By using x-ray diffraction and optical waveguide characterization, it has been shown that proton-exchanged layers on Z-cut LiNbO(3) can have as many as seven different crystallographic phases that are stable at room temperature. This study allows us to establish some correlation between fabrication parameters and the crystalline structure, the index profiles, and the propagation losses of waveguides prepared by this process.
Due to the large differences in lattice parameters and thermal expansion coefficients, the heteroepitaxial growth of 3C-SiC on Si mainly results in highly defective layers on strongly bent wafers. The defects may not be detrimental for very basic applications, but the bow is. In this article, we review several attempts to reduce the final curvature after epitaxial growth of 3C-SiC. One is the use of the "checkerboard" carbonization process which creates a macroscopic balance of the stress by the formation of a regular network of compressed and tensed areas. Another approach proposes to create, in situ, a random patchwork of tensed and compressed areas during the carbonization step. The other attempts use substrates other than standard Si, namely silicon on insulator and Si-Ge substrates for compliance effect and closer thermal expansion mismatch with SiC, respectively. All techniques provoke a significant reduction of the strain in the deposited 3C-SiC layers.
In this work the authors study the strain of 3C-SiC thin films grown on (001) on-axis silicon substrates. They use ex situ wafer curvature measurements to monitor the residual strain of silicon carbide film. At high temperature creep effects take place and modify the intrinsic strain of silicon carbide film. From the time and temperature dependences of these effects, they determine the creep exponent and the creep activation energy for 3C-SiC. Obtained values of N=2.6±0.3 and Q=5.6±1.0eV are similar to those reported in literature for hexagonal polytypes of silicon carbide.
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