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The adsorption process, molecular arrangement and protonation behavior of self-assembled monolayers (SAMs) of bipyridine thiol on Au(1 1 1) were investigated using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), with a view towards constructing a molecular ion sensor. When the bipyridine SAMs were immersed in a strong CF 3 SO 3 H solution for protonation of the bipyridine group, additional N(1s) XPS peaks were generated at higher binding peak positions where the origin of the peak was considered to be the N–H species. We further investigated the relationship between the immersion time for the SAMs and the probability of protonation. We observed a decrease in the probability of protonation with a longer immersion time for the SAMs. We consider that both the bipyridine molecular arrangements and the molecular density on the Au surface are crucial for controlling the probability of protonation based on the STM and XPS data.

We describe a procedure for fabricating sub-5 nm gap junctions with sub-100 nm electrode-width using conventional photolithography. The fabrication procedure involves two photolithographic processes followed by shadow evaporation and electromigration. After lift-off following the second metal shadow evaporation, a nanoscale wire with a diameter less than 100 nm is fabricated along a sidewall of the second patterned photo-resist. The nanowire is cut by a milliamp current flow, then a sub-5 nm gap metal junction with a sub-100 nm electrode-width is fabricated. The temperature dependence of the conductance of the molecular wires that were bridging the junctions over the ultrasmall gap indicated a hopping conduction behaviour. The results demonstrate that these junctions can be used in the study of conductance measurements through molecular wires.

Carbon nanotube (CNT) devices have been constructed by a post-synthesis alignment, due to difficulties to form a CNT directly on a substrate, whereas CNTs have been found to grow by irradiating an electron beam onto polyyne-containing carbon. This technique is a candidate to construct a CNT device without a metal catalyst by highly geometrically resolvable electron beam lithography. Two types of polyyne-containing carbon (well-aligned and amorphous) are observed and compared by a transmission electron microscope (TEM), providing insights on the formation mechanism and requirements for the precursor. The results suggest that a substantially aligned and not-condensed morphology is essential to form CNTs.

All-trans oligo(para-phenylenevinylene) (OPV) methyl thiols of a two-ring phenylene-vinylene dimer and a three-ring trimer have been synthesized to prepare self-assembled monolayers (SMS) onto an Au(1 1 1) surface. The molecular level morphologies of the monolayers prepared on Au surfaces were probed by scanning tunneling microscopy (STM) or atomic force microscopy (AFM). The soluble dimer formed a highly ordered structure lying down on the Au surfaces. The molecules of trimer stand slantwise on the Au surfaces, but the structure of monolayers is less ordered. Another longer OPV methyl thioacetate, a slightly soluble four-ring tetramer, has also been synthesized. Although it was difficult for aggregative molecules of the longer OPV to self-assemble on Au, we could successfully insert the tetramer into tetradecane-1-thiol monolayers on Au surfaces by an exchange reaction. The mixture monolayer showed that the isolated tetramer was adsorbed almost vertically on the Au surfaces.

We are investigating electrical properties of multiwalled carbon nanotube (CNT) probes for scanning tunneling microscopy (STM). To improve the electrical conduction and reduce the contamination at the interface to the gold base, we selected conductive CNTs and heated the base and CNT during the CNT attaching process. Before STM measurements, the probes were cleaned by annealing in vacuum for 4–8 h. With these treatments, we found a small number of tips exhibiting linear metallic current–voltage (I–V) curves on Au(111), while all the CNT tips attached on gold (not heated) exhibited nonlinear I–V curves. We discuss the possibility that the metallic behavior of the CNT probes may be caused by the diffused gold atoms along the CNT surfaces by the long heat treatment.

Oligo(para-phenylene-vinylene)-methanethiol of trimer and dimer have been synthesized to prepare monolayers onto Au(111). The trimer diluted in dichloromethane glows with a brilliant blue fluorescence when excited with UV light (365 nm). The absorption and emission spectra of the dimer diluted in CH 2 Cl 2 show a blue shift. The molecular level morphologies of the monolayers prepared on gold surfaces were probed by scanning tunneling microscopy or atomic force microscopy (AFM). The dimer is entire trans isomer, which formed highly ordered self-assembled monolayers (SAMs) on Au. The trimer is a mixture of cis–trans isomers, and did not form ordered monolayers on Au. However, the trimer molecules could be embedded in dodecanethiol SAM, and showed higher conductance than oligo(para-phenylene) molecules characterized using a conductive AFM.

