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Onuma, Toshiharu*; Miyashita, Atsumi; Yoshikawa, Masahito; Tsuchida, Hidekazu*; Iwasawa, Misako*
Heisei-21-Nendo Sentan Kenkyu Shisetsu Kyoyo Sokushin Jigyo "Chikyu Shimyureta Sangyo Senryaku Riyo Puroguramu" Riyo Seika Hokokusho, p.21 - 27, 2010/07
Silicon carbide, being a wide-band-gap semiconductor, is an attractive material in the development of electronic devices operated under extreme conditions such as high power, high temperature, and high radiation. SiC is particularly attractive for use in MOS technology because among the compound semiconductors only silicon carbide has the thermal oxide SiO
, which is a good insulator. However, it is known that SiO/SiC interfaces have a higher density of interface traps than SiO/Si interfaces and that the channel mobility of MOS devices is much lower than theoretically expected values. In order to improve these characteristics, it is important to understand the thermal oxidation process at the SiO/SiC interface. We performed large-scale first-principles molecular dynamics simulations of the SiO/SiC interface oxidation process. We also performed large-scale first-principles molecular dynamics simulations to generate amorphous SiO/SiC interface.
/SiC interface structure by the first-principles molecular dynamics simulationMiyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
Materials Science Forum, 556-557, p.521 - 524, 2007/00
SiC semiconductor devices are expected to be used in severe environments. However, SiC devices don't present the theoretically expected performance. This is considered to be attributed to the SiO/SiC interface defects that reduce electrical characteristics of devices. To generate the real device interface structure with the computer simulation, it is important to construct the a-SiO structure on SiC. The slab model using 444 atoms for a-SiO on a 4H-SiC (0001) crystal layer was constructed by using first-principles MD simulation. The heating and rapid quenching method was carried out to make an a-SiO/SiC interface structure. The heating temperature, the heating time and the speed of rapid quenching is 4000 K, 3.0 ps and -1000 K/ps, respectively. The interatomic distance and the bond angles of SiO layers agreed well with the most probable values in bulk a-SiO, and there were no coordination defects in the neighborhood of the SiC substrate.
/4H-SiC(0001) interface oxidation process; From first-principlesOnuma, Toshiharu*; Miyashita, Atsumi; Iwasawa, Misako*; Yoshikawa, Masahito; Tsuchida, Hidekazu*
Materials Science Forum, 556-557, p.615 - 620, 2007/00
We performed the dynamical simulation of the SiO/4H-SiC(0001) interface oxidation process using first-principles molecular dynamics based on plane waves and the slab model supercells method. The heat-and-cool method is used to prepare the initial interface structure. In this structure, there is no transition oxide layer or dangling bond at the SiO/SiC interface. As the trigger of the oxidation process, the carbon vacancy is introduced in the SiC layer near the interface. The oxygen molecules are added one by one to the empty sphere in the SiO layer near the interface in the oxidation process simulation. The molecular dynamics simulation is carried out at 2500 K. The oxygen molecule is dissociated and forms bonds with the Si atom in the SiO layer. The atoms of Si in the SiC layer at the SiO/4H-SiC(0001) interface are oxidized. Carbon clusters are formed in the interface layer. Oxygen molecules react with the carbon clusters and formed CO molecules.
Kinoshita, Motoyasu*; Geng, H. Y.*; Chen, Y.*; Kaneta, Yasunori*; Iwasawa, Misako*; Onuma, Toshiharu*; Sonoda, Takeshi*; Yasunaga, Kazufumi*; Matsumura, Sho*; Yasuda, Kazuhiro*; et al.
Proceedings of 2006 International Meeting on LWR Fuel Performance (TopFuel 2006) (CD-ROM), p.248 - 254, 2006/10
The New Crossover Project (NXO) is studying effect of fission irradiation on fuel material that research activity is crossing over universities, national and private laboratories. Simulation studies are being performed to find principal and triggering processes of the rim-structure formation in high burnup LWR fuel pellet, using accelerator irradiation and computational calculations. Accelerator irradiation, high energy electron irradiation, fission energy particle beam and ion implantation (ragegas atoms) and combined overlapping irradiations are being performed. For the target of irradiation, CeO isused as simulation of nuclear fuel. The initial results were such as planar structure made by Oxygen defects created by high energy electrons, and surface modification similar to grain-sub-division created by high fluence high energy particle irradiations.
