The authors studied the isolated water molecules and hydroxyl species on Cu(110) using a low-temperature scanning tunneling microscope (STM). A water molecule adsorbs on top of Cu atom and thermally hops along the atomic row at 6 K. The migration is also induced by STM via the excitation of molecule-substrate vibration. An isolated hydroxyl species, produced by dissociating a water molecule with the STM, adsorbs at the short-bridge site with its axis inclined along . The orientation was found to be dynamically flipped, wherein substantial isotope effect was observed in the rate.
We have investigated the formation of molecular ions and neutral molecules from adsorbed CH4, CD4 and N2 following 1 keV He+ ion irradiation. The thickness of the adsorbed layer was precisely controlled. For mono-layered methane, only monomer ions (CHx+) were desorbed, while a large number of heavy ions (CnHx+) up to n = 20 as well as heavy neutral molecules (CnHx) were desorbed from multi-layered film. Among the desorbed ions and neutral molecules, molecules with C-C covalent bonds such as acetylene and ethylene were found, which indicates that chemical bonds are newly formed by ion irradiation. Based on the results for thickness dependences of the mass spectra and calculation of He+ energy loss process from TRIM-Code, it was elucidated that the monomer ions are desorbed from the top surface layer through single electron excitation. On the other hand, the cluster ions are formed mainly in the inside of the layers along the nuclear track due to phonon excitation, which is produced by nuclear collision between incident He+ ions and adsorbed molecules.
Adsorption processes of thiolated cyclodextrins onto the self-assembeled monolayers of octanethiol formed on Au(111) substrates were investigated with a scanning tunneling microscope (STM). Our results revealed that the exchange of alkanethiolate molecules with the thiolated cyclodextrins occurred preferentially at the boundaries of the domains of a c(4×2) structure. Moreover, the adsorbed thiolated cyclodextrins were found to form one-dimensional chain structures. Our approach presented here provides a way to organize ordered structures of bulky molecules on solid substrates.
Formation of thin gate insulators with high electrical characteristics is a key technology to achieve high performance of semiconductor devices in the next generation. As for thin film transistors (TFTs) used in liquid crystal displays (LCDs), a new low temperature gate oxide formation technique is required to provide homogeneous gate insulators on rough poly-Si surfaces with substrate glass. We have developed two different methods for nitric acid oxidation of Si (NAOS) at 120oC: i) one-step NAOS using azeotropic nitric acid solutions (68wt%) to form ultrathin (i.e., ∼1 nm) SiO2 layers with an extremely low leakage current density, and ii) two-step NAOS using ∼40 and 68wt% nitric acid solution to form thick (i.e., ≥ 10 nm) SiO2 layers. A progress in the NAOS techniques is outlined in this report.
Experimental procedures, including preparation of samples and solutions, and a system for electrochemical measurements are explained, for obtaining cyclic voltammograms using Pt(111), (100), and (110) in a sulfuric acid solution.