• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1754-1756
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• 2000

Organic semiconductors based on fused-ring polycyclic aromatic hydrocarbon have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, pentacene thin films and electrode materials were deposited by Organic Molecular Beam Deposition(OMBD) and vacuum evaporation respectively. For the gate dielectric, polyamic acid was spin-coated and cured into polyimide at 350$^{\circ}C$. Electrical characteristics of the devices were investigated, where the channel length and width was 50${\mu}m$ and 5mm. It was found that field effect mobility was 0.012$cm^{2}/Vs$, and on/off current ratio was $10^5$.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.2
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• pp.141-149
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• 2015

In the fabrication of electronic circuits used in electronic products, molybdenum thin films are deposited on semiconductors to prevent oxidation. During the deposition, the presence of a particle or dust at the interface between the thin film and substrate causes the decrease of adhesion, performance, and life cycle. In this study, a damage measurement targeting two kinds of glass substrate, with and without particles, was performed in order to measure the change in the molybdenum thin film deposition area in the presence of a particle. Clean and dirty molybdenum thin film specimens were fabricated and directly deposited on a substrate using the sputtering method, and a reflection-type digital holographic interferometer was configured for measuring the damage. Reflection-type digital holography has several advantages; e.g., the configuration of the interferometer is simple, the measurement range can be varied depending on the magnification of a microscopic lens, and the measuring time is short. The results confirm that reflection-type digital holography is useful for the measurement of the damage and defects of thin films.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.66-69
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• 2018

This study was researched the electrical properties of semiconductor devices such as ITO, $SiO_2$, $V_2O_5$ thin films. The films of ITO, $SiO_2$, $V_2O_5$ were deposited by the rf magnetron sputtering system with mixed gases of oxygen and argon to generate the plasma. All samples were cleaned before deposition and prepared the metal electrodes to research the current-voltage properties. The electrical characteristics of semiconductors depends on the interface's properties at the junction. There are two kinds of junctions such as ohmic and schottky contacts in the semiconductors. In this study, the ITO thin film was shown the ohmic contact properties as the linear current-voltage curves, and the electrical characteristics of $SiO_2$ and $V_2O_5$ films were shown the non-linear current-voltage curves as the schottky contacts. It was confirmed that the electronic system with schottky contacts enhanced the electronic flow owing to the increment of efficiency and increased the conductivity. The schottky contact was only defined special characteristics at the semiconductor and the interface depletion layer at the junction made the schottky contact which has the effect of leakage current cutoff. Consequently the semiconductor device with shottky contact increased the electronic current flow, in spite of depletion of carriers.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.154-155
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• 2012

