Prediction on the physical properties of CuInS2 with various anion positions

Yiming Ren,Yonghong Hu,Haibo Zeng,Li Xue 한국물리학회 2018 Current Applied Physics Vol.18 No.3

The effects of various anion displacements (u) on electronic structures, elastic constants, Debye temperature and the minimum thermal conductivity of CuInS2 are studied by first-principles calculation. The lattice constant couples with the anion displacement, however, they are not consistent with the relation proposed by Abrahams and Bernstein. When the anion displacement varies from 0.2 to 0.3, the Cu-S bond length is elongated, while the In-S bond length is shortened, which cause the increase of band gap with anion displacement. The anisotropies of sound velocities and lattice thermal conductivities are also discussed. The results imply that the lattice thermal conductivity along [110] direction is the smallest and decreases with u. These research findings shed light on improving the thermoelectric properties by manipulating u and the direction of propagation.

ZnO nanowire lines and bundles: Template-deformation-guided alignment for patterned field-electron emitters

Jizhong Song,Xue Ning,Haibo Zeng 한국물리학회 2015 Current Applied Physics Vol.15 No.11

One-dimensional ZnO materials have been promising for field-emission (FE) application, but how to facially control the alignment of ZnO emitters is still a great challenge especially for patterned display application. Here, we report the fabrication of novel ZnO nanowire (NW) line and bundle arrays for patterned field-electron emitters. The effects of PS template size and heating time on the resulted ZnO nanoarrays were systematically studied. The deformation degree of PS templates was controlled and hence utilized to adjust the alignment of electrochemically deposited ZnO arrays. It was found that the length of NW lines and the density of NW bundles can effectively tuned by the PS template heating time. The optimal FE performance with turn-on electric field as low as of 4.4 V μm-1 and the fieldenhancement factor as high as of 1450 were achieved through decreasing the screening effect among the patterned field-electron emitters.

Controlling oxygen vacancies and properties of ZnO

Xiaoming Li,Jizhong Song,Yanli Liu,Haibo Zeng 한국물리학회 2014 Current Applied Physics Vol.14 No.3

Intrinsic defects in semiconductors play crucial roles on their electrical and optical properties. In this article, we report on a facile method to control concentration of oxygen vacancies inside ZnO nanostructures and related physical properties based on adjustment of thermal transformation conditions from ZnO2 to ZnO, including annealing atmosphere and temperature. ZnO2 spheres assembled with nanoparticles were formed through the reaction between zinc nitrate and hydrogen peroxide. Significantly, it was found that the adopted temperature and atmosphere have remarkable impact on the concentration of oxygen vacancies, which was revealed by the variations of featured Raman scattering peaks at 584 cm1. Furthermore, with the increase of oxygen vacancies inside ZnO, the optical band-gap was found to red-shift 350 meV and the room-temperature ferromagnetism became stronger up to 1.6 emu/mg. The defect formation and evolution were discussed according to the chemical equilibrium of decomposition reaction under special local heating environment. This work demonstrated that ZnO2 decomposition is an effective process to control the defect states inside ZnO and related properties.

Evolution of the optical spectra of an Ag/mesoporous SiO₂ nanostructure heat-treated in air and H₂ atmospheres

Hu, Jinlian,Lee, Woong,Cai, Weiping,Tong, Liuniu,Zeng, Haibo IOP Pub 2007 Nanotechnology Vol.18 No.18

<P>Evolution of the various optical spectra of Ag nanoparticles dispersed in mesoporous SiO<SUB>2</SUB> after heating alternately in H<SUB>2</SUB> and air atmospheres has been investigated. It has been observed that, in accordance with alternate heat treatment in H<SUB>2</SUB> and air, surface plasmon resonance (SPR) absorption of the Ag/mesoporous SiO<SUB>2</SUB> nanostructure alternately appeared and disappeared and its Raman scattering spectra reversibly increased and decreased. In contrast, its photoluminescence (PL) spectra alternately disappeared and appeared, whereas the infrared (IR) spectra did not change. Such novel optical sensitivities of silver nanoparticles are discussed on the basis of the changes in chemical states of silver induced by the interaction of silver nanoparticles with the atmospheres and the hosting medium. It is suggested that the chemical state of silver in mesoporous SiO<SUB>2</SUB> changes reversibly between Ag and the Ag<SUP>+</SUP> ion by the redox process. </P>

