My Scientific Activities in Akiyama Groups of Institute for Solid
State Physics.
ID: P 02307 Dr. Ji-Won
Oh
In
the early period of JSPS fellowship, I started to characterize a series of the 5~6-nm-thick (110) GaAs
layers treated with a growth-interrupt annealing by means of atomic force
microscopy (AFM) to obtain microscopic understanding of the mechanism and full
control of the surface in atomic scale. I focus on 1-ML deep semicircle pits shaped
like “fish” among these features to elucidate the formation mechanism of
atomically flat surface. Based on this observation, spatial distribution, areas
and ratio of long and short length of fish-like 1-ML-deep (0.02 nm) structures
inherent to Ga supply are being clarified.
This
result on fish was soon presented to the annual academic meeting of the
Japan Society of Physics in 2002. Moreover, the report on atomically flat (110)
GaAs surface formation was honored to be the cover story of Applied Physics
Letters published by American Institute of Physics among the many topics
published in the same volume. Together with experimental study, we investigated
theoretically using the first principles calculation for the epitaxial growth
mechanism of (110) GaAs
surface conducted
by Prof. Akira Ishi in Tottori University. We found that small migration
barrier energies for Ga and As, which explain the long atom-migration length
suggested by experiments.
Then,
I started to micro photoluminescence measurement on atomic steps on atomically
flat (110) GaAs quantum well where very long exciton migration is expected by
dramatically reduced scattering which originated from disorder in the well
structure.
However,
the measurement of carrier diffusion length with PL image was bothered by
elliptical appearance of excitation laser beam of caused by our Ti:Sa laser
system.
By
using the spatial filter, a micro-sized pinhole with objective lens of microscope,
I made the shape of excitation beam into a circle and measured the impressively
enhanced carrier migration length even up to a few micro meter scale on
atomically flat surface with growth-interrupt treatment.
I
presented this studies in the 11th meeting of modulated semiconductor
structure, which held in Nara in July of 2003 and published the paper to
Physica E: Low-dimensional Systems and Nanostructures. This was my first international
academic meeting after becoming JSPS fellow researcher, in which my studies have
presented internationally, and many scientists give the valuable advises and attention
to me.
Next,
I examined a number of band pass and cut filters to eliminate the excitation
wavelength and residual light emission from GaAs substrate bothering the PL
imaging. By using both the short-cut and long-cut filters instead of generally
used band-pass filters, I have succeeded to get the more vivid images of surface
structures embedded in quantum well with high contrast.
Then
my next aim was observing the overall surface image of (110) GaAs quantum well
sample with size of 3 mm. I succeeded to make an overall map consisting of
about 152 PL images of surface with spatial resolution of 0.9 mm. Based on the topological information
of characteristic surface step distributions on quantum well interface, I
started the measurement of spectra over a specific surface area with vertical
spot shift of 1 mm along sample. This attempt
needs, however, great experimental effort since it requires 100 spectra, for
example, to scan 0.1 mm distance.
However,
I have succeeded to get the continuous spectral peaks generated from atomic
steps distributed even in a few 100 mm with
the help of micro positioning system. With the overall
observation of the 6-nm-thick (110) quantum well with the area of 6.8 mm width and 3-mm length, we found local PL signals due to isolated 2- or 3-monolayer
(ML) islands, isolated 1-ML pits, and 1-ML islands and pits formed along the
cleavage atomic-step lines, and gradual change of the states across the full
range of the sample.
I
wish to thank students who constructed this system, especially to Yuhei Hayamizu
and Hirotake Itoh, both doctoral students. This research was presented at 9th
International Symposium on Advanced Physical Fields, APF-9, held at NIMS in
March, 2004 and attracted considerable attractions from researchers abroad as
well as domestic researchers.
The
results are finally submitted to the Journal of Applied Physics, published by
American Institute of Physics in May 2004 and our manuscript was soon accepted
by journal referees with very constructive and
encouraging comments. Moreover, they urged as speedy a publication as possible.
As results, publication of our reports was proceed
without a hitch and finally published in December issue of Journal of Applied
Physics.
Around the same time, another issues
containing developed theoretical interpretation on the characteristic surface
step formation on atomically flat (110) surface conducted by Prof. Akira Ishii was also
published in Thin Solid Films, published by Elsevier publication company.
I would like to deeply gratitude for Prof. Ishi’s contributions in the field of surface research
of GaAs (110) layer.
