[nanoPost] Plasma-synthesized self-organized quantum dot arrays for nanodevice applications

Research Centre Australia

Unique optical and electronic properties of low-dimensional semiconductors such as quantum dots have contributed to a
flourish of research interest.

Quantum dots are small structures whose sizes (typically 3-60 nm), on the scale of the
carrier de Broglie wavelength, produces high levels of spatial confinement for such carriers (electrons), namely quantumconfinement.
Quantum confinement of electron motion extends from three to zero dimensions corresponding to bulk
semiconductors, quantum wells, wires and dots respectively. The Ge-Si QD system is a nanostructure that has been
synthesized using many of the fabrication methods providing a broad field of comparison between the various methods.
In this work we investigate the fabrication of zero-dimensional Ge-Si(100) quantum dots (QD) on Si(100) wafer substrate.
A series of numerical experiments made on plasma deposition of Ge-Si Quantum Dots have demonstrated that the selfordering
processes can indeed take place in the plasma-surface systems. We have shown that the arrays deposited from
ionized fluxes demonstrate a clear tendency to the organization, due to the effect of electric field on growing QD and
subsequent quantum dot movement about substrate surface.
Hybrid Monte Carlo simulation method was used to determine the growth and displacement of germanium quantum dots
on Si (100) wafer substrate via plasma enhanced chemical vapor deposition. The plasma method of quantum dot
fabrication is shown to exhibit self-organized behavior. Peak quantum dot density was achieved with a total coverage of
0.42 with a population of 400 dots. The final mean radius of the quantum dot ensemble was observed to be 18 nm with
the mean radius of ~14 nm representing the value quantum dots were most uniform. Growth rates were found to be
higher for small and more isolated quantum dots while retarded for larger closely pack quantum dots, indicating selforganized
behavior to achieve uniform size distribution. The non-uniform adatom flux model of quantum dot
displacement indicated tendency for quantum dots to migrate into regions of lower population density, with magnitude
displacements showing an inverse dependence relation to quantum dot size. Observations qualitatively suggest spatially
self-organized behavior.