• Korean Journal of Materials Research
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• v.23 no.3
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• pp.183-189
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• 2013

$Cu_2ZnSn(S,Se)_4$ material is receiving an increased amount of attention for solar cell applications as an absorber layer because it consists of inexpensive and abundant materials (Zn and Sn) instead of the expensive and rare materials (In and Ga) in $Cu(In,Ga)Se_2$ solar cells. We were able to achieve a cell conversion efficiency to 4.7% by the selenization of a stacked metal precursor with the Cu/(Zn + Sn)/Mo/glass structure. However, the selenization of the metal precursor results in large voids at the absorber/Mo interface because metals diffuse out through the top CZTSe layer. To avoid the voids at the absorber/Mo interface, binary selenide compounds of ZnSe and $SnSe_2$ were employed as a precursor instead of Zn and Sn metals. It was found that the precursor with Cu/$SnSe_2$/ZnSe stack provided a uniform film with larger grains compared to that with $Cu_2Se/SnSe_2$/ZnSe stack. Also, voids were not observed at the $Cu_2ZnSnSe_4$/Mo interface. A severe loss of Sn was observed after a high-temperature annealing process, suggesting that selenization in this case should be performed in a closed system with a uniform temperature in a $SnSe_2$ environment. However, in the experiments, Cu top-layer stack had more of an effect on reducing Sn loss compared to $Cu_2Se$ top-layer stack.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.305-305
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• 2007

• Applied Microscopy
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• v.25 no.3
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• pp.82-89
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• 1995

High resolution transmission electron microscopic observations on quaternary $Zn_{1-x}Mg_{x}S_y$ $S_{1-y}$(x=0.13, y=0.16) on (001) GaAs substrate grown up to $1.2{\mu}m$ with 20nm ZnSe buffer layer at $300^{\circ}C$ by RIBER MBE system which has a single growth chamber were investigated by HRTEM working at 300kV with point resolution of 0.18nm. The ZnSe buffer layer maintains the coherency with the GaAs substrate. The stacking faults had begun at ZnSe buffer/$Zn_{1-x}Mg_{x}S_{y}S_{1-y}$ interface, whose length and spacing became larger than 60nm and wider than 40nm, respectively. The inverse triangular stacking fault was bounded by stacking faults which were formed on {111} planes with different variants. There exists rare stacking faults inside the triangular defect. The epilayer surrounded by the straight stacking faults, which had formed in the same direction, became the columnar structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.27-30
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• 2006

In this paper, the undoped and Co-doped $Zn_4SnSe_6$ single crystals grown by the chemical transporting reaction(CTR) method using iodine as a transporting agent are investigated. For the crystal growth, the temperature gradient of the CTR furnace was kept at $680^{\circ}C$ for the source zone and at $780^{\circ}C$ for the growth zone for 7days. It was found from the analysis of x-ray diffraction that the $Zn_4SnSe_6$ and $Zn_4SnSe_6Co^{2+}$ compounds have a monoclinic structure. The direct optical energy band gap of the $Zn_4SnSe_6$ and $Zn_4SnSe_6Co^{2+}$ single crystals at 300K were found to be 2.146eV and 2.042eV.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.36-43
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• 2000

In oder to enhance the selectivity of TMA(trimethylamine) gas, the ZnO-based films which were doped with $Al_2O_3$, $TiO_2, $In_2O_3$ and $V_2O_5$ catalysts with various weight percents were deposited in oxygen by RF magnetron sputtering method. To improve electrical stability of sensors, the ZnO-based films were annealed in oxygen at $700^{\circ}C$ for 1 hour. The TMA selectivity of sensors was defined by the magnitude($S_{TMA}/S_{DMA}$ and $S_{TMA}/S_{NH3}$) of TMA sensitivity relative to DMA and sensitivity ammonia($NH_3$) sensitivity, respectively. The $ZnO+Al_2O_3(4\;wt.%)+TiO_2(1\;wt.%)+In_2O_3(1\;wt.%)$ sensor showed high $S_{TMA}/S_{DMA}$ of 5.9 and $S_{TMA}/S_{NH3}$ of 26 to 160 ppm at the working temperature of $300^{\circ}C$ respectively.

• Korean Journal of Materials Research
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• v.15 no.5
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• pp.293-300
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• 2005

ZnO:Li epilayers were synthesized on sapphire substrates by the pulesd laser deposition (PLD) after the surface of the ZnO:Li sintered pellet was irradiated by the ArF (193 nm) excimer laser. The growth temperature was fixed at $400^{\circ}C$. The crystalline structure of epilayers was investigated by the photoluminescence (PL) and double crystal X-ray diffraction (DCXD). The carrier density and mobility of epilayers measured by van der Pauw-Hall method are $2.69\times10cm^{-3}$ and $52.137cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of epilayers obtained from the absorption spectra is well described by the Varshni's relation, $E_g(T)=3.5128eV{\cdot}(9.51\times10^{-4}eV/K)T^2/(T+280K)$. After the as-grown ZnO:Li epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO:Li has been investigated by PL at 10 K. The Peaks of native defects of $V_{zn},\;V_o,\;Zn_{int},\;and\;O_{int}$ showned on PL spectrum are classified as a donors or accepters type. We confirm that $ZnO:Li/Al_2O_3$ in vacuum do not form the native defects because ZnO:Li epilayers in vacuum existe in the form of stable bonds.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.137-141
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• 2005

The CMR properties and magnetic properties of sulphospinels $Zn_xFe_{1-x}Cr_2S_4$ have been explored by X-ray diffraction, magnetoresistance measurement, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structures in the range of x=0.05, 0.1, 0.2 are cubic at room temperature. Magnetoresistance measurement indicates that these system is semiconducting below about 160 K. The temperature of maximum magnetoresistance is almost consistent with Curie temperature. The Zn substitutions for Fe occur to increase the Jahn-Teller relaxation and the electric quadrupole shift. CMR properties could be explained with Jahn-Teller effect, and half-metallic electronic structure, which is different from both the double exchange interactions of manganite La-Ca-Mn-O system and the triple exchange interactions of chalcogenide $Cu_xFe_{1-x}Cr_2S_4$.

