PROPOSED PROJECT TITLE
Revealing magnetic information from a
thin layer surface by using the synchrotron X-ray scanning tunnelling microscopy
My Proposed research will be highlight on ‘Revealing
magnetic information from a thin layer surface by using the synchrotron
X-ray scanning tunnelling microscopy”
The observation of magnetic structure in real
space utilizing scanning probe microscopy (SPM) techniques or synchrotron-based
microscopy keeps on tremendously affecting our comprehension of nano magnetism.
Magnetic force microscopy (MFM) recognizes the forces between a magnetic specimen
surface and magnetic tip while spin polarized scanning tunnelling microscopy
(SP-STM) is sensitive to the spin orientation of tunnelling electrons. Despite
the fact that these strategies give high spatial resolution of specimen surface,
they do not have direct chemical contrast. On the other hand, chemical and
sensitivity can be proved by photoemission electron microscopy (PEEM). However,
photoelectron emission angles restrict the spatial resolution.
In order to conquer these restrictions, some
groups around the world have been developing instruments that combine
synchrotron radiation with the high spatial resolution of various SPM. As of
late, synchrotron X-ray scanning tunnelling microscopy (SX-STM) demonstrated
the ability to acquire elemental contrast with 2nm of resolution. The SX-STM
technique uses the energy-dependent absorption of X-rays to acquire information
about the composition of a sample. Core electrons are excited in the absorption
process into empty states above the Fermi energy, while a specific tip is
scanning over a specimen surface. In the meantime, auxiliary electrons are shot
out from the sample surface. The two commitments, i.e. X-ray energized tunnelling
and photo ejected electrons, adjust the ordinary tunnelling current and
subsequently provide the chemical contrast.
The proposed research methodology and
objectives are as follow:
The Cu (111)
surface will be cleaned by repeated cycle of Argon sputtering and annealing.
(ii) Cobalt atoms will be evaporated from electron
beam evaporator to Cu (111) surface in the load lock attached to SX-STM.
(iii) Localized spectroscopy with simultaneous topographic, elemental
and magnetic information will be studied by employing the synchrotron X-ray
scanning tunnelling microscope. The local investigation of the X-ray magnetic
circular dichroism(XMCD) at the Cobalt L2,3-edges of a
thin cobalt film grown on Cu(111) will be carried out.
(iv) Polarization dependent X-ray absorption spectra will be obtained
through a tunnelling non-conductive tip as a photoelectron detector.
Contradictory to conventional spin-polarized scanning tunnelling microscopy,
X-ray excitations will provide magnetic contrast even with a non-magnetic tip.
(v) Determination of topography and chemistry simultaneously as well
as the potential will be done to measure the actual size of magnetic moments
using the dichroism effect.
Facilities & Equipment required
(a) Electron beam evaporator: to deposit thin layer of cobalt on
(b) Soft X-rays (3-5 keV) beamline at Advanced Photon Source at
Argonne National Laboratory, Chicago: to probe the magnetic properties of a
(c) Synchrotron X-ray scanning tunnelling
microscopy (SX-STM) at Advanced Photon Source at Argonne
National Laboratory, Chicago: to
measure the local X-ray magnetic circular dichroism
Proposed research topic
X-ray magnetic circular dichroism(XMCD) is a difference of right
circularly polarized (RCP) and left circularly polarized (LCP) of two X-ray
absorption spectra in a magnetic field. The information about the magnetic
properties such as orbital magnetic moment and spin of the atom can be obtained
by analysing the difference in the spectrum.
Reasons for wishing to pursue PhD studies in
Hong Kong (about 200 words)
for wishing to study PhD in Hong Kong
I would like to pursue PhD in Hong Kong
because I believe the global issuses will be able to solve at international
leading research universities in Hong Kong.
The universities in Hong Kong are
enriched in world class experimental equipments and attractive life style.
To broaden my knowledge at high
performance universities in Hong Kong.
After graduating from Hong Kong, I will
be able to take part in building a modernized country (Myanmar).
Long-term career plan, aims and interests for
future development after graduation
carrier plan is that to develop a single molecule magnet which can tune the
transition temperature in which the molecule become ferromagnetic. To develop
the new way to store the data on single molecule bit by bit rather than transistor
Contribution that the applicant would like to
make to the development of research in Hong Kong and to society
I would like to develop a molecule
that can function as a magnet in Hong Kong. Then, we can use a single molecule
to store in formation. That is one bit of information per molecule device by
using a single magnet even smaller in Hong Kong.
Other remarks in relation to the application
for Hong Kong PhD Fellowship
HKPFS will be a very effective
program for the people like me from least developed country like Myanmar. It
will also help me to learn both scientific knowledge and east-meets-west