture. In the early 1960s, only one hypothesis was proposed to explain the anatomical basis of the meridians. By using different experimental approaches during the past 10 years, the number of scientific papers that report the discovery of different anatomical and physiological evidence confirming the existence of an anatomical basis for the meridian system has increased. Morphological science is greatly challenged to offer a new biomedical theory that explains the possible existence of new bodily systems such as the primo vascular system (PVS). The PVS is a previously unknown system that integrates the features of the cardiovascular, nervous, immune, and hormonal systems. It also provides a physical substrate for the acupuncture points and meridians. Announcements of the morphological architectonics and the function of the PVS fundamentally changed the basic understanding of biology and medicine because the PVS is involved in the development and the functions of living organisms. We propose a new vision of the anatomical basis for the PVS and the vital energy—called “Qi”—as an electromagnetic wave that is involved very closely with the DNA in the PVS. DNA provides genetic information and it functions as a store of information that can be obtained from the electromagnetic fields of the environment. The PVS is the communication system between living organisms and the environment, and it lies at the lowest level of life. The theory of the PVS could be a good basis for forming a new point of view of Darwin's evolutionary theory. Discoveries in morphological theory—such as discoveries with respect to the PVS—have not been made since the 18th century. For that reason, the PVS needs more attention.

Recently SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K. For thermoelectric device applications, it is necessary to have n-type materials with comparable ZT value. Here, we report that n-type SnSe single crystals were successfully synthesized by substituting Bi at Sn sites. In addition, it was found that the carrier concentration increases with Bi content, which has a great influence on the thermoelectric properties of n-type SnSe single crystals. Indeed, we achieved the maximum ZT value of 2.2 along b axis at 733 K in the most highly doped n-type SnSe with a carrier density of −2.1 × 1019 cm−3 at 773 K., The good thermoelectric figures of merit of p-type tin selenide single crystals are actively studied. Here, the authors show that n-type SnSe can also reach a figure of merit of around 2, at high temperatures, when doped with bismuth.