Younger generations have a better chance than their predecessors to make breakthroughs in the long-term difficult area of Solar to Chemical Energy Conversion, as evidenced in the history of many great inventions like the piston steam engine. In the next half a century or so, we will hopefully succeed in producing artificial fuels at reasonably low costs by utilizing solar energy without the expense of fossil fuels, through the development of the research fields discussed in this book.

We report here a theoretical study with quantum chemical calculations based on experimental results to understand highly efficient reduction of CO2 to formic acid by using zinc under hydrothermal conditions. Results showed that zinc hydride (Zn-H) is a key intermediate species in the reduction of CO2 to formic acid, which demonstrates that the formation of formic acid is through an SN2-like mechanism.

Chemical force microscopy using probe tips subjected to liquid-phase chemical modification enables the study of intermolecular forces on a nanoscale, as well as imaging of the chemical inhomogeneity of a sample’s surface with high spatial resolution. However, in adhesive force measurements, the adhesive force between the tip and the sample could easily be affected by interactions caused by molecules in both the contact and the noncontact parts. A novel method involving local chemical modification of the tip is presented. The method is performed by adding a solution of a modification reagent in ethanol when the cleaned tip is approaching the substrate’s surface. The adhesive forces between the substrate’s surface and various types of tips were investigated using atomic force microscopy. This novel method could be helpful for increasing the resolution of chemical force microscopy and for measuring the contact area between the tip and the substrate’s surface.

In order to improve power efficiency of organic electroluminescent (EL) devices, i.e., ITO/TPD/Alq3/Al, enhanced electron and hole injection at Alq3/Al and ITO/TPD interface, respectively, was attempted by designing proper charge injection at both interfaces. Enhanced charge recombination at TPD/Alq3 was also demonstrated. Here, ITO, TPD, Alq3, and Al are abbreviations for indium-tin-oxide, N, N’-diphenyl-N, N’-bis(3-methyl-phenyl)-1, 1’-biphenyl-4, 4’-diamine, tris(8-hydroxyquinoline) aluminum, and metal aluminum, respectively. Enhanced electron injection by introducing a thin layer of Li salts of fluoride, acetate, and benzoate was described. We have found that the electron injection was improved in the order of Li+, Na+, K+, Rb+, and Cs+, and Cs salts exhibited the best EL performance. Chemical modification of ITO has been attempted to fine-tuning the work function of ITO in order to reduce hole injection barrier height. EL characteristics were improved dramatically using ITO modified with H-, Cl-, and CF3-terminated benzoyl chlorides. By using reactive -COCl groups, ITO surfaces were covered quickly and the work function of ITO was changed widely depending upon permanent dipole moments introduced inpara-position of benzoyl chlorides. Correlation between the change in the work function of ITO and the EL characteristics was examined. The improvement of charge recombination was attained by increasing the interfacial areas, i.e. introducing a mixed layer of TPD and Alq3, or inserting a thin film of rubrene with a higher recombination efficiency.

Indium-tin-oxide (ITO) is the most widely used material as a transparent electrode due to its excellent transparency and high conductivity. The devices based on bare ITO, however, exhibited inefficient hole injection due to insufficient high work function and required high drive voltages. Thus, various surface treatments of ITO have been attempted to change the work function of ITO in order to reduce the hole injection barrier height. Electroluminescent (EL) characteristics of devices were improved dramatically using ITO chemically modified with H-, Cl-, and CF3-terminated benzoyl chlorides. By the use of reactive -COCl groups, ITO surfaces were modified quickly and the work function of the modified ITO was changed widely depending upon the permanent dipole moments introduced inp-position of benzoyl chloride. We also compared the performance of the EL devices with ITO modified with different binding groups (-SO2Cl, -COCl, and -PO2Cl2) of p-chlorobenzene derivatives. Finally, we examined the correlation between the change in the work function and the performance of the EL devices by the chemical modification and found that the enormous increase in ITO work function up to 0.9 eV is possible using phenylphosphoryl dichloride with a CF3-terminal group inp-position.

