Microstructural evolution and preferred orientation change of radiofrequencymagnetron sputtered ZnO thin films Y 2 O 3 thin films were deposited by reactive sputtering of an Y target in an Ar and O 2 gas mixture. Intrinsic stresses and the Ar content in the films were measured by the sine square psi method of x-ray diffraction and wavelength dispersive spectrometer, respectively. At low working pressures the films had high compressive stresses. As working pressure increased, compressive stress was relaxed. Ar content was high in the film that had high compressive stress. After annealing of the films at 700°C, the compressive stress was largely relaxed but the Ar content remained unchanged. These results clearly showed that compressive stress in Y 2 O 3 films was not caused by Ar entrapment as an impurity but by Ar bombardment. Intrinsic stress was almost independent of the O 2 /Ar flow ratio, showing that O bombardment was equal to Ar bombardment in affecting the intrinsic stress in Y 2 O 3 films. The independence of intrinsic stress with the O 2 /Ar flow ratio was explained by the concept of M i 1/2 ͕͓M i cos Ϯ͑M t 2 ϪM i 2 sin 2 ͒ 1/2 ͔/(M i ϩM t )͖ instead of the M t /M i ratio, where M t is the atomic mass of the target material, M i is the atomic mass of the sputtering gas, and is the scattering angle.
Al thin films with various residual stress and film thickness were deposited by bias sputtering. Residual stress and relative intensity of the (200) to (111) plane of Al thin films were measured by x-ray diffraction. When film thickness is fixed at 1 μm below the residual stress of ∼80 MPa, Al thin films have a (111) orientation, but above this stress, a (100) orientation. If Al thin films are in the high residual stress of ∼145 MPa, crystallographic orientation changes to a (100) from a (111) orientation as film thickness increases to 2 μm from 1 μm. However, Al thin films with the residual stress of ∼25 MPa have a (111) orientation regardless of film thickness. Total energy for Al thin films of a (100) and a (111) orientation was calculated as a function of residual stress and film thickness. These experimental results could be explained by the minimization of the sum of strain energy and surface energy in the films.
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