Electrical Characterisation of Low Dimension
Structures
Staff: Dr David Martin, and Dr Chao Zhang
A novel technique has been developed to probe the electrical characteristics
of resonance due to electron tunnelling through barriers in layered semiconductor
structures. The measurements reveal the details of multistable regions and are
coupled with spectroscopic techniques (see below) to give a description of the
physical processes involved in the tunnelling.
Imaging Physics
Staff: Associate Professor Bill Zealey, Mr Glen Moore and Mr Peter
Ihnat
Australian astronomers have access to one of the deepest photographic surveys
of the southern skies in the ESO/SERC Sky Survey. This astronomical research
programs depend on the efficient use and analysis of photographic images.
In order to fully exploit the ESO/SERC film surveys which is available the
group
has access using fast real time image digitising and analysis systems.
Medical
Physics
Staff: Dr Jagdish Mathur, Dr Anatoly Rozenfeld and Mr Greg Kaplan
Research in Medical Radiation Physics is undertaken
in collaboration with the Illawarra Cancer Care
Centre, St George Cancer Care Centre and ANSTO.
Monte Carlo
techniques for dose planning in mixed radiation fields, x-ray fields and Microdosimetry.
Monte Carlo codes such as the Los Alamos MCNP neutron photon transport code
and EGS4 electron gamma transport code are being used to determine dose distributions
within phantoms and patients, with the aim of introducing such techniques for
treatment planning. Monte Carlo techniques are also used for detector response
modelling and microscopic dose distribution models of biological cells.
Semiconductor Detectors for Nuclear Radiation Dosimetry
During radiation treatment of patients it is important to know the depth
dose distribution of each component of the radiation field. A new approach
using silicon
detectors is being developed for experimental verification of Monte Carlo dose
calculations in mixed gamma-neutron radiation fields such as occur in Boron
Neutron Capture Therapy (BNCT). The group recently began investigating dosimetry
using
micron sized silicon structures for surface dose measurements on medical linacs,
and for microdosimetry on the cellular scale.
Semiconductor Detector Properties
Charge collection in semiconductor radiation detectors,
using irradiation with charged particles and laser
beam, is being studied using fast electronics,
C-V,
I-V and DLTS techniques.
A recently commenced project involves studying radiation damage to ion-implanted
silicon detectors in non-uniform fast neutron fields. This research is
relevant to applications of silicon detectors in high energy physics
and medical imaging.
Observational Astrophysics
Staff: Associate Professor Bill Zealey, Mr Glen Moore and Mr Peter
Ihnat
Extragalactic Star Formation
Many galaxies appear to be undergoing recent, enhanced star formation. Several
of the larger low surface brightness galaxies show unusual structures associated
with tidally induced star formation. The continuum emission and gas dynamics
of these galaxies is being studied using the Australia Telescope.
Protostars and Jets
Stars are born in dense molecular clouds. Supersonic mass loss plays a major
role in the early evolution of most young stellar objects. Studies of outflows
at radio and infrared wavelengths are being conducted to understand the earliest
outflow phase of star formation.
Long Period Variable Stars in the Magellanic Clouds
The Magellanic Clouds present a unique opportunity to study complete samples
of stars which are believed to be precursors to planetary nebulae and supernova.
Measurements of these Long Period Variables (LPVs) provide information on
the evolutionary behaviour of stars in their late stages. In collaboration
with researchers at Mt Stromlo and Siding Spring Observatories the Department
has completed a search for LPV's in the Small Magellanic Cloud and established
the most complete database in existence.
Optical Spectroscopy of Semiconductors\
Staff: Professor Peter Fisher, Dr Carey Freeth, Dr Roger Lewis, Dr
David Martin, Dr Rodney Vickers and Dr Chao Zhang
Optical spectroscopy is used in the study
of the electronic states in elemental and compound
semiconductors. Absorption, photoluminescence
and
Raman spectroscopy utilise optically pumped Far-infrared laser state-of-the-art,
very high resolution, Fourier and grating spectrometers; 25 watt Ar+ laser;
dye and titanium-sapphire lasers; and a high field superconducting magnet.
Elementary excitations and impurities in semiconductors are the main areas
of interest. The materials include the new and technologically important
quantum well semiconductor structures. Under study are acceptor and band
states in bulk GaAs, Ge and Si and in quantum wells and heterostructures.
Externally applied magnetic fields and/or uniaxial stresses produce very
rich and detailed spectra. Theoretical support is provided for all areas
of this research.
Planetary Physics
Staff: Associate Professor Bill Zealey
The availability of archival CD ROM
images of Venus, Mars and the moons of
the outer planets supports the study of
planetary surfaces. Of particular
interest are the volcanic and impact structures on Mars, Venus and the
Earth/Moon system.
Theoretical Astrophysics
Staff: Dr Paul Nulsen
The Intracluster Medium
Many of the galaxies in the Universe are bound together by gravity into groups
or clusters, which may consist of anywhere from just a few to a few thousand
galaxies. Along with the galaxies, a large quantity of hot gas, often exceeding
the galaxies in total mass, is trapped in clusters by gravity. The gas is
so hot, from a few million to 100 million degrees, that it emits X-rays.
Theoretical and observational studies on the state, origin and fate of this
gas are continuing.
Galaxy formation
The process of galaxy formation is being studied in increasing detail. Galaxies
are believed to have formed by gravitational collapse of the primordial gas
which initially filled the Universe. It has been shown recently that most normal
galaxies undergo a phase, called a cooling flow, where hot gas cools slowly.
The cooling flow phase plays an important role during galaxy formation, accounting
for a number of their observed properties.
Jet formation and collimation
A new, hydrodynamical model for the formation of jets is being investigated.
Most current models rely on a magnetic field to couple rotational energy from
an accretion disk into a jet, whereas this model relies on frictional heating
of gas above a disk to drive and collimate the jet.
Theoretical Solid State Physics
Staff: Dr Chao Zhang
The optical properties and transport phenomena
of solids, especially semiconductors, are being studied,
along with superconductors and other many-electron
systems. Research in this field is carried out using
techniques of many-body theory, quantum dynamics, kinetic
theorem, band calculations and computer simulations.
Recent projects include: phonon and impurity related
optical absorption in III-V semiconductors, in particular,
the effects of magnetic field and stress; quantum tunnelling,
magnetotransport and quantum interference effects in
microstructures; exchange and correlation effects in
many-electron system under strong magnetic fields and
at low temperature; cyclotron resonance and magneto-optics
in extreme quantum limit. |
