• Korean Journal of Materials Research
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• v.17 no.1
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• pp.31-36
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• 2007

Nanoimprint lithography (NIL) is a new lithographic method that offers a sub-10nm feature size, high throughput, and low cost. One of the most serious problems of NIL is the stiction between mold and resist. The antistiction layer coating is very effective to prevent this stiction and ensure the successful NIL results. In this paper, an antistiction layer was deposited by VSAM (vapor self assembly monolayer) method on silicon samples with FOTS (perfluoroctyltrichlorosilane) as a precursor for making an antistiction layer. A specially designed LPCVD (low pressure chemical vapor deposition) was used for this experiment. All experiments were achieved after removing the humidity. First, the evaporation test of FOTS was performed for checking the evaporation temperature at low pressure. FOTS was evaporated at 5 Tow and $110^{\circ}C$. In order to evaluate the temperature effect on antistiction layer, chamber temperature was changed from 50 to $170^{\circ}C$ with 0.1ml of FOTS for 1 minute. Good hydrophobicity of all samples was shown at about $110^{\circ}$ of contact angle and under $20^{\circ}$ of hysteresis. The surface energies of all samples calculated by Lewis acid/base theory was shown to be about 15mN/m. The deposited thicknesses of all samples measured by ellipsometry were almost 1nm that was similar value of the calculated molecular length. The surface roughness of all samples was not changed after deposition but the friction force showed relatively high values and deviations deposited at under $110^{\circ}$. Also the white circles were founded in LFM images under $110^{\circ}$. High friction forces were guessed based on this irregular deposition. The optimized VSAM process for FOTS was achieved at $170^{\circ}C$, 5 Torr for 1 hour. The hot embossing process with 4 inch Si mold was successfully achieved after VSAM deposition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.878-881
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• 2004

When it converted solar energy or light energy into chemical energy, it studied the electric charge transfer property of the viologen which is used widely as the electron acceptor for the electric charge delivery mediation of the devices. It was formed monolayer in QCM by self-assembled viologen. The absorbed quantities of viologen's electron through peak current and to analyze the electron transfer property of viologen in redox reaction made experiments in cyclic voltammetry among the electrochemical process. It studied the electron transfer relation of viologen from changing the anion in 0.1M NaCl and $NaClO_4$ electrolyte and the interrelation between scan rate and peak current when scan rate increased twice.

• Polymer(Korea)
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• v.26 no.5
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• pp.634-643
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• 2002

Ultrathin film of polyamic acid having benzene and sulfonyloxyimide moieties was prepared using the Langmuir-Blodgett (LB) technique, and then photosensitive polyimide LB film was obtained by the thermal treatment of precursor polyamic acid multilayers at 200$\^{C}$ for 1 hr. The polyamic acid was synthesized by condensation polymerization under THF and pyridine cosolvent. All monomers and polymers were identified through elemental analysis, FT-IR and $^1$H-NMR spectroscopic measurements. The microarray patterning of photosensitive polyimide LB film on a gold substrate was generated with a deep UV lithography technique. The well-characterized monolayer of cytochrome c was immobilized on the microarray patterns using two different self-assembly processes. Physical and electrochemical properties of the self-assembled cytochrome c monolayer were investigated based on cyclic voltammetry and atomic force microscopy (AFM). Also, its application in bioelectronic device was examined.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.30-34
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• 2008

The transfer assembly (or transfer printing) technique is a promising method for fabricating multi-scale structures on various substrates including semiconductors and polymers, and has been applied to fabrication of flexible devices with superior performance to conventional organic flexible devices. The mechanical behaviors of the structures fabricated by the transfer assembly is a very important information for design and reliability evaluation purpose, but the measurement of the behaviors is difficult since their critical-dimensions are very tiny. In this study, Au films with nano-scale thickness were fabricated on a silicon substrate and their mechanical properties were measured using micro-tensile test. The Au films on the silicon substrate were then transferred to a PDMS substrate using the transfer assembly technique. Self-assembled monolayer (SAM) with a thiol group was used to enhance the transfer of Au films, and the mechanical behaviors were characterized using wrinkle-based test. The test results from micro-tensile and wrinkle-based test are compared to each other, and their implication to the transfer assembly technique is discussed.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.213-218
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• 2001

