High-dose V+ implantation in ZnO thin film structures

Abstract

In the last two decades, diluted magnetic semiconductors have attracted great attention as promising materials for spintronics applications. [K. Sato, H. Katyama-Yoshida, Jpn. J. Phys., Part 2 39 (2000) L555] theoretically predicted that ZnO doped with V, Cr, Fe, Co, and Ni can be ferromagnetic. This has been recently confirmed experimentally for vanadium doped ZnO films which were grown on sapphire substrates, using laser deposition technique [H. Saeki, H.N. Tabata, T. Kawai, Solid State Commun. 120 (2001) 439]. In the present work, high-dose vanadium implantation was used to produce Zn1−x VxO (x∼0.10) thin film structures (250nm thick) that had been epitaxially grown on sapphire substrates. Implantation with the dose 2×1016cm−2 was performed to reach a maximum vanadium concentration of 10at%. To avoid ZnO film amorphization due to radiation damage accumulation [S.O. Kucheyev, J.S. Williams, C. Jagadish, J. Zou, C. Evans, A.J. Nelson, A.V. Hamza, Phys. Rev. B 67 (2003) 094115], all implants were done at elevated temperatures 300 and 400°C and ion current density 10μA/cm2. X-ray diffraction, SIMS and photoluminescence techniques were exploited to study the implanted samples. No luminescence was observed in the implanted samples after implantation procedures. However, annealing at 800°C for 30min gave rise to ZnO crystal structure improvement. This implies that healing of implantation induced defects is possible even after heavy-ion bombardment. As a result, the photoluminescence peak at 3.359eV related to the donorbound exiton was detected.