• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.228-233
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• 2010

Mn-doped $Zn_2SiO_4$ phosphor particles having submicrometer sizes were synthesized by a solid-state reaction method using methyl hydrogen polysiloxane-treated ZnO, fumed $SiO_2$ and various Mn sources. The crystallization and photoluminescent properties of the phosphor particles were investigated by X-ray diffraction(XRD), scanning electron microscope(SEM), and by their photoluminescence(PL) spectra. Due to the effect of the dispersion and coherence of the methyl hydrogen polysiloxane-treated ZnO, the Mn-doped $Zn_2SiO_4$ particles were successfully obtained by a solid state method at $1000^{\circ}C$, and the maximum PL intensity of the prepared particles under vacuum ultra violet(VUV) excitation occurred at a Mn concentration of 0.02mol and a sintering temperature of $1000^{\circ}C$.

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.103-108
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• 2004

High-quality ZnO films were grown on sapphire (001) substrates by the atomic layer epitaxy (ALE) technique using DEZn as a Zinc precusor and $H_2O $ as an oxidant at both $170^{\circ}C$ and $400^{\circ}C$ which are in the ALE and the CVD process temperature ranges, respectively. The films were annealed in an oxygen atmosphere in the temperature range from 600 to 100$0^{\circ}C$ for an hour and then investigate photoluminescence (PL) properties using He-Cd laser. PL intensity tends to increases as the annealing temperature increase for both the annealed ZnO films grown at $170^{\circ}C$ and $400^{\circ}C$ , while PL did not nearly occur at the as-deposited ones. The PL intensity of the ZnO film grown at $400^{\circ}C$ is low after it is annealed at high temperature owing to a large number of Zn-Zn bonds although it has increased in the visible light wavelength region after annealing. In contrast the PL intensity has increased significant in the visible light region after annealing

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.295-298
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• 2011

ZnS:Mn, Dy yellow phosphors for White Light Emitting Diode were synthesized by a solid state reaction method using ZnS, $MnSO_4{\cdot}5H_2O$, S and $DyCl_3{\cdot}6H_2O$ powders as starting materials. The mixed powder was sintered at $1000^{\circ}C$ for 4 h in an air atmosphere. The photoluminescence of the ZnS:Mn, Dy phosphors showed spectra extending from 480 to 700 nm, peaking at 580 nm. The photoluminescence of 580 nm in the ZnS:Mn, Dy phosphors was associated with $^4T_1{\rightarrow}^6A_1$ transition of $Mn^{2+}$ ions. The highest photoluminescence intensity of the ZnS:Mn, Dy phosphors under 450 nm excitation was observed at 4 mol% Dy doping. The enhanced photoluminescence intensity of the ZnS:Mn, Dy phosphors was explained by energy transfer from $Dy^{3+}$ to $Mn^{2+}$. The CIE coordinate of the 4 mol% Dy doped ZnS:Mn, Dy was X = 0.5221, Y = 0.4763. The optimum mixing conditions for White Light Emitting Diode was obtained at the ratio of epoxy : yellow phosphor = 1:2 form CIE coordinate.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1030-1033
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• 2002

ZnO thin films on (100)p-type silicon substrates have been deposited by pulsed laser deposition(PLD) technique using an Nd:YGA laser with a wavelength of 266nm. The influence of the deposition parameters, such as oxygen pressure, substrate temperature and laser energy density variation on the properties of the grown film, was studied. The experiments were performed for substrate temperatures in the range of $200{\sim}500^{\circ}C$ and oxygen pressure in the range of $10^{-2}{\sim}10^2mTorr$. We investigated the structural, morphological and optical properties of ZnO thin films using X-ray diffraction(XRD), atomic force microscopy(AFM), photoluminescence(PL).

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.139-143
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• 1997

The photoluminescence characteristics of the zinc gallate have been investigated as a function of the composition and the firing atmosphere. Two distinct emission bands were observed whose peaks are 360 nm and 430 nm respectively. These emission bands are considered to be from two different emission centers. For $ZnO/Ga_2O_3$=49.3/50.7 or higher, 430 nm band is predominant and for $ZnO/Ga_2O_3$=49.2/50.8 or lower, 360nm band becomes predominant, whereas 430 nm band is almost completely suppressed. The shift of emission peak is though to be due to the change of the cation distribution with the zinc content in the spinel zinc gallate. Also, the emission centers responsible for the 360nm band are considered to be more efficient energy absorbers than the ones for the 430 nm band. Highly efficient green emitting phosphor was obtained by activating Zn-deficient zinc gallate with manganeses.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.776-780
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• 2000

ZnGa$_2$O$_4$thin films were prepared on Si(100) wafer in terms of RF power, substrate temperatures and Ar/O$_2$flow rate by RF Magnetron Sputtering. Photoluminescence(PL) measurement was employed to observe the emission spectra of ZnGa$_2$O$_4$films. The influences of various deposition parameters on the properties of grown films were studied. The optimum substrate deposition temperature for luminous characteristics was about 50$0^{\circ}C$ in this investigation. PL spectrum of ZnGa$_2$O$_4$ thin films showed broad band luminescence spectrum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.316-319
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• 2000

By RF magnetron sputtering ZnGa$_2$O$_4$thin films were prepared on Si(100) wafer in terms of RF power, substrate temperatures and Ar/O$_2$flow rate. Crystallographic orientation was characterized by x-ray diffraction(XRD). Surface morphology and microstructure were observed by scanning electron microscope(SEM). Photoluminescence(PL) measurement was employed to observe the emission spectra of ZnGa$_2$O$_4$films. The influences of various deposition parameters on the properties of grown films were studied. PL spectrum of ZnGa$_2$O$_4$thin films showed broad band luminescence spectrum.

• Korean Journal of Materials Research
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• v.18 no.12
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• pp.640-644
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• 2008

ZnO/ZnS core/shell nanocrystals (${\sim}5-7\;nm$ in diameter) with a size close to the quantum confinement regime were successfully synthesized using polyol and thermolysis. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses reveal that they exist in a highly crystalline wurtzite structure. The ZnO/ZnS nanocrystals show significantly enhanced UV-light emission (${\sim}384\;nm$) due to effective surface passivation of the ZnO core, whereas the emission of green light (${\sim}550\;nm$) was almost negligible. They also showed slight photoluminescence (PL) red-shift, which is possibly due to further growth of the ZnO core and/or the extension of the electron wave function to the shell. The ZnO/ZnS core/shell nanocrystals demonstrate strong potential for use as low-cost UV-light emitting devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.202-206
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• 2007

ZnO is a promising material to make high efficient ultraviolet(UV) or blue light emitting diodes(LEDs) because of its large binding energy and energy bandgap. In this study, we prepared ZnO thin films with p-type conductivity on silicon(100) substrates by RF magnetron sputtering in the mixture of $N_2$ and $O_2$. The process was accompanied by low pressure in-situ annealing in $O_2$ at $600^{\circ}C$ and $800^{\circ}C$ respectively. Hall effect in Van der Pauw configuration showed that the N-doped ZnO film annealed at $800^{\circ}C$ has p-type conductivity. Photoluminescence(PL) spectrum of the film annealed at $800^{\circ}C$ showed UV emission related to exciton and bound to donor-acceptor pair(DAP) as well as visible emission related to many intrinsic defects.