/SiC interfaceMiyashita, Atsumi; Yoshikawa, Masahito; Kano, Takuma; Onuma, Toshiharu*; Sakai, Takayuki*; Iwasawa, Misako*; Soneda, Naoki*
Annual Report of the Earth Simulator Center April 2004 - March 2005, p.287 - 291, 2005/12
Silicon carbide semiconductor device is expected to be used under a severe environment like the nuclear reactor and the space environment. On the semiconductor device interface, the electric charge state of the defect decides an electric characteristic. To emulate interfacial structure the 
interface structure is generated and the electronic geometry is decided by the first-principle molecular dynamics simulation with the earth simulator. The amorphous interface structure is made by medium-scale model of about 400 atoms. The heating temperature is 4000K, the heating time is 3.0ps, the speed of rapid cooling is -1000K/ps, and SiC movable layers in the interface are assumed to be 4 layers. In temperature 2200K the 
terminal was opened to make the layer more amorphous. The model has almost abrupt interface, however, some defects energy levels were still observed in the band gap. The energy levels are originated from interfacial oxygen. The localized electronic distribution of the dangling bond causes defect energy levels.
interface by the first-principles molecular dynamics simulationMiyashita, Atsumi; Onuma, Toshiharu*; Yoshikawa, Masahito; Iwasawa, Misako*; Nakamura, Tomonori*; Tsuchida, Hidekazu*
no journal, ,
Silicon carbide (SiC) semiconductor devices are expected to be used under severe environments such as outer space and/or nuclear power plants. However, at this time, SiC devices don't present the predictable performance, since defects at interface reduce electric characteristics of them. The relation among atomic structures, interfacial defects and electric characteristics is not clear. Therefore, we tried to solve these problems by the computer simulation. The SiO/SiC interface structure is generated and the electronic geometry is decided by the first-principle molecular dynamics (MD) simulation with the Earth-Simulator. The amorphous interface structure is made by heating and rapid quench calculation using 444 atoms model. The heating temperature is 4000K, the heating time is 3.0ps, and the speed of rapid quench is 
. After a rapid quench, the atomic structure became an almost perfect interfacial structure. However, a few defect energy levels were still observed in the band gap. The defect energy levels are originated from the localized electronic distribution of the interfacial oxygen.
thin films deposited on 4H-SiC(0001) substrates by capacitance-voltage methodYoshikawa, Masahito; Nakamura, Tomonori*; Miyashita, Atsumi; Onuma, Toshiharu*; Tsuchida, Hidekazu*
no journal, ,
no abstracts in English
/SiC interface structure by the first-principlesMiyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Yoshikawa, Masahito; Tsuchida, Hidekazu*
no journal, ,
no abstracts in English
Miyashita, Atsumi; Onuma, Toshiharu*; Sakai, Takayuki*; Iwasawa, Misako*; Yoshikawa, Masahito; Kano, Takuma; Soneda, Naoki*
no journal, ,
no abstracts in English
/4H-SiC(0001) interface oxidation process; Formation of carbon clusterOnuma, Toshiharu*; Miyashita, Atsumi; Iwasawa, Misako*; Yoshikawa, Masahito; Tsuchida, Hidekazu*
no journal, ,
no abstracts in English
/SiC interface by the simulation; First-principles molecular dynamicsMiyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
no journal, ,
no abstracts in English
Miyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
no journal, ,
no abstracts in English
/SiC interface structure by the first-principles, 2Miyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
no journal, ,
no abstracts in English
/4H-SiC(0001) interfaceOnuma, Toshiharu*; Miyashita, Atsumi; Iwasawa, Misako*; Yoshikawa, Masahito; Tsuchida, Hidekazu*
no journal, ,
no abstracts in English
and UONakamura, Jinichi; Kaneta, Yasunori*; Chen, Y.*; Geng, H.*; Iwasawa, Misako*; Onuma, Toshiharu*; Kinoshita, Motoyasu
no journal, ,
no abstracts in English
and CeONakamura, Jinichi; Chen, Y.*; Iwasawa, Misako*; Onuma, Toshiharu*; Kaneta, Yasunori*; Geng, H.*; Kinoshita, Motoyasu
no journal, ,
no abstracts in English
; Dimer and planar orderingNakamura, Jinichi; Geng, H.*; Chen, Y.*; Kaneta, Yasunori*; Iwasawa, Misako*; Onuma, Toshiharu*; Kinoshita, Motoyasu
no journal, ,
Miyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
no journal, ,
no abstracts in English
interface by the simulation; Difference of interface structure by temperature conditionMiyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
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C-face oxidation process; Difference between C-face and Si-faceOnuma, Toshiharu*; Miyashita, Atsumi; Iwasawa, Misako*; Yoshikawa, Masahito; Tsuchida, Hidekazu*
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no abstracts in English
