P. Eiamchai

Effect of Annealing Temperature on Structure and Optical Properties of Ta2O5 Thin Films Prepared by DC Magnetron Sputtering

Tantalum oxide (Ta2O5) films at 400 nm thickness were prepared at room temperature by DC reactive magnetron sputtering. The effect of annealing temperature on film crystallinity, microstructure and optical properties were investigated. In order to indentify the crystalline structure and film morphology, X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM) measurements were performance. The optical properties were determined by UV-Vis spectrophotometer and spectroscopic ellipsometry (SE). The result showed that, with the annealing treatment at high temperature (700-900°C), the as-deposited films were crystallized to orthorhombic phase of tantalum pentaoxide (β-Ta2O5). In addition, the transmittance spectrum percentage indicated 87%, which corresponded to the obtained optical characteristic. The refractive index varied at 550 nm from 2.17 to 2.21 with increased of the annealing temperature.

Optimizations of Sealing Conditions for Blank Silver Nanorod Used as SERS Substrates

Silver nanorods, prepared on Si substrates by sputtering deposition with the technique glancing-angle deposition (GLAD), were used as surface-enhanced Raman scattering (SERS) substrates. The prepared samples were categorized into two groups based on sealing conditions after the nanorod fabrications. The non-sealed SERS substrates were prepared by purging in the vacuum chamber with argon, oxygen, and ambient air. The sealed SERS substrates were enveloped with several types of packages, i.e., petri dishes, plastic bags, and foils, where they were all handled in a controlled glove box. The samples were characterized by field-emission scanning electron microscopy (FESEM) for the physical morphologies. The samples were further investigated by Raman spectroscopy for Raman spectra of blank substrates of each condition. The results showed that, in case of the non-sealed category, the SERS substrates purged under the argon gas was best optimized to prevent ambient contamination during prolonged period of time. In the case of the sealed category by different packages, the SERS substrates demonstrated the enhancement of the Raman-shift spectra with very small unwanted peaks, and in addition the extended lifetime.

Preparation of WO3 Nanorods by Glancing Angle DC Reactive Magnetron Sputtering Deposition for NO2 Gas Sensing Application

In this study, we present a tungsten trioxide (WO3) nanorods based gas sensor for NO2 sensing at operating temperature range 150-350 °C in purify dry air carrier. WO3 nanorods were fabricated by dc reactive magnetron sputtering with glancing angle deposition (GLAD) technique on silicon (100) wafer and alumina substrates interdigitated with gold electrode. The length of WO3 nanorods was varied from 370 nm to 620 nm. As-deposited nanorods were annealed at a temperature of 400 °C in air for 1 h. The microstructure and phase structure of WO3 nanorod were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), respectively. XRD of annealed WO3 nanorod showed polycrystalline phase. The WO3 nanorods length 420 nm exhibit excellent NO2 sensing properties with a maximum sensitivity of 360 at 250 °C operating temperature with fast response and recovery time.