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Advanced Quantum-Nano Materials & Optoelectronics Laboratory
 
 

QR code_Prof. Jihoon Lee

Kwangwoon Univ. KOR ver website

Kwangwoon Univ. Eng ver website

Kwangwoon College of Electronics and Informattion Engineering

Dept. of Electronics and Communications Engineering

 

University of Arkansas


Sam M. Walton College of Business

 

ERC 선도연구센터

BK 21 PLUS

Engineering Research Center, Holo-Digilog Human Media

Ministry of Science, ICT and Future Planning

Ministry Of Education

NIPA

KCC

Ministry of Education, Science and Technology

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ITRC Forum 2011

 

 

- Journal Editor -

3D Research

NRL cover

 

 

- Research Highlight -

 

Journal Cover: Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration

(Journal cover,
CrystEngComm)
Volume 18
Issue 19

(2016)

Journal cover,CrystEngComm Volume 16 Issue 21 (2014)

(Journal cover,
CrystEngComm)
Volume 16
Issue 21

(2014)

 

Physica Status Solidi (a)) Volume 209 issue 6

(Journal cover,
Physica Status Solidi (a))
Volume 209
Issue 6

(2012)

 

Journal cover, Physica Status Solidi (a) Volume 208 Issue 1 (2011)

(Journal cover,
Physica Status Solidi (a))
Volume 208
Issue 1

(2011)

 

( Journal cover, IEEE Transactions on Nanotechnology) Volume 9 Issue 2  (2010)
( Journal cover,
IEEE Transactions on Nanotechnology)
Volume 9
Issue 2

(2010)

 

Wiley's Material Science online portal, Materials Views

(Materials Views, Wiley's Material Science)
"Nano Rings and Nano Pyramids"
(2010)

 


(Journal cover, Physica Status Solidi (a)) Volume 207 Issue 2  (2010)
(Journal cover,
Physica Status Solidi (a))
Volume 207
Issue 2

(2010)

 

(Journal cover, Applied Physics Letters) Volume 89 Issue 20  (2006)
(Journal cover,
Applied Physics Letters)
Volume 89
Issue 20

(2006)

 



(2006 MRS Fall Meeting Scene)
"Self-Assembly of InGaAs Quantum Dot Molecules (QDMs)"
(2006)

 

(Journal cover, Applied Physics Letters) Volume 88 Issue 23  (2006)

(Journal cover,
Applied Physics Letters)
Volume 88
Issue 23

(2006)

 

www.nanowerk.com

(NanoWerk, Spotlight)
"Quantum dot necklaces and other QD chains"
(April 12, 2006)

 

 


- PUBLICATIONS -

Journal Papers


* AUTHORS (in the order of authorship)
** TYPE: A: article, B: full book, CB: chapter of book, E: editor, & R: review, V: Video journal
***
IF: ISI® impact factor
*** Trend of Impact Factor of journals with interest (JCR IF 2015
)

 

TITLE: Thermal peculiarity of AlAs-capped InAs quantum dots in a GaAs matrix
AUTHORS: V. G. Dorogan, Yu. I. Mazur, J. H. Lee, Zh. M. Wang, M. E. Ware, and G. J. Salamo
JOURNAL/BOOK TITLE: Journal of Applied Physics
VOLUME: 104                                 FIRST PAGE: 104303
YEAR OF PUBLICATION: 2008        
                           TYPE: A                      IF: 2.201

Abstract



 

GaAs and AlAs thin capping layers as well as postgrowth rapid thermal annealing (RTA) were applied to InAs quantum dots (QDs) grown by molecular beam epitaxy to study the tunability of optical properties of QDs by photoluminescence (PL) methods. The PL of AlAs-capped QDs shows double-peak structure, as opposed to GaAs-capped QDs, which is due to the formation of two families of QDs in the AlAs-capped sample confirmed by the power dependent PL measurements. The PL peak of the GaAs-capped samples subjected to RTA showed blueshift and narrowing with an increase in RTA temperature. This is the result of thermally enhanced In–Ga intermixing. More complex changes in the PL spectrum of AlAs-capped QDs during the RTA procedure were found and explained by the different In compositions in two branches of QDs. The features observed in the temperature dependences of PL peak energy of GaAs- and AlAs-capped samples were interpreted in terms of thermal escape of carriers from smaller QDs with further redistribution between larger QDs and different InAs content in two families of QDs. © 2008 American Institute of Physics. [DOI: 10.1063/1.3020521]

 


Graphical Abstract



J. Appl. Phys. 104, 104303 (2008)

 

TITLE: Energy Transfer within Ultralow Density Twin InAs Quantum Dots Grown by Droplet Epitaxy
AUTHORS: Bao-Lai Liang, Zhi-Ming Wang, Xiao-Yong Wang, Ji-Hoon Lee, Yuriy I. Mazur, Chih-Kang Shih, and Gregory J. Salamo
JOURNAL/BOOK TITLE: ACS NANO
VOLUME:2                                  FIRST PAGE: 2219
YEAR OF PUBLICATION: 2008                                   TYPE: A                      IF: 5.472

Abstract



 

Ultralow density (~10^6/cm2) of twin InAs quantum dot (QD) hybrid structure was grown by a droplet epitaxy technique. The photoluminescence (PL) from ensemble and individual twin InAs QD structures showed a bimodal behavior and an energy transfer between the well-separated (~190 nm) twin QDs, which was supposedly due to the special wetting ring that built the channel for exciton transfer. This research demonstrates a novel approach to fabricate lateral InAs QD pairs as the candidate for a laterally coupled QD molecule.

