ISO 11039:2012
(Main)Surface chemical analysis — Scanning-probe microscopy — Measurement of drift rate
Surface chemical analysis — Scanning-probe microscopy — Measurement of drift rate
ISO 11039:2012 defines terms and specifies measurement methods for characterizing the drift rates of scanning-probe microscopy (SPM) instruments in the X- and Y-directions and, for SPM instruments measuring topography, the drift rate in the Z-direction. Though the behaviour of the long-term drift rate might be nonlinear, both that and the behaviour of the short-term drift rate after a user-defined settling time can be characterized by either typical average or typical maximum drift rates. This International Standard is suitable for evaluating the drift rate based on SPM images. It is intended to help manufacturers quote drift figures in specifications in a meaningful and consistent manner and to aid users to characterize the drift behaviour so that effective experiments can be designed. These measurements are not designed for image correction.
Analyse chimique des surfaces — Microscopie par sonde à balayage — Mesurage du taux de dérive
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11039
First edition
2012-02-01
Surface chemical analysis — Scanning-
probe microscopy — Measurement of
drift rate
Analyse chimique des surfaces — Microscopie par sonde à balayage —
Mesurage du taux de dérive
Reference number
ISO 11039:2012(E)
©
ISO 2012
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ISO 11039:2012(E)
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ISO 11039:2012(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 2
4 Measurement method . 2
5 Requirements . 3
5.1 Instrument requirements . 3
5.2 Environment requirements . 3
6 Measurement procedures . 3
6.1 Initial check . 3
6.2 Basic characterization and the settling time . 4
6.3 Further characterization and fresh image areas . 5
6.4 Other specimens . 7
7 Measurement report . 7
Annex A (normative) Image correlation method . 8
Annex B (normative) Characteristic-marker method . 11
Annex C (normative) Non-periodic grating method .13
Annex D (informative) Guidance to users .16
Annex E (informative) Instrumental parameters to consider to reduce drift rates .17
Annex F (informative) Example of drift results and analysis .18
Bibliography .19
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ISO 11039:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 11039 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee
SC 9, Scanning probe microscopy.
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ISO 11039:2012(E)
Introduction
Scanning-probe microscopy (SPM) is a well-known microscopic technique for nanoscience and nanotechnology.
Working at, or close to, atomic-scale resolution, it is recognized that the time stability of such instruments is very
sensitive to their design, operating environment and usage. Among the many technical specifications of SPM,
the drift rate is an essential parameter. A knowledge of, and minimization of, drift in the X-, Y- and Z-directions
is required for designing many experiments. It is not only important for obtaining undistorted images and series
of images throughout an experiment, but is also critical when, for example, measuring physical properties,
monitoring dynamic behaviour, making micro/nanoassemblies, and manipulating materials at the nanoscale.
Furthermore, a knowledge of the instrumental drift rate is also important when selecting an instrument for
use. It is therefore desirable that manufacturers provide suitable information about the instrumental drift
characteristics in a common way. Many manufacturers provide closed-loop scanners in their instruments.
Unfortunately, drift is still present, although the magnitude of the drift rate is significantly reduced. Therefore,
practical methods to measure and characterize drift rates of SPM instruments in the X-, Y- and Z-directions are
required and are contained in this International Standard.
Two measures, the maximum and the average drift rates, are described for both the X-Y plane and the Z-axis.
The maximum drift rate is given as the maximum observed, for reasons of economy, after a small number of
fairly simple measurements. The maximum drift rate allows the user to design experiments that fall within the
working zone available given the duration of the intended experiments; however, the maximum observed X-Y
and Z-drift rates are based on a small number of observations and are less precise than the average drift rates
determined. To deduce a working zone, a rule of thumb is to assume that the maximum is twice the value of the
average. Clearly, in any population, the true maximum for a very large number of measurements would be very
large, but here it is expected that the user only expects some 90 % of experiments not to require repetition as a
result of the drift properties of the instrument. Depending on the importance of the measurements, users may, of
course, set themselves any chosen margin of safety based on the data derived using this International Standard.
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INTERNATIONAL STANDARD ISO 11039:2012(E)
Surface chemical analysis — Scanning-probe microscopy —
Measurement of drift rate
1 Scope
This International Standard defines terms and specifies measurement methods for characterizing the drift
rates of scanning-probe microscopy (SPM) instruments in the X- and Y-directions and, for SPM instruments
measuring topography, the drift rate in the Z-direction. Though the behaviour of the long-term drift rate might
be nonlinear, both that and the behaviour of the short-term drift rate after a user-defined settling time can be
characterized by either typical average or typical maximum drift rates.
