The Effects of Annealing Temperature on the Structural Properties of ZrB2 Films Deposited via Pulsed DC Magnetron Sputtering

Wei-Chun Chen,Chao-Te Lee,Hung-Pin Chen,James Su

doi:10.3390/coatings9040253

Wei-Chun Chen, Chao-Te Lee + Show 2 more

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https://doi.org/10.3390/coatings9040253

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Journal: Coatings	Publication Date: Apr 16, 2019
Citations: 5	License type: CC BY 4.0

Affiliation: National Applied Research Laboratories

Abstract

Zirconium diboride (ZrB2) thin films were deposited on a Si(100) substrate using pulsed direct current (dc) magnetron sputtering and then annealed in high vacuum. In addition, we discussed the effects of the vacuum annealing temperature in the range of 750 to 870 °C with flowing N2 on the physical properties of ZrB2 films. The structural properties of ZrB2 films were investigated with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The XRD patterns indicated that the ZrB2 films annealed at various temperatures exhibited a highly preferred orientation along the [0001] direction and that the residual stress could be relaxed by increasing the annealing temperature at 870 °C in a vacuum. The surface morphology was smooth, and the surface roughness slightly decreased with increasing annealing temperature. Cross-sectional TEM images of the ZrB2/Si(100) film annealed at 870 °C reveals the films were highly oriented in the direction of the c-axis of the Si substrate and the film structure was nearly stoichiometric in composition. The XPS results show the film surfaces slightly contain oxygen, which corresponds to the binding energy of Zr–O. Therefore, the obtained ZrB2 film seems to be quite suitable as a buffer layer for III-nitride growth.

Highlights

Zirconium diboride (ZrB2 ) is a relatively stable compound possessing a hexagonal crystal structure (AlB2 structure, P6/mmm), and its a-axis lattice parameter (a = 3.169 Å) is very close to that of GaN (a = 3.189 Å) [1]
We investigate the influence of the annealing temperature on ZrB2 thin films deposited on a Si substrate under high vacuum
For all the ZrB2 films annealed at various temperatures, the crystallite size was calculated from X-ray diffraction (XRD) profiles from reflections with a strong intensity percentage by measuring the full width at half maximum (FWHM) of the relevant peaks

Summary

Introduction

Armitage et al demonstrated a cleaning process for the ZrB2 (0001) surface utilizing an HF solution treatment combined with lower-temperature (1000 ◦ C) annealing [14] These methods are impractical for cleaning ZrB2 substrates to be used for GaN epitaxy because they require special equipment that is not available for GaN growth reactors. We investigate the influence of the annealing temperature on ZrB2 thin films deposited on a Si substrate under high vacuum. The effectiveness of this method is evaluated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS)

Materials and Methods

Results and Discussion

Conclusions