 


Graphical Abstract



ACS Nano, 2008, 2 (11), 2219-2224

 

TITLE: Super-low-density InGaAs semiconductor ring-shaped nanostructures
AUTHORS: Jihoon H. Lee, Zhiming M. Wang, M. E. Ware, Kushal C. Wijesundara, Mauricio Garrido, E. A. Stinaff and Gregory J. Salamo
JOURNAL/BOOK TITLE: Crystal growth & design
VOLUME: 8                                   FIRST PAGE: 1945
YEAR OF PUBLICATION: 2008                                   TYPE: A                      IF: 4.215

Abstract



 

We report on the ability to fabricate super low density InGaAs semiconductor ring-shaped nanocrystals on a GaAs (100) surface by molecular beam epitaxy. Specifically, we demonstrate densities down to 2.3 × 106 cm-2 with only self-assembled methods based on droplet epitaxy. This is several orders of magnitude lower than conventional nanostructures. The formation of these ring-shaped nanostructures is driven by a self-assembled indium nanodrilling mechanism and diffusion during crystallization.

 


Graphical Abstract



Crystal Growth & Design, Vol. 8, No. 6, 2008      Crystal Growth & Design, Vol. 8, No. 6, 2008


 

TITLE: “Spectroscopic observation of developing InAs quantum dots on GaAs ringlike-nanostructured templates
AUTHORS: Yu. I. Mazur, Z. Y. AbuWaar, T. D. Mishima,
J. H. Lee, G. G. Tarasov, B. L. Liang, V. G. Dorogan, M. E. Ware, Zh. M. Wang, M. B. Johnson, and G. J. Salamo
JOURNAL/BOOK TITLE: Journal of Applied Physics
VOLUME: 104                                    FIRST PAGE: 044310
YEAR OF PUBLICATION:2008                                   
TYPE: A                      IF: 2.201

Abstract



 

Spectroscopic study of the InAs quantum dot (QD) formation in GaAs ringlike nanostructures is carried out. Ga droplet epitaxy is used to form GaAs ringlike nanostructures. Subsequently InAs is deposited to obtain InAs QDs by self-assembly inside the holes of the nanostructures. Regularly spaced bands in the photoluminescence spectra exhibit state filling properties under increased excitation power. However, it is demonstrated that these bands do not represent excited states of a single ensemble of dots, but are separate ensembles with individual ground state energies, which are coupled through the GaAs ring structure on which they form. The most likely cause of these uniformly spaced ensemble energies is monolayer differences in the effective height of the dots. Temperature, excitation power density, and time dependent photoluminescence measurements are used to demonstrate the significance of the interdot coupling. The photoluminescent properties of these novel nanostructures make them candidates for optoelectronic applications. © 2008 American Institute of Physics. [DOI: 10.1063/1.2970149]

 


Graphical Abstract



J. Appl. Phys. 104, 044310 (2008)

J. Appl. Phys. 104, 044310 (2008)

 

TITLE: “The Growth and Characterization of Organized Nanostructures"
AUTHORS: J. H. Lee
JOURNAL/BOOK TITLE: (PhD Dissertation) The University of Arkansas Press
YEAR OF PUBLICATION: 2008                                    TYPE: B

 

 

TITLE: Evolution of InGaAs quantum dot molecules
AUTHORS: J. H. Lee, Kim. Sablon, Zh. M. Wang, and G. J. Salamo
JOURNAL/BOOK TITLE: Journal of Applied Physics
VOLUME: 103                                    FIRST PAGE: 054301
YEAR OF PUBLICATION:2008                                    TYPE: A                      IF: 2.201

Abstract



 

The formation and evolution process of self-assembled InGaAs quantum dot molecules (QDMs) are studied in terms of configuration, volume, and types of QDMs. QDMs are formed around self-assembled GaAs nanoscale island induced by adapting a hybrid growth approach combining droplet homoepitaxy and Stranski–Krastanov mode. In distinction from our previous results Lee et al., Appl. Phys. Lett. 89, 202101 (2006), hexa-QDMs are fabricated without the formation of background QDs, which can be due to a combinational effects of enhanced intermixing of Ga and In atoms, enhanced surface diffusion (high mobility) of adatoms, and higher In desorption rate due to the higher thermal energy provided during the fabrication of QDMs. In addition, a detailed evolution mechanism from bi-QDMs two QDs per each GaAs island to hexa-QDMs (six QDs per island) is proposed based on atom diffusion, material transfer, and equilibrium dimension (saturation) of QDs. Under a fixed InAs coverage, depending on postannealing process after liquid Ga droplet formation, highly uniform as well as various types of QDMs can be fabricated and the resulting configurations show a very strong correlation with the size of initial GaAs islands. With relatively smaller GaAs islands, quad-QDMs four QDs per island with a squarelike configuration were formed and also, quad-QDMs with a rectangularlike positioning were fabricated with relatively larger size of islands, while hexa-QDMs were formed with middle sized ones. Relatively, broader size distribution of GaAs nanoisland can be a direct result of Ostwald ripening, which can be well controlled by adjusting postgrowth interruption of liquid Ga droplets. © 2008 American Institute of Physics. [DOI: 10.1063/1.2890149]

 


Graphical Abstract



J. Appl. Phys. 103, 054301 (2008)       J. Appl. Phys. 103, 054301 (2008)


 

