Role Of Active Oxygen Species On Growth Of ZnO Using RF-PAMBE
- PDF / 213,679 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 236 Views
0891-EE08-04.1
Role Of Active Oxygen Species On Growth Of ZnO Using RF-PAMBE S. M. Durbin1, 3, W. C. T. Lee1, 3, M. Allen1,3, P. Miller2, 3, and R. J. Reeves2, 3 1 Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, New Zealand 2 Department of Physics, University of Canterbury, Christchurch, New Zealand 3 The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
ABSTRACT The effect of different oxygen species on the RF plasma-assisted molecular beam epitaxy growth of ZnO films was investigated. By varying the geometry of the aperture plate and also the RF power, the relative atomic content in the discharge was altered, and this is found to be correlated to the film quality. Further, growth rate studies performed in tandem with in-situ laser interferometry suggest that stoichiometric conditions may not result in saturation of growth rates.
INTRODUCTION ZnO growth by RF plasma-assisted molecular beam epitaxy (RF-PAMBE) has been studied extensively [1,2], yet there is still not a universal understanding in many of the growth process variables. For example, although the use of high RF power has already been shown to improve the crystal quality of ZnO films in terms of reduced X-ray diffraction FWHM [3], reports on relatively low power growth can still be found [4, 5]. This indicates that the optimum RF regime remains an open question for ZnO growth. In particular, with recent studies showing the importance of metastable molecular nitrogen (N2*) for RF-PAMBE growth of GaN [6] and the need for low power to generate the appropriate species [7], it is worth studying in detail the relationship between plasma source characteristics and ZnO film quality. Here, we report the effects of RF power and aperture configuration on the film quality from the perspective of plasma species.
EXPERIMENTAL DETAILS ZnO single crystal thin films were grown using a modified Perkin Elmer 430 MBE system with a base pressure of 10-9 Torr. (0001) sapphire substrates were mounted on molybdenum sample holders using indium, and outgassed at 650 °C for 1 hour before loading into the growth chamber. Active oxygen species were provided by flowing filtered 5N oxygen through an Oxford Applied Research MPD21 inductively-coupled RF plasma source operated between 150 and 500 W. The plasma discharge was characterised using a Jobin Yvon CCD-3000 spectrometer and a Stanford Research Systems residual gas analyser (RGA). 6N Zn metal was evaporated using a 60 cc effusion cell to provide a Zn flux of 1.4×1015 atoms/cm2·s. Prior to high temperature deposition at 650°C, a ZnO buffer layer ~50 nm in thickness was deposited at 300 °C. A He-Ne laser was used for in-situ growth rate measurements, which were calibrated by ex-situ profilometry. Electrical characteristics were measured using an EGK-2000 0.51 T Hall effect measurement system, and morphology studied using scanning electron microscopy (SEM) and reflection high-energy electron diffraction (RHEED).
0891-EE08-04.2
RESULTS AND DISCUSSION Figure 1 s
Data Loading...