This International Standard is suitable for evaluating the drift rate based on SPM images. It is intended to help
manufacturers quote drift figures in specifications in a meaningful and consistent manner and to aid users to
characterize the drift behaviour so that effective experiments can be designed. These measurements are not
designed for image correction.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 18115-2, Surface chemical analysis — Vocabulary — Part 2: Terms used in scanning-probe microscopy
3 Terms and definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18115-2 and the following apply.
3.1.1
drift
change in position of the probe tip, for a given positional setting by the instrument controller, relative to the
test specimen
NOTE Drift occurs in all parameters (e.g. X-, Y-, Z-displacements, laser positioning on the cantilever, intensity in
SNOM sources) but in this International Standard the term drift is restricted to the unintended change in position of the
probe tip for given scanner X-, Y- and Z-coordinates, relative to the test specimen.
3.1.2
drift rate
quotient of the linear displacement of the probe tip, for a given positional setting, relative to the test specimen
over a given time interval by that time interval
NOTE 1 The time interval is usually chosen to be the time between successive images.
NOTE 2 The drift rate may be given for each of the X-, Y- and Z-axes separately or as the magnitude of the resulting vector.
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ISO 11039:2012(E)
3.1.3
average drift rate
average of appropriate drift rates measured during a specified period of time
NOTE 1 The average drift rate may be given for each of the X-, Y- and Z-axes separately or as the magnitude of the
resulting vector.
NOTE 2 The average drift over a long period might be low if, by chance, the test specimen returns to its original position
whilst the average drift rate, being measured non-vectorially between successive images, remains high.
NOTE 3 The average drift rate obtained here is intended for designing experiments so that the effects of the drift can be
minimized or eliminated so that e.g. the important region of the test specimen remains in the field of view. Thus, the user
may multiply the average drift rate by a factor of 2 and add some safety factor to ensure that a certain fraction of the field
of view is maintained during the experiment.
3.1.4
maximum drift rate
maximum of the drift rates measured during a specified period of time
NOTE 1 The maximum drift rate may be given for each of the X-, Y- and Z-axes separately or as the magnitude of the
resulting vector.
NOTE 2 As in any set of measurements, the true maximum drift rate measured might increase slowly with the number
of measurements. The maximum value obtained here is intended for designing experiments so that the effects of the drift
can be minimized or eliminated so that e.g. the important region of the test specimen remains in the field of view. Thus, the
user may add some safety factor and a very accurate value of the maximum is not required.
3.1.5
settling time
time after selecting the area of the test specimen or point on the test specimen for measurement and the
commencement of the measurements for which the drift data are relevant
NOTE Settling times are often chosen to be from 5 min to 60 min, for convenience.
3.2 Abbreviated terms
AFM atomic-force microscope
NPG non-periodic grating
SPM scanning-probe microscopy
4 Measurement method
To characterize the drift behaviour of an SPM instrument, it is important to recognize that drift occurs as a
result of many processes, as shown in Annex E, and each of these processes causes an onset of drift that
might slowly reduce with time. Thus, after switching on the final part of the instrument, a drift behaviour may be
observed that, after a suitable waiting period, will generally be lower than that initially obtained. After inserting a
new test specimen into the measurement position, a similar behaviour occurs. After moving the specimen to a
new point using the specimen stage controls, a further drift will be initiated. Finally, after moving the SPM probe
to a new region of the specimen using the piezoelectric scanner, a fourth drift behaviour is seen. Each of these
behaviours might occur in a different direction and be of different magnitude. Indeed, each time this process
is repeated, all these might change in magnitude and direction. Nevertheless, after deciding on a certain
protocol for operating the instrument, typical average and maximum drift rate behaviours can be established.
Important in this protocol is the settling time, i.e. the period during which the instrument is allowed to stabilize
after selecting the area of the specimen or point on the specimen for measurement and the commencement
of the measurements for which the drift data are relevant. The average and maximum drift rates permit the
user to decide what influences the drift behaviour and hence what actions need to be taken to ensure that
the drift performance is suitable for the user’s requirements. This is described in Clause 6 and Annex E.
Subclause 6.1 describes an initial check to see if there is a significant drift behaviour that might need further
investigation. If the instrument is adequate, the investigation may cease. If further investigation is required, a
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ISO 11039:2012(E)
basic characterization is described in 6.2 to evaluate an appropriate settling time. For those interested in a
fuller characterization, the effects of changing operating conditions are evaluated in 6.3.
For the drift rate measurement, the following three methods are specified in this International Standard:
— image correlation method (see Annex A);
— characteristic-marker method (see Annex B);
— non-periodic grating method (see Annex C).
To facilitate the selection of the drift rate measurement method, guidance is given in Annex D.
5 Requirements
5.1 Instrument requirements
5.1.1 The SPM instrument shall have the capability of measuring and recording digital images of the specimen
surface, as a function of time, throughout the work.
