Energy and site selectivity in O-atom photodesorption from nanostructured MgO
- 作者：Kenneth M. Beck ; Alan G. Joly ; Oliver Diwald ; Slavica Stankic ; Paolo E. Trevisanutto ; Peter V. Sushko ; Alex ; er L. Shluger ; Wayne P. Hess
- 关键词：Density functional calculations ; Desorption induced by electronic transitions (DIET) ; Photon stimulated desorption (PSD) ; Atom emission ; Magnesium oxides ; Surface defects ; Excitons ; Laser control
- 刊名：Surface Science
- 出版年：2008
- 期刊代码：104_00396028
- 类别：ch
- 出版时间：1 June 2008
- 卷：602
- 期：11
- 页码：1968-1973
- 文件大小：528 K
摘要
We excite low-coordinated surface sites of nanostructured MgO samples using 4.7 eV UV laser pulses and observe dominant hyperthermal O-atom emission. Excitation of the same samples with 7.9 eV photons results in thermal O-atom desorption. These results are analyzed in the context of laser desorption models developed previously for alkali halide crystals and MgO. We detail two multi-step mechanisms for hyperthermal O-atom desorption, under surface selective excitation, based on exciton and hole trapping at three-coordinated (corner) O-atom sites, and evaluate the validity of each based on available experimental data and calculated results. The proposed models are significantly different from and more complex than the surface exciton desorption model established for alkali halides. Nonetheless, the principles of site-specific photo-excitation and exciton and hole localization induced atomic desorption are clearly extendable to a prototypical metal oxide.