Updated: May 14, 2026

Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers
Published on: September 27, 2018
John P George1, Jeroen Beeckman, Wouter Woestenborghs
1Department of Electronics and Information Systems, Ghent University, Sint-Pietersnieuwstraat 41, Gent, 9000, Belgium. John.PuthenParampilGeorge@elis.ugent.be.
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This study explores how adding a thin layer of lanthanum oxynitrate to silicon substrates can improve the quality of barium titanate (BaTiO3) thin films. Using a chemical solution method, the researchers found that a buffer layer of 8.9 nm thickness helped produce highly ordered BaTiO3 films with smooth surfaces and good electrical properties. X-ray analysis confirmed the films had a tetragonal crystal structure, and measurements showed a dielectric constant of 270 and polarization of 5 μC/cm². The results suggest that buffer layer engineering is important for creating functional ceramic films suitable for electronic applications.
Area of Science:
Background:
Thin film deposition techniques are widely used in electronics and materials science. However, achieving preferential crystallographic orientation in complex oxides like barium titanate remains a challenge. Prior research has shown that buffer layers can influence film orientation, but the specific role of lanthanum oxynitrate in this context is less clear. This gap motivated the investigation of how intermediate buffer layers affect BaTiO3 crystallization. No prior work had resolved the exact impact of buffer layer thickness and sintering conditions on film orientation. The study builds on known methods like chemical solution deposition but introduces a novel buffer layer system. The goal is to understand how buffer layers can improve film quality and electrical properties. This work addresses the need for better control over thin film morphology and functionality.
Purpose Of The Study:
The aim of this research is to explore the effect of a lanthanum oxynitrate buffer layer on the orientation and quality of BaTiO3 thin films. The specific problem is the difficulty in achieving uniform, crack-free, and highly oriented films on silicon substrates. The motivation stems from the need for reliable dielectric materials in microelectronics. The study focuses on optimizing buffer layer thickness and annealing conditions. It addresses the challenge of controlling crystal growth in perovskite materials. The research also seeks to evaluate the electrical performance of the resulting films. This work contributes to the broader goal of improving thin film deposition techniques. The findings may inform future studies on buffer layer engineering in ceramic films.
The study produced highly c-axis-oriented BaTiO3 films with a dielectric constant of 270 and remnant polarization of 5 μC/cm².
The buffer layer promotes uniform, crack-free film growth and enhances electrical properties like polarization and coercive field.
The buffer layer thickness of 7.2–8.9 nm was optimized to achieve tetragonal phase formation and high-quality film morphology.
X-ray diffraction confirmed the tetragonal perovskite phase and c-axis orientation of the BaTiO3 thin films.
Main Methods:
The researchers used chemical solution deposition to prepare BaTiO3 films. They deposited a lanthanum oxynitrate buffer layer on silicon substrates. The buffer layer thickness was controlled at 8.9 nm. Films were annealed under optimized conditions to promote crystallization. X-ray diffraction was used to analyze crystal orientation and phase purity. Scanning electron microscopy and atomic force microscopy evaluated film morphology. The study measured dielectric and polarization properties of the films. These methods allowed the team to correlate buffer layer parameters with film quality.
Main Results:
X-ray diffraction confirmed tetragonal perovskite phase formation in BaTiO3 films. The films showed strong c-axis orientation with minimal secondary phases. Scanning electron microscopy revealed smooth, crack-free surfaces. Atomic force microscopy indicated uniform grain distribution and density. Films deposited on a 7.2 nm buffer layer achieved a dielectric constant of 270. The measured remnant polarization was 5 μC/cm². Coercive field values reached 60 kV/cm. These results suggest the buffer layer significantly enhances film quality and electrical performance.
Conclusions:
The study demonstrates that a lanthanum oxynitrate buffer layer improves BaTiO3 film orientation and quality. The buffer layer thickness and sintering conditions are critical for optimal results. Films with c-axis orientation and high dielectric constants were successfully produced. The authors propose that buffer layer engineering is essential for functional thin films. The findings suggest that buffer layer composition and processing are key variables. The results align with the hypothesis that intermediate layers influence film crystallization. The study supports the use of lanthanum oxynitrate as an effective buffer material. These conclusions are based on the observed film morphology and electrical properties.
A dielectric constant of 270 indicates strong electrical performance, making the films suitable for high-performance capacitors.
The authors propose that buffer layer composition and processing are critical for achieving high-quality BaTiO3 thin films.