Frontiers of Engineering Reports on Leading-Edge Engineering From the 2000 NAE Symposium on Frontiers in Engineering (2001) / Chapter Skim
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Nanoscale aterials: Sysnthesis, Analysis, and Applications
Nanoscale aterials: Sysnthesis, Analysis, and Applications
Pages 93-104
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From page 93... ...
Gate oxides are approaching a thickness of a mere 2 nm, where quantum mechanical tunneling becomes a serious concern because of its negative effect on device lifetime. The number of dopant atoms in the active region of a transistor becomes so small that statistical variations become significant, giving rise to undesirable device-todevice variations in operation.
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From page 94... ...
How do we create such a superposition, and how do we manipulate it? Is this quantum world a nanoworld (atoms or quantum dots; Loss and DiVincenzo, 1998)
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From page 95... ...
One problem is that there is no equivalent to the size distillation step that worked so well for the CdSe quantum dots shown above. Second, nucleation can occur over a relatively long time window, giving rise to broad size distributions.
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From page 96... ...
of Ge quantum dots grown on Si(001~. Figure 2b shows a scanning electron microscopy image (Ross et al., 1999)
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From page 97... ...
The shape information is lost, but the size of the dots can be measured accurately, and growth can be followed in real time. This allows a detailed study of the time evolution of the quantum dot size distribution.
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From page 98... ...
The microscopy methods shown in Figure 2 are examples, but optical studies of single quantum dots are also feasible (Nirmal et al., 1996~. The electronic properties of single dots have been studied using electron energy loss in a specialpurpose scanning transmission electron microscope (Batson and Heath, 1993~.
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From page 99... ...
The quantum dot potential can be set by the use of a gate electrode in proximity to the quantum dot. As the gate potential is varied, the source-to-drain conductance oscillates with gate voltage intervals that correspond to the charging voltage of the quantum dot because of the addition of a single electron.
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From page 100... ...
These films represent an interesting application of quantum dots and nanocrystalline materials that is not to be overlooked: quantum dots as raw material in bulk quantities, used to assemble new nanostructural materials with superior mechanical, electrical, magnetic, or thermal properties. Thin-film semiconductors are another example of such an application.
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From page 101... ...
Like the hard magnetic films and solar cells discussed above, new material properties might be realized with the resulting nanostructural solids, at low costs. Nanostructural inks might present the largest opportunity for the practical application of quantum dots and nanocrystals in the next two decades.
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From page 102... ...
Although novel devices have been proposed and some demonstrated in the lab, there are at present no devices, or even device concepts, that threaten to unseat Si. Quantum dot lasers have seen more practical progress but have not yet seen commercial use.
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From page 103... ...
1996. Structural and optical characterization of InAs/InGaAs self-assembled quantum dots grown on (311)
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