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As CMOS technology extends beyond the current technology node, many challenges to conventional MOSFET were raised. Non-classical CMOS to extend and fundamentally new technologies to replace current CMOS technology are under intensive investigation to meet these challenges. The approach of hybrid silicon/molecular electronics is to provide a smooth transition technology by integrating molecular intrinsic scalability and diverse properties with the vast infrastructure of traditional MOS technology. Here we discuss: (1) the integration of redox-active molecules into Si-based structures, (2) characterization and modeling of the properties of these Si/molecular systems, (3) single and multiple states of Si/molecular memory, and (4) applications based on hybrid Si/molecular electronic system.

The electrochemical behaviors of bare/dithiol-modified gold electrode were studied in the PBS solution with/without dithiols. A pair of current peaks between -1.4 and -0.5 V is related to dithiol adsorption or re-adsorption. An oxidative peak at 0.37 V accompanied by a slight peak at 0.03 V is observed between -0.5 and 0.7 V for the bare gold electrode in the thiol solution, which is due to the formation of bilayer. When the potential is scanned to a very positive value at 1.2 V, a new oxidative peak at 1.07 V appears for the bare gold electrode in the dithiol solution or the PBS solution. The assembled dithiols are desorbed, and gold surface is exposed. The study indicates that the 1,3-propanedithiol modified electrodes should be used during the potential range of -0.8 to 0.8 V to keep the assembled layer stable.

Copper metal and its alloys are the most used in the industries because it holds excellent conductivity and natural corrosion protectiveness against air/moisture. However, copper undergoes degradation in presence of aggressive 3.5% NaCl. Protective coating is one of the practical methods to safeguard copper metal. In this study, 2-amino-4-methyl-pyridine (AMP) was coated as self-assembled monolayer method (SAM) with different immersion periods (12 h/24 h) and investigated the corrosion potential against 3.5% NaCl medium. Chemical composition of AMP/SAM/Cu was characterized using Fourier-transform infrared (FT-IR) spectroscopy and morphological analysis using atomic force microscopy (AFM) techniques. AMP’s corrosion inhibition potential were evaluated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDS) analyses. Quantum chemical calculations and molecular dynamics (MD) simulations explained the stronger adsorption of AMP over copper metal surface via self-assembly method. The corrosion analysis revealed that AMP’s SAM formation (24 h immersion) enhances the corrosion protection of Cu metal, which is mainly due to the uniform thin adhesive compact layer formation and blocks incoming corrosive chloride ions. EIS investigation evident that AMP forms an adhesive layer over the copper surface and prevents the diffusion of aggressive corrosive medium, while PP studies revealed that AMP acts via the mixed mode of corrosion inhibition mechanism. AMP’s significant inhibition efficiency 90% was confirmed via PP analysis. AFM analysis enabled the morphology image of AMP’s shielding over Cu surface and the molecular modeling investigation supported well for the Cu–N (from AMP) bond formation.

Asymmetric current–voltage (I/V) behaviors with respect to the polarity of the voltage bias were observed in the nematic liquid crystal (NLC) cells constructed with the gold film on the silicon wafer as one substrate and an indium-tin-oxide (ITO)-coated glass slide as the other substrate. A little smaller current resulted at the positive bias corresponding to the positive voltage bias being applied to the gold film relative to the ITO-coated glass slide. When the alkanethiol self-assembled monolayer (SAM) was introduced into the above NLC cell as the aligning layer, it was able to enhance the forward current significantly, but suppress the reverse current. A current rectification ratio of ~20 was obtained at 1.5 V in the NLC cell with SAM as the aligning layer. Besides, we also characterized the effect of the optical power of 632.8 nm on the asymmetric I/V behaviors in the NLC cells without SAM and with SAM as the aligning layer.

The development of highly sensitive detection of $\beta$-agonists compound by using surface plasmon resonance (SPR) immunoassay functionalized alkanethiols monolayer on gold surface was reported here. For the construction of robust SPR sensor surface, the illegal compound (as antigen) was immobilized onto gold succinimide-terminated monolayer to perform amide-coupling reaction. Structural characteristic of monolayer is an important issue for further application of selt-assembled monolayer (SAM)-based molecular electronics. This study focuses on the relation between structure of alkanethiols SAM of different chain length and its sensitivity of the detection. The surface structure is characterized by electrochemical methods and STM.