TITLE: Step bunch assisted two dimensional ordering of In0.19Ga0.81As/GaAs quantum dots on vicinal GaAs(001) surfaces
AUTHORS: Michael Hanke, Zhiming Wang , Yu Mazur , Jihoon Lee , Gregory Salamo , Martin Schmidbauer
JOURNAL/BOOK TITLE: Applied Physics Letters
VOLUME: 92                                    FIRST PAGE: 033111
YEAR OF PUBLICATION: 2008                                   TYPE: A                      IF: 3.726

Abstract



 

We have investigated the self-organized, step bunch assisted formation of In0.19Ga0.81As /GaAs quantum dots in vertical superlattices consisting of one, four, eight, and ten periods. Samples were grown by molecular beam epitaxy on vicinal 2°A and 2°B GaAs[001] substrates. Those with miscut along the [11¯0] (2°B) exclusively show step bunches of an aspect ratio larger than 10 but without the formation of quantum dots. This highly linear pattern is improved during subsequent periods as proved by high resolution x-ray diffraction and grazing incidence diffraction. On the other hand, a miscut along the [110] (2°A) initially causes a crosslike pattern of step bunches, which finally becomes a two-dimensional arrangement of individual quantum dots. © 2008 American Institute of Physics. [DOI: 10.1063/1.2838453]

 


Graphical Abstract



Appl. Phys. Lett. 92, 033111 (2008)

 

TITLE: Configuration Control of Quantum Dot Molecules by Droplet Epitaxy
AUTHORS: K. A. Sablon, J. H. Lee, Zh. Wang and G. J. Salamo
JOURNAL/BOOK TITLE: Applied Physics Letters
VOLUME: 92                                    FIRST PAGE: 203106
YEAR OF PUBLICATION: 2008                                   TYPE: A                      IF: 3.726

Abstract



 

We demonstrate that by changing the substrate temperature at which Ga droplets form and by varying the InAs deposition, we are able to control the configuration of quantum dots per GaAs mound. The size of the Ga droplets increases with increasing substrate temperature and resulting configurations show a very strong correlation with the size of initial GaAs islands. In distinction from previous reports, we attained two structures: quadmolecules and quantum rod pairs. Quadmolecules are elongated along the [011] crystallographic direction due to strain-driven processes and are directly formed at the edges of the GaAs mounds. On the other hand, quantum rod pairs formed along the [01−1] direction due to higher anisotropic diffusion. © 2008 American Institute of Physics. [DOI: 10.1063/1.2924308]

 


Graphical Abstract



Appl. Phys. Lett. 92, 203106 (2008)

Appl. Phys. Lett. 92, 203106 (2008)

 

TITLE: Near-field optical spectroscopy of Ga nanoparticles for plasmonics
AUTHORS: Antonio Llopis, Lin Jie, Arup Neogi, Jihoon Lee, Zhiming Wang, and Gregory J. Salamo
JOURNAL/BOOK TITLE: QELS - Technical Digest Series
Article number: 10132597                     ISBN: 978-1-55752-859-9
YEAR OF PUBLICATION: 2008                                   TYPE: A

Abstract



 


Near-field optical spectroscopy of nanoscale Ga droplets on GaAs exhibits quenching of photoluminescence emission due to coupling with surface plasmon. Ga droplets exhibit antenna like behavior associated with a red-shift in the near-field photoluminescence emission. ©2008 Optical Society of America.


 


Graphical Abstract



ⓒ 2008 OSA / CLEO/QELS 2008

 

TITLE: Formation of hybrid molecules composed of Ga metal particle in direct contact with InGaAs semiconductor quantum ring
AUTHORS: Jihoon H. Lee, Zhiming M. Wang, Kim. Sablon and Gregory J. Salamo
JOURNAL/BOOK TITLE: Crystal growth & design
VOLUME: 8                                   FIRST PAGE: 690
YEAR OF PUBLICATION: 2008                                        TYPE: A                      IF: 4.215

Abstract



 

We demonstrate the formation of hybrid molecules composed of a pair of a metal particle and a semiconductor quantum ring (QR) by using molecular beam epitaxy on a GaAs (100) surface. To form three-dimensional semiconductor InGaAs QRs with a hole in the center of the structure, a thin layer (10 monolayer) of GaAs was applied on InAs quantum dots, which transformed the distribution of surface free energy. These InGaAs QRs were then used as a template for the localization of Ga metal particles; there was one metal particle on a QR. By choosing the optimal surface temperature (most favorable thermal energy), the surface diffusion of Ga adatoms was effectively enhanced. This, in turn, allowed the localization of Ga metal particles on InGaAs QRs, consequently forming hybrid molecules. This study helps understand the formation of various types of hybrid molecules that will be used in applications in optoelectronics.

 


Graphical Abstract



Formation of hybrid molecules

Crystal Growth & Design, Vol. 8, No. 2, 2008Crystal Growth & Design, Vol. 8, No. 2, 2008

 

TITLE: Spatially localized formation of InAs quantum dots on shallow mesa- and trench patterns regardless of crystallographic directions
AUTHORS:
J. H. Lee, Zh. M. Wang, W. T. Black, Vas. P. Kunets, Yu. I. Mazur, and G. J. Salamo
JOURNAL/BOOK TITLE:
Advanced Functional Materials
VOLUME:
17                                FIRST PAGE: 3187
YEAR OF PUBLICATION:
2007                                    TYPE: A                      IF: 6.808

Abstract



 

We report on the ability to grow InAs quantum dots into patterns of any shape.We specifically demonstrate the spatial localization of InAs quantum dots on mesa and trench patterns varying from line, square and triangle patterns on GaAs (100) substrates by molecular beam epitaxy. Based on the underlying science, this growth approach enables the localization of InAs QDs on GaAs (100) by controlling the sidewall facets and InAs monolayer coverage.

