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SUBTHEMES
■ Identification and Manipulation of Atoms and Molecules
By using scanning tunnel microscopy,(STM) atomic force microscopy (AFM) and other scanning probe microscopy (SPM) technologies, it is attempted to establish technologies for identifying chemical species of,, for manipulating atoms and molecules, and for measuring, controlling and constructing structures of atomic levels.
■ Construction of Si Nanostructures Sized Less than 10 nm
Atomic layer masking technology using monatomic SiO2 film is combined with selective growth technology, to establish the technology to construct Si nanostructures sized less than 10 nm of reduced fluctuation,
To speak more specifically, nanostructures are formed from Ge,SiGe/Si, Ge,Si/SiO2/Si, metal/Si and GeN/Si, and so on, and characterized.
■ Development and Application of Materials with Innovative Electronic Properties
New materials with strong electronic correlation effects, such as transition metal oxide and organic molecule system, as well as new physical phenomena such as phase transition induced by light or current, and colossal magneto-resistance effects are explored. Moreover, in consideration of device applications, technology for constructing this film with atomic control will be developed.
■ Computer Simulation Technology
The microscopic mechanisms for behavior and functioning of atoms and molecules are theoretically studied for ultimately controlling materials at the atomic scale and producing desired functions. It is intended to solve these problems theoretically through the calculation of electronic state on the basis of the first principle.
REPRESENTATIVE ACHIEVEMENTS
■ Single Si Adatom Extracted with STM Probe from Si Surface
A single Si atom adsorbed on the surface of Si(111)-7x7 is successfully extracted by touching with a tungsten probe biased at -1 V, and pulling up. The figure at the top shows a set-up, and two figures at the bottom STM images of silicon surface before (left) and after (right) extracting single Si adatom (white point in the left figure).
■ Formation of Germanium (Ge) Quantum Dots with Position and Size Controlled by the Atomic Layer Silicon Oxide Film Technology
Left: An image of scanning reflected electron microscopy of specimen with atomic layer SiO2 film removed by using focused electron beam. (A while line represents an area of removed SiO2).
Right: An image of scanning reflected electron microscopy of nano-dots created on Si by atomic layer SiO2 masking technique. (Black points represent Ge nanodots.)
■ Etching of Nanostructures Using Metal Clusters as Nucleation Points
Arrays of silicon pillars are constructed on a silicon substrate by using an etching mask made of metal clusters, such as gold, silver,, iron and others. For positioning, the electron beam lithography was used. In an example shown at the right, silicon pillars of 20 nm diameter and 300 nm height were formed at 100 nm intervals by using iron cluster.
■ Phase Control of Perovskite-type Oxide and Its Theoretical Clarification
It was discovered that in perovskite-type oxide, the crystalline phase is changed by applying magnetic field to cause an enormous change in electrical conductivity (colossal magnetoresistance effect = CMR). Moreover, phase can be controlled by electric field and light illumination to change the resistivity extensively.
The basic mechanism for interaction among spin, charge and orbital of electron in these materials was theoretically clarified.
■ Detection of Point Mutation Site in DNA Base Sequence by Using Marker Protein
Owing to improved performance of mechanical probe device (SPM) and development of new technologies for specimen preparation and fixation, it has become possible to detect point mutation sites on DNA by using special protein.
The figure at the right shows AFM image of complex filaments composed of DNA of 1066 base pairs long and special protein.
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