Development of sputtering conditions for PZT micro actuator with high piezoelectric property by Au-Pt buffer layer

We developed a medical device to measure blood glucose levels automatically. This device is consisting of a micropump of PZT (Lead Zirconate Titanate) actuator to support during extraction of blood and administration of insulin. Thus, the micro-pump should be miniaturized because it needs to be mounted on the device, so that the device is not too big to be carried. However, a decreasing of piezoelectricity becomes a problem when volume of thinned PZT is reduced. Thus, we intended to create a PZT film which shows high piezoelectricity. In this study, it has been reported that the piezoelectricity is much more improve when PZT(111) and PZT(110) stagger evenly in thin films. In the present study, we aim to get the maximum piezoelectricity by using buffer layer which reduce the lattice mismatched. It has been reported that Au(111) takes first priority and orient PZT(111), and Pt(111) takes first priority and orient PZT(110). Therefore, the purpose of this study is a creation of the Au(111) and Pt(111) alternative arranged buffer layer for the PZT(111) and PZT(110) polycrystalline structure growth by using the non-alloyed target (which is a Pt thin foil with pinholes on Au target) and by the ECR(Electron Cyclotron Resonance) sputtering deposition method. The sputtering rate of Au and Pt are considered as the area of the target which is Au and Pt was set to 1:7. In order to invent the PZT buffer layer, the ECR sputtering target is made, which Au and Pt are equally distributed where the composition of Au and Pt is 1:1. As a result, the best sputtering condition of buffer layer production is 2256 eV in acceleration voltage, 0.75 seem in Ar gas flow rate and 645 °C in heat-treatment temperature because the difference between the peak strength ratio of Au(111) and the peak strength ratio of Pt(111) is small. An analysis of variance is performed. It is understood that the heat-treatment temperature shows the contribution rate and the significance are 89.78 % and 99 %.- Next, we use the response surface methodology, based on the result of the experimental design. Therefore, we decided that Ar gas flow rate and the heat-treatment temperature as 2 factors of the response surface methodology. The production condition is optimum when Ar gas flow rate is at 0.94 seem and the heat treatment temperature is at 707 °C. Next, the rate and the heat treatment temperature are fixed according to the optimized conditions and the experiment of acceleration voltage is conducted. The optimum production condition of the acceleration voltage is obtained and the result is 2394 eV. Moreover, we created PZT thin film on this Au-Pt buffer layer. As a result, this Au-Pt buffer layer is able to show higher piezoelectricity PZT.