| 초록 |
In epitaxial growth relation with large misfit system, introduction of buffer layer has been widely adopted to improve the crystallinity and so physical properties of the films to minimize the crystalline defects. In this study, ZnO having large misfit (18.28%) with sapphire was tried to be grown on very thin nitride buffer layers. For the creation of various kinds of nitride buffer layer, sapphire surface was modified by an irradiation of N2+ and mixed N2+ + H2+ high current ion beam with low energy generated from stationary plasma thruster (SPT). After the formation of nitride thin buffer layer, the chemical reaction between the induced AlN and Al-ON bonding with H plasma was investigated through exposure to H plasma at 200~400oC and for 10 -300 sec. The variation of the surface chemical bonding was monitored by XPS and the evolution of the surface morphology by AFM. And then ZnO growth (50-100 nm) was followed by UHV-PLD (ultra high vacuum pulsed laser deposition) and their optical and electrical properties were analyzed by XRD, TEM, PL, and Hall measurement. The rotation of ZnO grain growth was still observed with respect to that of sapphire substrate, but it was very interesting that deep level emission related to defects from the ZnO grown on nitride buffer layer was almost vanished in PL spectra. The different grain growth feature and the change of surface morphology were discussed in terms of different nitride buffer layers. |
