• Korean Journal of Materials Research
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• v.30 no.8
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• pp.399-405
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• 2020

In the present investigation we show the effect of Al doping on the length, size, shape, morphology, and sensing property of ZnO nanorods. Effect of Al doping ultimately leads to tuning of electrical and optical properties of ZnO nanorods. Undoped and Al-doped well aligned ZnO nanorods are grown on sputtered ZnO/SiO₂/Si (100) pre-grown seed layer substrates by hydrothermal method. The molar ratio of dopant (aluminium nitrate) in the solution, [Al/Zn], is varied from 0.1 % to 3 %. To extract structural and microstructural information we employ field emission scanning electron microscopy and X-ray diffraction techniques. The prepared ZnO nanorods show preferred orientation of ZnO <0001> and are well aligned vertically. The effects of Al doping on the electrical and optical properties are observed by Hall measurement and photoluminescence spectroscopy, respectively, at room temperature. We observe that the diameter and resistivity of the nanorods reach their lowest levels, the carrier concentration becomes high, and emission peak tends to approach the band edge emission of ZnO around 0.5% of Al doping. Sensing behavior of the grown ZnO nanorod samples is tested for H₂ gas. The 0.5 mol% Al-doped sample shows highest sensitivity values of ~ 60 % at 250 ℃ and ~ 50 % at 220 ℃.

• Korean Journal of Materials Research
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• v.13 no.5
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• pp.317-322
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• 2003

Bismuth layered structure ferroelectric thin films, $Bi_4$$Ti_3$$O_{12}$ / (BTO) and Nb-doped BTO (BTN) were prepared on the Pt(111)/Ti/$SiO_2$/Si(100) substrates by a sol-gel route. We investigated the Nb-doping effect on the grain orientation and ferroelectric properties. $Nb^{5＋}$ ion substitution for $Ti^{4＋}$ ion in perovskite layers of BTO decreased the degree of c-axis orientation and increased the remanent polarization (2Pr). The fatigue resistance of Nb-doped BTO thin film was shown to be superior to that of BTO, and the leakage current of Nb-doped BTO thin film was decreased about 1 order of magnitude compared with BTO. The improvement of ferroelectric properties with $Nb^{5＋}$ doping in BTO could be attributed to the changes in space charge densities and grain orientation in the thin film.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.372-377
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• 2013

Machinable SiC ceramics are prepared with the addition of $Al_2TiO_5$. Ready-to-press SiC and $Al_2TiO_5$ powders are mixed and pressureless sintered at $1750^{\circ}C$ and $1850^{\circ}C$ for 1 h. The weight ratios of the SiC and $Al_2TiO_5$ powders are 100 : 0, 100 : 10, and 100 : 20. After sintering, only SiC peaks are detected in the X-ray diffraction analyses. The density, strength, and grain size of the SiC increase with increases in the $Al_2TiO_5$ content and sintering temperature. The $Al_2TiO_5$-doped specimens are easy to micro-hole machine. Based on the density and strength data, the ceramics sintered at $1850^{\circ}C$ can be used as machinable ceramics.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.435-435
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• 2014

Eu(III)-doped Y2O3 nanorods were deposited onto a Si substrate using electrostatic spray system. The photoluminescence imaging profiles were compared between the electrospray film and powder form. Using electrostatic spraying technique is very advantageous to generate a uniform monolayer film without much clustering of nanorods. Strong emission peaks were observed between 580 and 730 nm in response to an indirect excitation transition. Our results indicate that the electrospray technique could be very useful for generating thin films for displays and sensors.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.325-328
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• 2008

This paper describes the electrical properties of poly (polycrystalline) 3C-SiC thin films with different nitrogen doping concentrations. In-situ doped poly 3C-SiC thin films were deposited by APCVD at $1200^{\circ}C$ using HMDS (hexamethyildisilane: $Si_2(CH_3)_6)$) as Si and C precursor, and $0{\sim}100$ sccm $N_2$ as the dopant source gas. The peak of SiC is appeared in poly 3C-SiC thin films grown on $SiO_2/Si$ substrates in XRD(X-ray diffraction) and FT-IR(Fourier transform infrared spectroscopy) analyses. The resistivity of poly 3C-SiC thin films decreased from $8.35{\Omega}{\cdot}cm$ with $N_2$ of 0 sccm to $0.014{\Omega}{\cdot}cm$ with 100 sccm. The carrier concentration of poly 3C-SiC films increased with doping from $3.0819{\times}10^{17}$ to $2.2994{\times}10^{19}cm^{-3}$ and their electronic mobilities increased from 2.433 to $29.299cm^2/V{\cdot}S$, respectively.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.356-362
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• 2019

