Structural Parameters Of Thin Films Research Articles

Determination of Optical and Structural Parameters of Thin Films with Differently Rough Boundaries

The optical characterization of non-absorbing, homogeneous, isotropic polymer-like thin films with correlated, differently rough boundaries is essential in optimizing their performance in various applications. A central aim of this study is to derive the general formulae necessary for the characterization of such films. The applicability of this theory is illustrated through the characterization of a polymer-like thin film deposited by plasma-enhanced chemical vapor deposition onto a silicon substrate with a randomly rough surface, focusing on the analysis of its rough boundaries over a wide range of spatial frequencies. The method is based on processing experimental data obtained using variable-angle spectroscopic ellipsometry and spectroscopic reflectometry. The transition layer is considered at the lower boundary of the polymer-like thin film. The spectral dependencies of the optical constants of the polymer-like thin film and the transition layer are determined using the Campi–Coriasso dispersion model. The reflectance data are processed using a combination of Rayleigh–Rice theory and scalar diffraction theory in the near-infrared and visible spectral ranges, while scalar diffraction theory is used for the processing of reflectance data within the ultraviolet range. Rayleigh–Rice theory alone is sufficient for the processing of the ellipsometric data across the entire spectral range. We accurately determine the thicknesses of the polymer-like thin film and the transition layer, as well as the roughness parameters of both boundaries, with the root mean square (rms) values cross-validated using atomic force microscopy. Notably, the rms values derived from optical measurements and atomic force microscopy show excellent agreement. These findings confirm the reliability of the optical method for the detailed characterization of thin films with differently rough boundaries, supporting the applicability of the proposed method in high-precision film analysis.

Detailed Structural and Morphological Characterization of InGaN Thin Films Grown by RF Magnetron Sputtering with Various Substrate Temperature

Indium Gallium Nitride thin film was successfully grown on the substrate using an RF magnetron sputter under condition of different substrate temperatures. Various experimental measurements were taken to understand effect of substrate temperature on the structure of thin film and results were analyzed. Grazing mode of XRD results confirmed that thin film has a hexagonal structure with plane for and substrate temperature. It was seen that structural parameters of thin film show a change with substrate temperature change. Reasons were discussed. Strain and stress values in thin film were calculated from experimental results and it was found that all thin film has compressive stress. Morphological parameters of thin film were measured by AFM and it was understood that these properties are varied by changing substrate temperature. Also, growth mode of some thin film was found to be layer-plus-island mode (Stranski-Krastanov growth mode), others was found to be layer by layer growth mode (Frank van der Merwe mode). SEM analysis gives that increasing substrate temperature worsened the surface structure of thin film; it is compatible with and supports XRD results. Compositional values in thin film were found from XPS analysis. In addition to our material, carbon and oxygen have also been obtained from XPS results, as expected. Detailed structural and morphological properties of thin film have been seen to change by changing substrate temperature and we believe this may play an important role in the production of based optoelectronic devices.

Avoiding blister defects in low-stress hydrogenated amorphous silicon films for MEMS sensors

Low-stress silicon-based thin films play a crucial role in microelectromechanical systems (MEMS) such as silicon microphones. To obtain low stress, post annealing is usually applied and, in particular, the residual stress of hydrogenated amorphous silicon (α-Si:H) can be finely tuned by properly adjusting the annealing temperature to obtain slightly tensile thin films. However, blister defects are unfortunately observed in the course of stress control by high temperature annealing. We study structural parameters of thin films that may induce blistering behaviors and propose a statistical prediction model as a guide to avoid the blistering disaster for MEMS chips. By optimizing the shape, size, and thickness of thin films, the non-blister α-Si:H thin film with low stress of around 63 MPa is demonstrated.

Morphological, structural, compositional properties and IR-spectroscopy of CdSe films deposited by close-spaced vacuum sublimation

The polycrystalline CdSe films were deposited by the close-spaced vacuum sublimation technique at the different substrate temperatures (373–873 K). Surface morphology, grain size and growth mechanism of the films were determined by the scanning electron microscopy. The X-ray diffraction analysis of structural and sub-structural properties of the films was carried out to study their phase composition and growth texture. The main structural parameters of thin films, such as texture, lattice parameter, grain size, scattering domain size and micro-stress level have been determined in the work depending on the condensation film conditions. RBS and FTIR analysis shows that obtained films in general are homogenous and pure. As a result, the growth conditions of CdSe polycrystalline films with good crystal quality were determined.

Background subtraction practice in X-ray reflectivity reciprocal space mapping and its influence on the structural parameters of thin films

Background subtraction practice in X-ray reflectivity reciprocal space mapping (XRRSM) is described and compared to the traditional specular reflectivity. XRRSM allows determining a more precise contribution of background to the reflectivity signal which manifests itself in an improvement of the resolution of interference fringes. Data analysis and influence of background subtraction determined by two methods on the structural parameters of thin film are discussed using simulated X-ray reflectivity.