Oral Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Voids in high dose H implanted and annealed ZnO (#100)

Jennifer Wong-Leung 1 , Keng S. Chan 1 , Lasse Vines 2 , Bengt G. Svensson 2 , Chennupati Jagadish 1
  1. Electronic Materials Engineering, Australian National University, Canberra, ACT, Australia
  2. Department of Physics, University of Oslo, Blindern, Oslo, Norway

ZnO is a promising material in the applications of transparent conductors, piezoelectric devices, spintronics, sensors and optoelectronic devices operating in the UV regions. The role of H in ZnO has received wide attention since Van de Valle [1] postulated that H acts as a shallow donor and may be the reason for the persistent high n-type conduction observed in native ZnO substrates. The high conductivity layer in ZnO formed by H implantation has been characterised by secondary mass ion spectrometry and scanning spreading resistance microscopy [2]. However, details of the microstructures of this layer are still not well understood. Our recent work [3-5] have identified the formation of voids in H implanted ZnO. The nanovoids created by H implantation were analysed in this paper and the surface energies of different surfaces were extracted from Wulff plots of the voids [3].
Single crystal ZnO substrates were implanted with 100keV H- with doses of ranging from 1×1016 to 1×1017 cm-2 at room temperature. Careful studies were designed to separate the effects on ZnO caused by ion implantation from the effects caused by hydrogen incorporation. Microstructures of H implanted ZnO were characterised by x-ray diffraction (XRD) and transmission electron microscopy after annealing [5]. Optical characteristics of H implanted ZnO was studied by cathodoluminescence [4]. The trend existing as a function of implantation dose was studied in detail by all techniques. XRD results show that H implantation causes the formation of a deformed layer with a larger c-parameter than the ZnO substrate [5]. This layer was also observed in N implanted ZnO [6]. Therefore, we believe that the elongation of c-parameter in the as-implanted layer, is an implantation related effect rather than a result of the hydrogen incorporation. Nanovoids were observed in all samples annealed above 600C.

  1. C. G. Van de Walle, “Hydrogen as a cause of doping in Zinc Oxide”, Phys. Rev. Lett. 85, 1012 (2000).
  2. E. V. Monakhov, J.S. Christensen, K. Maknys, B. G. Svensson and A. Yu. Kuznetsov, “Hydrogen implantation into ZnO for n+-layer formation”, Appl. Phys. Lett. 87, 191910 (2005).
  3. K. S. Chan, L. Vines, L. Li, C. Jagadish, B. G. Svensson and J. Wong-Leung, “Equilibrium shape of nano-cavities in H implanted ZnO”, Appl. Phys. Lett. 106, 212102 (2015).

  4. K. S. Chan, C. Ton-That, L. Vines, S. Choi, M. Phillips, B. G. Svensson, C. Jagadish, J. Wong-Leung, “Effects of high temperature annealing on defects and luminescence properties in H implanted ZnO”, Journal of Physics D: Applied Physics 47, 34 (2014) 1-6.
  5. K. S. Chan, L. Vines, K. Johansen, E. Monakhov, J. D. Ye, P. Parkinson, C. Jagadish, B. G. Svensson, J. Wong-Leung, “Defect formation and thermal stability of H in high dose H implanted ZnO”, Journal of Applied Physics 114, 8 (2013).
  6. G. Merceroz-Perillat, P. Gergaud, P. Marotel, S. Brochen, P. Jouneau and G. Feuillet, “Formation and annealing of dislocation loops induced by nitrogen implantation of ZnO”, J. Appl. Phys. 109, 023515 (2011).