Abstract
AlN thin films have been grown on R((1-12) surface-cut)-Al2O3, SiO2-glass and C((001) surface-cut)-Al2O3 substrates, by using a reactive-RF-sputter-deposition method. X-ray diffraction (XRD) shows that AlN film has (110) orientation of wurtzite crystal structure for R-Al2O3 and (001) orientation for SiO2-glass and C-Al2O3 substrates. The film thickness was analyzed by Rutherford backscattering spectroscopy (RBS) and it appears that XRD intensity does not show a linear increase with the film thickness but a correlation with the stress, i.e., deviation of the lattice parameter of the film from that of bulk. The film composition and impurities have been analyzed by ion beam techniques. Effects of high-energy ion beams are briefly presented on atomic structure (whether stress relaxation occurs or not), surface morphology and optical properties.
Highlights
It has been known that aluminum nitride (AlN) has a wide direct-bandgap (6.2 - 5.8 eV) [1,2] with hexagonalwurtzite crystal structure [3] and unique properties: good thermal conductivity (~3 W/cmK at 300 K) [4], good insulator (>1011 Ω·cm) [5], high dielectric constant [6], relatively small linear-expansion coefficients (5.3 and 4.2 × 10−6 K−1 along a- and c-axis) [7], high sound velocity (6 km/s) [8] and large hardness [9]
The film thickness was analyzed by Rutherford backscattering spectroscopy (RBS) and it appears that X-ray diffraction (XRD) intensity does not show a linear increase with the film thickness but a correlation with the stress, i.e., deviation of the lattice parameter of the film from that of bulk
X-ray diffraction (XRD) technique have been extensively employed to evaluate the crystalline quality and growth orientation of AlN films which have been grown by various techniques, chemical-vapor atomic-layer deposition [2], metal organic CVD [16], molecular beam epitaxy [17], ion beam enhanced deposition [5], reactive radio-frequency (RF) magnetron sputtering deposition [6,10,18], pulsed laser deposition (PLD) [19] on various substrates, sapphire [2,19], Si [5,14,15,16,18], SiC [17], Al [6], Mo [12] etc
Summary
It has been known that aluminum nitride (AlN) has a wide direct-bandgap (6.2 - 5.8 eV) [1,2] with hexagonalwurtzite crystal structure [3] and unique properties: good thermal conductivity (~3 W/cmK at 300 K) [4], good insulator (>1011 Ω·cm) [5], high dielectric constant [6], relatively small linear-expansion coefficients (5.3 and 4.2 × 10−6 K−1 along a- and c-axis) [7], high sound velocity (6 km/s) [8] and large hardness [9] Owing to these properties, AlN films have potential applications to electronic devices [10], surface acoustic wave (SAW) devices [11], actuator [12], transparent hard coatings and AlN composites to light-emitting devices [13]. For AlN on R-Al2O3, irradiation with high-energy (90 MeV Ni) ions was performed in order to study whether stress relaxation, surface smoothing and bandgap modification occur or not by ion irradiation
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