• 태양에너지
• /
• 제19권3호
• /
• pp.125-131
• /
• 1999

This paper deals with a novel structure of poly-Si solar cell. A grain boundary(GB) of poly-Si acts as potential barrier and recombination center for photo-generated carriers. To reduce unwanted side effects at the GB of poly-Si, we employed physical GB removal of poly-Si using chemical solutions. Various chemical etchants such as Sirtl, Yang, Secco, and Schimmel were investigated for the preferential GB etching. Etch depth about 10 ${\mu}m$ was achieved by a Schimmel etchant. After a chemical etching of poly-Si, we used $POCl_3$ for emitter junction formation. This paper used an easy method of top electrode formation using a RF sputter grown ITO film. ITO films with thickness of 300 nm showed resistivity of $1.26{\times}10^{-4}{\Omega}-cm$ and overall transmittance above 80%. Using a preferential GB etching and ITO top electrode, we developed a new fabrication procedure of poly-Si solar cells. Employing optimized process conditions, we were able to achieve conversion efficiency as high as 16.6% at an input power of 20 $mW/cm^2$. This paper investigates the effects of process parameters: etching conditions, ITO deposition factors, and emitter doping densities in a poly-Si cell fabrication procedure.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.78-79
• /
• 2008

In this paper, poly 3C-SiC thin films were grown on $SiO_2$/Si by atmospheric pressure chemical vapor deposition (APCVD) using HMDS, $H_2$, and Ar gas at $1100^{\circ}C$ for 30 min, respectively. And then, palladium films were deposited on poly 3C-SiC by RF magnetron sputter. Thickness, uniformity, and quality of these samples were performed by SEM. Crystallinity and preferred orientationsof palladium were analyzed by XRD. And Pd/poly 3C-SiC schottky diodes were fabricated and characterized by current-voltage measurements. Its electric current density Js and barrier height voltage were measured as $2\times10^{-3}$ A/$cm^2$, 0.58 eV, respectively. And these devices operated about $350^{\circ}C$. From results, Pd/poly 3C-SiC devices are promising for high temperature hydrogen sensor and applications.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.593-596
• /
• 1999

This paper presents a process optimization of antireflectiun (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a doble-layer AR(DLAR) coating of MgF$_2$/CeO$_2$, We investigated CeO$_2$ films as an All layer because they hale a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown CeO$_2$ film showed strong dependence on a deposition temperature. The CeO$_2$ film deposited at 400 $^{\circ}C$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgF$_2$ film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 7m to 1.1 7m. We achieved the efficiencies of solar cells greater than 15% with 3.12 % improvement with DLAR coatings . Further details on MgF$_2$, CeO$_2$ films, and cell fabrication Parameters are presented in this paper.

• Journal of Magnetics
• /
• 제14권1호
• /
• pp.11-14
• /
• 2009

We investigated the I-V curves and differential tunneling conductance of two, CoFeB/MgO/CoFeB-based, magnetic tunnel junctions (MTJs): one with a low tunneling magnetoresistance (TMR; 22%) and the other with a high TMR (352%). This huge TMR difference was achieved by different MgO sputter conditions rather than by different annealing or deposition temperature. In addition to the TMR difference, the junction resistances were much higher in the low-TMR MTJ than in the high-TMR MTJ. The low-TMR MTJ showed a clear parabolic behavior in the dI/dV-V curve. This high resistance and parabolic behavior were well explained by the Simmons' simple barrier model. However, the tunneling properties of the high-TMR MTJ could not be explained by this model. The characteristic tunneling properties of the high-TMR MTJ were a relatively low junction resistance, a linear relation in the I-V curve, and conduction dips in the differential tunneling conductance. We explained these features by applying the coherent tunneling model.

