• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.180-186
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• 2018

We report the discovery of Li-rich $Li_{1+x}[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y]O_2$ as a cathode material for rechargeable lithium-ion batteries in which a small amount of tetravalent vanadium ($V^{4+}$) is selectively and completely incorporated into the manganese sites in the lattice structure. The unwanted oxidation of vanadium to form a $V_2O_5-like$ secondary phase during high-temperature crystallization is prevented by uniformly dispersing the vanadium ions in coprecipitated $[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y](OH)_2$ particles. Upon doping with $V^{4+}$ ions, the initial discharge capacity (>$275mA\;h\;g^{-1}$), capacity retention, and voltage decay characteristics of the Li-rich layered oxides are improved significantly in comparison with those of the conventional undoped counterpart.

• 한국분말재료학회지
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• 제28권1호
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• pp.38-43
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• 2021

A high NIR-reflective black pigment is developed by Mn doping of Fe2O3. The pigment powders are prepared by spray pyrolysis, and the effect of the Mn concentration on the blackness and optical properties is investigated. Mn doping into the crystal lattice of α-Fe2O3 is found to effectively change the powder color from red to black, lowering the NIR reflectance compared to that of pure Fe2O3. The pigment doped with 10% Mn, i.e., Fe1.8Mn0.2O3, exhibits a black color with an optical bandgap of 1.3 eV and a Chroma value of 1.14. The NIR reflectance of the prepared Fe1.8Mn0.2O3 black pigment is 2.2 times higher than that of commercially available carbon black, and this material is proven to effectively work as a cool pigment in a temperature rise experiment under near-infrared illumination.

• 한국전기전자재료학회논문지
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• 제23권11호
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• pp.854-858
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• 2010

In this study, we have investigated the effects of Cr dopant on the sintering and electrical properties of ZnO-$Sb_2O_3$ (ZS) ceramics for varistor application. Spinel phases including $\alpha-$ and $\beta$-type was formed at ZS system and $\alpha$-spinel was stabilized by Cr doping in ZS system. Densification of ZS and ZSCr system was retarded to $1000^{\circ}C$ by the formation of spinel at $800^{\circ}C$. The morphology and its distribution of spinel phases in ZS system was homogeneous but disturbed by Cr doping. In ZSCr the densification of ZnO compared with ZS system was more retarded by low concentration of Zn interstitial defects induced by Cr doping in addition to the effect of spinel phase formation. The defects in each system were identified as attractive coulombic center (ZS: 0.13 eV, ZSCr: 0.12 eV) and singly charged oxygen vacancy $V_0^{\cdot}$ (ZSCr: 0.33 eV). In all ZS and ZSCr system have week varistor behavior by the formation of double Schottky barrier at grain boundary but its stability of barrier was very sensitive to sintering temperature.

• 한국전기전자재료학회논문지
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• 제27권5호
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• pp.292-296
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• 2014

We investigated the effect of Ta doping on the dielectric and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics prepared using a conventional ceramic processing. X-ray diffraction analysis revealed that Ta was perfectly substituted into Nb-sites in the range of 0 to 20 at%. As Ta content in the KNN increased, the sinterability of KNN ceramics was significantly degraded while the Ta doping enhanced the piezoelectric constant $d_{33}$, planar mode piezoelectric coupling coefficient ($k_p$), and electromechanical quality factor ($Q_m$). The highest values for $d_{33}$, $k_p$, and $Q_m$ was found to be 156 pC/N, 0.37, and 155, respectively.

• 한국전기전자재료학회논문지
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• 제18권4호
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• pp.285-296
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• 2005

Reduced pressure chemical vapor deposition technology has been used to study SiGe heterostructure epitaxy and device issues, including SiGe relaxed buffers, proper control of Ge component and crystalline defects, two dimensional delta doping, and their influence on electrical properties of devices. From experiments, 2D profiles of B and P presented FWHM of 5 nm and 20 nm, respectively, and doses in 5×10/sup 11/ ∼ 3×10/sup 14/ ㎝/sup -2/ range. The results could be employed to fabricate SiGe/Si heterostructure field effect transistors with both Schottky contact and MOS structure for gate electrodes. I-V characteristics of 2D P-doped HFETs revealed normal behavior except the detrimental effect of crystalline defects created at SiGe/Si interfaces due to stress relaxation. On the contrary, sharp B-doping technology resulted in significant improvement in DC performance by 20-30 ％ in transconductance and short channel effect of SiGe HMOS. High peak concentration and mobility in 2D-doped SiGe heterostructures accompanied by remarkable improvements of electrical property illustrate feasible use for nano-sale FETs and integrated circuits for radio frequency wireless communication in particular.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.62-66
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• 2002

The conventional floating zone(FZ) crystal and Czochralski(CZ) silicon crystal have resistivity variations longitudinally as well as radially The resistivity variations of the conventional FZ and CZ crystal are not conformed to requirement of dopant distribution for power devices and thyristors. These resistivity variations in conventional cystals limits the reverse breakdown voltage that could be achieved and forced designers of high power diodes and thyristors to compromise the desired current-voltage characteristics. So to produce high Power diodes and thyristors, Neutron Transmutation Doping(NTD) technique is the one method just because NTD silicon provides very homogeneous distribution of doping concentration. This procedure involves the nuclear transmutation of silicon to phosphorus by bombardment of neutron to the crystal according to the reaction $^{30}$ Si(n,${\gamma}$)longrightarrow$^{31}$ Silongrightarrow(2.6 hr)$^{31}$ P+$\beta$$^{[-10]}$ . The radioactive isotope $^{31}$ Si is formed by $^{31}$ Si capturing a neutron, which then decays into the stable $^{31}$ P isotope (i.e., the donor atom), whose distribution is not dependent on the crystal growth parameters. In this research, neutron was irradiated on FZ silicon wafers which had high resistivity(1000~2000 Ω cm), for 26 and 8.3hours for samples of HTS-1 and HTS-2, and 13, 3.2, 2.0 hours for samples of IP-1, IP-2 and IP-3, respectively, to compare resistivity changes due to time differences. The designed resistivities were approached, which were 2.l Ωcm for HTS-1, 7.21 Ω cm for HTS-2, 1.792cm for IP-1, 6.83 Ωcm for IP-2, 9.23 Ωcm for IP-3, respectively. Point defects were investigated with Deep Level Transient Spectroscopy(DLTS). Four different defects were observed at 80K, 125K, 230K, and above 300K.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.35-36
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• 2009