Although not published as paper, I also
conducted photoluminescence profiles
of ideal 2-D quantum well system under very weak excitation power and liquid He
temperature. With point
excitation measurement on an individual surface structure on atomically flat
surface with extremely low excitation powers, we expected very narrow line width of PL at (110) GaAs QW. However, the obtained linewidths of luminescence
(1.5~6 meV) were much broader than what we expected. The mechanism for broad
linewidth is still unclear.
Though the aim of my host research
group is to study
compound semiconductors using spectroscopy, especially investigating the
characterization of T-shaped quantum wire with micro photoluminescence technique,
I have conducted the series of joint study with another group within the
university and another university.
First,
I studied the surface morphology of horse-heart cytochrome C on glass substrate
with AFM, which is used to build organic light-emitting diode (OLED). I
discovered the organic tissues on substrate are also borderless even up to
atomically flat. This joint study with the Tajima Groups of ISSP was so
successful, that it was soon published to Solid State Communications.
Then, I also conducted the surface observation of thin film of soluble Metallophthalocyanine Salts, [FeIII(Pc)(CN)2], which compose an electroluminescence
(EL) devices having the Metal-Insulator-Metal structure by AFM. The appearance of films turned out
to be networks of grains connected with each other on the surface. The better performance
of EL device compared to ones with similar salts but with FeII is attributed to the denser
structures of grain. This joint study was also published to Japanese Journal of
Applied Physics in August 2004.
I am very appreciative of joint researchers in Tajima
groups and have the satisfaction of joint study.
Also,
I have been conducted another joint project on micro photoluminescence studies
of GaAsN Alloy, InGaAs Alloy on GaAs substrate with optoelectronics Lab in Saitama
University. These materials with huge band bowing and less band offset are
expected as a promising system for long wave semiconductor laser. The results
with photoluminescence by He-Ne laser, diode-pumped solid-state laser
excitation was presented, on regular basis, to the annual meeting of the
Japan Society of Applied Physics and was investigated for further studies and
publication to academic paper.
As an
extra effort to improve the operational conveniences, I conducted the partial
automation of measurement process together with Toshiyuki Ihara, a master
student.
Within
a period of 2 year, I got splendid achievement through this postdoctoral
program with Akiyama Groups in ISSP, my host research group. Accordingly, I
could publish 3 first-author papers and 5 subauthor papers with Dr. Masahiro
Yoshita and joint researchers in journals with high academic authority.
I would like to sincerely thank the members of Akiyama Laboratory, who helped
me a lot to accomplish the academic tasks during the years of this fellowship
and JSPS staffs and also Professor Akiyama.
Outline of My Research Activities in JAPAN
Academic meetings:
Domestic
2002
Annual
meeting (fall) of the physical society of Japan（Chubu University）
6—9
Sept. Presentation number：6pSA-12 Field: 4
Observation
of surface atomic steps on (110) GaAs quantum well manufactured by cleaved-edge
overgrowth method.
Ji-Won
Oh1*, Masahiro Yoshita1,
Hidefumi Akiyama1, Loren N. Pfeiffer2, Ken W. West2
1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST
2Bell Laboratories, Lucent
Technologies, U.S.A
2003 58th Annual meeting (spring) of the physical
society of Japan（Tohoku University）
28-31, March, 2003 Address number：30pYH-3
Field: 4
Micro-Photoluminescence from GaAs (110)
with atomically flat surface.
