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NPL’s nanoprobe facilities enable the characterisation and imaging of physical and chemical properties, and are part of the Quantum Metrology Institute. They integrate a uniquely broad and comprehensive set of state-of-the-art capabilities, and are especially suited for studies of solid state quantum materials or devices and providing reliable nanoscale characterisation techniques. The wide variety of modern instrumentation methods provide complementary solutions suitable for both industrial applications and fundamental research. Our expertise and capabilities offer solutions to problems such as:
We provide flexible solutions to tackle real problems in many different industries, such as semiconductors, sensors, advanced manufacturing, automotive and aerospace, life science, defence and security. We also have the knowledge to determine the most appropriate techniques and provide consultancy on interpretation of the results. Our expertise and facilities are listed below.
Work in this area is complex and unique so please contact us to discuss your exact requirements and challenges.
The low-temperature nanoprobe is a state-of-the-art system suitable for surface topography imaging with atomic resolution, density of states mapping and electrical characterisation of thin films, nanostructures and devices. It ranges from microns down to the atomic scale. Electrical characterisation is achieved via multiprobe transport measurements supported by the extremely accurate probe positioning. The instrument can probe a wide range of materials, from conventional metals and semiconductors, to novel nano and quantum materials. Structural and electrical information, such as conductance and impedance, is important for the semiconductor industry. The instrument can also be used for fundamental studies and applications, such as material growth control and validation or surface homogeneity. Studies of surface reactions at the atomic level are particularly useful for catalysts and gas sensing applications, as well as single-atom impurities and defects.
Technical details: the low-temperature nanoprobe UHV system (Scienta Omicron Technology GmbH) is equipped with 4 independently controlled probes, suited for scanning tunnelling microscopy, QPlus atomic force microscopy and electrical transport measurements (with two of the probes capable of microwave measurements). The operating temperature of the system ranges from ~4K to room temperature. A high-resolution scanning electron microscope (SEM) column is used for tip navigation and in-situ imaging (5-20 keV). The system features an optical fibre for sample illumination, 25mT out-of-plane magnetic field and additional contacts on the sample platform for back-gating. The preparation chamber capabilities include resistive/e-beam heating/annealing, Ar sputtering, e-beam deposition and tip preparation.
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Our NanoIR2-s microscope offers localised infrared (IR) spectroscopy and imaging with nanoscale resolution down to 10 nm, along with optical and advanced SPM capabilities. The modular nature of the system allows for measurement and characterisation of different nanoscale surface optoelectrical, thermal and magnetic properties. The system is suitable for studies of quantum materials and structures such as quantum wells, quantum dots, 2D materials, plasmonic metamaterials, semiconductors, polymer composites or biological samples. It can be used to study nanophotonic surface phenomena on 2D materials, such as surface phonon polaritons in hBN, surface plasmon polaritons in graphene or specific IR-adoption in virus-like peptide capsules.
Scanning near-field optical microscopy (SNOM) studies local quantum defects as well as properties such as refractive index, chemical structure and local stress, beyond the far field resolution limit by exploiting the properties of evanescent waves. Nanoscale IR spectroscopy and mapping with 10 nm spatial resolution, covering the low and mid-IR regions, provides optical and chemical information of the sample. Nanoscale mapping of thermal conductivity can be carried out via scanning thermal microscopy. The thermal analysis mode (nanoTA), where local thermal properties and material composition can be studied, is suitable for polymer characterisation. Multifunctional measurements are also possible, correlating advanced SPM techniques and combining measurements of topography, thermal, magnetic and electronic properties.
Technical details: The systems operates in two optical modes, s-SNOM and AFM-IR, working in the near-mid-IR range and is equipped with two mid-IR sources, a quantum cascade laser (QCL) tunable in the range 950-2000 cm-1 (5-10.5 μm) and an optical parametric oscillator (OPO) in the range 950-4000 cm-1 (2.5-10.5 μm).
Scanning thermal microscopy (SThM) is used to map the temperature or the thermal conductivity of a sample's surface or interface. The SThM probe has a nanoscale resistor on the probe's apex and the resistance of the probe is actively monitored for an indirect measurement of thermal properties.
SThM is performed in either a passive or active mode. In the passive mode, the probe resistance is monitored as a function of the probe position across the sample plane, spatially mapping the surface temperature distribution. This mode has suitable for nanoelectronics as it can provide precise locations of excessive heat generation and temperature gradients across materials and devices. In the active mode, the power supplied to the probe is controlled through a feedback mechanism in order to sensitively map the thermal properties of a sample, such as distributions of the thermal conductivity or Seebeck coefficients.
Our environmental scanning probe microscope is designed for probing continuous thin-films and patterned devices with nanometre resolution, including imaging of clusters of atomic defects. As a complementary technique, simultaneous (magneto)transport measurements can be performed on patterned devices, which allows for correlation of local work-function values with electronic properties on the micro-scale. In the case of un-patterned uniform samples, a permanent magnet can be used to measure magneto-transport properties in the van der Pauw geometry.
