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Home , Microscope, Raw material, Research and development

metrology addresses the challenges of inspecting graphene

Wide range of optical systems support graphene applications

In recognition of the importance of graphene, the www.graphene.manchester.ac.uk, where the crystalline was new wonder material that is ultra- and flexible first extracted from graphite, provides a comprehensive background to the material’s discovery and uses. It also gives an insight into example yet 200 times stronger than , Nikon Metrology graphene applications. include its use in long-lasting focuses on providing inspection solutions for research light bulbs that are about to be marketed, mobile phones that can of these new industrial and its application theoretically be bent double, and specialised infill material to realise areas. The purpose of this document is to advise on performance-enhancing carbon fibre tennis racquets and golf club shafts. excellent, proven methods for optically examining and measuring features on graphene in its raw and Producers of the , developers of products containing processed states. graphene, and researchers in and academe will all benefit from the coherent strategy that Nikon Metrology is putting forward. It brings together the company’s established and recently developed products that are suitable for non-contact inspection of the material Bill Clement, Development Director at Nikon Metrology, has and is coupled with a new advisory to help optimise their 28 years of experience in and coordinates the activities of utilisation. a team of experienced staff and across Europe. Their remit includes supporting into the inspection of Mr Clement said, “The graphene is amazingly open, with innovative materials and assisting in the realisation of components knowledge shared readily between experts and practitioners in the field. and products utilising these new materials. “We are modelling our graphene advisory service on the same spirit of Graphene is currently one of the most prominent of these. The openness and if a Nikon Metrology product is not the best solution for disruptive is extremely important, as it has the potential to a particular task, we will say so. revolutionise a host of applications from and medical through and to energy generation “However, we have a wealth of different equipment for optical and lighting. A visit to the UK’s of Manchester inspection, selection and quality control of various forms of chemically,

1 “ We have a wealth of different equipment for optical inspection, selection and quality control of various forms of chemically, epitaxially and micromechanically synthesised graphene sheet, layers and printed structures, from the Nano metric range up to typically one hundred microns thick.

Bill Clement, Director at Nikon Metrology

Researchers have developed a graphene-based, flexible LED display prototype that is incredibly thin and bright (Shutterstock gallery)

SMZ stereomicroscopes feature up to a Upright LV series are suited The JCM NeoScope benchtop scanning stunning 25:1 zoom ratio and are suited to for graphene layer thickness grading by SEM is capable of isolating platelets and shape/ of grade and sort graphene samples. Equipped identifying colour of slices or to examine graphene flakes. with a digital microscope , high graphene material that is assmbled on quality can be recorded for analysis. semicon, wafer or diced chips.

epitaxially and micromechanically synthesised graphene sheet, layers The next stage in the inspection process is provided by a Nikon and printed structures, from the Nano metric range up to typically one Metrology LV Eclipse series microscope, which has a range hundred microns thick. I should like to outline in this article what we of interchangeable nosepieces, allowing higher are able to provide.” and a full range of contrast techniques. Featuring episcopic and diascopic illumination of the sample, the model family including The first pillar of Nikon Metrology’s offering is its SMZ series of the LV100ND allows the user to see and judge how many layers stereomicroscopes equipped with a such as the thick the graphene is, according to the colours observed and Nikon DS-Ri2 or DS-fi2 with L3 or U3 controllers for capturing the edge contrast. Such detailed study is very fast indeed and and archiving images. Several are in use at the University of Manchester provides useful information on the suitability of the flake for for initial selection of suitable graphite flakes from which to isolate a next process as well as continually verifying the method of graphene. The British Government’s Chancellor of the Exchequer, George production. Osborne, was photographed at the university looking through one of the instruments at the official opening of the National Graphene Institute on A major advantage of the instrument over most other similar 20th March 2015. The research centre enables academics and industry microscopes on the market is that the image is the right way round and to side-by-side on graphene applications of the future. the right way up. It is a longstanding feature of LV Eclipse microscopes, which were developed for use in the industry, where The SMZ range, with its industry-leading 25:1 zoom, correct orientation of the image of the wafer or is is ideal for many tasks including initial grading and sorting of graphite essential. A majority of microscopes are designed primarily for medical samples owing to the instrument’s long working distance and wide field applications in which it may be less critical to see which way round of view. Combined with the stereoscopic image, they enable the sample’s a is viewed, so manufacturers may omit the required corrective texture and shape to be understood and then manipulated effectively. optics.

