Sol-Gel Derived Pyroelectric Barium Strontium Titanate Thin films for Infrared Detector Applications
- PDF / 71,854 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 61 Downloads / 216 Views
Sol-Gel Derived Pyroelectric Barium Strontium Titanate Thin films for Infrared Detector Applications Jian-Gong Cheng, Jun Tang, Shao-Ling Guo, Jun-Hao Chu National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China ABSTRACT Ba0.8Sr0.2TiO3 thin films that are suitable for infrared detector applications have been prepared with a sol-gel process using a highly diluted precursor solution. Columnar structure with grain size close to 200 nm was obtained with layer-by-layer homoepitaxy due to a very small thickness of individual layer. The measured pyroelecrtic coefficient is larger than 3.1×10-4 C/m2K at the temperatures ranging from 10 to 26 oC and reaches the maximum value of 4.1×10-4 C/m2K at 16.8 oC. The infrared detectivity of 4.6×107 cmHz1/2W-1 has been obtained at 19 oC and 10 Hz in the Ba0.8Sr0.2TiO3 films deposited on thick (500 µm) platinum coated silicon substrates. The better infrared response can be expected by the improvement in the thermal isolation of pyroelectric element and the electrode materials. INTRODUCTION Barium strontium titanate (BST) has been extensively studied for advanced dynamic random access memory (DRAM) and uncooled infrared detector applications [1, 2], due to its high dielectric constant and composition dependent Curie temperature (from 30 to 400 K). Thin films of BST have been prepared by many growth techniques, such as rf-magnetron sputtering, laser ablation, metalorganic chemical vapor deposition [3-5], and sol-gel process [6-8]. Compared to other deposition methods, sol-gel process offers some advantages, such as homogeneity, stoichiometry control, and the ability to coat large and complex area substrates. However, the sol-gel derived BST films always fail to display pronounced ferroelectric hysteresis loops [6-8], which makes it unsuitable for infrared detector applications. In this paper, we report on the deposition of pyroelectric Ba0.8Sr0.2TiO3 thin films that are suitable for infrared detector applications by a sol-gel process using a 0.05M solution precursor. EXPERIMENTAL DETAILS The starting materials were barium acetate, strontium acetate and titanium butoxide. Barium acetate and strontium acetate were mixed in a ratio of Ba/Sr of 4/1, and then dissolved into heated acetic acid. This was followed by an addition of equimolar amounts of titanium butoxide stabilized by appropriate acetylacetone under constant stirring. The mixture was then filtrated as CC11.10.1
the stock solution. The coating solution of 0.05 M was prepared by diluting the stock solution with acetic acid. The Ba0.8Sr0.2TiO3 films were deposited on Pt/Ti/SiO2/Si substrates by spin coating of the 0.05 M solution at 6000 rpm for 40 s. After coating of each layer, the films were given a pyrolysis heat treatment at 350 oC for 5 min to remove residual organics, and then annealed at 750 oC for 10 min in air. The average thickness of a single-coated as-annealed layer, measured by an ellipsometer, was found to be about 8 nm. The desired film t
Data Loading...
