ISTC consists of the Information Processing Center and the University Library. ISTC’s main purpose is to provide information services through computer facilities and library services.
Besides providing regular services, ISTC staff performed the following support activities in FY 2008.
|M. Ryzhii, A. Satou, V. Ryzhii, and T. Otsuji. High-frequency properties
of a graphene nanoribbon field-effect transistor. Journal of Applied
Physics, 104(11):114505(6), 2008.
|We propose an analytical device model for a graphene nanoribbon field-effect transistor
(GNR-FET) under the dc and ac operating conditions. The GNR-FET under
consideration is based on a heterostructure, which consists of an array of nanoribbons
clad between the highly conducting substrate (the back gate) and the top gate
controlling the dc and ac source-drain currents. Using the model developed, we derive
explicit analytical formulas for the GNR-FET transconductance as a function
of the signal frequency, collision frequency of electrons, and the top gate length. The
transition from the ballistic to strongly collisional electron transport is considered.
||V. Ryzhii, M. Ryzhii, A. Satou, and T. Otsuji. Current-voltage characteristics
of a graphene-nanoribbon field-effect transistor. Journal of Applied
Physics, 103:094510(8), 2008.
|We present an analytical device model for a field-effect transistor based on a heterostructure,
which consists of an array of nanoribbons clad between the highly
conducting substrate (the back-gate) and the top gate controlling the source-drain
current. The equations of the model of a grapheme-nanoribbon field-effect transistor
(GNR-FET) include the Poisson equation in the weak nonlocality approximation.
By using this model, we find explicit analytical formulas for the spatial distributions
of the electric potential along the channel and for the GNR-FET current-voltage
characteristics (the dependences of the source-drain current on the drain voltages as
well as on the back-gate and top-gate voltages) for different geometric parameters of
the device. It is shown that the shortening of the top gate can result in a substantial
modification of the GNR-FET current-voltage characteristics.
||V. Ryzhii, A. Satou, M. Ryzhii, T. Otsuji, and M. S. Shur. Mechanism
of self-excitation of terahertz plasma oscillations in periodically double-gated
electron channels. Journal of Physics: Condensed Matter, 20:384207(6), 2008.
|We develop a device model for a heterostructure device with an electron channel
and with a periodic system of interdigitated gates. Using this model, we find the
conditions of the self-excitation of plasma oscillations in portions of the channel.
It is shown that the self-excitation of plasma oscillations in these devices and the
terahertz emission observed in the experiments might be attributed to the electrontransit-
time effect in the barrier regions.
||V. G. Leiman, M. Ryzhii, A. Satou, N. Ryabova, V. Ryzhii, T. Otsuji,
and M. S. Shur. Analysis of resonant detection of terahertz radiation
in high-electron mobility transistor with nanostring/carbon nanotube as the
mechanically floating gate. Journal of Applied Physics, 104:024514(7), 2008.
|We develop a device model for a resonant detector of electromagnetic radiation with
a frequency in the terahertz (THz) range modulated by megahertz (MHz) or gigahertz
(GHz) signals based on a micromachined high-electron mobility transistor
(HEMT) with a metallized nanostring (NS) or metallic carbon nanotube (CNT) as
mechanically the floating gate and analyze the detector operation. The device model
describes both the NS/CNT mechanical motion and plasma effects in the HEMT
two-dimensional electron channel. Using this model, we calculate the output gate
alternating current and the detector responsivity as functions of the carrier (in the
THz range) and modulation frequencies, which are in the THz and MHz (or GHz
range), respectively. It is shown that the THz detector responsivity exhibits sharp
and high maxima under the conditions of both mechanical and plasma resonances.
||A. Satou, F. T. Vasko, and V. Ryzhii. Nonequilibrium carriers in
intrinsic graphene under interband photoexcitation. Physical Review B,
|We study nonequilibrium carriers (electrons and holes) in intrinsic graphene at low
temperatures under far-infrared (IR) and midinfrared radiation in a wide range of its
intensities. The energy distributions of carriers are calculated using a quasiclassical
kinetic equation which accounts for the energy relaxation due to acoustic phonons
and the radiative generation-recombination processes associated with thermal radiation
and the carrier photoexcitation by incident radiation. It is found that the
nonequilibrium distributions are determined by an interplay between weak energy
relaxation on acoustic phonons and generation-recombination processes as well as by
the effect of pumping saturation. Due to the effect of saturation, the carrier distribution
functions can exhibit plateaus around the pumping region at elevated intensities.