The promise of nano-crystalites (nc) as a technological material, for applications including display backplane, and solar cells, may ultimately depend on tailoring their behavior through doping and crystallinity. Impurities can strongly modify electronic and optical properties of bulk and nc semiconductors. Highly doped dopant also effect structural properties (both grain size, crystal fraction) of nc-Si thin film. As discussed in several literatures, P atoms or radicals have the tendency to reside on the surface of nc. The P-radical segregation on the nano-grain surfaces that called self-purification may reduce the possibility of new nucleation because of the five-coordination of P. In addition, the P doping levels of ${\sim}2{\times}10^{21}\;at/cm^3$ is the solubility limitation of P in Si; the solubility of nc thin film should be smaller. Therefore, the non-activated P tends to segregate on the grain boundaries and the surface of nc. These mechanisms could prevent new nucleation on the existing grain surface. Therefore, most researches shown that highly doped nc-thin film by using conventional PECVD deposition system tended to have low crystallinity, where the formation energy of nucleation should be higher than the nc surface in the intrinsic materials. If the deposition technology that can make highly doped and simultaneously highly crystallized nc at low temperature, it can lead processes of next generation flexible devices. Recently, we are developing a novel CVD technology with a neutral particle beam (NPB) source, named as neutral beam assisted CVD (NBaCVD), which controls the energy of incident neutral particles in the range of 1~300eV in order to enhance the atomic activation and crystalline of thin films at low temperatures. During the formation of the nc-/pm-Si thin films by the NBaCVD with various process conditions, NPB energy directly controlled by the reflector bias and effectively increased crystal fraction (~80%) by uniformly distributed nc grains with 3~10 nm size. In the case of phosphorous doped Si thin films, the doping efficiency also increased as increasing the reflector bias (i.e. increasing NPB energy). At 330V of reflector bias, activation energy of the doped nc-Si thin film reduced as low as 0.001 eV. This means dopants are fully occupied as substitutional site, even though the Si thin film has nano-sized grain structure. And activated dopant concentration is recorded as high as up to 1020 #/$cm^3$ at very low process temperature (＜ $80^{\circ}C$) process without any post annealing. Theoretical solubility for the higher dopant concentration in Si thin film for order of 1020 #/$cm^3$ can be done only high temperature process or post annealing over $650^{\circ}C$. In general, as decreasing the grain size, the dopant binding energy increases as ratio of 1 of diameter of grain and the dopant hardly be activated. The highly doped nc-Si thin film by low-temperature NBaCVD process had smaller average grain size under 10 nm (measured by GIWAXS, GISAXS and TEM analysis), but achieved very higher activation of phosphorous dopant; NB energy sufficiently transports its energy to doping and crystallization even though without supplying additional thermal energy. TEM image shows that incubation layer does not formed between nc-Si film and SiO2 under later and highly crystallized nc-Si film is constructed with uniformly distributed nano-grains in polymorphous tissues. The nucleation should be start at the first layer on the SiO2 later, but it hardly growth to be cone-shaped micro-size grains. The nc-grain evenly embedded pm-Si thin film can be formatted by competition of the nucleation and the crystal growing, which depend on the NPB energies. In the evaluation of the light soaking degradation of photoconductivity, while conventional intrinsic and n-type doped a-Si thin films appeared typical degradation of photoconductivity, all of the nc-Si thin films processed by the NBaCVD show only a few % of degradation of it. From FTIR and RAMAN spectra, the energetic hydrogen NB atoms passivate nano-grain boundaries during the NBaCVD process because of the high diffusivity and chemical potential of hydrogen atoms.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.420-425
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• 2012

The new organic semiconductors which are composed of divinylbenzene core unit and alkoxynaphthalene on both sides, 1,4-bis-2-(6-octyloxy)naphthalen-2-ylvinylbenzene (BONVB), 1,4-bis-2-(6-decyloxy)naphthalen-2-ylvinylbenzene (BDNVB) and 1,4-bis-2-(6-dodecyloxy)naphthalen-2-ylvinylbenzene (BDDNVB) were synthesized by Wittig reaction. The structures of obtained BONVB, BDNVB and BDDNVB were confirmed by FT-IR and mass spectroscopy. UV-absorption of thin film showed H-aggregates and J-aggregates due to closely packed structure between adjacent molecules. The characterization of vacuum-evaporated films by Xray diffraction (XRD) and atomic force microscopy (AFM) showed that the chain length of alkoxy group affects the crystallinity and morphology. BONVB with octyloxy group showed the mobility of $0.011cm^2/V{\cdot}s$, on/off ratio of $1.31{\times}10^5$, and a subthreshold slope of 0.93 V.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.302.1-302.1
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• 2016

