• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.181-181
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• 1999

Self-assembled monolayers(SAMs) of alkanethiol have been formed on the Cu(111) surfaces in vacuum. The thermal behavior of octanethiol-based SAMs on the Cu(111) surface have been examined in ultrahigh vacuum. Using X-ray photoelectron spectroscopy (XPS), it is found that the monolayers are stable up to about 500K in vacuum. Decomposition is signaled by a decrease in the intensity of C ls peak, accompanied by an increase of the intensity of the Cu 2p peak. However, the intensity of the S 2p peak doesn't change much as a function of annealing temperature. Thermal the decomposition mass spectra show that n-alkene is the predominant species desorbing from the surface in the 500-600K temperature range. The totality of these data leads to the conclusion that the monolayers decompose through the S-C bond cleavage by hydrogen elimination reaction, resulting in the desorption of hydrocarbon moiety as n-alkene. Following this initial decomposition step, Cu2S layers are observed on the surface. For comparison, attempts were also made to examine the thermal behavior of octanethiol-based SAMs on the Cu(111) surface in air. It has been shown that the SAMs on the Cu(111) surfaces begin to desorb with the oxidation of the thiolate to sulfonate at 400K. Upon annealing to 450K, the monolayer has almost completely desorbed as indicated by the virtual disappearance of the S 2p peak.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.901-904
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• 2010

Decylthiocyanate (DTC) self-assembled monolayers (SAMs) on Au(111) were prepared by solution and vapor phase deposition methods at $50^{\circ}C$ for 24 h. The formation and surface structure of DTC SAMs were examined using scanning tunneling microscopy (STM). STM imaging revealed that DTC SAMs formed in 1 mM ethanol solution at $50^{\circ}C$ were composed of small ordered domains with lateral dimensions of a few nanometers and disordered phases, whereas DTC SAMs formed in the vapor phase at $50^{\circ}C$ contained two ordered phases: a closely packed c($4{\times}2$) superlattice and a striped phase with an interstripe spacing of 2.6 - 2.8 nm. It was also found that the ordered domain and vacancy island formation for DTC SAMs on Au(111) differs significantly from that of decanethiol SAMs, suggesting that adsorption mechanism is different from each other. From this study, it was confirmed that DTC SAMs with a high degree of structural order can be obtained by vapor phase deposition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1270-1275
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• 2004

Standard positive photoresist techniques were adapted to generate nano-scale patterns of gold substrate using self-assembled monolayers (SAMs) and femtosecond laser. SAMs formed by the adsorption of alkanethiols onto gold substrate are employed as very thin photoresists, Alkanethiolates formed by the adsorption of alkanethiols are oxidized on exposure to UV light in the presence of air to alkylsulfonates. Specifically, it is known that deep UV light of wavelength less than 200nm is necessary for oxidation to occur. In this study, ultrafast laser of wavelength 800nm and pulse width 200fs is applied for photolithography. Results show that ultrafast laser of visible range wavelength can replace deep UV laser source for photo patterning using thin organic films. Femtosecond laser coupled near-field scanning optical microscopy facilitates not only the patterning of surface chemical structure, but also the creation of three-dimensional nano-scale structures by combination with suitable etching methods.

• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.553-557
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• 2005

The formation of striped phases of unsymmetric hexyl octadecyl disulfide ($CH_3(CH_2)_5SS(CH_2)_{17}CH_3$, HOD) and 1-hydroxyundecyl octadecyl disulfide ($CH_3(CH_2)_{17}SS(CH_2)_{11}$OH, HUOD) on Au(111) and graphite has been investigated by scanning tunneling microscopy (STM) to understand the self-assembly processes of dialkyl disulfides. STM imaging clearly shows the formation of striped phases having corrugation periodicities that are nearly consistent with the molecular length of alkanethiolate moieties formed after the S-S bond cleavage of dialkyl disulfide on a gold surface. On the other hand, self-assembled monolayers (SAMs) of dialkyl disulfides on a graphite surface displayed long-range, well-ordered monolayers with one striped pattern that shows periodicity as a function of molecular length via nondissociative adsorption. From a nonoscopic viewpoint, we have clearly demonstrated that dialkyl disulfide SAMs on gold form via S-S bond cleavage of disulfide.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.619-623
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• 2006