• Journal of Animal Science and Technology
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• v.60 no.11
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• pp.27.1-27.8
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• 2018

Background: Enteric methane ($CH_4$) accounts for about 70% of total $CH_4$ emissions from the ruminant animals. Researchers are exploring ways to mitigate enteric $CH_4$ emissions from ruminants. Recently, nano zinc oxide (nZnO) has shown potential in reducing $CH_4$ and hydrogen sulfide ($H_2S$) production from the liquid manure under anaerobic storage conditions. Four different levels of nZnO and two types of feed were mixed with rumen fluid to investigate the efficacy of nZnO in mitigating gaseous production. Methods: All experiments with four replicates were conducted in batches in 250 mL glass bottles paired with the ANKOM$^{RF}$ wireless gas production monitoring system. Gas production was monitored continuously for 72 h at a constant temperature of $39{\pm}1^{\circ}C$ in a water bath. Headspace gas samples were collected using gas-tight syringes from the Tedlar bags connected to the glass bottles and analyzed for greenhouse gases ($CH_4$ and carbon dioxide-$CO_2$) and $H_2S$ concentrations. $CH_4$ and $CO_2$ gas concentrations were analyzed using an SRI-8610 Gas Chromatograph and $H_2S$ concentrations were measured using a Jerome 631X meter. At the same time, substrate (i.e. mixed rumen fluid+ NP treatment+ feed composite) samples were collected from the glass bottles at the beginning and at the end of an experiment for bacterial counts, and volatile fatty acids (VFAs) analysis. Results: Compared to the control treatment the $H_2S$ and GHGs concentration reduction after 72 h of the tested nZnO levels varied between 4.89 to 53.65%. Additionally, 0.47 to 22.21% microbial population reduction was observed from the applied nZnO treatments. Application of nZnO at a rate of $1000{\mu}g\;g^{-1}$ have exhibited the highest amount of concentration reductions for all three gases and microbial population. Conclusion: Results suggest that both 500 and $1000{\mu}g\;g^{-1}$ nZnO application levels have the potential to reduce GHG and $H_2S$ concentrations.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.714-721
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• 2013

A stoichiometric mixture of evaporating materials for $ZnAl_2Se_4$ single-crystal thin films was prepared in a horizontal electric furnace. These $ZnAl_2Se_4$ polycrystals had a defect chalcopyrite structure, and its lattice constants were $a_0=5.5563{\AA}$ and $c_0=10.8897{\AA}$.To obtain a single-crystal thin film, mixed $ZnAl_2Se_4$ crystal was deposited on the thoroughly etched semi-insulating GaAs(100) substrate by a hot wall epitaxy (HWE) system. The source and the substrate temperatures were $620^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single-crystal thin film was investigated by using a double crystal X-ray rocking curve and X-ray diffraction ${\omega}-2{\theta}$ scans. The carrier density and mobility of the $ZnAl_2Se_4$ single-crystal thin film were $8.23{\times}10^{16}cm^{-3}$ and $287m^2/vs$ at 293 K, respectively. To identify the band gap energy, the optical absorption spectra of the $ZnAl_2Se_4$ single-crystal thin film was investigated in the temperature region of 10-293 K. The temperature dependence of the direct optical energy gap is well presented by Varshni's relation: $E_g(T)=E_g(0)-({\alpha}T^2/T+{\beta})$. The constants of Varshni's equation had the values of $E_g(0)=3.5269eV$, ${\alpha}=2.03{\times}10^{-3}eV/K$ and ${\beta}=501.9K$ for the $ZnAl_2Se_4$ single-crystal thin film. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnAl_2Se_4$ were estimated to be 109.5 meV and 124.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnAl_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-exciton for n = 1 and $C_{21}$-exciton peaks for n = 21.

• Electrical & Electronic Materials
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• v.10 no.3
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• pp.262-267
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• 1997

In order to improve the brightness and chromaticity of green emitting low voltage phosphor for FED, we examine PL, PLE and CL emission characteristics of ZnGa$_{2}$O$_{4}$:Mn,O prepared in Ar and vacuum. ZnGa$_{2}$O$_{4}$:Mn,O sintered in vacuum shows about 16 times as bright as the one fabricated in Ar and excellent chromaticity. In PL emission spectra of ZnGa$_{2}$O$_{4}$:Mn,O at low temperature of 9 K, two peaks are observed at 504 nm and 513 nm. At room temperature, the two peaks are superimposed due to the lattice thermal vibrational energy, and only one peak is observed at 509 nm. From PLE measurements, it is believed that the energy levels of the host lattice and Mn ions are coexisted. The energy transfer from the host lattice to the emission center of Mn$^{2+}$ ions occurs.s.