TOMITORI Laboratory
<Major Research Areas>surface science, nano-probe technology, nano mechanics

New frontier in surface science on nano scale: direct observation, measurements and fabrication of nano structures

Research activity

1Microscopic observation and analysis of atomic structures and electronic states at solid surfaces based on newly developed methods

　　Mainly, by using scanning probe microscopies (SPM) in ultrahigh vacuum (10-11 Torr), i.e., scanning tunneling microscopy (STM) and atomic force microscopy (AFM), which utilize an atomically sharpened tip to depict surface topography, we focus on revealing the nature of exotic solid surfaces. We also develop new methods to reveal surface features, if necessary, by applying analytical and physical principles to them.

2Fundamentals and applications of atomic scale physical analysis of semiconductors, metals, oxides and so on, including ultra-thin film growth and fabrication of nano structures with quantum effects and electron tunneling

　　We analyze the atomic structures and electronic states of solid surfaces and ultra-thin films on an atomic scale with SPM and other high-resolution microscopies. In addition, since heterostructures with specific crystal shapes attract much interest, we aim at fabrication of nano structures chiefly composed of V group semiconductors in a controlled manner, while observing them on an atomic scale. To understand the quantum nature of electrons and related phenomena, we develop surface analytical methods utilizing excitation with electrons field-emitted from an SPM tip and the standing wave in SPM, while examining the atomic structure and electronic states of the tip, which are of use in SPM applications.

3Creation and expansion of nano mechanics, manipulation and assembly of atoms and molecules. Analysis of chemical bond formation on the nano scale using non-contact atomic force microscopy

　　Non-contact atomic force microscopy can reveal surface structures of metals, semiconductors and even insulators on an atomic scale by measuring and utilizing the weak interaction force between an atomically sharpened tip and a sample; we refer to this method as nano-probe technology. This method will take us to a nano world, where individual atoms and molecules can be recognized and assembled, where chemical bond formation as interaction of forces can be analyzed, and where novel functionalized nano structures which manifest fascinating quantum mechanical features can be fabricated as required. We contribute to creation of this new field “nano mechanics”, leading to the next generation of science and technology of atoms and molecules.

Equipment

scanning tunneling microscope (STM) operated in ultrahigh vacuum (UHV), UHV non-contact atomic force microscope, fieldemission STM combined with an electron energy analyzer, scanning Auger electron microscope, ultrahigh resolution scanning electron microscope

The main research achievements in the past five years

1. A. Sasahara, C.L. Pang and M. Tomitori, Atomic scale analysis of ultrathin SiO2 films prepared on TiO₂(100) surfaces, J. Phys. Chem. C 114 20189-20194 (2010).
2. T. Nishimura, A. Itabashi, A. Sasahara, H. Murata, T. Arai and M. Tomitori, Adsorption state of 4,4"-diamino-p-terphenyl through an amino group bound to Si(111)-7x7 surface examined by X-ray photoelectron spectroscopy and scanning tunneling microscopy, J. Phys. Chem. C 114 11109-11114 (2010).
3. Z. A. Ansari, T. Arai, and M. Tomitori, Low-flux elucidation of initial growth of Ge clusters deposited on Si(111)-7x7 observed by scanning tunneling microscopy, Phys. Rev. B, 79 033302 (2009).
4. T. Arai and M. Tomitori, Electric conductance through chemical bonding states being formed between a Si tip and a Si(111)-7x7 surface by bias-voltage noncontact atomic force spectroscopy, Phys. Rev. B, 73, 073307 (2006).
5. Z. A. Ansari, T. Arai, and M. Tomitori, Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si (111)-7x7, Appl. Phys. Lett., 88, 171902 (2006).