 


Graphical Abstract




Adv. Funct. Mater. 2007, 17, 3187?3193

Adv. Funct. Mater. 2007, 17, 3187?3193

 

TITLE: Observation of change in critical thickness of In droplet formation on GaAs (100)
AUTHORS: J H Lee, Zh M Wang, and G J Salamo

JOURNAL/BOOK TITLE: Journal of Physics: Condensed Matter                       
VOLUME: 19                            FIRST PAGE: 176223                          
YEAR OF PUBLICATION: 2007                                     TYPE: A                    
  IF: 1.9

Abstract



 

We present a study on the formation of In droplets on GaAs(100) substrates as functions of substrate temperature and monolayer (ML) deposition by using molecular beam epitaxy (MBE) and atomic force microscopy (AFM). We specifically reveal the change in critical thickness of In deposition to form In droplets at different substrate temperatures. At a relatively high substrate temperature, the critical thickness of In droplets becomes relatively thinner as the amount of As atoms on the surface decreases. The control of the size and density of In droplets is also systematically discussed. This study provides an aid in understanding the formation of In droplets and thus can find applications in the formation of quantum structures and/or nanostructures based on droplet epitaxy.

 


Graphical Abstract



J. Phys.: Condens. Matter 19 (2007) 176223

 

TITLE: Self-assembled InAs quantum dot formation on GaAs ring-like nanostructure templates
AUTHORS: N. W. Strom, Zh. M. Wang, J. H. Lee, Z. Y. AbuWaar, Yu. I. Mazur, and G. J. Salamo
JOURNAL/BOOK TITLE:
Nanoscale Research Letters  
VOLUME:
2  
                            FIRST PAGE: 112
YEAR OF PUBLICATION:
2007                                      TYPE: A                      IF: 1.731

Abstract



 

The evolution of InAs quantum dot (QD) formation is studied on GaAs ring-like nanostructures fabricated by droplet homo-epitaxy. This growth mode, exclusively performed by a hybrid approach of droplet homo-epitaxy and Stransky-Krastanor (S-K) based QD self-assembly, enables one to form new QD morphologies that may find use in optoelectronic applications. Increased deposition of InAs on the GaAs ring first produced a QD in the hole followed by QDs around the GaAs ring and on the GaAs (100) surface. This behavior indicates that the QDs prefer to nucleate at locations of high monolayer (ML) step density.

 


Graphical Abstract



Nanoscale Res Lett (2007) 2:112?117

 

TITLE: Novel Morphologies of InAs Quantum Dot Growth on GaAs Surfaces Containing Nanostructures Formed by Droplet Epitaxy
AUTHORS:
J. H. Lee, Zh. M. Wang, B. L. Liang, K. Sablon, N. W. Strom and G. J. Salamo
JOURNAL/BOOK TITLE:
Material Research Society Symposium Proceeding    
VOLUME:
959                           FIRST PAGE: 0959-M08-02
YEAR OF PUBLICATION: 2007                                        TYPE: A

Abstract



 

Self-assembled InAs quantum dot clusters (QDCs) and InGaAs QD molecules (QDMs) have been demonstrated through a growth technique called “droplet epitaxy” by molecular beam epitaxy (MBE). For QDCs, the size and density of QDs can be controlled with variation of InAs monolayer coverages. For QDMs, Ga contribution from GaAs mound with the interaction of InAs deposition resulted in various number of InGaAs QDs per GaAs mound, ranging from 2 to 6 (bi-QDMs to hexa-QDMs) depending on the specific InAs monolayer deposition. High step density on sidewall of GaAs mound and anisotropy of surface diffusion gave a rise to preferential formation of InAs and InGaAs QDs around GaAs mounds. This hybrid growth approach combining droplet epitaxy and typical QD growth is relatively simple and flexible and doesn’t require further ex-situ surface preparation. This approach of QD arrangement can find applications in optoelectronics as well as physical study of QD interaction.

 


Graphical Abstract



Mater. Res. Soc. Symp. Proc. Vol. 959 ⓒ 2007 Materials Research Society

TITLE: Optical behavior of GaAs/AlGaAs ring-like nanostructures”,
AUTHORS:
Ziad Y. AbuWaar, Yuriy I.
Mazur, Jihoon H. Lee, Zhiming M. Wang, and Gregory J. Salamo
JOURNAL/BOOK TITLE:
Journal of Applied Physics 
VOLUME:
101                           FIRST PAGE: 024311                          
YEAR OF PUBLICATION:
2007                                         TYPE: A                      IF: 2.201

Abstract



 

Atomic force microscopy and photoluminescence (PL) measurements were carried out to investigate the role of the morphology of GaAs/Al0.3Ga0.7As ringlike nanostructures on their optical properties. A small amount of Ga material (less than three monolayers) was used to fabricate single ringlike and double ringlike DRL nanostructures using droplet epitaxy technique. The height of the ringlike nanostructures increased with the increase of the Ga material while the corresponding PL emission energy was found to decrease as the ringlike nanostructure height increased. The PL peak energy showed a blueshift with increasing excitation intensity that can be understood as due to state filling while increasing temperature showed that the peak energy of the larger DRL nanostructures redshifts at a lower rate than the small ones due to larger confinement potential and lower energy emissions. © 2007 American Institute of Physics. [DOI: 10.1063/1.2425194]