Polyyne-containing carbon has been shown to be converted to carbon nanotubes (CNTs) and carbon onions by irradiating an electron beam. The carbon, which is prepared by a reduction of poly(tetrafluoroethylene) (PTFE), is unstable, reactive, and it is used as a precursor to form carbon nanostructrues. A precise transmission-electron-microscope (TEM) observation reveals that some nanostructures, fibrous and spherical, are already formed in the carbon before the irradiation. The nanostructures are assumed to be formed during the reduction of PTFE. The spherical carbon is well graphitized, whereas the fibrous is not. The reduction is carried out at 0 °C, which is not enough for the fibrous carbon to be well graphitized. The findings suggest a possibility to form a CNT without an electron beam via a reactive polyyne precursor, and are expected to lead an as-designed CNT synthesis.

We demonstrate a high yield production scheme to fabricate sub-10 nm co-planar metal-insulator-metal junctions without using electron beam lithography. The fabricating procedure contains two photolithographys followed by shadow evaporation. Ultrasmall gaps were formed in the crossing region of the two metal layers during the evaporation of the second layer. The sizes of the gaps were estimated using scanning electron microscopy images. Poly (3-hexylthiophene-2,5-diyl) layers were deposited on the junctions using a special ink-jet technique. The results of the conductivity measurement of the molecular layer indicate that these junctions can be used in the study of molecular sensors.

Carbon nanotubes (CNTs) have attracted much attention for their unique properties, although their formation mechanism is not well understood. The authors have been studying a technique to form CNTs by an electron beam that is carried out in a transmission electron microscope (TEM) and is compatible with in situ and real-time observation of the growth. The observation, where a precursor (polyyne-containing carbon) is heated and irradiated by an electron beam, shows that the growth occurs in two steps: rapid formation of rodlike carbon (first step) and slow graphitization of its wall (second step). The hollow inside the CNT is not formed in the first step and develops during the second. The formation mechanism is discussed in relation to in situ observations.

Polyyne-containing carbons are transformed to multi-wall carbon nanotubes (CNTs) in a transmission electron microscope. This technique has an advantage to observe the CNT growth in an in-situ way, and the CNTs have been found to grow in a two-step process: quick formation (a few seconds) of rod-like carbons, and slow formation (1 min) of the hollows inside the rods accompanied by graphitization of the walls. The technique has a possibility to be applied to fabricate CNT devices. Thus the growth conditions (heating temperature and its duration) were investigated and are discussed in this paper. The heating duration affects the number of graphene layers of the wall, while the temperature does not affect the length, the diameter, and the number of graphene layers. The longer heating duration, which corresponds to less supply of the precursor due to its evaporation in vacuum, leads to thinner walls and more round-shaped caps. This finding corresponds to the formation mechanism, i.e. growth from the bottom in a solid phase, which has been assumed for this technique.

The mechanism of the carbon nanotube (CNT) formation and its graphitization has not been well understood and is still under controversy. The authors have been studying a new process to form CNTs, where polyyne-containing carbons are heated and irradiated by an electron beam in a transmission electron microscope (TEM). The technique is compatible to an in-situ observation and was applied to a high-resolution TEM (HRTEM) to elucidate the graphitization mechanism. The observation shows that micro-graphenes exist from the beginning of the formation process and develop to form highly ordered graphene layers through fusion and rearrangement of the premature layers, accompanied by evaporation of micro-graphenes. The CNT formation mechanism focusing on its graphitization is presented and discussed.

A new way to form carbon nanotubes (CNTs), carbon nanocapsules (CNCs), and carbon nanoparticles (CNPs), where polyyne-containing carbons are heated and irradiated by an electron beam in a transmission electron microscope (TEM), has been developed. The technique was applied to carry out an in-situ observation of those formation processes. Though the CNPs have been reported to be formed accompanied by the CNTs, the CNPs and the CNCs were found to be formed independently from the CNTs. The CNTs are preferentially inside of the polyyne-containing carbon films, while the CNPs/CNCs are outside of the films. The difference of the inside and the outside are discussed to lead to understanding of the CNC and CNP formation process. From the in-situ observation, the existence of metal particles, the high surface energy, the high wettability, and the high viscosity of the polyyne-containing carbons are assumed to be relevant to the preferential formation of CNCs/CNPs to CNTs.