5.1.2 The instrument shall maintain its dimensional calibration throughout the work.
5.2 Environment requirements
5.2.1 The instrument should, if possible, be operated under the required, or better, environment conditions
specified in the manufacturer’s documented instructions.
5.2.2 It is recommended that the measurement be performed in controlled conditions with the temperature
stable within ±1 °C and the relative humidity preferably less than 50 %. The laboratory environment should be
clean, with levels of electromagnetic interference, ambient vibration and ambient noise which are sufficiently low
that they do not influence the characterization of the instrument. The measured data will relate to the instrument
used in whatever operating conditions are selected and might or might not be relevant to any other operating
conditions. Suggested ways to improve the operating conditions, likely to lead to improved drift characteristics,
are provided in Annex E.
6 Measurement procedures
6.1 Initial check
6.1.1 Select the probe in accordance with the manufacturer’s documented instructions.
6.1.2 Operate the instrument in the manner and operating mode for which drift data are required. For low-drift
performance, keep as much of the instrument operational continuously and switch on remaining items more
than 1 h before conducting measurements.
NOTE Different operating modes might lead to different amounts of drift if different amounts of power are supplied to
different parts of the instrument.
6.1.3 Prepare the test specimen together with any reference material required for the measurement method.
When using the image correlation method of Annex A, it is preferable to have obvious features within the field
of view. For the characteristic-marker method of Annex B, there will need to be at least two sharp features at a
distance of approximately a quarter of the image size in from two opposite corners of the field of view. For the
non-periodic grating method of Annex C, obtain a suitable grating. Ensure, as far as possible, that these items
are clean in order to avoid probe tip contamination. Particulate matter might move during analysis, causing
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ISO 11039:2012(E)
erroneous drift determination. Particulates can be removed by washing in, for example, high-purity iso-propyl
alcohol with ultrasonic agitation. Ensure that any solvents used do not adversely affect the specimen.
6.1.4 Mount the specimen in accordance with the instrument operator’s manual or in-house documented
procedures.
NOTE Poor specimen-mounting methods might increase the drift behaviour.
6.1.5 Optimize the image acquisition parameters in accordance with the instrument operator’s manual or in-
house documented procedures.
NOTE High tip loads will cause tip wear and this might lead to imprecision in the drift measurements.
6.1.6 Set the scan field of view to a suitable value to define the drift behaviour. If uncertain about the behaviour,
5 μm is a suitable value for initial studies. Select a region of the specimen with at least two sharp features at a
distance roughly a quarter of the image size in from two opposite corners if using the characteristic-marker method
of Annex B or obvious features across the field of view if using the image correlation method of Annex A. Scan the
specimen with the frame time used for the studies for which this characterization is required (e.g. 5 min to 10 min).
6.1.7 Record two successive images. Determine the X-, Y- and Z-drift rates in accordance with the selected
method listed in Annex A to Annex C, using images that all have the same X- and Y-scan directions.
NOTE Some instruments scan with the slow scan firstly in one direction and secondly in the reverse direction. There might
be a shift between these images. By restricting the analysis to one direction, issues associated with this shift are removed.
6.1.8 If the measured drift rates are significantly smaller than the minimum drift rates required to conduct the
required experiments, the instrumental operating conditions are satisfactory and no further drift characterization
will be required. The initial check may be considered complete and the evaluation terminated. If the measured
drift rates are not significantly smaller than the minimum drift rates required to conduct experiments, or if further
characterization is required, proceed to 6.2. If the measured drifts exceed 20 % of the scan size in the X-, Y- or
Z-directions, increase the relevant scan size to satisfy that condition and repeat 6.1.7.
6.2 Basic characterization and the settling time
6.2.1 Continue from 6.1.8 and record a series of successive images for 2 h. For measuring the drift rate
performance, the time at which the specimen position has been set and the image area has been selected is
taken as the origin of time. For each change in specimen position or imaged area, a new time origin is established.
6.2.2 Determine the X-, Y- and Z-drift rates as in 6.1.7.
6.2.3 Observe the variation of the drift rate with time and decide a practical time after setting the specimen
in position and addressing the selected point on the specimen for which the drift rate is adequate for the work
intended. This is the settling time. If the drift rate after 2 h is too high for the intended use of the instrument,
continue for a longer period or consider operational improvements to the instrument or use the equipment as
suggested in Annex E, and repeat 6.1.1 to 6.2.2.
NOTE 1 An example of such measurements is shown in Figure 1. In that example, if 9 nm/min is an acceptable drift
rate in the X-Y plane, further data could be recorded with no delay after identifying a new point on the specimen for study.
If 4 nm/min is acceptable, a settling time of 1 h is required after starting with a new specimen.
NOTE 2 Occasionally, it might be found that the drift rate increases with time as the several independent cont
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