Selective vapor deposition of conductive poly(3,4-ethylenedioxythiophene) (PEDOT), thin films has been carried out on self assembled monolayers patterned oxide substrate. Since the 3,4-ethylenedioxythiophene(EDOT) monomer can be polymerized only in the presence of oxidant such as $FeCl_3$, the PEDOT thin film is selectively deposited on patterned $FeCl_3$, which only adsorbs on the partly removed SAMs region due to the inability of $FeCl_3$ to adsorb on SAMs. Therefore, the partly removed SAMs can act as an adsorption layer for the $FeCl_3$ and also as a glue layer for the deposition of PEDOT, resulting in the significantly increased adhesion of PEDOT to $SiO_2$ substrate. The use of UV lithography and Cr patterned quartz mask provided the formation of SAMs patterns on oxide substrates, which allowed for the selective deposition of conductive PEDOT thin films.$^{oo}The$ new process was successfully developed for the selective deposition of PEDOT thin films on SAMs patterned oxide substrate, providing a new way for the patterning of vapor phase deposition of PEDOT thin films with accurate alignment and addressing the inherent adhesion issues between PEDOT and dielectrics.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2549-2554
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• 2009

The structures of 1,n-alkanedithiol (n = 2, 4, 6, 8, 10) self-assembled monolayers (SAMs) on a Au(111) substrate were investigated by electrochemical measurements and theoretical calculations. The results of the experimental techniques indicated that the dithiols, except n = 2, showed an upright molecular structure in the SAMs, in which alkanedithiols were bound to the Au surface via only one thiol functionality and the other one faced up to the air. The results also suggested that the formed dithiol SAMs were densely packed and highly oriented. Except ethanedithiol, which was thought to form a bilayer, the reductive desorption peak potentials of 1,n-alkanedithiol (n = 4, 6, 8, 10) SAMs were more negative than those of the corresponding monothiol ones in 0.1 M KOH solutions. This illustrates that the dithiol SAMs had higher stability than the corresponding monothiol ones. The major part of the high stability may be attributed to the van der Waals interaction among the sulfur atoms on top of the dithiol SAMs. The molecular modeling calculation showed that the structures of dithiol SAMs were similar to those of the corresponding monothiol SAMs and that all the dithiol SAMs, except ethanedithiol, were more stable than the corresponding monothiol SAMs. The calculated energy differences between dithiol and monothiol SAMs decreased with the increment of alkyl-chain length.

• Journal of Sensor Science and Technology
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• v.23 no.5
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• pp.295-298
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• 2014

A novel approach to fabricating high-performance glucose sensors is reported, which is based on the process of self-assembled monolayers (SAMs). In this study, we have particularly used ${\alpha}$-lipoic acid (LA) SAMs for the glucose sensors. To our best knowledge, this study is the first one to use LA as SAMs for this purpose. N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) were deliberately attached at the same time on the LA SAM. Then, glucose oxidase ($GO_X$) and horseradish peroxidase (HRP) were sequentially immobilized. Thus, the HRP/$GO_X$/NHS-EDC/LA-SAM/Au/Cr/glass working electrode was developed. The glucose-sensing capability of the fabricated sensor was systematically measured by the use of cyclic voltammetry in the range of 1-30 mM glucose in phosphate-buffered saline. The result showed a good sensitivity, that is, as high as $27.5{\mu}A/(mM{\cdot}cm^2)$. This result conspicuously demonstrates that LA can be one of promising substances for use as SAMs for accurately monitoring trace levels of glucose concentration in human blood.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.115-118
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• 2005

Currently, molecular devices are reported utilizing active self-assembled monolayers (SAMs) containing the nitro group as the active component, which has active redox centers [1]. SAMs are ordered molecular structures formed by the adsorption of an active surfactant on a solid surface. The molecules will be spontaneously oriented toward the substrate surface and form an energetically favorable ordered layer. During this process, the surface-active head group of the molecule chemically reacts with and chemisorbs onto the substrate In this paper, the electrical properties of the 4'4- di(ethynylphenyl)-2'-nitro-1-benzenethiolate was confirmed. This material is well known as a conducting molecule having possible application to molecular level negative differential resistance (NDR) device. To deposit the self-assembly monolayers onto the gold electrode, the prefabricated Au(1 l l) substrates were immersed into 0.5[mM/l] self-assembly molecule in THF solution. Then, the electrical properties and surface morphologies of 4' 4-di(ethynylphenyl)-2' -nitro-1-benzenethiolate were measured by using the ultra-high vacuum scanning tunneling microscopy (UHV-STM).

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.141-142
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• 1998

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.289-292
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• 2012

Au electrodes modified with self-assembled monolayers (SAMs) were used to control the work function of source/drain electrodes in triethylsilylethynyl anthradithiophene (TES ADT)-based organic thin film transistors (OTFTs). By using benzothiol (BT) and pentafluorobenzothiol (PFBT) SAMs, the hole injection barrier between Au and the highest occupied molecular orbital (HOMO) of TES ADT was controlled. After a solvent annealing, TES ADT OTFTs with PFBT SAM-treated Au electrodes were found to exhibit high field-effect mobilities of $0.05\;cm^2/Vs$ and on/off current ratios of $10^6$.