In this work, we demonstrate 800V 4H-SiC power DMOSFETs with several structural alterations to obtain a low threshold voltage ($V_{TH}$) and a high figure of merit ($V_B^2/R_{SP,ON}$). To optimize the device performance, we consider four design parameters; (a) the doping concentration ($N_{CSL}$) of current spreading layer (CSL) beneath the p-base region, (b) the thickness of p-base ($t_{BASE}$), (c) the doping concentration ($N_J$) and width ($W_J$) of a JFET region, (d) the doping concentration ($N_{EPI}$) and thickness ($t_{EPI}$) of epi-layer. These parameters are optimized using 2D numerical simulation and the 4H-SiC DMOSFET structure results in a threshold voltage ($V_{TH}$) below ~3.8V, and high figure of merit ($V_B^2/R_{SP,ON}$>${\sim}200MW/cm^2$) for a power MOSFET in $V_B$-800V range.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.661-664
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• 1999

The piezoelectric properties and the doping effect of Nb$_2$O$_{5}$ for 0.95 PbZr$_{x}$ Ti$_{1-x}$ -O$_3$+0.05 Pb(Mnsub 1/3/Nb$_{2}$3/)O$_3$ compositions have been investigated. In the composition of 0.95PbZr$_{0.51}$Ti$_{0.49}$O$_3$+0.05Pb(Mn$_{1}$3/Nb/syb 2/3/)O$_3$ the values of k$_{p}$ and $\varepsilon$$_{33}$ $^{T}$ are maximized, but Q$_{m}$ was minimized (k$_{p}$ =0.57, Q$_{m}$ =1550). The grain size was suppressed and the uniformity of grain was improves with doping concentration of Nb$_2$O$_{5}$ far 0.95PbZr$_{0.51}$Ti$_{0.49}$O$_3$+0.05Pb(Mn$_{1}$3/Nb/syb 2/3/)O$_3$. sample. The values of k$_{p}$ first decreased slightly when a small amount of Nb$^{5+}$ is doped and then decreased when the Nb$^{5+}$ concentration is further increased. The Q$_{m}$ . OR the Other hand. increased monotonously with doping concentration of Nb$_2$O$_{5}$ .{5}$ . .

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.24-27
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• 2014

In this study, the effects of Mn-doping and the electrode materials on the memory characteristics of $ZnO_xS_{1-x}$ resistive random access memory (ReRAM) devices on plastic are investigated. Compared with the undoped Al/$ZnO_xS_{1-x}$/Au and Al/$ZnO_xS_{1-x}$/Cu devices, the Mn-doped ones show a relatively higher ratio of the high resistance state (HRS) to low resistance state (LRS), and narrower resistance distributions in both states. For the $ZnO_xS_{1-x}$ devices with bottom electrodes of Cu, more stable conducting filament paths are formed near these electrodes, due to the relatively higher affinity of copper to sulfur, compared with the devices with bottom electrodes of Au, so that the distributions of the set and reset voltages get narrower. For the Al/$ZnO_xS_{1-x}$/Cu device, the ratio of the HRS to LRS is above $10^6$, and the memory characteristics are maintained for $10^4$ sec, which values are comparable to those of ReRAM devices on Si or glass substrates.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.403-406
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• 2000

The piezoelectric properties and the doping effect of N $b_2$ $O_{5}$ and Mn $O_2$for 0.95PbZ $r_{x}$ $Ti_{x}$ $O_3$+0.05Pb(M $n_{0.42}$ $W_{0.26}$S $b_{0.32}$) $O_3$ compositions have been investigated. In the composition of 0.95PbZ $r_{0.54}$ $Ti_{0.46}$ $O_3$+0.05Pb(M $n_{0.42}$ $W_{0.26}$S $b_{0.32}$) $O_3$the Values Of $k_{p}$ find and $\varepsilon$$_{33}$ $^{T}$ are maximized, but $Q_{m}$ Was minimized ( $k_{p}$ =0.51, $Q_{m}$ =1750). The grain size was suppressed and the uniformity of grain was improved with doping concentration of N $b_2$ $O_{5}$ for 0.95PbZ $r_{0.54}$ $Ti_{0.46}$ $O_3$+0.005Pb(M $n_{0.42}$ $W_{0.26}$S $b_{0.32}$) $O_3$sample. The values of $k_{p}$ increased and the values of $Q_{m}$ slightly decreased when 0.5 wt% of N $b_2$ $O_{5}$ is doped. And the values of $k_{p}$ was the same formation of the N $b_2$ $O_{5}$ dopant when 0.5 wt% of M $n_2$ $O_{5}$ is doped. But the values of $Q_{m}$ was deeply decreased when 0.5 wt% of Mn $O_2$is doped. As a experiment results under high electric field driving, this piezoelectric ceramics are very stable. Conclusively, piezoelectric ceramic compsiton investigated at this paper is suitable for application to high power piezoelectric devices.. devices..ices.. devices..