• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.10
• /
• pp.83-90
• /
• 1998

The effects of dopant activation anneal on GOI (Gate Oxide Integrity) of MOS capacitor with amorphous silicon gate electrode were investigated. It was found that the amorphous silicon gate electrode was crystallized and the dopant atoms were sufficiently activated by activation anneal. The mechanical stress of gate electrode that reveals large compressive stress in amorphous state, was released with increase of anneal temperature from $700^{\circ}C$ to 90$0^{\circ}C$. The resistivity of gate electrode polycrystalline silicon film is decreased by the increase of anneal temperature. The reliability of thin gate oxide and interface properties between oxide and silicon substrate greatly depends on the activation anneal temperature. The charge trapping characteristics as well as oxide reliability are improved by the anneal of 90$0^{\circ}C$ compare to that of $700^{\circ}C$ or 80$0^{\circ}C$. Especially, the lifetimes of the thin gate oxide estimated by TDDB method is 3$\times$10$^{10}$ for the case of $700^{\circ}C$ anneal, is significantly increased to 2$\times$10$^{12}$ for the case of 90$0^{\circ}C$ anneal. Finally, the interface trap density is reduced with relaxation of mechanical stress of gate electrode.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.63-63
• /
• 2010

Using both experimental and theoretical approaches, we have investigated the adsorption properties of an organic molecule (HATCN), which is used in OLEDs as an efficient hole injection layer, on metal and inert surfaces. We have also studied the structural and electronic properties of such interfaces and the dependences on deposition thickness. We have observed different trends in work function changes with different surfaces. Our photoelectron spectroscopic measurements have revealed an abnormal phenomenon in HATCN on a metal (Cu) surface: the work function decreases at lower coverage (~monolayer) of HATCN on a metal (Cu) surface, but it increases back and becomes higher than that of a bare Cu surface at higher coverage. It has, on the contrary, been observed that the work function of graphene surface just increases as the HATCN coverage increases. Our first-principles density functional calculations has not only verified our experimental observations, but also disclosed the underlying mechanism of such abnormal and different work function behaviors. We have found that the change in work function results from mutual polarization induced by the geometrical deformation and the bond dipole formed at the interface due to the charge redistribution. At low coverage of HAT-CN on Cu substrate, the former reduces the work function significantly by pulling down the vacuum level, while the latter tends to push up the vacuum level resulting in the work function increase.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.462-462
• /
• 2014

The effect of rear passivation for passivated emitter and rear cell (PERC) using ozone and H2O oxidant of atomic layer deposited (ALD) Al2O3 was studied by post-annealing in N2 and forming gas ambients. Rear surface of PERC solar cell was passivated by Al2O3 grown by ALD with ozone and H2O oxidant. Al2O3 grown by ALD with ozone oxidant has been known to have many advantages, such as lower interface defects, low leakage current density. Its passivation quality is better than Al2O3 with H2O. Al2O3 layer with 10 nm and 20 nm thickness was grown at $150^{\circ}C$ with ozone oxidant and at $250^{\circ}C$ with H2O oxidant. And then each samples were post-annealled at $450^{\circ}C$ in N2 ambients and at $850^{\circ}C$ in forming gas ambients. The passivation quality was investigated by measuring the minority carrier lifetime respectively. We examined atomic layer deposited Al2O3 such as growth rate, film density, thickness, negative fixed charge density at AlOx/Si interface, and reflectance. The influences of process temperature and heat treatment were investigated using Sinton (WCT-120) by Quasi-Steady State Photoconductance (QSSPC) mode. Ozone-based ALD Al2O3 film shows the best carrier lifetime at lower deposition temperature than H2O-based ALD.

• Journal of KIISE:Computer Systems and Theory
• /
• v.36 no.5
• /
• pp.371-379
• /
• 2009

Conventional sensor node operating systems do not support sensor abstraction for sensor applications. So, application programmers have to take charge of developing the hardware and the device drivers for the applications by themselves. In this paper, we present an as architecture to support sensor abstraction. The as provide not only application programmers with API library to access sensor devices, but also sensor developers with HAL library to access sensor hardware. This can reduce the development burden of application programmers significantly. In this paper, at first, we define the sensor HW interface to ease the attachment of sensors. Second, we describe the sensor access API for application programmers. Third, we define the HAL library for sensor device programmers to use. Finally, we show that the as can support sensor abstraction by illustrating the sample programs.

• Imaging Science in Dentistry
• /
• v.48 no.2
• /
• pp.87-96
• /
• 2018

Purpose: The present study aimed to evaluate which of the following imaging methods best assessed misfit at the tooth-restoration interface: (1) bitewing radiographs, both conventional and digital, performed using a photostimulable phosphor plate (PSP) and a charge-coupled device (CCD) system; (2) panoramic radiographs, both conventional and digital; and (3) cone-beam computed tomography (CBCT). Materials and Methods: Forty healthy human molars with class I cavities were selected and divided into 4 groups according to the restoration that was applied: composite resin, composite resin with liner material to simulate misfit, dental amalgam, and dental amalgam with liner material to simulate misfit. Radiography and tomography were performed using the various imaging methods, and the resulting images were analyzed by 2 calibrated radiologists. The true presence or absence of misfit corresponding to an area of radiolucency in regions subjacent to the esthetic and metal restorations was validated with microscopy. The data were analyzed using a receiver operating characteristic (ROC) curve, and the scores were compared using the Cohen kappa coefficient. Results: For bitewing images, the digital systems (CCD and PSP) showed a higher area under the ROC curve (AUROC) for the evaluation of resin restorations, while the conventional images exhibited a larger AUROC for the evaluation of amalgam restorations. Conventional and digital panoramic radiographs did not yield good results for the evaluation of resin and amalgam restorations (P<.05). CBCT images exhibited good results for resin restorations(P>.05), but showed no discriminatory ability for amalgam restorations(P<.05). Conclusion: Bitewing radiographs (conventional or digital) should be the method of choice when assessing dental restoration misfit.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1295-1297
• /
• 1993

