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Quantum confinement in silicon clathrate quantum dots
Brawand, Nicholas P.
Brawand, Nicholas P.
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2013
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2014-05-01
Abstract
The relationship between crystal structure and quantum confinement is quantified by computationally analyzing sets of silicon quantum dots associated with nine types of clathrates. Density functional theory is used to show that bulk energy gap between the highest occupied and lowest unoccupied Kohn-Sham orbitals varies by more than 1 eV, both above and below that of diamond silicon. The approach is also used to relate dot size to energy gap to identify a linear correlation between quantum confinement sensitivity and bulk-crystal effective mass. All clathrates are found to have a confinement sensitivity less than that of diamond silicon. Bulk properties (gap and effective mass) can therefore be used to identify clathrate semiconductors with promising optoelectronic properties. For example, the combined gap and confinement sensitivity of Type VII clathrate results in a low energy gap for quantum dots within 1 to 2 nm in diameter, making type VII worthy of consideration for efficient multiple exciton generation and other optoelectronic applications.
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