2 221 µm 183 µm

Height step 1.09 nm

With measuring performance far into the sub- range, the BW surface profiler provides an efficient and economical method for evaluating the suitability of graphene flakes. Deficiences in layers of flakes with height differences as minimal as 1 nanometre are identified by the BW white light interferometer.

Graphs courtesy of Dr. Peter Blake, Graphene Industries Ltd.

In Mr Clement’s opinion, the process of graphene production and graphene flake and the capability of the process that produced it. Naturally component development requires the use of both SMZ and LV Eclipse the image is upright and the right way round, so printed or etched features microscopes as a minimum. The third stage would be to investigate are presented correctly to the operator. the material structure in significantly closer detail, for which three alternatives exist. Thirdly, , for which a raster-scanning, high resolution probe microscope is used, provides a large amount of First is the benchtop scanning (SEM), such as the dimensional information of the sample in the X, Y and Z axes, as well as JCM 6000 NeoScope, which is presented to customers as the result of indicating its magnetic and chemical properties. This type of equipment a collaboration between Nikon and Tokyo-based JEOL, who are experts provides highly accurate and detailed data, with each inspection generally in many areas including electron microscopy. The simple and affordable, taking many hours to complete, unlike a Nikon BW interferometer which touch-panel-controlled imaging combines the high resolution and can return results within 20 seconds. depth of field of a powerful SEM with the familiarity of a digital camera. Its magnification of up to x60,000 allows the quality of raw graphene to In addition to these front-line instruments, Nikon Metrology has other be inspected in very high detail when compared with optical microscopy. products in its range that are proving useful and relevant for graphene inspection and quality control. One is the iNEXIV video coordinate An enhancement to the SEM, which can be retrofitted, is energy measuring systems, whose large field of view, long working dispersive (EDS) employing X-ray emissions from the scan distance and wide XYZ stroke enable easy, automatic measuring of 3D area. Backscattered electron images display compositional information components. They are therefore ideal for checking the dimensions of a resulting from different chemical elements within a sample and their graphene sample. Some models, such as the confocal NEXIV VMR- . EDS allows areas of interest to be analysed, elements K3040C (Z120x), employ an Eclipse LV optical with a top-of-the- identified and their relative proportions to be measured. Notably, this range confocal imaging option for increasing the optical Z-axis resolution equipment is positioned safely and out of sight under the covers of the and contrast of the image, enabling highest quality for making coordinate JCM 6000 NeoScope, rather than being an external and vulnerable measurements with great speed over extended X/Y areas. It is well suited, addition mounted on the side. for example, to examining printed graphene structures extending beyond a microscope’s field of view. The second instrument offered for detailed sample inspection is an enhanced version of the LV Eclipse microscope, designated BW range, Underpinning the use of all Nikon’s measuring and inspection microscopes equipped for white light interferometry (WLI). It includes interferometry is an advanced range of manually driven and motorised, high precision objectives manufactured by a special team in a world-class factory stages with for automated large area recording functionality. They in Japan, together with a high speed digital camera and a Nikon- derive from the manufacturer’s long experience in semiconductor wafer developed, dedicated software algorithm combining all the product handling and inspection. The NWL200 series of wafer loaders are capable elements for providing outstanding Z-axis data. of transferring graphene samples on a wafer automatically to a microscope stage, with improved wafer sensing functions and edge- A BW microscope is a very high speed and repeatable solution that chipping detection to help prevent damage. 3-axis micromanipulators for provides information of the graphene sample primarily in the Z-axis. As high precision control of samples under a microscope can be provided. thickness and surface quality of the layers are often the parameters that are needed most, the BW is very well suited to graphene inspection. With More information at measuring performance far into the sub-nanometre range, WLI provides www.nikonmetrology.com an efficient and economical method for evaluating the suitability of a [email protected]

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