We investigated an annealing effect of self-assembled monolayers (SAMs) generated from derivatives of terphenylmethanethiols and tetradecanethiol (C14) on Au(111) using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy, and contact angle measurement. STM data revealed that the molecules were partially desorbed by the annealing process at temperatures where the contact angle of the hexadecane began to decrease. The decreases in contact angles of both the CF3- and CH3-terminated terphenyl SAMs were caused by annealing at 180 °C for 1 h, while a similar decrease began at a lower temperature of 150 °C in the C14 SAMs. From the STM data, a large amount of CH3-terminated terphenyl molecules remained after annealing at 180 °C for 3 h, while a small amount of molecules were observed in the other two SAMs. These data demonstrate that the CH3-terphenyl-derivatized thiol SAM had the highest thermal stability of the three SAMs, and the molecular backbone structure and end group were crucial for de...

Barrier height of self-assembled monolayers (SAMs) on Au(111) was measured using scanning tunneling microscopy (STM) with a vertical modulation. We obtained nanometer scale STM images of alkanethiol SAMs, and binary component SAM films fabricated by an implantation technique. Local barrier height on the alkanethiol SAM at the depressions and the domain boundaries is larger than that on the domains where the molecular lattice is visible, probably due to the molecular density or orientation. A molecular resolution contrast was obtained at a conjugated molecule embedded in the alkanethiol SAM, reflecting the difference in the molecular species. We found that the tip-sample interaction force affects the barrier height measurements, especially when the tunneling gap is small, e.g., on nonanethiol SAM at the tunneling resistance smaller than 50 GΩ.

We have investigated an insertion process of conjugated molecules, 4-biphenylmethanethiol (BP) and [1,1′:4′,1″-terphenyl]-4-methanethiol (TP) into preassembled n-alkanethiol self-assembled monolayers on Au(111) using scanning tunneling microscopy (STM). Ex situ STM observation revealed that the insertion process is dependent on an organic solvent in which the conjugated molecules dissolve. The insertion of conjugated molecules with three phenyl rings (TP) was faster than that with two phenyl rings (BP). By analyzing the STM images, the lower limits of resistances for single BP and TP molecules were obtained as 22±5 and 36±5 GΩ, respectively.

We have studied the phase-separation of self-assembled monolayers (SAMs) of dialkyl disulfides on Au surface. Initially, the heat-induced phase-separation of SAMs consisting of unsymmetric disulfide molecules (CF 3 (CF 2 ) 5 (CH 2 ) 2 SS(CH 2 ) 7 CH 3 ) of hydrocarbon and fluorocarbon chains was investigated. We proved that the dimer structure cleaved on the Au surface. Subsequently, we formed one-dimensional nanostructures utilizing an anisotropic phase-separation of SAMs consisting of a mixture of the above unsymmetric disulfide and a symmetric disulfide of hydrocarbon (CH 3 (CH 2 ) 7 SS(CH 2 ) 7 CH 3 ). The wire-like structure with a width of 5 nm and a length ≈100 nm was observed by scanning tunneling microscopy.

We have succeeded in the formation of one-dimensional wire-like structure in the self-assembled monolayers (SAMs) made from the mixture of an unsymmetric disulfide consisting of hydrocarbon and fluorocarbon chains and a symmetric disulfide of hydrocarbon chains on Au(111). By focusing on co-adsorption process of the above two disulfide molecules onto the Au surface, it is found that an exchange reaction should take place and a part of the symmetric disulfide molecules was replaced by the unsymmetric disulfides during immersion in the solution. The molecules having fluorocarbons were also found to replace hydrocarbons on Au surface.