Presented are the STM images of self-assembled monolayer of 2-mercaptoethanol on Au(111). Striped structures of ($6{\times}3_{\frac{1}{2}}$), ($5{\times}3_{\frac{1}{2}}$), ($4{\times}3_{\frac{1}{2}}$) and compact-($5{\times}3_{\frac{1}{2}}$) were observed after annealing at $80^{\circ}C.$ Analysis of the ordered structures revealed that the basic fundamental units of the ordered structures were three crystallographically non-equivalent ($3_{\frac{1}{2}}{\times}3_{\frac{1}{2}}$) $R30^{\circ}$ assemblies, and that the way of combination of the assemblies produced the four different structures. The($6{\times}3_{\frac{1}{2}}$) structure ( $\theta$ = 0.33) was composed of one ($3_{\frac{1}{2}}{\times}3_{\frac{1}{2}}$)$R30^{\circ}$ assembly, while the ($5{\times}3_{\frac{1}{2}}$) ( $\theta$ = 0.30) and ($4{\times}3_{\frac{1}{2}}$) ( $\theta$ = 0.38) structures were consisted of two ($3_{\frac{1}{2}}{\times}3_{\frac{1}{2}}$) $R30^{\circ}$ assemblies, separated by 5a and 4a, respectively. Furthermore, the compact-(5X 3½) structure ( $\theta$ = 0.50) was obtained by overlapping three ($3_{\frac{1}{2}}{\times}3_{\frac{1}{2}}$) $R30^{\circ}$ assemblies. In spite of the diversity in the adsorption structures, all the adsorption sites of 2-mercaptoethanol were fundamentally identical. On the other hand, the unannealed primitive SAM of 2-mercaptoethanol was characterized by two observations: a short-range order keeping the adsorbed molecules at approximately $3_{\frac{1}{2}}$ a and the small domains of the striped structures supporting that the observed surface structures on the annealed surface were the extension of the primitive layer of 2-mercaptoethanol. Comparing these observations with the already published structures of ethanthiol, it was concluded that the interaction between the hydroxyl groups of 2-mercaptoethanol might play a significant role in the adsorption step of 2-mercaptoethanol on Au(111) to organize the adsorption structures different from those of ethanthiol.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.366-370
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• 2006

We investigated the negative differential resistance (NDR) property of self-assembled 4,4-di(ethynylphenyl)-2'-nitro-l-(thioacetyl)benzene ('nitro-benzene'), which has been well known as a conducting molecule [1], Self-assembly monolayers (SAMs) were prepared on Au (111), which had been thermally deposited onto pre-treated $(H_2SO_4: H_2O_2=3:1)$ Si, The Au substrate was exposed to a 1mM solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing of the sample, it was exposed to a $0.1{\mu}M$ solution of nitro-benzene in dimethylformamide (DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. Following the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2$, and finally blown dry with $N_2$. Under these conditions, we measured the electrical properties of SAMs using ultra high vacuum scanning tunneling microscopy (UHV-STM) and scanning tunneling spectroscopy (STS) [2]. As a result, we confirmed the properties of NDR in between the positive and negative region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.918-921
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• 2003

The electrochemical behavior of vilogen self-assembled monolayer has been investigated with QCM, which has been known as ng order mass detector. The self-assembly process of viologen was monitored using resonant frequency(${\Delta}F$) and resonant resistance(R). The QCM measurements indicated a mass adsorption for viologen assembling on the gold surface with a frequency change about 300, 135 Hz and calculated its surface coverage($\Gamma$) to be $5.02{\times}10^{-9}$ and $1.64{\times}10^{-9}mol/cm^2$. Also a reversible redox process was observed and analyzed with an ionic interaction at the Viologen/solution interface using ${\Delta}F$.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1305-1306
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• 2006

A monolayer assembly of anthracene-viologen linked thiol ($AMVC_{8}SH$) was fabricated on a gold electrode by self-assembly method. Structural property of the self-assembled monolayers (SAMs) was carried out by optical and electrochemical method. Firstly, we investigated PL spectrum and UV/visible absorption for the optical properties in solution state. Secondly, we determined the characteristics of charge transfer in different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the PL spectrum and UV/visible absorption were observed and the well-defined shape peaks were nearly equal charges during redox reactions and existed to an excellent linear relationship between the scan rates and existed to currents. The mass change was determined during redox reaction. The mass change behavior of SAMs was not only governed by the mobility of the ion in the viologen but the valence of the ion in the electrolyte solution.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.2020-2021
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• 2007

Viologen derivative has been widely investigated because of their well-electrochemical behavior including the electron acceptor for the electric charge delivery mediation of the devices. The viologen exist in three main oxidation states, namely, $V^{2+}{\rightleftarrows}V^{{\cdot}+}{\rightleftarrows}V^0$. These redox reactions are highly reversible and can be cycled many times without significant side reaction. In this paper, we determined the time dependence to resonant frequency shift of QCM during self-assembly process and the electrochemical behavior of the self-assembled viologen monolayers by electrochemical QCM method. The redox reactions of viologen were highly reversible and the EQCM has been employed to monitor the electrochemically induced adsorption of SAMs during the redox reactions.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.417-428
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• 2018

In this study, we fabricated hierarchically self-assembled thin films composed of graphene oxide (GO) sheets and gold nanoparticles (Au NPs) using the Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques and investigated their gas-sensing performance. First, a thermally oxidized silicon wafer ($Si/SiO_2$) was hydrophobized by depositing the LB films of cadmium arachidate. Thin films of ligand-capped Au NPs and GO sheets of the appropriate size were then sequentially transferred onto the hydrophobic silicon wafer using the LB and the LS techniques, respectively. Several different films were prepared by varying the ligand type, film composition, and surface pressure of the spread monolayer at the air/water interface. Their structures were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and their gas-sensing performance for $NH_3$ and $CO_2$ was assessed. The thin films of dodecanethiol-capped Au NPs and medium-sized GO sheets had a better hierarchical structure with higher uniformity and exhibited better gas-sensing performance.