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A Review of SnSe: Growth and Thermoelectric Properties
NGUYENVAN QUANG,김정대,조성래 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.8
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.
Thermoelectric Properties of Hot-Pressed Bi-Doped n-Type Polycrystalline SnSe
Nguyen, Van Quang,Nguyen, Thi Huong,Duong, Van Thiet,Lee, Ji Eun,Park, Su-Dong,Song, Jae Yong,Park, Hyun-Min,Duong, Anh Tuan,Cho, Sunglae Springer US 2018 NANOSCALE RESEARCH LETTERS Vol.13 No.1
<P><B>ᅟ</B></P><P>We report on the successful preparation of Bi-doped n-type polycrystalline SnSe by hot-press method. We observed anisotropic transport properties due to the (h00) preferred orientation of grains along the pressing direction. The electrical conductivity perpendicular to the pressing direction is higher than that parallel to the pressing direction, 12.85 and 6.46 S cm<SUP>−1</SUP> at 773 K for SnSe:Bi 8% sample, respectively, while thermal conductivity perpendicular to the pressing direction is higher than that parallel to the pressing direction, 0.81 and 0.60 W m<SUP>−1</SUP> K<SUP>−1</SUP> at 773 K for SnSe:Bi 8% sample, respectively. We observed a bipolar conducting mechanism in our samples leading to n- to p-type transition, whose transition temperature increases with Bi concentration. Our work addressed a possibility to dope polycrystalline SnSe by a hot-pressing process, which may be applied to module applications.</P><P><B>Highlights</B></P><P><P>We have successfully achieved Bi-doped n-type polycrystalline SnSe by the hot-press method.</P><P>We observed anisotropic transport properties due to the [h00] preferred orientation of grains along pressing direction.</P><P>We observed a bipolar conducting mechanism in our samples leading to n- to p-type transition.</P></P><P><B>Electronic supplementary material</B></P><P>The online version of this article (10.1186/s11671-018-2500-y) contains supplementary material, which is available to authorized users.</P>
On the weal law of large numbers for sequences of Banach space valued random elements
Nguyen Van Quang,Le hong Son 대한수학회 2006 대한수학회보 Vol.43 No.3
We establish a weak law of large numbers for sequenceof random elements with values in p-uniformly smooth Banachspace. Our result is more general and stronger than some well-known ones.
Nguyen, Van Quang,Baynosa, Marjorie Lara,Nguyen, Van Hoa,Tuma, Dirk,Lee, Yong Rok,Shim, Jae-Jin Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.486 No.-
<P><B>Abstract</B></P> <P>Metal oxide/graphene photocatalysts have been attracting considerable attention in solving environmental pollution problems because of the limitations of the semiconductor-based photocatalysts. In this study, highly efficient and inexpensive zinc oxide (ZnO) nanoparticles with three different morphologies, such as nanospheres, nanodisks, and nanorods, anchored on reduced graphene oxide (RGO) were synthesized in solvent mixtures with different ethanol to water ratios. Among the three morphologies, the nanospherical ZnO/RGO (sZG) composite exhibited the highest methylene blue (MB) and rhodamine B removal efficiencies at 99% and 98%, respectively, after only 60 min under low-power (40 W) ultraviolet irradiation at a low catalyst loading of 0.1 g L<SUP>−1</SUP>. This nanocomposite also showed excellent photocatalytic stability under UV irradiation, retaining 96% efficiency even after 15 cycles of MB degradation. Moreover, the sZG composite exhibited a high MB degradation efficiency of approximately 99% after 100 min at a low catalyst loading of 0.2 g L<SUP>−1</SUP> under solar light illumination. The excellent photocatalytic performance and high stability of this low-cost nanospherical ZnO/RGO composite exemplarily highlights the potential of sustainable next-generation photocatalysis for treating wastewater containing organic pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Size/morphology of ZnO particles were controlled by the water-ethanol solvent ratio </LI> <LI> The critical roles of ZnO seed and HMTA in forming the particles were investigated. </LI> <LI> Catalytic performance was controlled by the morphology of ZnO nanoparticles and RGO </LI> <LI> Nanospherical ZnO/RGO showed an excellent MB photodegradation efficiency of 99%. </LI> <LI> Nanospherical ZnO/RGO exhibited a remarkable stability (96% after 15 cycles). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Nguyen, Van Quang,Shin, Yooleemi,Duong, Anh Tuan,Cho, Sunglae,Meny, Christian Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.772 No.-
<P><B>Abstract</B></P> <P>We systematically investigated the influence of the Co content on the magnetic and transport properties of spinel Co<SUB>x</SUB>Fe<SUB>3-x</SUB>O<SUB>4</SUB> (0 ≤ x ≤ 1) thin films on MgO (001) substrates prepared by molecular beam epitaxy. Our films exhibited the spinel structure as expected. The Verwey transition was clearly observed in Fe<SUB>3</SUB>O<SUB>4</SUB> and Co<SUB>0.6</SUB>Fe<SUB>2.4</SUB>O<SUB>4,</SUB> while it disappeared with higher Co contents. Electrical resistivity increased with the Co content from 0.003 Ω-cm for x = 0 to 1.5 Ω-cm for x = 1 at 300 K. As expected, magnetization curves show an increase of the coercive fields of the samples with the Co content. In addition, the samples reveal complex magnetic properties that are explained by a reorientation of the anisotropy easy axis from the crystal 〈111〉 directions to the 〈100〉 directions with the Co content.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have successfully grown the epitaxial spinel Co<SUB>x</SUB>Fe<SUB>3-x</SUB>O<SUB>4</SUB>/MgO (100) thin films. </LI> <LI> The electrical resistivity increased with Co content. </LI> <LI> Verwey transition temperature was increased then disappeared with Co content. </LI> <LI> The samples showed complex magnetic properties with the presence of Co. </LI> <LI> The complex magnetic properties are due to reorientation of anisotropy easy axis. </LI> </UL> </P>
Marcinkiewicz-Zygmund law of large numbers for blockwise adapted sequences
Nguyen Van Quang,Le Van Thanh 대한수학회 2006 대한수학회보 Vol.43 No.1
In this paper we establish the Marcinkiewicz-Zygmund strong law of large numbers for blockwise adapted sequences. Some related results are considered.
Weak law of large numbers for adapted double arrays of random variables
Nguyen Van Quang,Nguyen Ngoc Huy 대한수학회 2008 대한수학회지 Vol.45 No.3
The aim of this paper is to extend the “classical degenerate convergence criterion” and the Feller weak law of large numbers to double adapted arrays of random variables. The aim of this paper is to extend the “classical degenerate convergence criterion” and the Feller weak law of large numbers to double adapted arrays of random variables.