engleski

Structural analysis of inhomogeneous SnOx thin films

SnOx as a thin film solar cell material is heavily investigated which reflects its importance in energy-related research. As a low cost way of deposition, the spray pirolysis by Atmospheric Pressure Chemical Vapor Deposition (APCVD) becomes popular in many industrial production lines. The growth of solar cell structure is in most cases “transport limited growth”, e.g. the film growth follows the surface roughness of SnOx surface that is determined by its crystal type, orientation, grain size and microstrain. Therefore, it is of paramount importance to examine carefully those crystallographic features by the structural analysis. In this study, SnOx thin films were deposited by APCD on the glass substrate in two sequential steps. In the first step the precursor that contains only Sn and O atoms is sprayed on the surface of hot glass and after that heated in oven for some time. In second step, the precursor contains fluorine as a dopand. The type of precursor affects the crystal size and other structural properties. As result, the films are inhomogeneous in depth. Due to the complex nature of as-deposited material, a careful layered (along the depth) structural analysis is a must in order to collect very local information about the materials microstructure as required in solar cell design. Suitable structural analysis is XRD probing of the material in the grazing incidence mode. With such approach the resulting synchrotron XRD pattern represents the signature of the material at specific depth measured by incident angle. As obtained XRD patterns are fully processed with the Rietveld refinement in order to get information about crystallite sizes, microstrain and preferred orientation. Such information, particularly the gradient of crystallite size distribution calculated perpendicular to the film surface is valuable data as a feedback information to the thin film deposition conditions, since Davore ajde dopisi mozda ovdje zasto je bitna velicina kristalita po dubini, veci uz povrsinu ili manji ili kako je vec. Moreover, films are examined by GISAXS (Grazing Incidence Small Angle X-ray Scattering) from the synchrotron source and AFM (Atomic Force Microscopy) completing the structural characterization of material.

thin film deposition; x-ray diffraction

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