 


Graphical Abstract




J. Appl. Phys. 101, 024311 (2007)

 

TITLE: Formation of Self-Assembled Sidewall Nanowires on Shallow Patterned GaAs (100)”,
AUTHORS:
J. H. Lee, Zh M Wang, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo
JOURNAL/BOOK TITLE:
IEEE Transactions on Nanotechnology  
VOLUME: 6                              FIRST PAGE: 70
YEAR OF PUBLICATION:
2007                                         TYPE: A                      IF: 2.154

Abstract



 

The formation of “sidewall nanowires” on shallow patterned mesa strips with a modulation depth of only 35 nm on GaAs (100) was demonstrated using molecular beam epitaxy. While self-assembled GaAs sidewall nanowire formation is observed near mesa strips running along [011], relatively thinner AlAs/GaAs layers are formed on identical mesa strips running along [01-1]. Cross-sectional atomic force microscopy (XAFM) on (011) and (01-1) and AFM on (100) are used to understand the formation of the different morphology of the nanostructures, depending on the direction of the mesas. The data indicates that anisotropic surface diffusion of adatoms, resulting from the characteristic (2 4) GaAs (100) surface reconstruction, is responsible for the sidewall nanowire formation and for the different morphology observed along different directions.

 


Graphical Abstract



IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 6, NO. 1, JANUARY 2007


IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 6, NO. 1, JANUARY 2007


 

TITLE: Self-Organization of InAs Quantum-Dot Clusters Directed by Droplet Homoepitaxy
AUTHORS: Zh. M. Wang, B. L. Liang, K. A. Sablon, J. H. Lee, Yu. I. Mazur, N. W. Strom, and G. J. Salamo
JOURNAL/BOOK TITLE:
Small   
VOLUME:
3                              FIRST PAGE: 235
YEAR OF PUBLICATION:
2007                                       TYPE: A                      IF: 6.525

Abstract



 

Recently, droplet heteroepitaxy of GaAs/AlGaAs has attracted much attention due to its demonstrated capability of producing nanostructures with interesting geometrical shapes such as quantum single and double ringlike structures. In the droplet-heteroepitaxy approach, Ga is deposited on an AlGaAs surface to create liquid Ga droplets, and these droplets are exposed to an As flux that transforms the droplets into GaAs nanocrystals. In principle, this same approach can e modified into a similar process of GaAs homo epitaxy, which also allows one to structure GaAs surfaces at the nanometer scale. In this droplet-homoepitaxy approach, the nanostructures formed by the droplets can then be used to encourage the growth of subsequent heteronanostructures such as self-assembled InAs quantum dots (QDs).

 


Graphical Abstract



small 2007, 3, No. 2, 235 ? 238small 2007, 3, No. 2, 235 ? 238

 

TITLE: Survival of Atomic monolayer steps during oxide desorption on GaAs (100)
AUTHORS:
J. H. Lee, Zh. M. Wang, and G. J. Salamo
JOURNAL/BOOK TITLE: Journal of Applied Physics
VOLUME:
100                           FIRST PAGE: 114330                          
YEAR OF PUBLICATION:
2006                                         TYPE: A                      IF: 2.201

Abstract



 

Significant surface pitting and a degraded surface roughness are almost always observed on GaAs (100) surface after conventional thermal oxide desorption. Here we report on the use of a Ga-triggered low temperature oxide desorption method that can be used to preserve the atomic monolayer (ML) steps. By providing an external supply of atomic Ga at a relatively low substrate temperature of 450 °C without an As4 overpressure, this technique resulted in an atomically smooth GaAs ML steps with a root mean square roughness of 0.25 nm, nearly identical to as-grown GaAs surface (0.2 nm). The demonstrated results show the potential for applications in optoelectronics such as regrowth and patterned substrate growth. © 2006 American Institute of Physics. [DOI: 10.1063/1.2401649]

 


Graphical Abstract



J. Appl. Phys. 100, 114330 (2006)

 

TITLE: Observation of Ga droplet formation on (311)A and (511)A GaAs surfacess
AUTHORS:
Ziad Y AbuWaar, Zhiming MWang, J. H. Lee, Gregory J Salamo
JOURNAL/BOOK TITLE:
Nanotechnology 
VOLUME:
17                            FIRST PAGE:
4037          
YEAR OF PUBLICATION:
2006                                           TYPE: A                      IF: 3.446

Abstract



 

Using (100) GaAs substrates as a reference, we present a study of the formation of Ga droplets on (311)A and (511)A GaAs substrates in which the effect of both the substrate temperature and the amount of Ga supplied on the droplet density and height for the three different surfaces have been investigated. Droplets on (100) substrates show a round shape; however, they appear as elongated balls with tails along the [¯233] direction of the (311)A substrate and the [¯255] direction of the (511)A substrate. It has been found that the Ga droplets on (511)A surfaces have lower densities and higher heights than those on (100) substrates. In contrast, Ga droplets on (311)A surfaces have lower heights and much higher densities compared to those for both (100) and (511)A. We observed that the decrease in the droplet density with increasing growth temperature for both (311)A and (511)A is more than twice that for the (100)GaAs surface due to the larger drop in the nucleation rate. Based on these observations, we offer a physical explanation based on the thermodynamics and the anisotropy of the high-index surfaces.