Ji-Won Oh1*,
Masahiro Yoshita1, Hidefumi Akiyama1, Loren N. Pfeiffer2,
Ken W. West2
1
Institute for Solid State Physics, University of Tokyo, and CREST, JST
2Bell
Laboratories, Lucent Technologies, U.S.A
2004
59th Annual meeting (spring) of the physical society of Japan（Kyusyu
University）
27-30, March, 2003 Presentation number：28pPSB-6
Field:
4
Microphotoluminescence
characterization of atomic steps with characteristic patterns
on
the atomically flat GaAs (110) surface of a quantum well
Ji-Won
Oh1*, Masahiro Yoshita1,
Hidefumi Akiyama1, Loren N. Pfeiffer2, Ken W. West2
1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST
2Bell Laboratories, Lucent
Technologies, U.S.A
2004
59th Annual meeting (spring) of the physical society of Japan（Aomori
University）
27-30, March, 2003 Presentation number：28pPSB-6
Field:
4
PL profiles of ideal 2-D quantum well system with atomically flat surface under very weak excitation power and liquid He temperauture
Ji-Won
Oh1*, Masahiro Yoshita1,
Hidefumi Akiyama1, Loren N. Pfeiffer2, Ken W. West2
1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST
2Bell Laboratories, Lucent Technologies, U.S.A
① 2003 64th annual
meeting of Japan Society of Applied Physics ( Fukuoka University) 30-31, August to 1-2, Sept
Presentation
number：21pYC-4 Field: 13-7 Basic Study of
Crystal Growth
Low
and anisotropic barrier energy for adatom migration on a GaAs (110) surface
studied by first-principles calculations
Akira
IshiiA，Tsuyoshi AkisakaA，Ji-Won
OhB,
Masahiro YoshitaB, Hidefumi AkiyamaB
Tottori
UniversityA，Institute for Solid State
Physics, University of Tokyo, and CREST, JST B
Presentation
number：1p-K-7 Field：13.3
III-V epitaxial crystal
Photoluminescence
from dilute GaAsN alloy
Saitama
University1，1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST 2,School of
Engineering, University of Tokyo3, Takashi Aoki1，Toshikazu
Morioke1，Ji-Won Oh2，Hidefumi
Akiyama2，Yasuto Hijikata 1，Hiroyuki
Yaguchi1，Sadashi Yoshida1,Ooichiro Aoko3，Kentaro
Onabe3
Presentation
number：1p-K-8 Field：13.3
III-V epitaxial crystal
Photoluminescence
from dilute GaAsN alloy on GaAs substrate
Saitama
University1，1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST 2,School of
Engineering, University of Tokyo3, Toshikazu Morioke1,
Takashi Aoki1, Ji-Won Oh2，Hidefumi
Akiyama2，Yasuto Hijikata 1，Hiroyuki
Yaguchi1，Sadashi Yoshida1,Ooichiro Aoko3，Kentaro
Onabe3
② 2003 51th annual meeting of
Japan Society of Applied Physics (Tokyo University of Technology) 28-31, March
Presentation
number：30p-YG-8
Photoluminescence
from extremely dilute GaAsN alloy
Saitama
University1，1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST 2,School of
Engineering, University of Tokyo3, Takashi Aoki1，Toshikazu
Morioke1，Ji-Won Oh2，Hidefumi
Akiyama2，Yasuto Hijikata 1，Hiroyuki
Yaguchi1，Sadashi Yoshida1,Ooichiro Aoko3，Kentaro
Onabe3
Presentation
number：Unidentified
Emission
properties and I-V characteristics of an organic EL device using cytochrome c
Shingo
Ikeda, Masaki Matsuda, Hiroyuki Tajima, Yoriko Ando, Ji-Won Oh, Hidefumi
Akiyama
ISSP,
The University of Tokyo
③ 2003 65th annual meeting of
Japan Society of Applied Physics (Tohoku Gakuin University) 1-4, Sept
Presentation
number：3p-W-7
Nitrogen
Concentration Dependence of Improvement in the Luminescence Efficiency of GaAsN
Alloys by Laser Irradiation
Saitama
University1，1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST 2,School of
Engineering, University of Tokyo3, T Toshikazu Morioke1 Takashi
Aoki1，，Ji-Won Oh2，Hidefumi
Akiyama2，Yasuto Hijikata 1，Hiroyuki
Yaguchi1，Sadashi Yoshida1,Ooichiro Aoko3，Kentaro
Onabe3
Academic meetings:
International
The
11th International Conference on Modulated Semiconductor Structures -MSS11-
July
14 - 18, 2003 Nara, Japan
PA-55(poster
presentation)
Carrier
Diffusion on Atomically Flat (110) GaAs Quantum Wells
Ji-Won
Oh1*, Masahiro Yoshita1,
Hidefumi Akiyama1, Loren N. Pfeiffer2, Ken W. West2
1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST
2Bell Laboratories, Lucent Technologies, U.S.A
The
7th Atomically Controlled Surfaces, Interfaces and Nanostructures
November
16 - 20, 2003, Nara, Japan
20D57(Oral presentation) at Surface/Interface Structures
and Properties section.
