Plasma enhanced atomic layer deposition of magnesium oxide as a passivation layer for enhanced photoluminescence of ZnO nanowires

The growth characteristics and film properties of magnesium oxide (MgO) thin films fabricated by plasma enhanced atomic layer deposition (PE-ALD) and thermal ALD (Th-ALD) were comparatively investigated for passivation layer applications. For both processes, well-saturated growth characteristics were observed, with a higher saturated growth rate for Th-ALD. X-ray photoemission analysis showed that very high purity MgO film with virtually no carbon contamination was deposited by PE-ALD. X-ray diffraction and transmission electron microscopy analysis showed that the PE-ALD MgO thin films had a larger grain size than the Th-ALD MgO thin films and were predominantly (1 1 1) crystal orientation. The photoluminescence analysis showed enhanced luminescence properties of the ALD MgO shell/ZnO nanowires. In particular, PE-ALD MgO showed greater enhancement of the luminescence properties than Th-ALD MgO.