 


Graphical Abstract



Observation of Ga droplet

 

TITLE: Multiple vertically stacked quantum dot clusters with improved size homogeneity
AUTHORS:
J. H. Lee, Zh. M. Wang, B. L. Liang, K. A. Sablon, N. W. Strom, and G. J. Salamo
JOURNAL/BOOK TITLE: Journal of physics D: Applied physics
VOLUME:
40                            FIRST PAGE: 198                                
YEAR OF PUBLICATION:
2006                                         TYPE: A                      IF: 2.104

Abstract



 

clusters within a GaAs matrix are investigated on GaAs (1 0 0) by atomic force microscopy. Droplet homoepitaxy (GaAs nanostructures on planar GaAs) is used to create tiny GaAs nano-mound templates elongated along [0 1−1]. Due to a high density of monolayer steps on the edge of nano-mounds, deposited InAs prefer to form in clusters around the nano-mound templates. By varying the subsequent InAs monolayer coverages and growth temperatures, two distinctive sizes of quantum dots (QDs) are formed around the nano-mounds for the layer stacking. With a fixed GaAs barrier thickness (10 nm) in between the layers, the resulting QDs from the stacked layers show significant improvement in their size uniformity.

 


Graphical Abstract



J. Phys. D: Appl. Phys. 40 (2007) 198?202

 

TITLE: Annealing effect in InAs quantum dots grown on GaAs droplet template
AUTHORS:
B. L. Liang, Zh. M. Wang, J. H. Le, K. Sablon, Yu. I. Mazur, G. J. Salamo
JOURNAL/BOOK TITLE:
Applied Physics Letters
VOLUME:
89                            FIRST PAGE: 213103
YEAR OF PUBLICATION:
2006                                           TYPE: A                      IF: 3.726

Abstract



 

The authors report on the use of GaAs islands, formed by the droplet epitaxy growth technique, as a template for the growth of clusters of InAs quantum dots. Surface morphology measurements show that the shape and dimensions of the GaAs islands and consequently the formation of InAs quantum dots depend strongly on the annealing temperature and annealing time. This can be explained by the diffusion of gallium atom during the annealing process and the selective formation of InAs quantum dots on the misoriented GaAs island sidewalls. © 2006 American Institute of Physics. [DOI: 10.1063/1.2396928]

 


Graphical Abstract



Appl. Phys. Lett. 89, 213103 (2006)


TITLE: Journal cover of the volume 89, issue 20 of Applied Physics Letters"
AUTHORS: J. H. Lee, Zh. M. Wang, N. W. Strom, Yu. I. Mazur and G. J. Salamo
JOURNAL/BOOK TITLE: Applied Physics Letters
VOLUME: 89                             FIRST PAGE: 202101
YEAR OF PUBLICATION: 2006       TYPE: A        IF: 3.726
APL 89 20
 

 

TITLE:InGaAs quantum dot molecules around self-assembled GaAs nano-mound templates"
AUTHORS:
J. H. Lee, Zh. M. Wang, N. W. Strom, Yu. I. Mazur and G. J. Salamo
JOURNAL/BOOK TITLE:
Applied Physics Letters
VOLUME:
89                            FIRST PAGE: 202101                                                         
YEAR OF PUBLICATION:
2006                                          TYPE: A                      IF: 3.44

(Featured on the Journal cover of the volume 89, issue 20 of Applied Physics Letters)
(Selected as one of the most downloaded articles of November 2006)


Abstract



 

Several distinctive self-assembled InGaAs quantum dot molecules (QDMs) are studied. The QDMs self-assemble around nanoscale-sized GaAs moundlike templates fabricated by droplet homoepitaxy. Depending on the specific InAs monolayer coverage, the number of QDs per GaAs mound ranges from two to six (bi-QDMs to hexa-QDMs). The Ga contribution from the mounds is analyzed in determining the morphologies of the QDMs, with respect to the InAs coverages ranging between 0.8 and 2.4 ML. Optical characterization shows that the resulting nanostructures are high-quality nanocrystals. © 2006 American Institute of Physics. [DOI: 10.1063/1.2388049]

 


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Appl. Phys. Lett. 89, 202101 (2006)

Appl. Phys. Lett. 89, 202101 (2006)

 

TITLE: Structural evolution in strained In0.18Ga0.82As staking multilayer on vicinal GaAs surfaces
AUTHORS:
V. Yazdanpanah, Zh. M. Wang, J. H. Lee, and G. J. Salamo
JOURNAL/BOOK TITLE:
New Journal of Physics 
VOLUME:
8                            FIRST PAGE: 233                                                         
YEAR OF PUBLICATION:
2006                                          TYPE: A                      IF: 3.44

Abstract



 

Strain relaxation mechanisms for the growth of m-layers of In0.18Ga0.82As/GaAs on a GaAs(100) substrate, tilted 2? towards the [0–11] direction, have been studied by molecular beam epitaxy (MBE) and atomic force microscopy (AFM). While dislocations alone provide a strain relaxation mechanism for nominal GaAs(100), additional strain relaxation mechanisms were observed for a vicinal GaAs(100) substrate. For m  8, step bunching provided a mechanism for strain relaxation. For m 10, in addition to the step bunching, bunched corners along two [051] and [0–1–5] directions provided the mechanism for strain relaxation. These surface patterns provide potential to act as a template for the growth of more uniform and organized nanostructures. For m = 16, the formation of dislocations provided an additional route for strain relaxation.