Alkanethiol self-assembled monolayers (SAMs) on Au(111) deposited in a vacuum were studied on the nanometer scale using a scanning tunneling microscope (STM). After about 17 h from the gas dose of 4200-6000 langmuirs nonanethiol, two-dimensional crystallized domains were observed. The areas covered with the molecules and the bare gold surface were identified by topography, current-voltage characteristics, and the threshold voltage required to modify the surface. By applying 2.6-3.0 V to the sample, we could extract molecules and create holes with diameters of 2-5 nm in the SAM film. Applying 14 voltage pulses of 2.6 V to a 10 nm diameter circle on the sample locally removed the SAM film. We could then observe the dynamic formation process of the SAM film with molecular resolution using the STM, and within 5 min, the removed area was seen to be almost recovered with the molecular lattice except for a small number of incurable defects. Since the recovered area looked identical to the pristine film, we concluded that the molecules can be locally extracted without causing damage to the gold substrate under this condition.

We have studied phase-separation and patterning of self-assembled monolayers (SAMs) on Au(111). In this study, we used an ethanol solution of mixed unsymmetric disulfide with hydrocarbon and fluorocarbon chains [CF3(CF2)5(CH2)2S–S(CH2)7CH3], and a symmetric disulfide of hydrocarbon chains [CH3(CH2)7S–S(CH2)7CH3], to derive the SAMs. Then we obtained a wire-like structure with a width of 5 nm extending to about 100 nm in these SAMs after they were annealed at 100°C for 8 h. The formation of nanowires indicated that anisotropic nucleation of hydrocarbon parts along the [112] direction of the Au surface occurred.

We observed molecular resolution images of dibutylamino-triazine-dithiol films on Au(111) with scanning tunneling microscopy. In contrast to the more extensively studied alkanethiols which have only one binding site, the triazine-dithiol has two possible binding sites. The periodic structure of bright spots with different shapes and contrast aligned along the 〈112〉 directions with a spacing of 0.75 nm and 1 nm were imaged. The domain size of the film is 15 nm at most, which is considerably smaller than that of alkanethiol films. The structural stability upon annealing indicates a stronger binding energy of the triazine-dithiol as compared with the alkanethiol. We propose models of the molecular arrangement assuming that the two sulfur atoms of the molecule bind to the substrate.

We observed a step formation on Au (111) surface with a scanning tunneling microscope (STM) after the disappearance of the \sscriptsize(22 \atop-1 0 \atop2) reconstruction. Upon exposure to air, the spacing of the reconstructed pattern increased, and finally the pattern disappears. By applying negative voltage pulses to the STM tip, we made depressions of 1–6 atomic layers deep on this surface. Then suddenly a monoatomic step appeared, running almost straight, but detouring around one of the depressions. Since the depth of each depression remained the same as that before the step formation, the step was generated by a dislocation and not by a movement of a top surface layer. The relative position of the step to the detoured depression suggests that the dislocation was created on the surface and then penetrated into the bulk.

We have investigated the control of bundle structures of single-walled carbon nanotubes (SWNTs) in organic solvents using atomic force microscopy (AFM) and transmission electron microscopy (TEM). We have reported herein that organic amines are effective in untangling the bundled SWNTs in N,N-dimethylformamide (DMF). When Bucky paper was sonicated in DMF with 1% organic amine for 1 h, AFM images clearly showed mainly individual SWNTs. The time-dependent TEM observation revealed that the role of amine is to prevent rebundling of SWNTs in organic solvents.

A selective formation between carbon nanotubes (CNTs) and carbon nanoparticles (CNPs) has been found, where polyyne-containing carbons are heated and irradiated by an electron beam in a transmission electron microscope. The CNPs are formed outside the polyyne-containing carbons that are partially damaged by water and oxygen, while the CNTs, inside the carbons that are protected. This gives insight on a CNT and CNP formation mechanism, which is discussed in this paper.

When molecules exist between electrodes, the barrier shape is deformed. A square one-dimensional potential model was made and the I–V curves were calculated using the free electron and the WKB approximation. The curves show a characteristics change when the adsorbate has the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) near the Fermi level. It indicates that the LUMO's contribution to the tunneling current is larger than that of the HOMO. The charging effect is also discussed on the basis of the uncertainty principle. Provided an isolated liquid crystal molecule is observed, the charging energy is estimated to be about 1 eV. Since this energy is larger than the thermal energy at room temperature, it should be detected. However, the lifetime of the electron is estimated to be short enough to blur the effect. The lifetime is expected to limit the energy resolution of the tunneling spectroscopy as well.

