Quantitative Data Processing in Scanning Probe Microscopy

SPM Applications for Nanometrology

Petr Klapetek

• Publisher: Elsevier
• Year: 2018
• eBook ISBN: 9780128133484
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Nanoscience

Quantitative Data Processing in Scanning Probe Microscopy: SPM Applications for Nanometrology, Second Edition describes the recommended practices for measurements and data processing for various SPM techniques, also discussing associated numerical techniques and recommendations for further reading for particular physical quantities measurements. Each chapter has been revised and updated for this new edition to reflect the progress that has been made in SPM techniques in recent years. New features for this edition include more step-by-step examples, better sample data and more links to related documentation in open source software. Scanning Probe Microscopy (SPM) techniques have the potential to produce information on various local physical properties. Unfortunately, there is still a large gap between what is measured by commercial devices and what could be considered as a quantitative result. This book determines to educate and close that gap. Associated data sets can be downloaded from http://gwyddion.net/qspm/ - Features step-by-step guidance to aid readers in progressing from a general understanding of SPM principles to a greater mastery of complex data measurement techniques - Includes a focus on metrology aspects of measurements, arming readers with a solid grasp of instrumentation and measuring methods accuracy - Worked examples show quantitative data processing for different SPM analytical techniques

Chapter 1

Motivation

Abstract

We present the basic classification of Scanning Probe Microscopy instrumentation with respect to its quantitative measurements capabilities and also to the book organization. Basic terms used in metrology, like metrological traceability, uncertainties, and their budget, are explained and their use in quantitative Scanning Probe Microscopy discussed. A brief comparison to alternative routes to get the quantitative information is provided as well.

Keywords

Scanning Probe Microscopy; Traceability; Uncertainty

1.1 Why “Quantitative” Scanning Probe Microscopy?

Despite its tremendous advancement in the last twenty years, scanning probe microscopy (SPM) is still not considered as a really quantitative experimental technique. Besides dimensional SPM measurements that are regularly accepted as providing “accurate” results, there is an increasing number of other physical quantities measuring and mapping modes that are producing more or less qualitative results, with no firm relation to any absolute value. The reason is simple. The nanoscale tip–sample interaction is very complex, containing many different components, and some of them are still not properly understood, and some of these components can be even hardly separated one from the other. Moreover, the geometry and composition of both tip and sample are not known (we measure only the result of their mutual interaction), which makes all the theoretical models even more complicated. The more advanced SPM technique we use, the farther it is from being a metrology tool.

Since most of the SPM users have no access to a specialized metrology SPM system, their ability of converting results to quantitative ones (i.e. accurate and traceable, with known uncertainty) is limited to a proper instrument calibration, a good measurement strategy, and a detailed analysis of obtained results. Proper understanding of basic physical phenomena taking place between tip and sample is crucial for this task. Similarly, knowledge of all typical artifacts and accuracy bottlenecks and use of artifact detection and removal techniques should be a daily bread for an SPM researcher.

The aim of this book is to provide the reader a reference for a quantitative SPM analysis in practical situations, namely when using commercial instruments. We provide a description of the basic ideas necessary for the quantitative understanding of different SPM techniques operation, including dimensional, mechanical, electrical, magnetic, thermal, and optical modes. We discuss the physical model of the tip–sample interaction for each particular case and list basic calibration and traceability strategies. The influence of different tip and sample geometry or their material properties on quantitative measurements is analyzed. Techniques for modeling realistic data and processing the measurement results are reviewed, and their practical application to user data is described. Whenever possible, publicly available software tools are reviewed from the point of their applicability and accuracy.

This book would like to address the typical questions of a newcomer or a casual user. Scientific literature is full of excellent results obtained using SPM, like individual atom chemical identification [1] or building fascinating nanostructures to study quantum mechanical phenomena [2]. When this is compared to the possibilities of a standard commercial instrument, even a new and really expensive one, the reader can get significantly disappointed. The data that are produced by the instrument are at first sight only colorful images. Most of the measured quantities have nonphysical units like nanoamperes for force or volts for temperature. If there is some calibration of quantitative data treatment built-in in the instrument, then it is limited to the very basic approaches only, even to those proved in the literature as very poor ones. In this book, we would like to show what needs to be done to get maximum of data that a “standard” commercial instrument produces and which directions to take to improve accuracy and reliability of such results.

For illustration, we can sketch several sample questions that this book would like to address:

• • How can I calibrate my SPM to get accurate results?
• • How precisely can I measure dimensions of nanoobjects?
• • How can I interpret force–distance curves?
• • What spatial resolution can I expect in thermal/magnetic/electric/optical measurements and how to evaluate it?
• • Can I resolve different chemical species in ambient SPM measurements?
• • Can I measure the local material refractive index using SPM?

What the book does not address? We focus on data processing and analysis; all the information related to the measurement process itself is limited to its influence on the obtained data. Technical discussion on how microscopes are built is therefore only short, and we do not describe most of the modes that need special equipment, which is not available in any commercial instruments, even if these could lead to challenging results. If the use of some additional equipment is suggested, then it is usually outside of the microscope, used only for obtaining some additional information (e.g. calibration of the probes). The majority of this text is related to ambient measurements, even if most of the approaches are valid also in vacuum conditions. We do not discuss special issues related to UHV and low-temperature SPMs since this is still a statistically minor field ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Preface to the Second Edition
• Preface to the First Edition
• Chapter 1: Motivation
• Chapter 2: Instrumentation Principles
• Chapter 3: Data Models
• Chapter 4: Basic Data Processing
• Chapter 5: Dimensional Measurements
• Chapter 6: Force and Mechanical Properties
• Chapter 7: Friction and Lateral Forces
• Chapter 8: Electrostatic Fields
• Chapter 9: Magnetic Fields
• Chapter 10: Local Current Measurements
• Chapter 11: Thermal Measurements
• Chapter 12: Optical Measurements
• Chapter 13: Sample Data Files
• Chapter 14: Numerical Modeling Techniques
• Index