Measurements of intrinsic electronic properties of a material are carried out in vacuum or well controlled environments so they are not affected by environmental adsorbates and contamination. The technique allows visualisation of areas with different doping amounts or type and of different number of layers in 2D materials or defect structures. This technique allows accurate monitoring of environmental effects, restoration of intrinsic properties by mild vacuum annealing and measurements for long time stability and reproducibility
Technical details: Our system is based on a custom-modified NT-MDT Aura SPM system. By operating in frequency or amplitude modulated Kelvin probe force microscopy (KPFM), simultaneous topographic and electrical characterisation is performed, with nanometre resolution below ~50 nm and 10 mV, respectively. Local work-function maps can be also obtained providing quantifiable insights on the electrical properties of the sample. The environmental system can perform measurements in ambient, vacuum (up to 10-6 mbar), and highly controlled (humidity, gas atmosphere, temperature) environment. The latter includes a combination of gases at variable concentrations as low as tens of parts-per-billion using mass flow controllers, as for example nitrogen dioxide (NO2), or under different levels of relative humidity from 0-90%.
Frontiers of graphene and 2D material-based gas sensors for environmental monitoring
Contactless measurements of graphene charge density variation in a controlled humidity environment
Raman microscopy and spectroscopy are simple, non-destructive and rapid measurement techniques for characterisation of structural, chemical and optoelectronic properties of materials for validation and quality control. Our system is a Renishaw inVia confocal Raman microscope coupled to an Innova Bruker AFM. Due to the simple, fast and non-invasive nature of Raman and photoluminescence (PL) measurements, it enables the analysis of either small area samples or large-scale wafers, probing properties such as strain, electronic doping, distribution and size of defects or structural phases. As well as resolving features down to sub-micron scale, the technique produces high definition and high-resolution chemical and structural maps. It is ideal for the characterisation of thin films, low-dimensional materials, powders or patterned devices.
Technical details: Measurements can be carried out using visible (532 nm and 633 nm laser wavelength) and UV light (325 nm laser wavelength). Measurements can be performed in variable environmental conditions: ambient, 0-90% relative humidity, gas atmosphere, and at temperatures ranging from -196 °C to 600 °C. Combination of gases can be introduced into the gas cell at variable concentrations, as low as tens of parts-per-billion, using mass flow controllers, and polarised Raman measurements can be done using this system. In addition, the system allows for co-localised Raman/AFM measurements, simultaneously probing of Raman, topography and electronic properties of materials by conductive-AFM, scanning Kelvin probe microscopy, providing correlation with physical properties of samples at the nanoscale. Tip-enhanced Raman spectroscopy is an extra feature that the system can offer for chemical specificity and imaging at high spatial resolution, down to 10 nm.
Correlation of structural, nanomechanical and electrostatic properties of single and few-layers MoS2
Carrier type inversion in quasi-free standing epitaxial graphene: studies of local electronic and structural properties
Unique excitonic effects in tungsten disulphide monolayers on two-layer graphene
The magneto-optical Kerr effect (MOKE) uses polarised light to probe the magnetic properties of materials. The MOKE system at NPL has a field of view of a few mm down to a resolution of 200 nm and allows the study of the surface magnetisation of a wide range of samples, with both in-plane and out-of-plane fields. We can examine thin films, magnetic devices, and bulk materials to understand domain structure of magnetic materials, study quantum spintronic materials and devices and provide confidence in product development. This technique is useful for magnetic memories, magnetic sensors, radio-frequency and microwave devices, logic and non-Boolean devices.
Standard magnetic force microscopy (MFM) provides qualitative mapping of a sample’s magnetic stray field at the surface. Nanoscale characterisation of magnetic fields is important for fundamental and applied research on magnetic materials and devices. NPL has developed a new method to offer quantitative MFM measurements which provides quantitative values of the stray field.
This unique MFM scanning technique can be combined with other systems and techniques to allow in-field measurements, up to 150 mT of in-plane or 100 mT of out-of-plane field. It can examine electrostatic compensation using Kelvin-probe microscopy (KPFM), ideal for electrically biased devices or other materials where the surface charge is important, especially for 2D semiconductor materials. Measurements can be carried out over a range of environmental conditions, such as a vacuum down to the 10-6 mbar or up to 100 °C. It also has the capability to electrically monitor the sample while imaging, which allows the study of local electrical, magnetic or thermal gating effects.
V-shaped domain wall probes for calibrated magnetic force microscopy
Calibration of multilayered magnetic force microscopy probes
Direct writing of room temperature and zero field skyrmion lattices by a scanning local magnetic field
Transfer function determination for quantitative MFM: modelling and verification
Magnetic imaging using geometrically constrained nano-domain walls
Individual skyrmion manipulation by local magnetic field gradients’
Our nanoprobe facilities and expertise are part of the wider quantum activities in NPL known as the Quantum Metrology Institute.
Work in this area is complex and unique so please contact us to discuss your exact requirements and challenges.
Find out more about NPL's work on 2D materials
Find out more about NPL's work on low loss electronics
Find out more about NPL's work on Nanoscale magnetic consultancy
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