Antisticking layers (ASLs) on UV nanoimprint lithography (UV-NIL) molds were characterized by scanning probe microscopies (SPMs) in addition to macroscopic analyses of work of adhesion and separation force. Local physical properties of the ASLs were measured by atomic force microscopy (AFM) and friction force microscopy (FFM). The behavior of local adhesive forces measured with AFM on several surfaces was consistent with that of work of adhesion obtained from contact angle. The ASLs were coated by two different processes, i.e., one is a vapor-phase process and the other a spin-coating process. The homogeneity of the ASLs prepared by the vapor-phase process was better than that of those prepared by the spin-coating process. In addition, we measured the thicknesses of ASL patterns prepared by a lift-off method to investigate the effect of the ASL thicknesses on critical dimensions of the molds with ASLs and found that this effect is not negligible.

Most problems in photomask fabrication such as pattern collapse, haze, and cleaning damage are related to the behavior of surfaces and interfaces of resists, opaque layers, and quartz substrates. Therefore, it is important to control the corresponding surface and interface energies in photomask fabrication processes. In particular, adhesion analysis in microscopic regions is strongly desirable to optimize material and process designs in photomask fabrication. We applied the direct peeling (DP) method with a scanning probe microscope (SPM) tip and measured the adhesion of resist patterns on Cr and quartz surfaces for photomask process optimization. We measured adhesion and frictional forces between the resulting collapsed resist pillar and the Cr or the quartz surface before and after the sliding. We also studied the effect of surface property of the Cr and quartz surfaces to resist adhesion. The adhesion could be controlled by surface modification using silanes and surface roughness on Cr blanks. We also discuss the relationship between the adhesion observed with the DP method and the properties of the modified surfaces including water contact angles and local adhesive forces measured from force-distance curves with an SPM.

We demonstrate here that light emission of an electroluminescent (EL) device was enhanced on chemically modified ITO areas over a patterned ITO anode with a self-assembled monolayer (SAM) of 4-chlorophenylphosphoryl dichloride (ClC6H4OPOCl2: CPPDC) prepared by micro-contact printing (μ-CP). The EL device was fabricated by vapor-depositing a hole transport layer, a light emitting and electron transport layer, and a C6H5COOLi/Al bilayer cathode on the patterned ITO anode. The enhanced light emission under lower drive voltages on the modified areas can be interpreted by the increase in the work function of the ITO covered with the SAM measured with a Kelvin probe force microscope (KPFM) and thus the decrease in the hole injection barrier height. In addition, we could demonstrate the much smaller pattern images than the previously reported ones [F. Nüesch, Y. Li, L.J. Rothberg, Appl. Phys. Lett. 75 (1999) 1799] by the use of ink-pads.

We studied stability of indium-tin-oxide (ITO) surfaces chemically modified with -SO2Cl and -PO2Cl2 binding groups of para substituted benzene derivatives as well as those oxidized with UV ozone by measuring time dependence of the work function and water contact angle after their surface modifications. It seems most likely from the effect of water contents in environments upon their time changes that water is the primary reactant for degradation of the chemically modified and oxidized ITO surfaces.

Most problems in photomask fabrication such as pattern collapse, haze, and cleaning damage are related to the behavior of surfaces and interfaces of resists, opaque layers, and quartz substrates. Therefore, it is important to control the corresponding surface and interface energies in photomask fabrication processes. In particular, adhesion analysis in microscopic regions is strongly desirable to optimize material and process designs in photomask fabrication. We applied the direct peeling (DP) method with a scanning probe microscope (SPM) tip and measured the adhesion of resist patterns on Cr and quartz surfaces for photomask process optimization. We also studied the effect of tip shape on the reproducibility of adhesion measurements and the dependence of collapse behavior on the resist profile. We measured lateral forces between the resulting collapsed resist pillar and the Cr or the quartz surface before and after the sliding and related these observed lateral forces to the static and kinetic frictional forces, respectively. We also studied the effect of surface modification of the Cr and quartz surfaces with silanization reagents on adhesion measured with the DID method. Resist adhesion could be controlled by surface modification using silanes. We also discuss the relationship between the adhesion observed with the DIP method and the properties of the modified surfaces including water contact angles and local adhesive forces measured from force-distance curves with an SPM. (C) 2009 The Japan Society of Applied Physics

To understand the origin of the open-circuit voltage of heterojunction photovoltaic (HJ-PV) cells with small-molecular-weight organic thin films, HJ-PV cells with ITO/donor (20 nm)/fullerene (40nm)/bathocuproine (10nm)/Al were studied using three kinds of donors and four types ITOs with different work functions.