Solution-processed amorphous metal-oxide thin-film transistors (TFTs) are considered as promising candidates for the upcoming transparent and flexible electronics due to their transparent property, good performance uniformity and possibility to fabricate at a low-temperature. In addition, solution processing metal oxide TFTs may allow non-vacuum fabrication of flexible electronic which can be more utilizable for easy and low-cost fabrication. Recently, for high-mobility oxide TFTs, multi-layered oxide channel devices have been introduced such as superlattice channel structure and heterojunction structure. However, only a few studies have been mentioned on the bias illumination stress in the multi- layered oxide TFTs. Therefore, in this research, we investigated the effects of bias illumination stress in solution-processed bilayer oxide TFTs which are fabricated by the deep ultraviolet photochemical activation process. For studying the electrical and stability characteristics, we implemented positive bias stress (PBS) and negative bias illumination stress (NBIS). Also, we studied the electrical properties such as field-effect mobility, threshold voltage ($V_T$) and subthreshold slop (SS) to understand effects of the bilayer channel structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.301.2-301.2
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• 2016

Metal-oxide thin-film transistors (TFTs) have gained a considerable interest in transparent electronics owing to their high optical transparency and outstanding electrical performance even in an amorphous state. Also, these metal-oxide materials can be solution-processed at a low temperature by using deep ultraviolet (DUV) induced photochemical activation allowing facile integration on flexible substrates [1]. In addition, high-dielectric constant (k) inorganic gate dielectrics are also of a great interest as a key element to lower the operating voltage and as well as the formation of coherent interface with the oxide semiconductors, which may lead to a considerable improvement in the TFT performance. In this study, we investigated the electrical properties of solution-processed high-k strontium-doped AlOx (Sr-AlOx) gate dielectrics. Using the Sr-AlOx as a gate dielectric, indium-gallium-zinc oxide (IGZO) TFTs were fabricated and their electrical properties are analyzed. We demonstrate IGZO TFTs with a 10-nm-thick Sr-AlOx gate dielectric which can be operated at a low voltage (~5 V).

• Transactions on Electrical and Electronic Materials
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• v.16 no.5
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• pp.234-240
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• 2015

Amorphous oxide-based thin-film transistors (TFTs) have drawn a lot of attention recently for the next-generation high-resolution display industry. The required field-effect mobility of oxide-based TFTs has been increasing rapidly to meet the demands of the high-resolution, large panel size and 3D displays in the market. In this regard, the current status and major trends in the high mobility oxide-based TFTs are briefly reviewed. The various approaches, including the use of semiconductor, dielectric, electrode materials and the corresponding device structures for realizing high mobility oxide-based TFT devices are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.376-376
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• 2011

I-III-VI2 chalcopyrite compounds, particularly copper, indium, gallium selenide(Cu(InxGa1-x)Se2, CIGS), are effective light-absorbing materials in thin-film solar application. They are direct band-gap semiconductors with correspondingly high optical absorption coefficients. Also they are stable under long-term excitation. CIS (CIGS) solar cell reached conversion efficiencies as high as 19.5%. Several methods to prepare CIS (CIGS) absorber films have been reported, such as co-evaporation, sputtering, selenization, and electrodeposition. Until now, co-evaporation is the most successful technique for the preparation of CIS (CIGS) in terms of solar efficiency, but it seems difficult to scale up. CIS solar cells have been hindered by high costs associated with a fabrication process. Therefore, inorganic colloidal ink suitable for a scalable coating process could be a key step in the development of low-cost solar cells. Here, we will present the preparation of CIS photo absorption layer by a solution process using novel metal precursors. Chalcopyrite copper indium diselenide (CuInSe2) nanocrystals ranging from 5 to 20nm in diameter were synthesized by arrested precipitation in solution. For the fabrication of CIS photo absorption layer, the CuInSe2 colloidal ink was prepared by dispersing in organic solvent and used to drop-casting on molybdenum substrate. We have characterized the nanoparticless and CIS layer by XRD, SEM, TEM, and ICP.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.382-384
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• 2009

In this study, high stable oxide thin-film transistors (TFTs) have been developed by using several approaching techniques, which including a change of the channel composition ratio in multi-component oxide semiconductors, a change of TFT structure with interfacial dielectric layers, a control of interface roughness, a channel-doping method, and so on.