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This article presents a study of the influence of the sputtering parameters on the preferred orientation of polycrystalline aluminum nitride thin films. Aluminum nitride films were grown by rf reactive sputtering of an aluminum target in an N2/Ar gas mixture for different values of the deposition parameters: total pressure, nitrogen content in the discharge gas, and substrate bias voltage. The preferred orientation of the films was analyzed by x-ray diffraction. Films with different preferred orientations were obtained, ranging from c-axis oriented films to films with the c axis tilted by up to 61.6° from the substrate normal. The different mechanisms influencing the preferred orientation of the films have been considered, especially the transfer of energy to the adatoms on the substrate by particle bombardment. An analysis of the relation between the deposition parameters and the crystal orientation has allowed us to determine the relative importance of the different particles in the supply of energy to the substrate. We have found that Ar ion bombardment of the film during growth is the most influential mechanism on the preferred orientation of the films. As bombardment becomes more energetic, microcrystals in the film tend to grow with the c axis along the surface normal. The energy of Ar bombardment can be best controlled through the substrate bias voltage, a characteristic that we have employed to obtain AlN films exhibiting pure (00.2) preferred orientation and rocking curves with a full width at half maximum as low as 4.2°.

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Articles you may be interested inSynthesis and characterization of 10nm thick piezoelectric AlN films with high c-axis orientation for miniaturized nanoelectromechanical devices Appl. Phys. Lett.

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Raman spectroscopy provides nondestructive information about nanoscaled semiconductors by modeling the phonon confinement effect. However, the Raman spectrum is also sensitive to the temperature, which can mix with the size effects borrowing the interpretation of the Raman spectrum. We present an analysis of the Raman spectra of Si nanowires (NWs). The influence of the excitation conditions and the temperature increase in the NWs are discussed. The interpretation of the data is supported by the calculation of the temperature inside the NWs with different diameters.