The aim of this workpackage is to produce atomic step height standards based on silicon surfaces and on other appropriate crystals. The step heights should fullfil several criteria; they need to allow excellent traceable calibration at the sub nanometre and nanometre level of the vertical axes of AFMs and they need to be useable as height resolution artefacts or as calibration tools for optical microscopes. Due to the challenging nature of both sample production and sample measurement the tasks will run in parallel and results will feed back into the tasks to enable refinement of the activities.
For a traceable calibration of the highest level, crystalline flat regions surrounded by large terraces separated by monoatomic or double layer steps, need to be produced. This will allow the ISO 5436 step height fitting algorithm to be used in the calibration. The large areas on the base and on the terraces allow an appropriate leveling of the tilt and the mean value of the lower and upper level to be determined. Another possibility will be the preparation of samples with a large number of steps, so called staircases which are effectively a set of equidistant terraces. Using discretised monoatomic steps would allow us to apply more “pitch like” averaging techniques, such as the gravity centre method which would reduce the measurment uncertainty in a single step.
Leading NMI: NPL
The aims of this WP is to produce prototype samples of laterally patterned standards, which can be used in fundamental research (e.g. surface science) as well as prototypes of standards required for industrial application. These aims will be achieved by using the periodic surface structures on single crystal surfaces, which can be regarded as invariants of nature in this context. Si(111)-7x7 and Si(100)-2x1 surfaces will be used for this purpose.
As STMs, operated in UHV, are widely used in surface science the specially prepared surface reconstruction with its periodic unit cell can be used as a lateral pitch standard traceable to the SI base units if it is investigated by MetSTM.
The WP will provide samples that are appropriate for the verification of the flatness of AFM and/or optical microscopes as well as for the provision of samples for pitch calibration which have structures in the 5 nm range. In the case of silicon a first step towards the lateral calibration of the atomic structure of the Si(111)-7x7 will be made. This will be very important for the instruments used in surface science.
The prepared silicon samples will be cut and annealed in order to achieve large flat crystalline terraces of several microns in size. On some of these samples Pd and other appropriate materials (e.g. Pb) will be evaporated on the clean surface in order to obtain a very reproducible self-aligned metallic island within the Si(111)-7x7 unit cell. The UHV-STM will be used to verify the quality of the growing process and it will be used to make a first in-situ calibration of the pitch of such structures. For this reason both axes (x and y) of the UHV-STM need to be equipped with a laser interferometer to do the measurement in a traceable way.
Later the sample will be passivated, e.g. by oxygen, and brought in to the air for further investigations. Measurements by AFM, metrological AFM and AFM combined with an x-ray interferometer will be undertaken to verify the quality of the metallic pattern and to calibrate the pitch of the pattern in air, and an uncertainty budget will be set up.
Measurements and comparison with other AFMs will be done. The prototype standards will be applicable for use in a broad range of microscopes, therefore measurements will also be undertaken in SEMs.
The stability of the samples will be investigated based on the experience obtained in WP1.
Leading NMI: PTB
The aim of this workpackage is to provide sample models for use as future lateral standards. These will be based on diblock copolymers (BC). Patterned nanostructures under 50 nm will be studied and fabricated using BC that match the requirements defined by AFM users (e.g. the JRP-Partners operating AFMs). By means of this silicon compatible technology, different morphologies and dimensions will be obtained by accurately planning and choosing the polymers. The polymeric masks, once one of the two phases is removed using plasma, will be propagated to silicon dioxide and to silicon. INRIM will provide silicon dioxide and silicon substrates that have been patterned using Electron Beam Lithography (EBL). These substrates and patterns will be used for the formation of lateral resolution standards from self-assembled BC (REG(PMO)). The targeted dimensions will range from 5 nm to 50 nm. After direct self-assembly, annealing and selective phase removal, the polymeric nanostructured mask will be propagated to the different materials, which constitute the bilayer substrate, by conventional micromachining processes.
Leading NMI: INRIM
The aim of this workpackage is to study the feasibility of using the DNA nano-origami technique for the construction of 3D calibration standards for use in scanning probe microscopes. DNA origami is a method that allows the fabrication of complex two- and three- dimensional molecular nanostructures from DNA with precisely defined dimensions and with an unprecedented yield. For DNA origami, hundreds of rationally designed “staple” oligonucleotides are hybridised to a long single-stranded DNA “scaffold” strand, which forces it to assume a specific shape. The resulting objects are fully addressable by their DNA sequence, and this property can be utilised to decorate origami objects with nanocomponents in a unique, sequence-specific manner. Hence, in addition to arbitrary shapes, DNA origami allows arbitrary patterns to be created with resolution well below 10 nm. Moreover, it is possible to link individual DNA origami structures into larger (several micrometres) periodic one- or two-dimensional arrays. All this makes the DNA origami technique a very interesting candidate for the fabrication of nanostructures which could serve as lateral and vertical calibration standards. DNA origami can also be used to characterise AFMs when operating in liquid measurement mode, which is not possible with many other calibration standards.
Leading NMI: MIKES
The aim of the impact workpackage is to transfer the knowledge developed within the JRP to stakeholders, collaborators and to other interested parties in order to generate the largest possible impact. The stakeholders will benefit from the outcomes of the project. Publishing the outcome from the project in high impact international scientific journals and in more general Trade Journals will disseminate the results to an even wider community. The public website will collect relevant background material, links to related work and to recent scientific results. Thus, the website will be an easy access point for all the interested parties, and especially for end-users, to obtain information about the project. In addition, the comparison and the project workshops will provide the stakeholders with information on how to use crystalline structures as length standards for Nanoscale measurements.
As a major outcome of the project the use of crystalline structures as length standards will be scientifically and metrologically demonstrated and validated by the partners. This will improve the capabilities of the JRP-Partners in challenging nanometrology measurement and it will enable users of various microscopes to perform traceable nanometre scale measurements using the new methods and structures which are developed. In future this might lead to a new kind of mise en pratique for the realisation of the metre utilising crystalline standards.
Leading NMI: MIKES
The project will be managed and coordinated by PTB.
Leading NMI: PTB