• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.160-164
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• 2003

Materials processing by ultrashort pulsed laser is actively being applied to micromachining technology due to its advantages with regard to non-thermal machining. In this study, materials processing with ultrashort pulses was studied by using the high repetition rate of a 800 nm Ti:sapphire regenerative amplifier. This revealed that the highly precise micromachining of metallic thin film and bulk glass with a minimal heat affected zone (HAZ) could be obtained by using near damage threshold energy. Grooves with diffraction limited sub-micrometer width were obtained with widths of 620 nm on Cr thin film and 800 nm on a soda-lime glass substrate. The machined patterns were investigated through SEM images. We also phenomenologically examined the influence of variations of parameters and proposed the optimal process conditions for microfabrication.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.896-898
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• 2009

The printed electrodes of organic thin-film transistors (OTFTs) were fabricated by screen printing using nanoparticle silver pastes. The screen printed OTFT corresponds to channel lengths between 7.6 to 82.6 ${\mu}m$ (designed L=10 to 80 ${\mu}m$) on the $150{\times}150mm^2$ paper. The channel length deviations for 40 to 80 ${\mu}m$ patterns were less than 5 %. However, the channel lengths for 10 to 30 ${\mu}m$ patterns were increased by 20 %. The screen printed bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene) OTFTs obtained had a field-effect mobility as large as 0.08 (${\pm}0.02$) $cm^2$/Vs, an on/off current ratio of $10^5$ and a subthreshold slope of 1.95 V/decade.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.393-400
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• 2012

In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.35-42
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• 2001

Nanotribological characteristics between a Si$_3$N$_4$ AFM tip and hydrophobic thin films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes in various ranges of normal load. Plasma-modified thin polymeric films were deposited on Si-wafer (100). Results showed that wetting angle of plasma-modified thin polymeric film increased with the treating time, which resulted in the hydrophobic surface and the decrease of adhesion and friction. Nanotribological characteristics of these surfaces were compared with those of other hydrophobic surfaces, such as DLC, OTS and IBAD-Ag coated surfaces. Those of OTS coated surface was superior to those of others, though wetting angle of plasma-modified thin polymeric film is higher.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.254-255
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• 2012

Interest in nano-crystalline silicon (nc-Si) thin films has been growing because of their favorable processing conditions for certain electronic devices. In particular, there has been an increase in the use of nc-Si thin films in photovoltaics for large solar cell panels and in thin film transistors for large flat panel displays. One of the most important material properties for these device applications is the macroscopic charge-carrier mobility. Hydrogenated amorphous silicon (a-Si:H) or nc-Si is a basic material in thin film transistors (TFTs). However, a-Si:H based devices have low carrier mobility and bias instability due to their metastable properties. The large number of trap sites and incomplete hydrogen passivation of a-Si:H film produce limited carrier transport. The basic electrical properties, including the carrier mobility and stability, of nc-Si TFTs might be superior to those of a-Si:H thin film. However, typical nc-Si thin films tend to have mobilities similar to a-Si films, although changes in the processing conditions can enhance the mobility. In polycrystalline silicon (poly-Si) thin films, the performance of the devices is strongly influenced by the boundaries between neighboring crystalline grains. These grain boundaries limit the conductance of macroscopic regions comprised of multiple grains. In much of the work on poly-Si thin films, it was shown that the performance of TFTs was largely determined by the number and location of the grain boundaries within the channel. Hence, efforts were made to reduce the total number of grain boundaries by increasing the average grain size. However, even a small number of grain boundaries can significantly reduce the macroscopic charge carrier mobility. The nano-crystalline or polymorphous-Si development for TFT and solar cells have been employed to compensate for disadvantage inherent to a-Si and micro-crystalline silicon (${\mu}$-Si). Recently, a novel process for deposition of nano-crystralline silicon (nc-Si) thin films at room temperature was developed using neutral beam assisted chemical vapor deposition (NBaCVD) with a neutral particle beam (NPB) source, which controls the energy of incident neutral particles in the range of 1~300 eV in order to enhance the atomic activation and crystalline of thin films at room temperature. In previous our experiments, we verified favorable properties of nc-Si thin films for certain electronic devices. During the formation of the nc-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. The more resent work on nc-Si thin film transistors (TFT) was done. We identified the performance of nc-Si TFT active channeal layers. The dependence of the performance of nc-Si TFT on the primary process parameters is explored. Raman, FT-IR and transmission electron microscope (TEM) were used to study the microstructures and the crystalline volume fraction of nc-Si films. The electric properties were investigated on Cr/SiO2/nc-Si metal-oxide-semiconductor (MOS) capacitors.

• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.237-240
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• 2012

In this study, PEDOT thin films polymerized with Iron(III)tosylate ($Fe(PTS)_3$) and grown on atomically smooth and highly dense 3-aminopropyltriethoxysilane self-assembled monolayer (APS-SAM) surfaces by VPP method have been investigated. PEDOT thin films were synthesized on APS self-assembled $SiO_2$ wafer surface at two different concentrations (20 wt% and 40 wt%) and growth time (3 and 30 minutes), and then their sheet resistance were measured and compared. PEDOT thin films grown with 20 wt% $Fe(PTS)_3$ oxidant are highly conductive when compared with the film grown with 40 wt% $Fe(PTS)_3$, as ascertained by the measured sheet resistance values down to 0.06 ${\Omega}/cm$. It clearly suggests that 20 wt% is more effective oxidant concentration for VPP than 40 wt% even though the film grown with 40 wt% oxidant has better quality than the film with 20 wt% $Fe(PTS)_3$ does.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.12-17
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• 2019

In this study, the Ag nano-dots structure and silicon nitride film were applied to the textured wafer surface to improve the light trapping effect of mono-crystalline silicon solar cell. Ag nano-dots structure was formed by performing a heat treatment for 30 minutes at 650℃ after the deposition of 10nm Ag thin film. Ag thin film deposition was performed using a thermal evaporator. The silicon nitride film was deposited by a Hot-wire chemical vapor deposition. The effect of light trapping was compared and analyzed through light reflectance measurements. Experimental results showed that the reflectivity increased by 0.5 ~ 1% under all nitride thickness conditions when Ag nano-dots structure was formed before nitride film deposition. In addition, when the Ag nano-dots structure is formed after deposition of the silicon nitride film, the reflectance is increased in the nitride film condition of 70 nm or more. When the HF treatment was performed for 60 seconds to improve the Ag nano-dot structure, the overall reflectance was improved, and the reflectance was 0.15% lower than that of the silicon nitride film-only sample at 90 nm silicon nitride film condition.

• Transactions of Materials Processing
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• v.13 no.1
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• pp.59-64
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• 2004

Nano-scratch tests were performed on PMMA thin films spin-coated on a Si substrate using an atomic force microscopy (AFM) with loads ranging form 10nN to 100nN. At low loads, a ridge pattern was formed on the PMMA thin film surface. No wear particles were observed during the pattern-forming mild wear. At high loads, severe wear by plowing occurred, accompanied by wear particles. The film with the highest hardness showed the highest wear resistance. Friction force generated during the scratching was measured, which was closely related with surface deformation of the film. A simple empirical equation to deduce scratch hardness of the film from a linear fixed-distance scratch test was proposed, and scratching-speed dependency of the scratch hardness was displayed.

• Journal of Integrative Natural Science
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• v.6 no.4
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• pp.211-214
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• 2013

In this study, in order to investigate how consecutive treatments of glass surface with HF acid and water vapor/Ar plasma affect the quality of 3-aminopropyltriethoxysilane self-assembled monolayer (APS-SAM), poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were vapor phase-polymerized immediately after spin coating of FeCl3 and poly-urethane diol-mixed oxidant solution on the monolayer surfaces prepared at various treatment conditions. For the film characterization, various poweful tools were used, e.g., FE-SEM, an optical microscope, four point probe, and a contact angle analyzer. The characterization revealed that HF treatment is not desirable for the synthesis of a high quality PEDOT thin film via vapor phase polymerization method. Rather, sole treatment with plasma noticeably improved the quality of APS-SAM on glass surface. As a result, a highly dense and smooth PEDOT thin film was grown on uniform oxidant film-coated APS monolayer surface.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.133-136
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• 2005

In the case of contacts between semiconductor and metal in semiconductor devices, they tend to be unstable because of thermal budget. To prevent these problems we deposited W-C-N diffusion barrier for preventing the interdiffusion between metal and semiconductor. The thickness of the barrier is $1,000{\AA}$ and the pressure is 3 mTorr during the deposition. In this work we coated LSMO (CMR material) on W-C-N diffusion barrier and then we studied the interface effects between LSMO layer and W-C-N diffusion barrier. We got results that the magnetic characteristics of LSMO thin film are still maintained after annealing at $800^{\circ}C$ for 3 hr because W-C-N thin diffusion barrier was prevented the diffusion of oxygen between LSMO and Si substrate.