4.E.4 International Collaborations
CSPIN is not only a partnership of talent between two universities, but also includes talent from
other countries as integral parts of the proposed research plans of both IRGs. Examples of our ongoing
and proposed international collaborations are described below:
IRG 1: The arrays of nanostructures fabricated in IRG1 enable several international
collaborations. Salamo and Johnson will continue to collaborate with F.A. Hegmann of the University of
Alberta (Canada) on terahertz pulse spectroscopy experiments that probe anisotropic photoconductivity
and mobility in nanostructures. These contactless measurements of conductivity and mobility have
already been performed on InGaAs quantum dot chains fabricated by Salamo. We will extend this
collaboration to other nanostructures fabricated by CSPIN. Johnson also proposes to collaborate with
M.H. Kuok of the National University of Singapore and David Lockwood of the National Research
Council (Canada) on Brillouin scattering of Nickel nano-ring arrays. The experiments will be carried out
in Singapore on nano-rings fabricated by CSPIN, with theory support from Canada.
Salamo collaborates with Mathieu Chauvet at the Université de Franche Comte (France) on
optical switching of spatial solitons in AlGaAs waveguides. We are working toward a reconfigurable
optical interconnect device with quantum dots in the guiding slab. Xiao and Salamo also work with
W. Ted Masselink and R. Köhler of Humboldt-Universität zu Berlin on the transport properties of selforganized quantum dots and wires and x-ray diffuse scattering by III-V quantum dot arrays, respectively.
The latter work has confirmed that the vertical stacking of quantum dots is tilted, and we are currently
developing a model to explain this behavior. Further work is also targeted toward Mn doped dot arrays
with a focus on determining the nature and amount of Mn and on magneto-optical effects. Salamo and
Xiao are also in partnership with J.W. Tomm and C. Linau of the Max-Born-Institut für Nichtlineare
Optik und Kurzzeitspektroskopie. We are working together on femtosecond time resolved spectroscopy
and on near-field low temperature microscopy on the QD, QWR, and QR arrays. We are exploring
excitation at one location in the array and examining emission at other locations due to tunneling of
excited carriers. Salamo also has a started a collaboration with G. Tränkle and H. Kissel of the
Ferdinand-Braun-Institut für Höchstfrequenztechnik. We will form a team together with Masselink on
developing electron beam lithography on patterned substrates, which will then be used as substrates for
self-assembled organized growth. We will use cathodoluminescence to explore individual nanosize
elements of the array in order to observe their individual structure.
IRG 2: Salamo, Santos, and Murphy propose to collaborate with W. Ted Masselink of
Humboldt-Universität zu Berlin on the development of micro-Hall sensors made from narrow gap
material grown at CSPIN. This project will be coupled to the collaboration with Hitachi on the
development of mesoscopic read-head sensors. Santos, a graduate student and two undergraduates made
several visits to NTT Basic Research Laboratories (Japan) during the past three years to collaborate on
ballistic transport experiments with Yoshiro Hirayama’s group. Each student stayed in Japan for ~10
weeks. Most of the travel and lodging costs were funded by an AWARE (American Workforce and
Research and Education) supplement from the NSF Office of International Science and Engineering.
Murphy and Santos propose to continue to send students to NTT to fabricate mesoscopic devices from
narrow gap material produced at CSPIN. Experiments on these devices will be conducted at NTT and
CSPIN.
The collaboration with NTT has benefited participating students in both their scientific and
cultural educations. The CSPIN students, including two Americans, were welcomed into the Quantum
Solid State Physics Group. They worked closely with their Japanese hosts and lived in the same NTTowned dormitories as Japanese employees. The results of their collaborative experiments have been
presented at three international conferences and are described in three publications. Additionally, four
CSPIN students visited Japan for one week to participate in NTT Summer Schools on Quantum
Computing (2002) and Transport Properties in Quantum Nanostructures (2004). We will explore similar
opportunities with other international collaborators and plan to apply for appropriate supplemental
funding from the NSF Office of International Science and Engineering.