• Korean Journal of Materials Research
• /
• v.7 no.10
• /
• pp.856-862
• /
• 1997

박막형 CdTe/CdS 태양전지의 배면전극(back contacts)물질로서 Cu도핑된 ZnTe 박막(ZnTe:Cu)을 전착법(electroplating)으로 제조하는 연구를 수행하였다. Sulfate계의 전해질 수용액에서 CdTe 기판과 투명전극으로 코팅된 유리(In$_{2}$O$_{3}$: Sn, ITO)기판 위에 ZnTe 박막을 코팅하는 방법으로써 potentiostat와 기판(cathode), Pt counter electrode, Ag/AgCI 표준전극으로 구성된 장치를 사용하여 pH=2.5-4, T=70-8$0^{\circ}C$, 0.02M $Zn^{2+}$ 1x$10^{-4}$M TeO$_{2}$, 0.2M $K_{2}$SO$_{4}$조건에서 -0.800 Vs~-0.975 V 범위의 전압(V$_{a}$ )에 걸쳐 실험하였다. ITO박막을 기판으로 사용하여 cyclic voltammogram을 작성한 결과 약 -0.50 V 에서 Te환원 peak이 나타났다. Auger electron spectroscopy (AES)로 조성분석한 결과 표면에서 Zn signal이 강하게 나왔고 시편의 두께에 따라 Zn의 signal감소하는 반면 Cd signal은 증가하는 것이 확인되었다. SEM 사진으로부터 ZnTe의 표면이 작은 입자 (0.2$\mu\textrm{m}$ 이하)로 구성되어 있으며 낮은 V$_{a}$ 에서는 입자가 작아지면서 조직이 치밀해짐이 관찰되었다. Optical transmission방법에 의하여 ITO기판위에 입혀진 박막의 밴드갭은 2.5 eV으로 측정되었다. 수용액중의 Cu$_{2+}$와 triethanolamine(TEA)은 산성용액에서 착물형성이 이루어지지 않았으며 1,10-phenanthroline과는 pH=2에서도 착물이 형성되었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.33-34
• /
• 2005

In this study, in odor to develop low temperature sintering multilayer piezoelectric actuator and ultrasonic vibrator, PMN-PNN-PZT ceramics were fabricated using $Li_2CO_3$ and $Na_2CO_3$ as sintering aids and their piezoelectric and dielectric characteristics were investigated according to the addition of dopant CuO and $Fe_2O_3$, respectively. The CuO added PMN-PNN-PZT ceramics improved mechanical quality factor Qm due to the acceptor doping effect. And also, $Fe_2O_3$ reacted as softner in this composition system in addition to the increase of grain size and sinterability. Taking into consideration electromechanical coupling factor kp of 0.62, dielectric constant $\varepsilon_r$, of 1275, Piezoelectric $d_{33}$ constant of 377[pC/N] and mechanical quality factor Qm of 975, it was concluded that the ceramics with the $Fe_2O_3$, added composition sintered at 900[$^{\circ}C$] were best for the multilayer piezoelectric actuator and ultrasonic vibrator application.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1306-1312
• /
• 2018

The Mn-doped copper nitride ($Cu_3N$) films with Mn concentration of 2.0 at. % have high crystallinity and uniform surface morphology. We found that the as-synthesized Mn-doped $Cu_3N$ films show suitable optical absorption in the visible region and the band gap is ~1.48 eV. A simple photodetector based on Mn doped $Cu_3N$ films was firstly fabricated via magnetron sputtering method. The fabricated device with doping of Mn demonstrated high photocurrent response and fast response shorter than 0.1 s both for rise and decay time superior to the pure $Cu_3N$. Furthermore, the energy levels of Mn-doped Cu3N matched well with ITO and Ag electrode. The excellent photoelectric properties reflect a good balance between sensitivities and response rate. Our investigation reveals the excellent potential of Mn-doped $Cu_3N$ films for application of photodetectors.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.119-119
• /
• 2011