• Advances in materials Research
• /
• 제4권4호
• /
• pp.227-233
• /
• 2015

We present a method, supported by theoretical analysis, for optimizing the usage of the critical rare earth element dysprosium in $Nd_2Fe_{14}B$ (NdFeB)-based permanent magnets. In this method, we use Dy selectively in locations such as magnet edges and faces, where demagnetization factors are largest, rather than uniformly throughout the bulk sample. A200 nm thick Dy film was sputtered onto a commercial N-38, NdFeB magnets with a thickness of 3 mm and post-annealed at temperatures from $600-700^{\circ}C$. Magnets displayed enhanced coercivities after post-annealing and as much as a 5 % increase in the energy product, while requiring a total Dy content of 0.06 wt. % - a small fraction of that used in the commercial grade Dy-NdFeB magnets. By assuming all Dy diffused into NdFeB magnets, the improvement in energy product corresponds to a saving of over 1% Dy (critical element). Magnets manufactured using this technique will therefore be higher performing which would potentially broaden the application space of these magnets in the traction motors of hybrid and pure electric vehicles, and wind generators.

• E2M - 전기 전자와 첨단 소재
• /
• 제8권5호
• /
• pp.558-563
• /
• 1995

Dynamic characteristics of TbFeCo magneto-optical recording media at 680nm wavelength region were studied by means of computer simulation of disc structure and optimization of process variables during sputter deposition. With the slightly reduced Kerr rotation angle due to the reduced wavelength of optical laser source, the improved recording density in TbFeCo magneto optical media showing the CNR greater than 50dB could be achieved by only adjusting the thickness of dielectric and the recording layers when the wavelength of light source is changed from 780nm to 680nm. In addition, the recording power margin of 5mW and the 2mW minimum recording power was realized, It was shown from the present study that the increase in laser power density demonstrated feasibility of low cost and low power laser diode with the reduced optimum recording power.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집
• /
• pp.558-561
• /
• 2001

Vanadium oxide ($VO_{x}$) thin films are very good candidate material for uncooked infrared (IR) detectors due to their high temperature coefficient of resistance (TCR) at room temperature. But, the deposition of $VO_{x}$ thin films showing good electrical properties is very difficult in micro bolometer fabrication process using sacrificial layer removal because of its low process temperature and thickness of thin films less than 1000${\AA}$. This paper presents a new fabrication process of $VO_{x}$ thin films having high TCR and low resistance. Through sandwich structure of $VO_{x}$(100${\AA}$)/V(80${\AA}$)/$VO_{x}$(500${\AA}$) by sputter method and post-annealing at oxygen ambient, we have achieved high TCR more than -2%/$^{\circ}C$ and low resistance less than $10K\Omega$ at room temperature.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
• /
• pp.1651-1652
• /
• 2006

In this study, the 2-step methode by ALD equipment was used to improve the characteristics of ZnO thin films used in a piezoelectric layer when the FBAR devices of a SMR type are fabricated. The Height of formed buffer layer was $400{\AA}$ and ZnO thin film of $13600{\AA}$ was deposited by RF sputter on the buffer layer. When ZnO thin films are deposited, deposition conditions such as pressure, injection time of source and purge time were changed variously. The characteristics of piezoelectric layer such as a crystal orientation and micro-structure of deposited ZnO thin films were studied by SEM, AFM and XRD.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.418-419
• /
• 2007

Effects of Fe catalyst film and carbon nanotube (CNT) growth temperature on the characteristics of carbon nanotube were investigated in thermal chemical vapor deposition (CVD) process. Fe catalyst was prepared by DC magnetron sputter with thickness of 5-40 nm and pre-treated with ammonia gas. CNTs were grown at $700-900^{\circ}C$. It was found that the island formation of catalyst is necessary for the CNT growth. The diameter of these CNTs shows a strong correlation with the catalyst film thickness and growth temperature.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.74-75
• /
• 2007

We report on the characteristics of organic light-emitting diodes with Al cathode deposited by specially designed twin target sputter(TTS) system. It was found that the Al cathode films grown by TTS system were amorphous structure with nanocrystallines due to low substrate temperature during sputtering process. Effective confinement of high-density plasma between two Al targets lead to low temperature sputtering process on organic layer. Moreover, organic light-emitting diodes with Al cathode deposited by TTS system exhibited low leakage current density of $4{\times}10^{-6}\;mA/cm2$ at -6 V indicating plasma damage due to bombardment of energetic particles such as ions and $\gamma$-electrons was effectively restricted in the ITS system. Sputtering method using ITS system is expected to be applied in organic electronics and flexible displays due to its low temperature and plasma damage free deposition process.