การเตรียมฟิล์มบางด้วยระบบแมกนิตรอนสปัตเตอริงแบบพัลส์ดีซี จากเป้า Ca3Co4O9 และ CaMnO3

Abstract

Thin films were deposited on the glass substrates by an asymmetric bipolar pulsed-dc magnetron sputtering system from the Ca₃Co₄O₉ and CaMnO₃ targets of 3.218 g/cm³ and 2.862 g/cm³ densities, respectively. The sputtering targets were pellets of 60 mm diameter and 2.5 mm thick which were made by the sintering of powder precursors obtained from a solid state reaction method. The depositions were carried out under an argon flow rate of 15.0±0.1 sccm and the pulsed frequency of 17.24 kHz for the deposition time of 1 hr. The anode positive pulse was set at the same current-voltage of 20 mA 100 V with the cathode negative current fixed at 120 mA and the target output voltages of 260-280 V. Optical emissions from the plasma during the deposition were measured in the wavelength range of 360-800 nm using a high resolution spectrometer. The as-deposited film thickness was initially estimated from the optical interference using Tolansky's Fizeau fringe method and was obtained from the ellipsometic measurement. The crystal structure was studied by X-ray diffraction. The thermoelectric properties were assessed by Seebeck coefficient and electrical resistivity measurements at room temperature. The Seebeck coefficient was obtained from the measurement of thermoelectric voltage as a function of temperature difference across the film surface. The electrical resistivity was measured by the standard Van der Pauw four-probe method. The power factor was calculated. It was found that the optical emission spectrums show that the Ca, Mn, Co and O atoms were sputtered from the targets onto the glass substrates. The as-deposited Ca-Co-O and Ca-Mn-O films thickness values are 0.435±0.003 m and 0.449±0.001 m, respectively. X-ray diffraction patterns clearly showed the amorphous nature of the as-deposited films. The determination of thermoelectric properties of the Ca-Co-O film gave the Seebeck coefficient of 0.146±0.009 mV/K, electrical resistivity of 0.473±0.009 .cm, and a power factor of 4.531±0.685  W/m×K² at room temperature. The Ca-Mn-O film baring a high resistance was not the experimental determination of thermoelectric properties. Post deposition annealing and the doped metals are expected to be one of the candidates for good thermoelectric properties. This will be further investigated.