Nanoscale studies of functional materials using scanning probe microscopy

• Main Author: Wittborn, Jesper
• Format: Doctoral Thesis
• Language: English
• Published: KTH, Materialvetenskap 2000
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3000

This thesis deals with developing suitable modifications ofScanning Probe Microscopy (SPM) for investigations offunctional properties of materials. In order to make itpossible to investigate a number of properties of variousfunctional systems<b>using SPM the following new techniques have beendeveloped</b>:     A magnetic force microscope (MFM) having capability ofboth dc- and ac-mode detection.     A method to extract switching field distributions fromseries of MFM images.     A novel technique for magnetic microscopy using anon-magnetic probe to investigate the magnetostrictiveresponse of ferromagnetic materials, capable of 1 nmresolution.     A technique to determine the magnetostriction at lowexternal fields using AFM.     A technique for AFM studies of ferroelectric domainsusing the inverse piezoelectric effect of ferroelectricmaterials.     A technique for studying the relative stiffnessdistribution in composite materials using AFM.     Scanning friction microscopy.     Methods for determining the structure ofnanoindents. Using the techniques highlighted above, we have studied<b>functional materials of current interest from bothtechnological and basic research points of view</b>. Some of the materials and the main results obtainedare:     The role of magnetism arising from chains of nano-sizedmagnetite particles bio-mineralized in magneto-tacticbacteria is a topic of growing interest today. We use MFMtechniques to investigate magnetic flux reversal phenomena insuch chains. It is found that: 1.2.It is noteworthy that from our MFM measurements on singlemagnetosomes of 50 nm we havedetected magnetic moments as small as 3.1·10-14emu. Such detection is not possible by anyother technique known today. 1.2. 1. 2. It is noteworthy that from our MFM measurements on singlemagnetosomes of 50 nm we havedetected magnetic moments as small as 3.1·10-14emu. Such detection is not possible by anyother technique known today.     Evaluation of magnetostrictive properties of smallstructures is extremely important and relevant to informationstorage media and read/write heads, in particular, as storagedensities beyond 30 gigabytes is pursued. In this thesis astudy of domain wall width of submicron man-made Co dots ispresented with a newly developed magnetostrictive imagingtechnique. Domain wall width of ~35 nm have been observed inmagnetic dots of 250 nm diameter. Additionally, we found thatdue to magnetostatic coupling the dots influence theneighboring domains to align ferromagnetically. The studiespresented herein are the first such to be reported inliterature.     From an investigation of epitaxially grown ferroelectricPbZr0.65Ti0.35O3(PZT) thin films the existence of orderedpolydomain configurations in grains larger than 200 nm aredemonstrated.     For an understanding of the interaction between thecomponents of composite materials the relative stiffness wasdetermined for a composite material consisting of TiNinclusions in an Al2O3matrix. This would be a new approach to studythe local mechanical properties of future nano-compositematerials. Preliminary investigations of the structure of nanoindentson a variety of materials demonstrate potentially richpossibilities to study the hardness at various depths inadvanced nanostructured materials