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4 Eb2S °r— 3(1 -v)C-d b,l,E,v, and d denote thickness, length, Young's modulus, Poisson's ratio of the substrate and thickness of the deposited film, respectively.

In general, the residual stresses in thin films consist of thermal stress cr^ and intrinsic stress <7 lo which is produced during the deposition. The thermal stress is caused by the mismatch of thermal expansion coefficients (TEC) between the film and the substrate. Hence, it can be expressed as follows(3).

ar a denote TECs of a film and a substrate, Tt is the substrate temperature during deposition and Tt is room temperature, respectively.


Figure 1. An example of the change of an interferometer image, a: The surface of the AI203 substrate before deposition, b : The surface of La, xSrsMn03 film on the A1203 substrate (T = 900 °C)

Results and Discussion

XRD patterns of La^Sr^CrO, and La, ^Sr^MnO, films on the three kinds of substrates agree with each other. Crystal structures of both kinds of films were almost cubic. The differences of the atomic ratios between the films and the powder were measured by ICP and EDX. Ratio of La to other atoms in the films slightly increased with the increasing substrate temperature n, but the differences are within 5%.

The dependence of the residual stresses in the films on TEC of the substrate is shown in Fig.2. The plus sign of the residual stress corresponds a tensile stress. All residual stresses of the films on SP and MgO substrates are compressive. Elastic moduli £/(l-vf) of La,.SrCr03 films and La, xSrxMnO, films are calculated at 290 GPa and 220 GPa from the dependence of the slope Ao/Aa on the temperature difference T-Tt.

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