As shown, at sufficiently strong mid-IR pumping, the population inversion can occur
below the pumping energy. The graphene dc conductivity as a function of the pumping
intensity exhibits a pronounced nonlinearity with a sublinear region at fairly
low intensities and a saturation at a strong pumping. However, an increase in the
pumping intensity in very wide range leads only to a modest increase in the carrier
concentration and, particularly, the dc conductivity. The graphene conductivity at
mid-IR irradiation exhibit strong sensitivity to mechanisms of carrier momentum
||T. Matsunaga, M. Ohtake, J. Haruyama, Y. Ogawa, R. Nakamura,
Y. Yokota, T. Morota, C. Honda, M. Torii, M. Abe, T. Nimura, T. Hiroi,
T. Arai, K. Saiki, H. Takeda, N. Hirata, S. Kodama, T. Sugihara, H. Demura,
N. Asada, J. Terazono, and H. Otake. Discoveries on the lithology of
lunar crater central peaks by SELENE Spectral Profiler. GEOPHYSICAL
RESEARCH LETTERS, 35:L23201, 2008.
|This paper summarizes the results so far using data obtained by the Spectral Profiler,
measuring precise composition of minerals on the materials in lunar surface
||J. Haruyama, M. Ohtake, T. Matsunaga, T. Morota, C. Honda,
Y. Yokota, M. Abe, Y. Ogawa, H. Miyamoto, A. Iwasaki, C. M. Pieters,
N. Asada, H. Demura, N. Hirata, J. Terazono, Sasaki S, K. Saiki, A. Yamaji,
M. Torii, and J.-L. Josset. Long-Lived Volcanism on the Lunar Farside
Revealed by SELENE Terrain Camera. Science, 323(5916):905–908, 2009.
|We determined model ages of mare deposits on the farside of the Moon on the basis
of the crater frequency distributions in 10-meter-resolution images obtained by the
Terrain Camera on SELENE (Selenological and Engineering Explorer) (Kaguya).
||A. Satou, M. Ryzhii, F. T. Vasko, T. Otsuji, and V. Ryzhii. Graphene
under optical pumping: nonequilibrium distributions, population inversion,
and terahertz lasing. In Proc. SPIE, Vol. 7211 (2009), pp. 721119-721119-11,
|We study nonequilibrium carriers (electrons and holes) in an intrinsic graphene at low
temperatures under farand mid-infrared optical pumping in a wide range of its power
densities. The energy distributions of carriers are calculated using a quasiclassic kinetic
equation which accounts for the energy relaxation due to acoustic phonons and
the radiative generation-recombination processes associated with thermal radiation
and the carrier photoexcitation by incident radiation. It is found that the nonequilibrium
distributions are determined by an interplay between weak energy relaxation on
acoustic phonons and generation-recombination processes as well as by the effect of
pumping saturation. Due to the effect of pumping saturation, the carrier distribution
functions can exhibit plateaus whose width increases with increasing pumping power
density. The graphene steady-state conductivity as a function of the pumping power
density exhibits a pronounced nonlinearity with a sub-linear region at fairly low power
densities. As shown, at certain pumping power density the population inversion as
well as the dynamic negative conductivity can take place in terahertz and far-infrared
frequencies, suggesting the possibility of utilization of graphene under optical pumping
for optoelectronic applications, in particular, lasing at such frequencies.
||J. Terazono, N. Asada, H. Demura, N. Hirata, K. Saiki, A. Iwasaki,
R. Oka, T. Hayashi, T. Suzuki, and H. Miyamoto. Web-GIS based Collaboration
Environment Using Scientific Data of the Moon. In The XXI Congress
of The International Society for Photogrammetry and Remote Sensing, pages
1497–1500. ISPRS, Jul. 2008.
|This paper summarizes the collaboration environment based on Web-GIS system
intended for use by planetary scientists.
||J. Terazono, S. Tanaka, S. Sakamoto, J. Watanabe, and N. Wakabayashi.