This study examined the synthesis of large area graphene and the change of its characteristics depending on the ratio of CH4/H2 by using the thermal CVD methods and performed the experiments to control the electron-hole conduction and Dirac-point of graphene by using chemical doping methods. Firstly, with regard to the characteristics of the large area graphene depending on the ratio of CH4/H2, hydrophobic characteristics of the graphene changed to hydrophilic characteristics as the ratio of CH4/H2 reduces. The angle of contact also increased to 78$^{\circ}$ from 58$^{\circ}$. According to the results of Raman spectroscopy showing the degree of defect, the ratio of I(D)/I(G) increases to 0.42% from 0.25% and the surface resistance also increased to 950 ${\Omega}$ from 750 ${\Omega}$/sq. As for the graphene synthesis at the high temperature of 1,000$^{\circ}$ by using CH4/H2 in a Cu-Foil, the possibility of graphene formation was determined as a function of the ratio of H2 included in the fixed quantity of CH4 as per specifications of every equipment. It was observed that the excessive amount of H2 prevented graphene from forming, as extra H-atoms and molecules activated the reaction to C-bond of graphene. Secondly, in the experiment for the electron-hole conduction and the Dirac-point of graphene using the chemical doping method, the shift of Dirac-point and the change in the electron-hole conduction were observed for both the N-type (PEI) and the P-type (Diazonium) dopings. The ID-VG results show that, for the N-type (PEI) doped graphene, Dirac-point shifted to the left (-voltage direction) by 90V at an hour and by 130 V at 2 hours respectively, compared to the pristine graphene. Carrier mobility was also reduced by 1,600 cm2/Vs (1 hour) and 1,100 cm2/Vs (2 hours), compared to the maximum hole mobility of the pristine graphene.

• Journal of Electrical Engineering and Technology
• /
• v.1 no.3
• /
• pp.371-375
• /
• 2006

Effects of $Ag_2O$ doping on the electromagnetic properties in the BiSrCaCuO superconductor. The electromagnetic properties of doped and undoped $Ag_2O$ in the BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers. It was confirmed experimentally that a larger amount of magnetic flux was trapped in the $Ag_2O$ doped sample than in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. We have fabricated superconductor ceramics by the chemical process. A high Tc superconductor with a nominal composition of $Bi_2Sr_2Ca_2Cu_3O_y$ was prepared by the organic metal salts method. Experimental results suggest that the intermediate phase formed before the formation of the superconductor phase may be the most important factor. The relation between electromagnetic properties of Bi HTS and the external applied magnetic field was studied. The electrical resistance of the superconductor was increased by the application of the external magnetic field. But the increase in the electrical resistance continues even after the removal of the magnetic field. The reason is as follows; the magnetic flux due to the external magnetic field penetrates through the superconductor and the penetrated magnetic flux is trapped after the removal of the magnetic flux. During the sintering, doped $Ag_2O$ was converted to Ag particles that were finely dispersed in superconductor samples. It is considered that the area where normal conduction takes place increases by adding $Ag_2O$ and the magnetic flux penetrating through the sample increases. The results suggested that $Ag_2O$ acts to amplify pinning centers of magnetic flux, contributing to the occurrence of the electromagnetic properties.

• Current Photovoltaic Research
• /
• v.2 no.4
• /
• pp.147-151
• /
• 2014

A boron doping process using a boron tri-bromide ($BBr_3$) as a boron source was applied to form a $p^+$ emitter layer on an n-type mono-crystalline CZ substrate. Nitrogen ($N_2$) gas as an additive of the diffusion process was varied in order to study the variations in sheet resistance and the uniformity of doped layer. The flow rate of $N_2$ gas flow was changed in the range 3 slm~10 slm. The sheet resistance uniformity however was found to be variable with the variation of the $N_2$ flow rate. The optimal flow rate for $N_2$ gas was found to be 4 slm, resulting in a sheet resistance value of $50{\Omega}/sq$ and having a uniformity of less than 10%. The process temperature was also varied in order to study its influence on the sheet resistance and minority carrier lifetimes. A higher lifetime value of $1727.72{\mu}s$ was achieved for the emitter having $51.74{\Omega}/sq$ sheet resistances. The thickness of the boron rich layer (BRL) was found to increase with the increase in the process temperature and a decrease in the sheet resistance was observed with the increase in the process temperature. Furthermore, a passivated emitter solar cell (PESC) type solar cell structure comprised of a boron doped emitter and phosphorus doped back surface field (BSF) having Ni/Cu contacts yielding 15.32% efficiency is fabricated.