The target compound in this research is clenbuterol as farmers used illegally to increase their profit gain. For the detection of clenbuterol, indirect competitive inhibition method was used. In this work, the SPR senses the dielectric constant change at the interface from the binding of the unreacted antibody to antigen-immobilized on the sensor surface. By this method, clenbuterol can be detected within ppt level and only requires 5min per sample. Furthermore, shorter chain alkanethiol sensor surface produces higher sensitivity in the detection process.

The photopatterning process of self-assembled monolayer has been used as template for fabricating biomolecular microstructures. Alkanethiolates formed by the adsorption of 1-octanethiol molecules on a gold substrate were oxidized by the irradiation of deep UV light and then developed with deionized water. The resulting positive patterned substrate was immersed into a dilute ethanolic solution of 11-mercaptoundecanoic acid (11-MUDA). Cytochrome c monolayers were immobilized onto the patterned gold substrate by self-assembly technique and their electrochemical properties were investigated through the measurements of cyclic voltammetry. Also, I–V characteristics of biomolecular multilayers consisting of cytochrome c and green fluorescent protein (GFP) were studied with a scanning tunneling microscope (STM).

The fabrication of nanodevices and nanosystems having dimensions smaller than 100 nm requires the ability to produce, control, manipulate, and modify structures at the nanometer scale. Physical and chemical nanolithography techniques have been demonstrated to be promising because of the low cost and high throughput. Although the physical and chemical nanolithography techniques can pattern small features on single chips or across an entire wafer, there are considerable challenges when dealing with complex nanostructures, alignment and multilevel stacks. In this paper, the problems are reviewed and potential solutions suggested.

The synthesis of thiol-derivatized cobalt phthalocyanine complex, 2,3,9,10,16,17,23,24-octa (butylthiophthalocyaninatocobalt(II) (CoOBTPc) is described. Cyclic voltammetric data of this complex in DMF showed five quasi-reversible and reversible, diffusion-controlled redox couples, comprising both the phthalocyanine ring and central metal redox processes. The CoOBTPc complex forms a self-assembled monolayer (SAM) on gold electrode. The investigation of the integrity of this SAM, using the established cyclic voltammetric methods in aqueous alkaline solutions, gave evidence about the formation of a stable and easily reproducible monolayer. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor in alkaline pH is limited to a potential window of between −0.20 and +0.55 V vs Ag/AgCl.

An approach toward molecular information storage employs redox-active molecules attached to an electroactive surface. The chief advantages of such molecular capacitors include higher charge density and more versatile synthetic design than is afforded by typical semiconductor charge-storage materials. An architecture containing two triple-decker sandwich coordination complexes and an S-acetylthiomethyl-terminated tether has been designed for multibit storage. Each triple decker is composed of two phthalocyanines, one porphyrin, and two europium atoms. The oxidation potentials of each triple decker are tuned through the use of different substituents on the phthalocyanines (t-butyl, methyl, H) and porphyrins (pentyl, p-tolyl). Interleaving of the four cationic oxidation states of each triple decker potentially affords eight distinct oxidation states. Two dyads were examined in solution and in self-assembled monolayers (SAMs) on a Au surface. One dyad exhibited eight distinct states in solution and in the SAM, thus constituting a molecular octal counter. The potentials ranged from −0.1-+1.3 V in solution and +0.1-+1.6 V in the SAM. Taken together, this approach provides a viable means of achieving multibit information storage at relatively low potential.

