The primary mechanism of optical memoristive devices relies on phase transitions between amorphous and crystalline states. The slow or energy‐hungry amorphous–crystalline transitions in optical phase‐change materials are detrimental to the scalability and performance of devices. Leveraging an integrated photonic platform, nonvolatile and reversible switching between two layered structures of indium selenide (In₂Se₃) triggered by a single nanosecond pulse is demonstrated. The high‐resolution pair distribution function reveals the detailed atomistic transition pathways between the layered structures. With interlayer “shear glide” and isosymmetric phase transition, switching between the α‐ and β‐structural states contains low re‐configurational entropy, allowing reversible switching between layered structures. Broadband refractive index contrast, optical transparency, and volumetric effect in the crystalline–crystalline phase transition are experimentally characterized in molecular‐beam‐epitaxy‐grown thin films and compared to ab initio calculations. The nonlinear resonator transmission spectra measure of incremental linear loss rate of 3.3 GHz, introduced by a 1.5 µm‐long In₂Se₃‐covered layer, resulted from the combinations of material absorption and scattering.

Residual stress in coatings often affects the service performance of coatings, and the residual stresses in some local areas even lead to premature failure of coatings. In this work, we characterized the residual stress of local micro-areas of a nanocrystalline Cr₂O₃ coating deposited on a Si wafer through micro-Raman spectroscopy, including the depositional edge zone where the electrode was placed, the micro-area containing Cr₂O₃ macroparticles, and other micro-areas vulnerable to cracks. To accurately measure the thickness of the coating, we combined optical interferometry and direct measurement by a profilometer. The results indicate the existence of in-plane tensile residual stress on the Cr₂O₃ coating. In thick coatings, the residual stress is independent of the coating thickness and is stable between 0.55 GPa and 0.75 GPa. As the coating thickness is less than 0.8 μm, the residual stress is directly related to the coating thickness. This in-plane tensile stress is considered as the origin of the observed microcrack, which can partially release the stress.

We developed an experimental metrology for measuring local strain in molecular beam epitaxially (MBE) grown crystalline chalcogenide thin films through micro-Raman spectroscopy. For In₂Se₃ and Bi₂Se₃ on c-plane sapphire substrates, the transverse-optical vibrational mode (A₁ phonon) is most sensitive to strain. We first calibrated the phonon frequency–strain relationship in each material by introducing strain in flexible substrates. The Raman shift–strain coefficient is −1.97 cm^–1/% for the In₂Se₃ A₁(LO + TO) mode and −1.68 cm^–1/% for the Bi₂Se₃ A_1g² mode. In₂Se₃ and Bi₂Se₃ samples exhibit compressive strain and tensile strain, respectively. The observations are compliant with predictions from the opposite relative thermal expansion coefficient between the sample and the substrate. We also map strain cartography near the edge of as-grown MBE samples. In In₂Se₃, the strain accumulates with increasing film thickness, while a low strain is observed in thicker Bi₂Se₃ films.

Nano-indentation is a destructive measurement that introduces non-uniform residual stress around each nano-indentation. Herein, the residual stress distribution around a Berkovich nano-indentation on (001)- and (111)-plane silicon was studied by micro-Raman mapping. All of the in-plane stress state components around the indentation were obtained specifically for the (001)- and (111)-plane silicon based on the expanding cavity model and the Raman-mechanical relationship. Calculating the distribution regularity of the residual stress, the effect of different crystal planes and crystal orientations was further analyzed. Finally, the stress near the vertex of the indentation was revised owing to the crack.

The unique photoelectric properties of phosphorene typically include anisotropy, hence the nondestructive and rapid identification of its crystal orientation is a key point to the investigation and application of phosphorene. Currently, the orientation identification by analyzing the A_g¹ mode based on parallel-polarized Raman has severe requirements for the applicable Raman system. Therefore, it is necessary to develop a more general, convenient, and accurate method for determining the crystal orientation of phosphorene. In this paper, a method of orientation identification was proposed by using a Raman system without an analyzer and quantifying the correlation between the intensities of A_g¹ and A_g² modes with the change of the incident polarization direction. By using mechanically peeled phosphorene as specimens, Raman measurements were carried out under the Raman configurations of both parallel polarization and with no analyzer. The results show that the crystal orientation of phosphorene can be accurately identified by quantifying the Raman intensities of both A_g¹ and A_g² modes using the Raman system without an analyzer.