CaltechTHESIS
  A Caltech Library Service

Ultrafast electron crystallography : principles and applications

Citation

Yang, Ding-Shyue (Jerry) (2009) Ultrafast electron crystallography : principles and applications. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05082009-170032

Abstract

During the last 20 to 30 years, the development and application of time-resolved experimental techniques with a femtosecond temporal resolution have brought to us much knowledge about the fundamental processes in physics, chemistry and biology. Nevertheless, standard spectroscopic methods have their limitation in the determination of the transient structures during ultrafast dynamics at the atomic level, because the spatial resolution is restricted by the wavelength of the probe pulse used. In contract, with the scheme of femtosecond optical initiation and electron probing and through the diffraction phenomenon, ultrafast electron crystallography (UEC) was recently developed as a time-resolved structure-probing technique for condensed-matter studies. The short wavelength and small pulse duration of the highly accelerated electrons used provide the atomic-scale spatiotemporal resolution. In addition, the large electron–matter interaction enables the detection of small transient changes as well as the investigation of surface and interfacial phenomena. This thesis describes the principles of UEC and its applications to a variety of systems, ranging from nanometer-scale structures to highly correlated materials and to interfacial assemblies. By using a prototype semiconducting material, we elucidated the fundamental processes at work in different parts of the femtosecond-to-nanosecond time range; this investigation led to a conceptual change from the consideration of laser-induced heating to the examination of nonequilibrium structural modifications as a result of the transient dynamical changes in, e.g., carriers, the crystal potential, and phonons. On the basis of such an understanding, we observed and understood the colossal unidirectional expansion induced by the photoexcitation of nanostructures to be a potential-driven result rather than a thermal one. For highly correlated materials, we showed the effectiveness of UEC in resolving the transient intermediate structures during phase transformations as well as identifying new phases in the nonequilibrium state. An important breakthrough made by UEC was the confirmation of the anisotropic involvement of lattice in the electron pairing mechanism for high-temperature superconductors. In interfacial assemblies, we also found a nonequilibrium phase transformation in water and the phenomenon of ultrafast annealing for a better order in a self-assembled monolayer. With these successful experiences, we expect more condensed-matter studies by UEC to come.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:electron-lattice coupling; nanostructures; phase transition
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Awards:The Herbert Newby McCoy Award, 2009
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Zewail, Ahmed H.
Thesis Committee:
  • McKoy, Basil Vincent (chair)
  • Zewail, Ahmed H.
  • Rees, Douglas C.
  • Yeh, Nai-Chang
Defense Date:5 May 2009
Author Email:yang (AT) caltech.edu
Record Number:CaltechETD:etd-05082009-170032
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05082009-170032
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1685
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:14 May 2009
Last Modified:26 Dec 2012 02:40

Thesis Files

[img]
Preview
PDF (00TitlePageAcknowledgeAbstractLists.pdf) - Final Version
See Usage Policy.

191Kb
[img]
Preview
PDF (01Chapter1-Introduction.pdf) - Final Version
See Usage Policy.

1181Kb
[img]
Preview
PDF (02Chapter2-Principles.pdf) - Final Version
See Usage Policy.

5Mb
[img]
Preview
PDF (03Chapter3-Experimental.pdf) - Final Version
See Usage Policy.

2828Kb
[img]
Preview
PDF (04Chapter4-Part_I-GaAs.pdf) - Final Version
See Usage Policy.

4Mb
[img]
Preview
PDF (05Chapter5-Part_I-ZnO-nanowires.pdf) - Final Version
See Usage Policy.

5Mb
[img]
Preview
PDF (06Chapter6-Part_II-VO2.pdf) - Final Version
See Usage Policy.

13Mb
[img]
Preview
PDF (07Chapter7-Part_II-La2CuO4.pdf) - Final Version
See Usage Policy.

3004Kb
[img]
Preview
PDF (08Chapter8-Part_II-Ba2Sr2CaCu2O8.pdf) - Final Version
See Usage Policy.

4Mb
[img]
Preview
PDF (09Chapter9-Part_III-IceHOPG.pdf) - Final Version
See Usage Policy.

5Mb
[img]
Preview
PDF (10Chapter10-Part_III-IceSiH.pdf) - Final Version
See Usage Policy.

11Mb
[img]
Preview
PDF (11Chapter11-Part_III-SAMGold.pdf) - Final Version
See Usage Policy.

1104Kb
[img]
Preview
PDF (12Chapter12-Part_III-Theoretical.pdf) - Final Version
See Usage Policy.

6Mb
[img] PDF (CompleteThesis.pdf) - Final Version
See Usage Policy.

64Mb

Repository Staff Only: item control page