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.260-260
• /
• 1999

We compared c-axis tunneling characteristics of small stacked intrinsic Josephson junctions prepared on the surface of pristine, I-, and HgI$_2$-intercalated Bi$_2Sr_2CaCu_2O_{8+x}$ (Bi2212) single crystals. The R(T) curves are almost metallic in I-Bi2212 specimens, but semiconducting in HgI$_2$-Bi2212 ones.· The transition temperatures were 82.0 K, 73.0 K, and 76.8 K for pristine Bi2212, I-Bi2212, and HgI2-Bi2212 specimens, respectively, consistent with p-T$_c$ phase diagram. Current-voltage (IV) characteristics of both kinds of specimens show multiple quasiparticle branches with well developed gap features, indicating Josephson coupling is established between neighboring CuO$_2$ planes. The critical current I$_c$ of I-Bi2212 is almost the same as of that of pristine crystals, but I$_c$ is much reduced in Hgl$_2$-Bi2212. In spite of expanded interlayer distances, the interlayer coupling is not significantly affected in I-Bi2212due to holes generated by iodine atoms. The coupling in HgI$_2$-Bi2212 is, however, weakened due to inertness of HgI$_2$ molecules and the expansion of interlayer distance. Relation between the superconducting transition temperature T$_c$ and the critical current I$_c$ seems to contradict Anderson's interlayer-pair-tunneling theory but agree with a modified version of it.

• Transactions on Electrical and Electronic Materials
• /
• v.11 no.3
• /
• pp.126-129
• /
• 2010

(1-X) $(Na_{0.5}K_{0.5})NbO_3-X$ $K_4CuNb_8O_{23}$ (NKN-X KCN) ceramics were produced using the conventional solid state sintering method, and their sinterability and electric properties were investigated. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCN content and the sintering temperature. In particular, the KCN addition to the NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 2.0 mol% sintered at $1,150^{\circ}C$ possesses the optimum properties (${\varepsilon}_r=241$, $d_{33}=78$, $k_p=0.34$ and $Q_m=1,121$). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• Transactions on Electrical and Electronic Materials
• /
• v.13 no.6
• /
• pp.283-286
• /
• 2012

(1-X)$(Na_{0.5}K_{0.5})NbO_3-XK_{5.4}Cu_{1.3}Ta_{10}O_{29}$ (NKN-KCT) lead-free piezoelectric ceramics have been synthesized by the conventional solid state sintering method, and their sinterability and piezoelectric properties were investigated. Typically, this material is sintered between 1,025 and $1,100^{\circ}C$ for 2 hours to achieve the required densification. Crystalline structures and Microstructures were analyzed by X-ray diffraction and scanning electron microscope. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCT content and the sintering temperature. In particular, the KCT addition to NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 1.0 mol% sintered at $1,050^{\circ}C$ exhibited optimum properties (${\varepsilon}_r$=246, $d_{33}$=95, $k_p$=0.38 and $Q_m$=1,826). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• Journal of the Korean Ceramic Society
• /
• v.51 no.6
• /
• pp.549-553
• /
• 2014

$CoSb_3$-based skutterudite compounds are candidate materials for thermoelectric power generation in the mid-temperature range (600 - 900 K) because their thermoelectric properties can be enhanced by doping and filling. The joining property of thermoelectric module electrodes containing thermoelectric materials is of great importance because it can dominate the efficiency of the thermoelectric module. This study examined the properties of $CoSb_3$/Al/Ti/CuMo joined by the spark plasma sintering technique. Titanium thin foil was used to prevent the diffusion of copper into $CoSb_3$ and Aluminum thin foil was used to improve the adhesion between $CoSb_3$ and Ti. The insertion of an Aluminum interlayer between the Ti and $CoSb_3$ was effective for joining $CoSb_3$ to Ti by forming an intermediate layer at the Al-$CoSb_3$ boundary without any micro cracks. Specifically, the adhesion strength of the Ti/Al/$CoSb_3$ joining interface showed a remarkable improvement compared with our previous results, without deterioration of electrical property in the interface.