Properties of oxynitride films oxidized by $N_2O$ gas after thermal oxidation and $N_2O$ oxide films directly oxidized using $N_2O$ gas on the bare silicon wafer have been studied. Through the AES analysis, Nitrogen pile-up at the interface of Si/oxynitride and Si/$N_2O$ oxide has observed. Also, it could be presumed that there are differences in the mechanism of the growth of film by observing film growth. $N_2O$ oxide and oxynitride films have the self-limited characteristics. Therefore, it will be possible to obtain ultra-thin films. Nitrogen pile-up at the interfaces Si/oxynitride and Si/$N_2O$ oxide strengthens film structure and improves dielectric reliability. Although fixed charge densities and interface trap densities of $N_2O$ oxide and oxynitride films has somewhat higher than those of thermal $SiO_2,\;N_2O$ oxide and oxynitride films showed improved I-V characteristics and constant current stress.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.75.2-75.2
• /
• 2013

Atomic layer deposition (ALD), utilizing self-limiting surface reactions, could offer promising perspectives for future efficient energy conversion devices. The capabilities of ALD for surface/interface modification and construction of novel architectures with sub-nanometer precision and exceptional conformality over high aspect ratio make it more valuable than any other deposition methods in nanoscale science and technology. In the context, a variety of researches on fabrication of active materials for energy conversion applications by ALD are emerging. Among those materials, one-dimensional nanotubular titanium dioxide, providing not only high specific surface area but also efficient carrier transport pathway, is a class of the most intensively explored materials for energy conversion systems, such as photovoltaic cells and photo/electrochemical devices. The monodisperse, stoichiometric, anatase, TiO2 nanotubes with smooth surface morphology and controlled wall thickness were fabricated via low-temperature template-directed ALD followed by subsequent annealing. The ALD-grown, anatase, TiO2 nanotubes in alumina template show unusual crystal growth behavior which allows to form remarkably large grains along axial direction over certain wall thickness. We also fabricated dye-sensitized solar cells (DSCs) introducing our anatase TiO2 nanotubes as photoanodes, and studied the effect of blocking layer, TiO2 thin films formed by ALD, on overall device efficiency. The photon convertsion efficiency ~7% were measured for our TiO2 nanotubebased DSCs with blocking layers, which is ~1% higher than ones without blocking layer. We also performed open circuit voltage decay measurement to estimate recombination rate in our cells, which is 3 times longer than conventional nanoparticulate photoanodes. The high efficiency of our ALD-grown, anatase, TiO2 nanotube-based DSCs may be attributed to both enhanced charge transport property of our TiO2 nanotubes photoanode and the suppression of recombination at the interface between transparent conducting electrode and iodine electrolytes by blocking layer.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.6
• /
• pp.2023-2035
• /
• 1996

In the present study, the characteristics of the electrical deformation of a bubble and a drop under a uniform electric field have been investigated to understand EHD heat transfer enhancement by an electric field. The deformation of the bubble and the drop have been studied theoretically using an electric normal stress acting on their interfaces and assured by the numerical analysis and the experiment. From the variation of bubble volume and free energy, it is found that a bubble is compressed in an electric field and free energy had larger value with increasing W and the permittivity of a dielectric fluid. The electric normal stress induced on the interface of the bubble and the drop is different. Because of the surface charge induced at the drop interface, the electric normal stress acting on the drop is much larger than that of the bubble. The drop is, therefore, deformed much more than the bubble. In addition, the experimental and numerical results show that the aspect ratio and the contact angle of the bubble increase with increasing W.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.3
• /
• pp.500-508
• /
• 2008

For efficient compatible system between medical clinics, the medical information has to be built on a standardized protocol such as a HL7 for text data and a DICOM for image data. But it is difficult to exchange information between medical clinics because the systems and softwares are different and also a structure of data and a type of code. Therefore we analyze a structure of DICOM file and design an integrated database for effective information sharing and exchange. The WISD system suggested in this paper separate the DICOM file transmitted by medical clinics to text data and image data and store it in the integrated DB(database) by standardized protocol respectively. It is very efficient that each medical clinic can search and exchange information by web browser using the suggested system. The WISD system can not only search and control of image data and patient information through integrated database and internet, but share medical information without extra charge like construction of new system.

• Journal of Adhesion and Interface
• /
• v.22 no.4
• /
• pp.153-157
• /
• 2021

Graphene, a two-dimensional carbon allotrope, has outstanding mechanical and electrical properties. In particular, the charge carrier mobility of graphene is known to be about 100 times higher than that of silicon, and it has received attention as a core material for next-generation electronic devices. However, graphene is very sensitive to environmental conditions, especially vulnerable to moisture or oxygen. It becomes a disadvantage in that the stability of the graphene-based electronic device, so various attempts are being made to solve this problem. In this work, we report a method to greatly improve the stability by controlling the surface energy of the polymer layer used for transferring the insulating layer of the graphene field-effect transistor. As the surface energy of the polymer used as the insulating layer was lowered, the stability could be improved by effectively controlling the adsorption of impurities in the atmosphere such as water molecules or oxygen.