Four new manganese(III) phthalocyanines (3a–d), octasubstituted at the peripheral position with pentylthio, decylthio, benzylthio, and phenylthio groups, respectively, were synthesized. Their specific electrochemical, spectroscopic and microscopic properties in solution and as self-assembled monolayers on gold were characterized. The UV-vis spectra confirmed red-shifted Q bands for all the complexes, due to the effect of the central metal and the electron-donating substituents. Three redox couples were visible during cyclic voltammetry studies for the four complexes, and spectroelectrochemistry confirmed the couples as corresponding to Mn^IIIPc^-2/Mn^IIPc^-2 (II) (metal reduction), Mn^IIPc^-2/Mn^IIPc^-3 (III) (ring reduction) and Mn^IIIPc^-1/Mn^IIIPc^-2 (I) (ring oxidation). Electrochemistry was also used to determine the blocking characteristics of the MnPc self-assembled monolayers on gold, which proved to be highly dependent on the type of substituent. Other methods of characterization included Raman spectroscopy, atomic force and scanning electrochemical microscopy analyses of the SAMs.

The synthesis of a new carbonyl ruthenium(II) deuteroporphyrin-IX lipoic acid derivative (Ru(PLip)(CO)) (4) and its self-assembly on Au(111) surfaces were accomplished. Ru(PLip)(CO) 4 was prepared by reduction of the ester groups of carbonyl-ruthenium(II) deuteroporphyrindimethylester 1 and further esterification with D,L-α-lipoic acid 3. The self-assembly of Ru(PLip)(CO) 4 was confirmed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The S2p XP spectrum of SAM formed by Ru(PLip)(CO) showed the S2p_3/2 peak at 162.4 eV which corresponds to thiolated species bounded to gold. The influence of the interaction of porphyrin moieties on SAM stability was studied. The reductive desorption voltammogram of Ru(PLip)(CO) 4 self-assembled on gold showed an intense reduction peak at -1.02 V while when pyridine was coordinated to the central ruthenium(II) the reductive desorption peak was shifted to -0.85 V. The capacity of the modified Ru(PLip)(CO) gold electrode to detect nitric oxide (NO) was investigated by cyclic voltammetry. An irreversible reduction peak which increased with time on NO exposure was registered at -0.69 V indicating NO coordination to ruthenium(II).

Formation of self-assembled monolayers (SAMs) of three porphyrin and one phthalocyanine derivatives on thin ZnO film was studied by monitoring absorption spectra of the samples. The compounds were equipped with carboxylic or phosphate groups to bind to the surface. The SAM formation was found to be fast. The layer was formed in less than 15 min for all studied porphyrins, and 30 min was sufficient to form phthalocyanine layer. For porphyrins with different anchor groups the SAM formation was too fast to see any difference between the anchoring groups. The stability of SAMs was tested then by immersing the samples into neat solvents. Upon immersion the SAMs were gradually losing the absorbance for all the compounds with degradation trends being in line with p$K_a$ values of the binding groups of the same type. However, even for the weakest binding group the SAM was relatively stable after a few tens of minutes of washing, which was sufficient to remove physisorbed compounds but the SAM was essentially not destroyed. Comparison of SAMs on thin films with SAMs on ZnO nanorods and TiO₂ nanoparticle films indicated the same fast layer formation but relatively weaker SAMs stability, showing 20–40% faster absorption losses during the washing.

This organic thin-film systems that are based on silicon-carbon covalent bonds have been shown to lead to densely packed alkyl monolayers that have potential bio-passivation or bio-sensing applications. Presented are electrical impedance spectroscopy (EIS) characterisations of a series of alkyl monolayers [CH₃(CH₂)_mCH=CH₂; m = 7, 9, 11, 13, 15] that were covalently linked to Si(111) wafers. The characterizations reveal capacitance, conductance and geometrical properties of the monolayers. The capacitance properties yield estimates of thicknesses for the monolayers that increase proportionally with each additional CH₂ unit and are consistent with the known physical properties of these films such as dielectric constants and chain canting angles. This study illustrates that EIS charcterizations are able to probe immobilized surfaces on silicon with sub-atomic resolution which is so important in the development of practical bio-passivation or bio-sensing applications.