Since a scanning tunneling microscope (STM) was developed, an observation of living cell surface has been one of the final aims in the biological application of STM. By developing a new style of STM which was combined with an optical microscope and with a novel system for the centering of both images, we successfully got the STM images of living cell surface of T24 cells (human bladder cancer cell line) and CHO cells (Chinese hamster ovary fibroblast) cultured on highly oriented pyrolytic graphite under the appropriate condition (V greater than 8.0 V, I less than 0.2 nA). Unexpectedly, the living T24 cell showed a slightly uneven surface with a steep foot slope. The CHO cell showed more rough surface with steeper slope of cell foot. Although the STM system had a fine spatial resolution less than 3 nm, the profile of living cell surface covered with electrolyte was clear only when the scanning area was more than 10 microns square.

Molecules of liquid crystals(LCs) adsorbed on highly-oriented pyrolytic graphite(HOPG) were imaged by scanning tunneling microscopy(STM). Planar layer structures induced by the HOPG surface were obtained. Molecular packing models for the STM images are introduced with the aid of a molecular orbital calculation. Also we discuss the rearrangement of the LC alignment during the continuous STM measurement.

Adsorbed molecules of copper phthalocyanine (CuPc) and liquid crystals on graphite were measured by scanning tunneling microscopy (STM) and spectroscopy (STS) in air. The islands of molecules of CuPc were detected by STM. Tunneling spectra taken simultaneously with STM showed characteristic peaks correlated with local topographic features. In the observation of a nematic liquid crystal on graphite, one reproducible molecular pattern was found, for which a model of molecular ordering is proposed. Ordinary spectroscopy was found to be difficult due to a large polarization current caused by the liquid surrounding the tip. Bias voltage dependent images of the molecules which demonstrate electronic structure effects were obtained.

In 1994, individual molecules in alkanethiol self-assembled monolayers (SAMs) were imaged using scanning tunneling microscopy (STM). Since this breakthrough, the electric conduction of individual molecules has been estimated using scanning probe methods. In this chapter, we describe methods for evaluating the electric properties of conjugated molecules embedded in alkanethiol SAMs. First, the electrical conduction and barrier height measurements of SAMs and single molecules using STM are described. Here we discuss a method for estimating the molecular resistance based upon analysis of STM cross-sectional profiles. Secondly, the electrical conduction measurements of SAMs using conductive probe AFM (CP-AFM) are described. Finally, we describe related methods that enable applications like molecular devices.

Because graphene films have one-atom thickness, the morphology of the transparent sheets could have a greater effect on the performance of organic light-emitting diode (OLED) devices with graphene films than on that with indium tin oxide (ITO). In this study, we have evaluated the polymer OLED devices with graphene films synthesized by plasma treatment on poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) sheets having high flatness. The results imply that the surface roughness of the transparent sheets predominantly affects the luminescence of polymer OLED devices with graphene films. The suppression of leakage current and a luminescence higher than 8000 cd/m2 at 15 V were attained for the devices on the transparent sheet with higher flatness in spite of the presence of large sharp spikes.

Voltage‐dependent images of liquid crystals on graphite were observed in air by scanning tunneling microscopy (STM). Molecular rows of liquid crystals and the atomic pattern of the graphite substrate were imaged with high (above 1 V) and low (below 0.1 V) bias voltages, respectively. Patterns of molecules, grain boundaries, and distinguishable defects of the liquid crystal arrangement were reproduced even after imaging the substrate in the same area. This indicates that the graphite lattice can be seen by STM without touching or disturbing the adsorbed molecules on it. A resonant tunneling model is proposed to explain the phenomenon.

We have confirmed that a self-assembled monolayer (SAM) film of octadecanethiol (ODT), CH3(CH2)17SH, can be formed on a cleaved GaAs (110) surface, by using an atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Circular depressions were observed on the surface after film formation. The area of the circular depressions increased with immersion time, indicating that the solution oxidized the interface between ODT molecules and the GaAs surface, resulting in removal of ODT molecules. The oxidation was considerably faster in pure ethanol solution than that in ODT solution, demonstrating that the SAM film protects the GaAs surface from oxidation. High-resolution lateral force microscope (LFM) images revealed a periodic structure that had two types of lines: periodic lines 0.57 nm apart and lines rotated 55° with respect to them. A structural model of the SAM successfully explained both the features in high-resolution LFM images and the depression depth observed in AFM images.

