|Author's Email Address
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|| Materials and Optoelectronic Science|
|Type of Document
||Epitaxial Growth of Mg-doped ZnO by Molecular Beam Epitaxy|
|Date of Defense
||The present study aims at studying the surface morphology, crystallinity and optical emission property of Mg added ZnO grown by molecular beam epitaxy. Zn1-xMgxO epitaxial films were first grown at a fixed Zn flux of 1×10-7 mbar and Mg flux of 4×10-10 to 6.2×10-9 mbar on sapphire substrates at 400 oC. The corresponding Mg content (x) is in a range of <0.01 to 0.17. Scanning electron microscopy observations indicated that the surface of the films are flat. The orientation relationship between the film and the substrate is: (0001)Zn1-xMgxO∥(0001)Al2O3和[101 ‾0] Zn1-xMgxO∥[112 ‾0] Al2O3. The full width at half maximum (FWHM) of the (0002) reflection in rocking curve measurement is in a range of 3.83 o to 4.81 o. Photoluminescence results showed that the intensities of both the near band-gap emission and the deep level emission increases with increasing Mg content. The former has FWHM values of 0.16-0.21 eV. |
While the epitaxial films were grown at a high Zn flux of 5×10-7 mbar and Mg flux of 2×10-9 to 9.6×10-9 mbar on sapphire and LiAlO2 substrates at 400 oC, the film surface are at high roughness. The FWHM of (0002) rocking curve is 4.43 o to 5.71 o for films grown on sapphire and is relatively larger of 6.88 o to 8.18 o for films grown on LiAlO2, respectively. These films possess a stronger near band-gap emission and a lower deep level emission as compared to the films grown at a low Zn flux.
After annealed at 600 oC in oxygen or nitrogen, the FWHMs of the (0002) rocking curve for most of the epilayers decreased slightly. The photoluminescence results were rather distinct. For samples having low Mg content (x<0.05), the intensity of the near band-gap emission increases 50-200 ％ after annealed in oxygen. The intensity of the near band-gap emission did not change but that of the deep level emission decreases ~50 ％ for the film having x=0.16 after annealing in oxygen. The emission characteristics basically do not change after annealed in nitrogen.
||D. Gan - chair|
M.M.C. Chou - co-chair
L.W. Chang - advisor
Indicate in-campus at 2 year and off-campus access at 99 year.|
|Date of Submission