$BaSiO_3:RE^{3+}$ (RE = Sm or Eu) phosphor powders with different concentrations of activator ions are synthesized using the solid-state reaction method. The effects of the concentration of activator ions on the structural, photoluminescent, and morphological properties of the barium silicate phosphors are investigated. X-ray diffraction data reveals that the crystal structure of all the phosphors, regardless of the type and the concentration of the activator ions, is an orthorhombic system with a main (111) diffraction peak. The grain particles agglomerate together to form larger clusters with increasing concentrations of activator ions. The emission spectra of the $Sm^{3+}$-doped $BaSiO_3$ phosphors under excitation at 406 nm consist of an intense orange band at 604 nm and three weak bands centered at 567, 651, and 711 nm, respectively. As the concentration of $Sm^{3+}$ increases from 1 to 5 mol%, the intensities of all the emission bands gradually increase, reach maxima at 5 mol% of $Sm^{3+}$ ions, and then decrease significantly with further increases in the $Sm^{3+}$ concentration due to the concentration quenching phenomenon. For the $Eu^{3+}$-doped $BaSiO_3$ phosphors, a strong red emission band at 621 nm and several weak bands are observed. The optimal orange and red light emissions of the $BaSiO_3$ phosphors are obtained when the concentrations of $Sm^{3+}$ and $Eu^{3+}$ ions are 5 mol% and 15 mol%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.430-431
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• 2009

In this study, europium doped strontium silicate ($Sr_2SiO_4:Eu^{2+}$) phosphor has been synthesized by conventional solid-state method and investigated luminescent characteristic. $SrCO_3$ and $SiO_2$ were mixed together by 2:1 mole ratio. Also $NH_4Cl$ was added as a flux. The mixture were sintered at $800^{\circ}C$, $1000^{\circ}C$ for 3h under the atmosphere (5% $H_2$/95% $N_2$). This phosphor can be applicated to the yellow phosphor for white LED because it has yellow emission band (540nm), which emits efficiently under the 370nm excitaion energy.

• Journal of Information Display
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• v.1 no.1
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• pp.35-41
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• 2000

Manganese-doped $Zn_2SiO_4$ phosphors well known as a green emitter with high luminescence efficiency were prepared by the homogeneous precipitation method, and their photoluminescence properties under vacuum-ultraviolet (VUV) excitation were investigated. $Zn_2SiO_4$:Mn phosphors obtained by this method have exhibited a high luminance of property and a spherical shape of particles. In particular, the green emission intensity of zinc orthosilicate prepared as containing around 2 mole% of manganese was much stronger than that of the commercial $Zn_2SiO_4$:Mn phosphor, while the decay time was longer. However, addition of $Al^{3+}$ and $Li^+$ into $Zn_2SiO_4$:Mn composition has significantly diminished the decay time of the phosphor without much degradation of the emission intensity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.155-159
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• 2003

Polycrystalline $Ti_{1-x}Co_xO_2$ thin films on $SiO_2$ (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition. Microstructures and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed $Ti_{1-x}Co_xO_2$ thin films with $x{\leq}0.05$ showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the $Ti_{1-x}Co_xO_2$ (TCO) phases. On the other hand, in case of thin films above x=0.05, Co clusters formed in a homogeneous $Ti_{1-x}Co_xO_2$ Phase, and the overall ferromagnetic (FM) properties depended on both $FM_{TCO}$ and $FM_{Co}$. Co clusters with about 10nm-150nm size decreased the value of Mr (the remanent magnetization) and increased the saturation magnetic field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.199-200
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• 2009

This paper describes the electrical properties of polycrystalline (poly) 3C-SiC thin films with different nitrogen doping concentrations. The in-situ-doped poly 3C-SiC thin films were deposited by using atmospheric-pressure chemical vapor deposition (APCVD) at $1200^{\circ}C$ with hexamethyldisilane (HMDS: $Si_2$ $(CH_3)_6)$ as a single precursor and 0 ~ 100 sccm of $N_2$ as the dopant source gas. The peaks of the SiC (111) and the Si-C bonding were observed for the poly 3C-SiC thin films grown on $SiO_2/Si$ substrates by using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses, respectively. The resistivity of the poly 3C-SiC thin films decreased from $8.35\;{\Omega}{\cdot}cm$ for $N_2$ of 0 sccm to $0.014\;{\Omega}{\cdot}cm$ with $N_2$ of 100 sccm. The carrier concentration of the poly 3C-SiC films increased with doping from $3.0819\;{\times}\;10^{17}$ to $2.2994\;{\times}\;10^{19}\;cm^{-3}$, and their electronic mobilities increased from 2.433 to $29.299\;cm^2/V{\cdot}S$.