 


Graphical Abstract



New Journal of Physics 8 (2006) 233

 

TITLE: Low density InAs quantum dots grown on GaAs nanoholes”,
AUTHORS:
B. L. Liang, Zh. M. Wang, J. H. Lee, K. Sablon, Yu. I. Mazur, G. J. Salamo
JOURNAL/BOOK TITLE: Applied Physics Letters
VOLUME:
89                            FIRST PAGE: 043113
YEAR OF PUBLICATION:
2006                                          TYPE: A                      IF: 3.726

Abstract



 

A growth technique combining droplet epitaxy and molecular beam epitaxy (MBE) is developed to obtain a low density of InAs quantum dots (QDs) on GaAs nanoholes. This growth technique is simple, flexible, and does not require additional substrate processing. It makes possible separate control of the QD density via droplet epitaxy and the QD quality via MBE growth. In this letter the authors report the use of this technique to produce InAs QDs with a low density of 2.7 x 10^8 cm^−2 as well as good photoluminescence properties. The resulting samples are suitable for single QD device fabrication and applications. © 2006 American Institute of Physics. [DOI: 10.1063/1.2244043]

 


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Appl. Phys. Lett. 89, 043113 (2006)       Appl. Phys. Lett. 89, 043113 (2006)

 

TITLE: Evolution between self-assembled single and double ring-like structures
AUTHORS:
J. H. Lee, Zh. M. Wang, Z. Y. AbuWaar, N. W. Strom and G. J. Salamo
JOURNAL/BOOK TITLE:
Nanotechnology 
VOLUME:
17                            FIRST PAGE: 3973          
YEAR OF PUBLICATION:
2006                                           TYPE: A                      IF: 3.446

Abstract



 

The evolution between lattice-matched GaAs/Al0.3Ga0.7As single and double ring-like nanostructures is studied, with an emphasis on the construction and destruction of the observed outer ring. Using droplet epitaxy, this was achieved by directly controlling the Ga surface diffusion on GaAs(100). Double ring-like nanostructures were observed at relatively low temperatures under a fixed As4 flux (beam equivalent pressure (BEP) of 6.4 μTorr) and at a fixed temperature under a high As4 flux. The construction of the outer ring can be controlled through surface diffusion by varying the substrate temperature or the As4 flux. Single ring-like nanostructures were realized both at relatively high temperatures under a fixed As4 flux, and at low temperatures under a relatively low As4 flux.

 


Graphical Abstract




Nanotechnology 17 (2006) 3973?3976


TITLE: Journal cover of volume 88, issue 23 of Applied Physics Letters
AUTHORS:
Zh M Wang, J. H. Lee, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo
JOURNAL/BOOK TITLE:
Applied Physics Letters
VOLUME:
88    FIRST PAGE: 233102
YEAR OF PUBLICATION:
2006                   TYPE: A                 IF: 3.726
Journal cover of volume 88, issue 23 of APL
 

 

TITLE: Localized Formation of InAs Quantum Dots on Shallow- patterned GaAs (100)
AUTHORS:
Zh M Wang, J. H. Lee, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo
JOURNAL/BOOK TITLE:
Applied Physics Letters
VOLUME:
88    FIRST PAGE: 233102
YEAR OF PUBLICATION:
2006                   TYPE: A                 IF: 3.726

(Featured on the Journal cover of volume 88, issue 23 of Applied Physics Letters)

|Abstract



 

Selective formation of InAs quantum dots on the sidewalls of mesa strips along both [01−1] and [011] directions of a GaAs100 surface is demonstrated. This result is in sharp contrast to observations on traditionally deep-patterned substrates, where quantum dots are formed on top mesas and at bottom trenches. This distinction is explained kinetically and energetically. These results may encourage application of organized arrays of quantum dots. © 2006 American Institute of Physics. [DOI: 10.1063/1.2209157]

 


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Appl. Phys. Lett. 88, 233102 (2006)

 

TITLE: Size and density control of InAs quantum dot ensembles on self-assembled nano- structured templates
AUTHORS:
J. H. Lee, Zh. M. Wang, B. L. Liang, K. A. Sablon, N. W. Strom, and G. J. Salamo
JOURNAL/BOOK TITLE:
Semiconductor Science and Technology 
VOLUME: 21                            FIRST PAGE: 1547
YEAR OF PUBLICATION:
2006                                         TYPE: A                      IF: 1.434

Abstract



 

New morphologies of InAs quantum dot (QD) ensembles forming on self-assembled GaAs nano-holed island templates are demonstrated. Droplet homoepitaxy (GaAs/GaAs) is used to generate holed nanoscale-sized mounds that appear to elongate along [0 1 ¯1]. Depending on the InAs monolayer (ML) coverages, subsequent InAs deposition forms different sizes and shapes of QD ensembles. While we initially observe the formation of the QDs at the hole sites when less InAs is deposited, QDs form around the edges of the mounds with greater InAs deposition. By varying the InAs depositions and growth temperatures, we demonstrate an ability to control the size and density of QDs. The observed decrease in the necessary critical thickness required for the InAs 2D–3D transition may be due to the higher density of monolayer steps on the sidewalls of the holes and on the edges of the mounds. This hybrid growth approach overcomes some limitations of typical QD growth on planar GaAs surfaces and may find applications in optoelectronics.

