We examine the effects of substrates on the low temperature photoluminescence (PL) spectra and phase transition in methylammonium lead iodide hybrid perovskite (CH3NH3PbI3) thin films. Structural characterization at room temperature with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy indicated that while the chemical structure of films deposited on glass and quartz was similar, the glass substrate induced strain in the perovskite films and suppressed the grain growth. The luminescence response and phase transition of the perovskite thin films were studied by PL spectroscopy. The induced strain was found to affect both the room temperature and low temperature PL spectra of the hybrid perovskite films. In addition, it was found that the effects of the glass substrate inhibited a tetragonal to orthorhombic phase transition such that it occurred at lower temperatures.

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To investigate the stress effect on the E2high Raman vibration mode, we grew heteroepitaxial ZnO films on c-plane sapphire with different strain states by changing the film thicknesses between 5 and 100 nm. To determine the relationship between the observed frequency of the E2high mode with the biaxial residual stress of the ZnO thin films, the out-of-plane strain of films were measured with x-ray diffraction from which the residual stress was calculated. The biaxial residual stress and E2high frequency were related linearly by a factor of ∼170 MPa/cm−1, which is in agreement with reported values from high pressure investigations of bulk ZnO.

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