Comparitive study of solution grown Strontium fluoride (SrF2) and Berillium iodide (BeI2) thin films and their possible applications

Semi conducting halide thin films of strontium fluoride (SrF2) and berylium iodide (BeI2) were successfully deposited on glass slides at 320K and pH of 8, 9, 10 and 12 using solution growth technique. A complexing agent, ethylenediamine-tetra acetate (EDTA), with pH oppose that of bath constitutions, was used to bath reagents to enhance control and stabilize the deposition pH at different values suitable for film growth. X-ray diffraction method was used to confirm the depositions. Electron micrographs of the films reveal uniform surface depositions. Absorbance (A) spectra data were measured by a single beam spectrophotometer (Pharmacia LKB Biochrom 4060) at wavelength range 200nm to 900nm. Other optical and solid state properties were calculated from the data and compared with other deposited thin films. The average optical and solid state properties of strontium fluoride thin films include absorbance ranging from 0.034 to 0.086, transmittance 0.820 to 0.925, refractive index 1.51 to 1.88, electrical conductivity 0.40 to 0.49(ohm-cm)–1, film thickness 0.013 to 0.074μm and band gap 2.65 to 2.75 + 0.05eV. For berylium iodide films the absorbance ranges from 0.204 to 0.302, transmittance 0.499 to 0.625, refractive index 2.41 to 2.61, electrical conductivity 0.62 to 0.68(ohm-cm) –1, film thickness 0.202 to 0.362μm and band gap 2.20 to 2.75 + 0.05eV. Films with refractive index lower than 1.9 could be employed in antireflection coatings, eyeglass coating and solar thermal control coatings. Those with refractive index greater than 1.9, could be useful in construction of poultry houses, solar cells and anti dazzling coatings. Journal of Science and Technology Vol. 26 (3) 2003: pp. 11-1

Solution Grotwh, Characterization and Possible Applications of Beryllium Fluoride (BeF2) Thin Films Deposited at 320K and at pH of 7 - 12

Solution growth technique (SGT) was successfully used to deposit good quality BeF2 thin films on glass slides at 320K for 3 hours and at pH of 7 – 12. The bath constituents were beryllium nitrate-4-water, and sodium fluoride as starting materials, sodium hydroxide as complexing agent and ethelemediamine tetra-acetate to vary the pH values. Effects of pH and bath constitutions were also investigated. Our numerous investigations reveal that beryllium fluoride thin films were produced only in alkaline medium. The deposited thin films modify the optical properties of the glass substrates at various wavelength regions. Average transmittance (T) values ranges from 0.615 – 0.904, reflectance (R) from 0.052 – 0.175, coefficient of absorption (a) (0.106 – 0.486) x10-4 cm-1 and refractive index (n) from 1.59 – 2.43. Values of solid-state properties such as band gap (Eg) range from 2.22-2.66 eV, electrical conductivity (s) from 0.73 – 1.26) X10-5 (W-cm)-1 and film thickness (t) from 465 - 214Å. Films with refractive index (n) lower than 1.8 have high transmittance (T) and low reflectance (R) while those with refractive index (n) greater than 1.8 have low transmittance (T) and high reflectance (R). The possible applications of the deposited beryllium fluoride (BeF2) thin film in optical, architectural, agricultural and electronics industries were also discussed. (Nigeria Journal of Pure and Applied Physics: 2003 2 (1): 21-27