First Principles calculation of the
epitaxial growth of GaAs(110)
as an atomically flat substrate for nano
structure
A. IshiiA.
Tsuyoshi AisakaA; Ji-Won OhB, Masahiro YoshitaB;
Hidefumi AkiyamaB
A Department of Applied Mathematics and Physics, Tottori University
B Institute for Solid State Physics, University of Tokyo, and CREST, JST
The 9th International Symposium
on Advanced Physical Fields (APF-9). "Characterization
of Artificial Nanostructures
and Nanomaterials".
March 1-4,2004, NIMS, Tsukuba,
Ibaraki Prefecture, Japan
P03
(Poster presentation)
Atomically Smooth Interface with
Characteristic Step Edges in a (110) GaAs Quantum Well
revealed by Microphotoluminescence
Technique
Ji-Won
Oh1*, Masahiro Yoshita1,
Y. Hayamizu1, Hidefumi Akiyama1,
Loren
N. Pfeiffer2, Ken W. West2
1 Institute for Solid State
Physics, University of Tokyo, and CREST, JST
2Bell Laboratories, Lucent Technologies, U.S.A
Academic Journal
Papers:
Applied
Physics Letters
82 (2003) 1709
Step-edge
kinetics driving the formation of atomically flat (110) GaAs surfaces
Ji-Won
Oh1*,
Masahiro Yoshita1, Hidefumi Akiyama1, Loren N. Pfeiffer2,
Ken W. West2
1 Institute
for Solid State Physics, University of Tokyo, and CREST, JST,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2Bell
Laboratories, Lucent Technologies, Murray Hill, New Jersey, 07974, U.S.A
Control
of MBE surface step-edge kinetics to make an atomically smooth quantum well
Masahiro
Yoshita1, Ji-Won Oh1, Hidefumi Akiyama1,
Loren N. Pfeiffer2, Ken W. West2
1 Institute
for Solid State Physics, University of Tokyo, and CREST, JST,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2Bell
Laboratories, Lucent Technologies, Murray Hill, New Jersey, 07974, U.S.A
A
light-emitting diode fabricated from horse-heart cytochrome c
H.Tajima,
S. Ikeda, M. Matsuda, N. Hanasaki, Ji-Won Oh, H. Akiyama
Institute
for Solid State Physics, University of Tokyo,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
Applied
Physics Letters
83
(2003) 4187
Low
and anisotropic barrier energy for adatom migration on a GaAs (110) surface
studied by first-principles calculations
Akira
Ishiia, Tsuyoshi Aisakaa, Ji-Won Ohb,
Masahiro Yoshitab, and Hidefumi AkiyamaB
1
Tottori University, Koyama, Tottori 680-8552, Japan
Institute
for Solid State Physics, University of Tokyo, and CREST, JST,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
Carrier
Diffusion on Atomically Flat (110) GaAs Quantum Wells
Ji-Won
Oh1*,
Masahiro Yoshita1, Hirotake Itoh1, Hidefumi Akiyama1,
Loren N. Pfeiffer2, Ken W. West2
1 Institute
for Solid State Physics, University of Tokyo, and CREST, JST,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2 Bell
Laboratories, Lucent Technologies, Murray Hill, New Jersey, 07974, U.S.A
43
(2004) L1187-L1189 (No. 9A/B)
Novel
Electroluminescence Properties of Thin Films Using Soluble
Metallophthalocyanine Salts
Shingo
Ikeda, Masaki Matsuda, Yoriko Ando, Ji-Won Oh, Noriaki Hanasaki,
Hiroyuki Tajima and Hidefumi Akiyama
Institute
for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
Thin
Solid Films
464-465
(2004) 38-41
Formation
mechanisms of monolayer pits having characteristic step-edge shapes on annealed
GaAs (110) surfaces
Akira
IshiiA, Tsuyoshi AisakaA, Ji-Won OhB,
Masahiro YoshitaB, and Hidefumi AkiyamaB, Loren N.
PfeifferC, Ken W. Westc
A Tottori University, Koyama,
Tottori 680-8552, Japan
B Institute for Solid State
Physics, University of Tokyo, and CREST, JST,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
C Bell Laboratories, Lucent
Technologies, Murray Hill, New Jersey, 07974, U.S.A
96 (2004)
Ji-Won
Oh1*,
Masahiro Yoshita1, Yuhei Hayamizu1, Hidefumi Akiyama1,
Loren N. Pfeiffer2, Ken W. West2
1 Institute
for Solid State Physics, University of Tokyo, and CREST, JST,
5-1-5
Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2 Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey, 07974, U.S.A