We studied the ion catching behavior of nanoscale molecular domains of bipyridine thiol embedded in alkanethiol self-assembled monolayers (SAMs) on Au(111) by scanning tunneling microscopy (STM) to construct and demonstrate the possibility of a molecular sensor. We used a bromine-terminated bipyridine thiol molecule, in which a bipyridine unit is connected to a conjugated phenylene–ethynylene system, and then successfully observed the protonation response of the bipyridine molecule. When the Au substrate was immersed into dilute CF3SO3H solution, the apparent height of bipyridine spots became lower after this treatment. On the other hand, when the substrate was immersed into 0.1 mM Pd complex solution, the apparent height of bipyridine spots became higher than that in the initial state. These findings demonstrate the possibility of constructing cation sensor using several molecular domains, and the different ion catching behaviors of bipyridine molecules may lead to the development of highly selective molecular sensors.

We synthesized the peptide nanorings of cyclo[-(D-Ala-L-Gln)3], cyclo[-(D-Cys-L-Gln)3], cyclo[-D-Cys-L-His-D-Ala-L-Asn-Gly-L-Gln-] and cyclo[-(L-Gln)5], and studied the way in which the difference in the type and/or number of component amino acid residues changes the self-assembling morphology of the nanorings on gold substrates by atomic force microscopy. The study revealed that cyclo[-(D-Ala-L-Gln)3] formed nanotube bundles through inter-ring hydrogen bonds, while the nanorings of cyclo[-(D-Cys-L-Gln)3] adhered to the gold surface directly due to the high affinity of thiol to gold. In contrast, a random amino acid sequence of cyclo[-D-Cys-L-His-D-Ala-L-Asn-Gly-L-Gln-] resulted in many isolated nanotubes, which were first observed in the present study. While the D,L-peptide nanotubes have very straight forms, the homo-L-peptide of cyclo[-(L-Gln)5] formed interesting randomly branching nanotubes that were entwined and grew on the substrate. Scanning tunneling microscopy was also performed and high-resolution images of both the peptide nanotubes and the nanotube bundles were obtained.

We demonstrate a procedure for fabricating back-gate-type sub 5 nm gap junctions without using electron beam lithography. The fabricating procedure contains two photolithographic processes followed by shadow evaporation and oxygen plasma ashing. Oligo(para-phenylenevinylene) trimers (OPV3) attached to methylthiol at both ends were bridged between these junctions. The temperature dependence of OPV3 conductance indicated the characteristic behavior of hopping conduction. The results indicate that these junctions can be used in the study of conductance measurements through molecular wires.

We observed image changes induced by the polarity change of electric fields, by scanning tunneling microscopy (STM), for pre-assembled alkanethiol self-assembled monolayers (SAMs) embedded with small amounts of the bipyridine moiety. In the case of bipyridine dithiol molecules, STM experiments revealed that the apparent thickness of the molecular protrusions was larger under the positive bias. In this case, it was considered that the image change was caused by a conductance difference with different polarities of the tip bias. However, for the bromine-terminated bipyridine molecules, the thickness of the molecular protrusions was larger under negative bias, contrary to the case of dithiol type molecule. We considered that this image change was caused by an actual molecular conformational change because of the strong dipole moment of bromine-terminated bipyridine molecule.

We attached multiwall carbon nanotubes (CNTs) to the top of a Au tip using a manipulation system, and used the tip as a probe for a scanning tunneling microscope (STM). We measured Au(111) surfaces using an ultrahigh-vacuum-STM with an electrochemically etched Au tip and a multiwall CNT tip attached to the top of the Au tip. When the CNT tip was cleaned by heating in a coil filament, we observed the 22×√3 reconstruction of clean Au(111). With an uncleaned CNT tip, many adsorbates were observed along the reconstruction, which may be contaminants desorbed from the CNT tip. The stability of the CNT tip depends on its length, diameter and the contact to the base material. Thus far, we have obtained good resolution using a CNT with a length of less than 200 nm. We found that when the CNT was not vertical to the sample surfaces, the tip-surface interaction increased the stability of the CNT tip.

