Research on the surface in Au-Pt buffer layer for the high piezoelectric PZT

Abstract

We are developing device to measure blood glucose levels automatically. This device consist of a micropump of PZT(Lead Zirconate Titanate) actuator for sucking blood and administering insulin. The pump should be miniaturized, because it is too large to be carried. However, a decreasing of piezoelectricity affected by reduction volume of thinned PZT becomes a problem. Thus, we intended to create a PZT film which shows high piezoelectricity. In previous study, it was reported that the piezo-electricity becomes maximum when PZT(111) and PZT(110) stagger evenly in thin films. In this 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 to create alternately arranged buffer layer of the Au(111) and Pt(111) 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. As a creation technique of the Au-Pt buffer layer, an easy sputtering technique was adopted by controlling the relative composition ratio. Here, by using this ECR sputtering machine, surface treatment on Si substrate by sub ion gun. Considering the sputtering rate of Au and Pt the target area of Au and Pt was set to 1:3. Furthermore, the evaluation value of Au-Pt buffer layer is a peak strength ratio. Au and Pt is deposited on Si(111) substrate which Au(111) and Pt(111) are more prior in crystal growth. By removed natural oxidation film from Si substrate, Au(111) and Pt(111) crystal orientation were considered to become more priority oriented. As for a washing technique of Si substrate, a natural oxide film removal method was performed by HF (Hydrofluoric Acid) and sub ion gun sputtering. Here, Au-Pt composite target were sputtered on Si substrate which washed with HF etching. We know that the crystal orientation of Au and Pt was dispersed. The crystal orientation is distributed because the surface of Si(111) was changed, affected by HF. Therefore, a film of Au-Pt buffer layer is performed after changing a natural oxide film removal technique to surface treatment by using sub ion gun sputtering. The natural oxide film on the Si substrate surface was removed by using ECR sputtering. After that, buffer layer is created by using the Au-Pt composite target. As a result from Au-Pt buffer layer which deposited as existed method, approximately 135 [%] of the increasing of the crystal growth was observed. Therefore, Au(111) and Pt(111) have more priority in crystal growth by a natural oxide film removal by using sputtering.