Thesis assignments

Piezomechnical properties at the nanoscale for NEMS actuation

Piezoelectric materials have the ability to convert electrical energy into mechanical energy. The downscaling of these materials has led to the field of piezo micro electro mechanical systems (MEMS) with many applications such as scanning probe microscopy, energy harvesters or inkjet print heads. In this project we will attempt to understand these materials on a unit cell scale and further decrease the device-size into the submicron domains. As the material’s dimensions start to decrease its properties will change generally decreasing the characteristics. This change will be studied and with this knowledge we will try to increases the properties of small scale devices making new applications for these piezoelectric materials possible.

In the overall project we focus mostly on epitaxially grown PZT (Pb(Zr,Ti)O3) films on different substrates with the use of pulsed laser deposition (PLD). PZT is chosen due to its high piezoelectric coefficients. In order to understand the workings of thin films we study these materials using methods and techniques such as XRD (X-Ray Diffraction), PFM (Piezo Force Microscopy), ferroelectric/polarization loops, HRSEM (High Resolution Scanning Electron Microscopy) and laser Doppler vibrometer height sensing. From these measurements we gain insight into important aspects such as the domain wall movement, unit cell deformation, polarization and material lifetime. With the final aim of improving our thin film materials and make devices at the nanoscale for NEMS actuation.

In this bachelor assignment the goals is to look at samples of STO(KTO)/SRO/PZT/SRO/Au with PZT of a composition of 50/50 and 40/60 and compare and understand what happens to the domain of the PZT under the influence of an externally applied electric field using the XRD. The question will be what happens to the domain intensity, domain unit cell size and if there is a splitting in the PZT(50/50) domain which gives a single XRD peak without an applied field.

The project will require the student to understand and follow the processing of the materials which will be done with the supervisor. This will consist of growing the PZT layer, of different compositions, on either STO or KTO with the use of PLD, etching the sample using photolithography and depositing electric contacts through sputtering. The main focus of the project will be on the analysis of these samples. The student will initially need to understand XRD and make a plan of how the sample can be studied. After this the student will use the XRD machine and apply an external electric field in order to obtain data about the samples. The student will then need to analyze this data and use it to see what is happening to the material and ultimately write a model to explain his findings.

For more information contact : Fox Huang (