We investigated binary-component self-assembled monolayers (SAMs) and fabricated small domains of a conjugated molecule in preassembled n-alkanethiol SAM films using an implantation technique. We measured the height of the domains by scanning tunneling microscopy and found that, when the size is smaller than ∼5 nm, the observed height of the conjugated molecular domains depends on their lateral size. This size dependence of the domain height indicates that the vertical conductance of the domains should depend on the domain size (number of molecules). When many molecules are interacting, the molecular orbitals are affected, which should cause changes in the electron tunneling and conductance. The degree of the intermolecular interaction was estimated by introducing an effective conductance between the molecules using a classical model similar to a resistor network.

Heat-induced phase separation of fluorocarbon-hydrocarbon self-assembled monolayers (SAMs) on a Au(111) surface was studied by scanning tunneling microscopy (STM), atomic force microscopy (AFM) and friction force microscopy (FFM). Phase-separated domains were depressed by 0.3 nm with a lateral dimension of 20–200 nm. The friction forces on the higher parts were smaller than those on the lower domains. The higher parts were assigned to the hydrocarbon chains, because the fluorocarbon chains should have a larger friction force acting on them than the hydrocarbon chains against the silicon nitride tip. Phase separation suggests cleavaging of the S–S bonds of disulfides in the SAMs. XPS measurements clearly showed an increase in the isolated Au–S binding species, suggesting the existence of the thiolate (monomer).

Adsorption and thermal or photodecomposition of triethylgallium (TEG) and trimethylgallium (TMG) on Si(111)-7×7 were investigated using a home-built scanning tunneling microscope (STM), Auger electron spectroscopy (AES), and thermal desorption spectroscopy (TDS). Adsorption of TEG and TMG at room temperature gave bright protrusions of Ga(C2H5)x(a) and Ga(CH3)x(a) (x=2, 3) on atop sites of Si adatoms with a slight preference for center adatoms over comer ones. The Ga(C2H5)x(a) and Ga(CH3)x(a) species were decomposed by UV irradiation probably due to absorption of UV photons by these adsorbates. Thermal decomposition of TEG on the 7×7 surface led to severe carbon deposition, particularly at low initial coverage of TEG, in contrast to the result reported on Si(100)-2×1.

Modifications of the phase‐separated surface of polystyrene–polyethyleneoxide (PS‐PEO) blend films were carried out by using an atomic force microscope. On PEO, contrary to PS, a scanning of a tip with large forces of 50 nN resulted in a modification of surface and increased the elastic stiffness. The modification was seen as regular stripes perpendicular to the scanning direction, which may be caused by the rearrangement of the PEO folding structure as a result of a balance of various forces during scanning. This rearrangement may increase the density of the films and hence causes the increase of the elastic stiffness. On the stripes, molecular images were obtained with friction force microscope, reflecting the folding structure of PEO.

The modification of gold surfaces with scanning tunneling microscopy in ultrahigh vacuum was investigated. At a tunneling resistance higher than 1 GΩ, a hole was created by applying a negative voltage pulse to a gold tip, and a mound by a positive one. The existence of a critical field together with the polarity dependence suggests that a mechanism of the modification would be the field evaporation of positive Au ions. On the other hand, at a low resistance, a mound adjacent to a hole was often created by the negative pulse and the current kept flowing even after the voltage pulse. These results indicate that the formation of a mound in the case of negative pulses is a result of necking after the massive transfer of gold from the surface to the tip apex. The size of the hole created by applying the negative pulse with the threshold voltage decreased as the initial tunneling resistance decreased.

Adsorption and photochemical decomposition of triethylgallium [Ga(C2H5)3] on Si(111) at room temperature were investigated by means of low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), scanning tunneling microscopy (STM) and mass spectroscopy (MS). Ga(C2H5)3 was adsorbed on Si(111) until its saturation, at which point LEED and STM indicated disordered adsorption of the molecules. Irradiation of ultraviolet light onto the Ga(C2H5)3-saturated surface caused carbon incorporation contrary to the case of pyrolysis. Ethyl species were proposed to result from the photon absorption processes of the molecules.