The impact of Mg content on the structural, electrical and optical properties of MgZnO alloys: A first principles study

Yonghong Hu,Bo Cai,Ziyu Hu,Yanli Liu,Shengli Zhang,Haibo Zeng 한국물리학회 2015 Current Applied Physics Vol.15 No.3

The structural, electronic and optical properties of wurtzite MgZnO with Mg concentration ranging from 0 to 0.5 are studied using the first principle calculations. It's found that the lattice constants c and specific volume V of the MgZnO alloys decrease and their band gap widens as Mg concentration increases, which are in agreement with our experimental results. A particular Mg concentration is found to exist at around 0.375, equals to which the corresponding MgZnO alloy has the minimum width of the top valence band. This indicates that Mg concentration may be used to tune the electronic properties of MgZnO alloy. Meanwhile, it's also found that the energy response range of the optical spectrums decreases with the increase of Mg concentration. There are different energy shifts toward high energy (blue shift) of the peaks in the optical spectrums with the increase of Mg concentration, which are explained by the variations of the density of states in details. So the electronic and optical properties of MgZnO may be tuned through Mg concentration, and our research results may provide meaningful references to the development and design of photoelectric devices.

An Ångström-level <i>d</i>-spacing controlling synthetic route for MoS₂ towards stable intercalation of sodium ions

Zhang, Kan,Li, Ping,Guo, Shiying,Jeong, Jong Yeob,Jin, Bingjun,Li, Xiaoming,Zhang, Shengli,Zeng, Haibo,Park, Jong Hyeok The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.45

<P>In this paper, we precisely controlled the <I>d</I>-spacing of vertically aligned MoS2 arrays ranging from 6.2 to 10 Å <I>via</I> heating-controlled deintercalation of NH4<SUP>+</SUP> ions. The finely controllable interlayer nanoarchitecture resulted in an optimal <I>d</I>-spacing of 7.3 Å, which on nitrogenous reduced graphene oxide (N-RGO) delivered a reversible capacity of 295 mA h g<SUP>−1</SUP> after 2000 cycles at 1 A g<SUP>−1</SUP> for Na<SUP>+</SUP> intercalation.</P>

Defect-Induced Epitaxial Growth for Efficient Solar Hydrogen Production

Zhang, Kan,Kim, Jung Kyu,Park, Bumsu,Qian, Shifeng,Jin, Bingjun,Sheng, Xiaowei,Zeng, Haibo,Shin, Hyunjung,Oh, Sang Ho,Lee, Chang-Lyoul,Park, Jong Hyeok American Chemical Society 2017 Nano letters Vol.17 No.11

<P>Epitaxial growth suffers from the mismatches in lattice and dangling bonds arising from different crystal structures or unit cell parameters. Here, we demonstrate the epitaxial growth of 2D MoS2 ribbon on 1D CdS nanowires (NWs) via surface and subsurface defects. The interstitial Cd-0 in the (1(2)over-bar10) crystal plane of the [0001]-oriented CdS NWs are found to serve as nucleation sites for interatomically bonded [001]-oriented MoS2, where the perfect lattice match (similar to 99.7%) between the(10(1)over-bar1) plane of CdS and the (002)-faceted in-plane MoS2 result in coaxial MoS2 ribbon/CdS NWs heterojunction. The coaxial but heterotropic epitaxial MoS2 ribbon on the surface of CdS NWs induces delocalized interface states that facilitate charge transport and the reduced surface state. A less than 5-fold ribbon width of MoS2 as hydrogen evolution cocatalyst exhibits a similar to 10-fold H-2 evolution enhancement than state of the art Pt in an acidi electrolyte, and apparent quantum yields of 79.7% at 420 nm 53.1% at 450 nm, and 9.67% at 520 nm, respectively.</P>