We demonstrate here a new sample preparation method satisfying requirements for ideal single-molecule conductance measurements using break junction methods. By diluting a targeted dithiol in an insulating self-assembled monolayer of a short methane thiolate with an adamantane cage on Au(1 1 1), we succeeded in constructing reproducible conductance histograms with clear peaks for the dithiol using all measured conductance traces.

In this study, we fabricated glass substrates covered with hydrophilic and hydrophobic silanes to investigate the effect of wettability of these surfaces on DNA molecular combing. As the hydrophilic and the hydrophobic silane, a mercapto-terminated (HS(CH2)3Si(OCH3)3) and a methyl-terminated one (CH3(CH2)3Si(OCH3)3) were used, respectively. The wettability was controlled by changing the molar ratio of the two components in the mixed monolayer. From the results of the DNA molecular combing, it was shown that the mercapto terminals on the surfaces were hardly dissociated into S− groups in aqueous buffers with pH 5.5 and 8.0. In addition, it was found that the length of the immobilized DNA molecules on the hydrophilic surfaces was shorter than that on the hydrophobic ones.

We studied a surface modification technique for indium tin oxide (ITO) anodes without precleaning and resist banks for manufacturing organic light-emitting diodes (OLEDs) by inkjet printing. The ITO surface modified by inductively coupled plasma (ICP) with an optimized CF4/O2 (7:3) gas mixture improved both its hydrophilicity and its work function, while the resist surface treated by the plasma became hydrophobic. The resist and ITO surfaces treated by plasmas of various gas mixtures (i.e., CF4, CF4/Ar (1:2), CF4/O2 (x:1; x=1, 7/3, 4, and 9) were analyzed by X-ray photoelectron spectroscopy (XPS) of the C 1s, F 1s, O 1s, and In 3d5/2 core levels. On the uncleaned ITO surfaces modified by CF4/O2 plasmas, organic contaminants were removed more efficiently and the deposition of CFx on the remaining contaminants decreased with increasing oxygen. The amount of F in the form of InFx increased using the CF4/O2 (7:3) plasma in comparison with that using the CF4/Ar and CF4 plasmas. We investigated the effect of adding oxygen to CF4 on the change in gaseous species produced in the plasma chamber by mass spectrometry. In the CF4/O2 (7:3) plasma, the peak intensities of F+, HF+, F2+, O+, and O2+ were higher than those in the CF4 plasma. The results suggest that In2O3 was generated by the oxidation of indium with O, and InFx was generated by the fluoridation of indium with HF. By introducing InFx onto ITO surfaces using the CF4/O2 plasma, the hole-injection energy barrier could be reduced.

Stretch lengths of pure gold mono-atomic wires have been studied recently with an electrochemical scanning tunneling microscope (STM). Here, we will report a study of stretch lengths of gold mono-atomic wires with and without 1,6-hexanedithiol (HDT) using the STM break-junction method. First, the stretch length was measured as a function of electrode potentials of a bare Au(1 1 1) substrate and a gold STM tip in a 0.1 M NaClO4 aqueous solution. Second, a self-assembled monolayer (SAM) was fabricated on an Au(1 1 1) substrate by dipping the substrate into a 1 mM HDT ethanol solution. At last, we measured the stretch length of gold mono-atomic wires on a substrate covered with the SAM in place of the bare Au(1 1 1) substrate. We compared the electrode potential dependence of the stretch lengths of gold mono-atomic wires covered with and without HDT. We will discuss the effect of the electrode potential on the stretch lengths by taking account of electrocapillarity of gold mono-atomic wires.

It was reported recently that the diamine-terminated molecules show two sets of single molecular conductance peaks in the conductance histogram. Although we found another set of conductance value of 1,4-diaminobutane in a lower current range, it was difficult to determine the conductivity definitely because the compound has different conformations with different gauche contents within its molecular chain. To make it easier to determine and analyze a single molecular conductance we measured here the conductance of 1,4-phenylenediamine, whose conformation cannot be changed in terms of the gauche contents. As a result, new sets of conductance other than those reported recently [L. Venkataraman, J.E. Klare, C. Nuckolls, M.S. Hybertsen, M.L. Steigerwald, Nature 442 (2006) 904] were observed.

The sections in this article are Introduction Surface Treatment of Substrate Chalcogenide Electrodes Adsorption of Acids to Chalcogenides Adsorption of Organic Sulfur Compounds Surface Modification Dialkyl Chalcogenide Compounds Thiols Dithiols, Disulfides, and Other Sulfur Compounds Characterization and Applications Summary Acknowledgments