Atomically flat substrates of gold were prepared by evaporation onto cleaved mica for scanning tunneling microscopic and spectroscopic studies of adsorbates. The surface morphology was investigated with a scanning tunneling microscope (STM) and a scanning electron microscope. The STM data were analyzed through a fractallike statistical procedure. Bulk crystallography was also investigated by means of X-ray diffraction. On the gold substrate showing hydrophilic characteristics, monolayer Langmuir-Blodgett film of cadmium arachidate was deposited, and successfully imaged by STM.

It is reported that small pits are made in a graphite surface by applying voltage pulses using a scanning tunneling microscope (STM). A shallow hole, whose diameter was about 10 nm, was formed by creating the pits along the circumference of a circle. The depth of the hole was about 0.35 nm, which is very close to the interlayer distance of graphite. The result indicates the possibility of cutting a piece of layered material by monolayer thickness using an STM. The chemical process of pit formation is discussed.

Molecules of liquid crystals adsorbed on graphite were observed by scanning tunneling microscopy (STM). Liquid crystals of both smectic and nematic phases provided periodic STM images of 3-nm-spacing lines, seemingly composed of molecules with their axes vertical to the line. Detailed investigation of the images revealed that several different patterns existed in smectic liquid crystal. On the other hand, nematic liquid crystal exhibited one reproducible pattern. Monolayer, multilayer, and dimer-based molecular arrangements are discussed. Models for the molecular arrangement of the nematic liquid crystal are proposed.

The scanning tunneling microscope (STM) was invented less than five years ago by G. Binnig and H. Rohrer. In 1986 they were honored with the Nobel prize in physics, together with E. Ruska who invented the transmission electron microscope in 1933. The principles of the STM and the construction of the instruments are described by dividing them into several key technologies: (i) vibration isolation; (ii) course and fine positionings and scannings; (iii) thermal drift, hysteresis, and creep of piezoactuaters; (iv) metal probes; and (v) electronic control circuits. Surface structures recently observed by the STM on metals, semiconductors, etc. are reviewed. The future development of the STM is mentioned very briefly.

Vibration isolation technology for scanning tunneling microscopy (STM) to suppress the external mechanical perturbation down to a subatomic scale is described. The system is simplified into two subsystems, a tunneling assembly and a supporting table. Each of them has its own mechanical eigenfrequency. The principle of the isolation exists in making the two eigenfrequencies very different from each other. A theory of isolation developed is based on a model of multiply coupled oscillators with damping. Experimental results of the isolation characteristics for the two types of isolators constructed, one consisting of two‐stage coil springs and the other of multiply stacked metal plates with rubber pieces among them, are well explained by the theory. STM images of graphite are obtained by using these isolators combined with various tunneling assemblies. Thereby the basis for design of the isolators is clarified.

A helium refrigerator system equipped with low-temperature centrifugal compressors is proposed. This refrigerator, named L-system refrigerator, is operated almost below the temperature of liquid nitrogen. It has higher reliability and capability of long time continuous operation free from the contamination of helium with oil and from wear of moving part. It also has an advantage that the control of refrigeration power is easily achieved by adjusting the speed of compressors. The direct input power to the L-system refrigerator is lower, but it thermal efficiency is almost same as the conventional one, when the energy necessary to make liquid nitrogen is taken into account.A L-system refrigerator with refrigeration power of 1, 500W at 20K level is designed based on the experimental results of the low-temperature centrifugal compressor developed at Electrotechnical Laboratory. Its refrigeration power at 20K varies from 930W to 2, 000W almost lineary by changing the rotational speed of the compressors from 500rps to 720rps. The direct input power is 17kW to 35kW, but it consumes 310kg to 630kg of liquid nitrogen par hour.Large capacity helium refrigerators with high reliability and efficiency will be materialized when L-system refrigerators are built near the region where a large bulk of coolant is easily obtained, such as a LNG repository.

A small‐size scanning tunnel microscope (STM) developed to provide an easy operation for both tip and sample setting is applied to three‐dimensional topographic measurements of microlithography patterns. The patterns having a grid structure with 160 nm in periodicity, 20–30 nm in groove width, and 40–50 nm in groove depth are fabricated on Si substrates using a technique of enhanced chemical etching by focused ion beam. The STM images are compared with two‐dimensional scanning electron microscope images. Fairly good resolution of topographic maps for a large area is obtained for the fine groove structures. The large‐area images are further processed to correct the piezoscanners’ nonlinearity, which becomes conspicuous for large‐area scanning.