Ten Years in Lunar and Planetary Exploration Outreach: The
Moon Station Challenge. In Proc. The 40th Lunar and Plaentary Science
Conference, page 1231. LPI and NASA, Mar. 2009.
|We continued activity of pubic outreach for lunar and planetary exploration since
1998. Currently the website is becoming one of the major portal in space development
field in Japan.
||J. Terazono, M. Yoshikawa, and N. Wakabashi. Space Education
Strategy Using Data Obtained by Lunar and Planetary Missions. In Proc.
The 26th International Symposium on Space Technology and Science. JSASS,
Jun. 2008. Transactions of Space Technology Japan, Volume 7, pp. Tu 25-
Tu 29 (2009).
|The outreach of lunar and planetary missions are important for public approach. Here
we presents some advanced attempt to show currently ongoing lunar and planetary
||J. Terazono, Y. Kitazawa, H. Kanamori, S. Tanaka, and T. Okada.
An investigation of lunar mission of shallow structure exploration using artificial
moonquake. In Proc. The 26th International Symposium on Space
Technology and Science. JSASS, Jun. 2008. Transactions of Space Technology
Japan, Volume 7, pp. Tk 13-Tk 16 (2009).
|We investigated the possibility of survey of lunar shallow structure using artificial
||J. Terazono, S. Bhalla, T. Izumita, N. Asada, H. Demura, and N. Hirata.
Construction of Lunar Nomenclature Search System. In Proc. The 26th
International Symposium on Space Technology and Science. JSASS, Jun. 2008.
|We constructed the search system from lunar feature name to display its detailed
data using QBO-based database technology.
||J. Terazono, N. Asada, H. Demura, N. Hirata, K. Saiki, A. Iwasaki,
R. Oka, T. Hayashi, T. Suzuki, H. Miyamoto, J. Haruyama, M. Ohtake,
M. Matsunaga, S. Sobue, H. Okumura, T. Fujita, and A. Yamamoto. Integrated
Lunar Web-GIS Environment Using Data Obtained by Lunar Exploration.
In Proc. The 40th Lunar and Plaentary Science Conference. LPI and
NASA, page 1232, Mar. 2009.
|Web-based GIS is one of the suitable platform for organizing lunar and planetary
data. Here we show our current improvement of the integrated lunar data environment
based on the open-source and open-standard technology.
||J. Terazono, S. Sobue, H. Okumura, N. Asada, H. Demura, N. Hirata,
T. Fujita, and A. Yamamoto. Web-GIS based collaboration environment
and remote GIS application experiment using lunar exploration data. In
Truong Zuan Luan Venkatesh Raghavan, Nguyen Quang Luat and Ho Dinh
Duan, editors, Proceedings of International Symposium on GeoInformatics for
Spatial-Infrastructure Development in Earth and Allied Sciences, pages 239–
244. JVGC, Dec. 2008.
|We are now constructing Web-GIS based system using past lunar exploration data.
This system will include the latest results of lunar exploration such as Kaguya,
Japanese lunar explorer, and Chandraaan-1 and LRO.
||J. Terazono. The Concept of XML-based Lunar and Planetary Data
Format. In Proceedings of Fifty Years after IGY- Modern Information Technologies
and Earth and Solar Sciences. AIST, Nov. 2008.
|Several data format are currently used in lunar and planetary field, however, these
format are now becoming less compatible with modern information technology. The
author proposes the newly established XML-based data format for this field and
||I. Shinohara, Y. Kasaba, Y. Yamamoto, M. Abe, T. Okada, T. Imamura,
S. Sobue, and J. Terazono. Planetary Data Archiving Plan at
ISAS/JAXA. In Proc. 37th COSPAR Scientific Assembly. COSPAR, page
2867, Jul. 2008.
|This presentation summarizes the activity of data archiving and organizing at
||Junya Terazono. Saishin・Tsuki no kagaku － Nokosareta nazo o
toku －, pages 185–211. NHK Publishing, Tokyo, 2008.
The book of lunar science based on the latest discovery (in Japanese)
||TManabu Kanzawa. Master Thesis: Online Geographic Information
System Supporting Collaborative Work for Multiple Users, The University of
Thesis Sub-advisor: Junya Terazono
||Shota Kikuchi. Master Thesis: Development of Operation Plan and
Log Management System for LISM on KAGUYA, The University of Aizu, 2009.
Thesis Sub-advisor: Junya Terazono