Carrier relaxation and lattice heating dynamics in silicon revealed by femtosecond electron diffraction

被引:73
作者
Harb, Maher
Ernstorfer, Ralph
Dartigalongue, Thibault
Hebeisen, Christoph T.
Jordan, Robert E.
Miller, R. J. Dwayne
机构
[1] Univ Toronto, Inst Opt Sci, Toronto, ON M5S 3H6, Canada
[2] Univ Toronto, Dept Phys, Toronto, ON M5S 3H6, Canada
[3] Univ Toronto, Dept Chem, Toronto, ON M5S 3H6, Canada
关键词
D O I
10.1021/jp064649n
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We report on the use of femtosecond electron diffraction to resolve the dynamics of electron-phonon relaxation in silicon. Nanofabricated free-standing membranes of polycrystalline silicon were excited below the damage threshold with 387 nm light at a fluence of 5.6 mJ/cm(2) absorbed (corresponding to a carrier density of 2.2 x 10(21) cm(-3)). The diffraction pattern was captured over a range of delay times with a time resolution of 350 fs. All of the detected Bragg peaks exhibited intensity loss with a time constant of less than 2 ps. Beyond the initial decay, there was no further change in the diffracted intensity up to 700 ps. We find that the loss of intensity in the diffracted orders is accounted for by the Debye-Waller effect on a time scale indicative of a thermally driven process as opposed to an electronically driven one. Furthermore, the relaxation time constant is consistent with the excitation regime where the phonon emission rate is reduced due to carrier screening.
引用
收藏
页码:25308 / 25313
页数:6
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