 


Graphical Abstract



Semicond. Sci. Technol. 21 (2006) 1547:1551

 

TITLE: InGaAs quantum dots grown on B-type high index GaAs substrates: surface morphologies and optical properties
AUTHORS:
B. L. Liang, Zh. M. Wang, Yu. I. Mazur, V. V. Strelchuck, K. Homles, J. H. Lee, G. J. Salamo
JOURNAL/BOOK TITLE:
Nanotechnology
VOLUME:
17                            FIRST PAGE: 2736                              
YEAR OF PUBLICATION:
2006                                       TYPE: A                      IF: 3.446

Abstract



 


We systematically investigated the correlation between morphological and optical properties of InGaAs self-assembled quantum dots (QDs) grown by solid-source molecular beam epitaxy on GaAs (n11)B (n = 9, 8, 7, 5, 3, 2) substrates. Remarkably, all InGaAs QDs on GaAs(n11)B under investigation show optical properties superior to those for ones on GaAs(100) as regards the photoluminescence (PL) linewidth and intensity. The morphology for growth of InGaAs QDs on GaAs (n11)B, where n = 9, 8, 7, 5, is observed to have a rounded shape with a higher degree of lateral ordering than that on GaAs(100). The optical property and the lateral ordering are best for QDs grown on a (511)B substrate surface, giving a strong correlation between lateral ordering and PL optical quality. Our results demonstrate the potential for high quality InGaAs QDs on GaAs(n11)B for optoelectronic applications.


 


Graphical Abstract



Nanotechnology 17 (2006) 2736?2740 doi:10.1088

 


TITLE: Highlighted in the NanoWerk Sport light, April 12th, 2006
AUTHORS:
J. H. Lee, Zh M Wang, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo
JOURNAL/BOOK TITLE:
Nanotechnology  
VOLUME:
17                            FIRST PAGE: 2275
YEAR OF PUBLICATION:
2006                         TYPE: A          IF: 3.446
Link: QD necklaces and other QD chains
QD necklaces and other QD chains
 

 

TITLE: Selective growth of InGaAs/GaAs quantum dot chains on pre-patterned GaAs (100)
AUTHORS:
J. H. Lee, Zh M Wang, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo
JOURNAL/BOOK TITLE:
Nanotechnology  
VOLUME:
17                            FIRST PAGE: 2275
YEAR OF PUBLICATION:
2006                         TYPE: A          IF: 3.446

(Highlighted in the NanoWerk Sport light, April 12th, 2006)

Abstract



 

Self-organized InGaAs quantum dot chains grown by molecular beam epitaxy were investigated using vertical stacking techniques on pre-patterned GaAs(100) substrates. The results demonstrate the formation of quantum dot (QD) chains only on desired spatial regions. In addition to QD chains, the results show that almost any shape of lines of QDs are possible depending on the faceted pre-patterned substrate. The experimental results suggest that this approach has the potential to be used to fabricate single QD chains or necklaces or almost any pattern.

 


Graphical Abstract



Nanotechnology 17 (2006) 2275?2278


 

TITLE: Ga-Triggered oxide desorption from GaAs (100) and non-(100) Substrates
AUTHORS: J. H. Lee, Zh. M. Wang, and G. J. Salamo
JOURNAL/BOOK TITLE: Applied Physics Letters 
VOLUME: 88                           FIRST PAGE: 252108                          
YEAR OF PUBLICATION: 2006                                       TYPE: A                      IF: 3.726


Abstract



 

Surface pit formation is observed to occur for conventional thermal oxide desorption, regardless of the GaAs surface index. The resulting surface roughening can be substantially reduced by depositing an appropriate amount of Ga in the absence of As flux. The amount of Ga required to optimize the quality of the oxide-free GaAs surface is found to be different for different indexed substrates and is dependent on the oxide thicknesses. Due to the flexibility of the GaAs surface reconstruction, the Ga-triggered oxide desorption is observed to be much more robust than was previously believed. © 2006 American Institute of Physics.

 


Graphical Abstract

APPLIED PHYSICS LETTERS 88, 252108 2006

 

TITLE: “Control of the morphology of quantum dot structures on III-V semiconductors"
AUTHORS: J. H. Lee
JOURNAL/BOOK TITLE: (M. S. Thesis) The University of Arkansas Press
YEAR OF PUBLICATION: 2005                                       TYPE: B

 

 

TITLE: Surface ordering of (In,Ga)As quantum dots controlled by GaAs substrate indexes
AUTHORS: Zh. M. Wang, Sh. Seydmohamadi, J. H. Lee, and G. J. Salamo
JOURNAL/BOOK TITLE: Applied Physics Letters
VOLUME: 85                            FIRST PAGE: 5031                              
YEAR OF PUBLICATION: 2004                                        TYPE: A                      IF: 3.726

Abstract



 

Self-organized surface ordering of (In,Ga)As quantum dots in a GaAs matrix was investigated using stacked multiple quantum dot layers prepared by molecular-beam epitaxy. While one-dimensional chain-like ordering is formed on singular and slightly misorientated GaAs(100) surfaces, we report on two-dimensional square-like ordering that appears on GaAs(n11)B, where n is 7, 5, 4, and 3. Using a technique to control surface diffusion, the different ordering patterns are found to result from the competition between anisotropic surface diffusion and anisotropic elastic matrix, a similar mechanism suggested before by Solomon [Appl. Phys. Lett. 84, 2073 (2004)].
© 2004 American Institute of Physics. [DOI: 10.1063/1.1823590]

 


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Appl. Phys. Lett., Vol. 85, No. 21, 22 November 2004

Appl. Phys. Lett., Vol. 85, No. 21, 22 November 2004


 
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