We present a review on recently-developed "surface-programmed assembly" strategy for massive production of nanotube/nanowire-based devices. In this process, surface molecular patterns guide the assembly and alignment of nanotubes/nanowires onto specific locations on solid substrates without relying on external forces. The assembled structures were further utilized to fabricate functional devices such as field effect transistors and sensors. Control experiments provided us rich scientific insights including "sliding kinetics" and "lens effect" during the assembly process. Since this method does not require high-temperature processing steps or unconventional fabrication facilities, it is readily available to conventional device industry and may open up new nanodevice industry based on carbon nanotubes and nanowires.

The effect of substrate chemistry on surface phase separation of polyurethane films were investigated by using self-assembled monolayer (SAM) with chemically different modifications, i.e. hydroxy (–OH) and methyl (–CH₃) end groups. Results showed that hydrophilic (–OH) and hydrophobic end groups (–CH${}_3)$ could respectively promote the aggregation of hard and soft segments at polyurethane–substrate interface, which further regulates the phase separation of polyurethane surface that contacts the substrate. The aggregation of hard segments tended to enhance the surface smoothness of polyurethane films, especially on hydrophilic substrates with hydroxy modification. Further analysis of tensile testing revealed that the regulation of surface phase separation had no effect on the shape memory effect of polyurethane films. These findings suggest that the chemical properties of the substrates could regulate the phase separation and may provide some guidance on the design of specific polyurethane with desired morphology and properties.

It is well known that dropwise condensation enhances the condensation heat transfer coefficient significantly compared with film condensation. In the present study, dropwise condensation heat transfer characteristics on titanium corrugated tubes were investigated. Two corrugated tubes with different corrugation pitch and depth were tested at the steam pressures of 5 and 10kPa. To promote dropwise condensation, silane-based SAM was coated. For bare corrugated tubes, significant enhancement of condensation heat transfer was noted, especially for the 2.1/0.2 (corrugation pitch/corrugation depth in mm) tube. For SAM-coated tubes, the heat transfer enhancement was significant (2.61 at 5kPa and 2.45 at 10kPa) for the smooth tube. For the corrugated tubes, however, the enhancement decreased to 1.78 and 2.22 for 8.7/0.4 tube and to 1.26 and 1.52 for 2.1/0.2 tube. The present results suggest that corrugations may not be as an effective heat transfer method for dropwise condensation as it is for film condensation. This result was supported by the photos taken by mist spray, which suggested that surface tension drained condensation by corrugations is not a major heat transfer mechanism for dropwise condensation on corrugated tubes.

Gas-phase synthesized vanadium–mesitylene 1:2 V(mes)₂ cluster cations were size-selectively deposited onto a long-chain alkanethiolate self-assembled monolayer-coated gold substrate under ultrahigh vacuum conditions. Examination of the resultant clusters was conducted by infrared reflection absorption spectroscopy (IRAS) and temperature programmed desorption (TPD), showing the clusters molecularly adsorbed and maintaining a sandwich structure on the substrate.

The photopatterning process of self-assembled monolayer has been used as template for fabricating biomolecular microstructures. Alkanethiolates formed by the adsorption of 1-octanethiol molecules on a gold substrate were oxidized by the irradiation of deep UV light and then developed with deionized water. The resulting positive patterned substrate was immersed into a dilute ethanolic solution of 11-mercaptoundecanoic acid (11-MUDA). Cytochrome c monolayers were immobilized onto the patterned gold substrate by self-assembly technique and their electrochemical properties were investigated through the measurements of cyclic voltammetry. Also, I–V characteristics of biomolecular multilayers consisting of cytochrome c and green fluorescent protein (GFP) were studied with a scanning tunneling microscope (STM).

Novel processes for fabricating micro/nano sized oxide devices employing self-assembled monolayers (SAM) were developed. SAM of PTCS (phenyltrichlorosilane) was modified to have a phenyl / hydroxyl-group pattern by UV irradiation using a photomask and was used as a template to arrange inorganic fine particles. Surface modification of micro/nano sized inorganic particles and chemical reactions between those particles and SAM were studied. Two-dimensional arrangement of functional particles on a SAM in a controlled manner through the formation of strong chemical bonds, such as amide or ester bonds, can be applied to the future microelectronics and photonics.