Imaging Materials from Biology to Electronics using Piezoresponse Force Microscopy (PFM) and NTEGRA Instruments from NT-MDT

Topics Covered

Background
Introduction
Hexagonal Domains in Lithium Niobate
Ferroelectric Domain Patterns in Multiferroic Manganite
The Equipment

Background

NT-MDT Co. was established in 1991 with the purpose to apply all accumulated experience and knowledge in the field of nanotechnology to supply researchers with the instruments suitable to solve any possible task laying in nanometer scale dimensions. The company NT-MDT was founded in Zelenograd - the center of Russian Microelectronics. The products development are based on the combination of the MEMS technology, power of modern software, use of high-end microelectronic components and precision mechanical parts. As a commercial enterprise NT-MDT Co. exists from 1993.

Introduction

The electro-mechanical coupling behaviour of many materials in systems from bio based cell membranes and proteins to ferroelectric and piezoelectric electronic materials can now be analysed in great detail via Piezoresponse Force Microscopy (PFM).

This imaging technique is of particular interest in the development of novel electronic devices for example those based on ferroelectric domain switching - systems of great potential for future developments in areas such as computer memory.

PFM uses a scanning force microscope operating in the contact mode with an alternating voltage applied to the probe tip (see Fig 1). This technique is particularly attractive as it has a high lateral resolution of only ~10-20 nm together with an astonishing sensitivity of ~0.1 pm/V.

Figure 1. Schematic set-up of a scanning force probe operating as a Piezoresponse Force Microscope. If you’d like to see full animations, please, visit this page

The imaging of ferroelectric domains using this technique is possible due to the fact that ferroelectric behaviour implies piezoelectricity, and consequently mapping the piezoelectric response of a material provides a direct image of its ferroelectric domain structure.

Hexagonal Domains in Lithium Niobate

Figure 2. The image illustrates the hexagonal domain structure of Lithium Niobate - a structure typically produced by the room temperature electric field poling. Lithium Niobate is an important material for use in telecommunications and optical devices such as wave guides and modulators.

The sample was kindly given by C. Gawith, Optoelectronics Research Centre University of Southampton. Image courtesy of T. Jungk, A. Hoffmann, E. Soergel, University of Bonn.

Ferroelectric Domain Patterns in Multiferroic Manganite

Figure 3. The image was produced from the polished surface of a z-cut ferroelectric single crystal using PFM. The irregular nature of the image illustrates breaking ferroelectric order by the random fields.

Scan size 50 x 50 µm, produced using a NTEGRA Solaris system with AFM head. The sample was kindly given by Dr. M. Fiebig. Image Courtesy Dr. T. Jungk, Dr. F. Johann, Dr. A. Hoffmann, Dr. E. Soergel, University of Bonn, Germany