• Surface Analysis (XPS/UPS, SIMS, AFM)
• Chemical Analysis (NMR, DSC, TGA, FTIR)
• Microstructural Charaterisation (SEM, TEM, XRD)

Surface Analysis (XPS/UPS, SIMS, AFM)

• X-ray Photoelectron Spectroscopy (XPS)
• Time-of-Flight Secondary Ion Mass Spectrometer (ToF-SIMS)
• Variable Temperature Scanning Tunneling Microscopy (VT-STM)
• Atomic Force Microscopy (AFM)

X-ray Photoelectron Spectroscopy (XPS)

X-ray Photoelectron Spectroscopy (XPS), also known as electron spectroscopy for chemical analysis (ESCA), is highly surface-specific technique due to the short range of the photoelectrons that are excited from the solid. The energy of the photoelectrons leaving the sample is determined using an analyser and this gives a spectrum with a series of photoelectron peaks. The binding energy of the peaks is characteristic of different elements. This can thus be used (with appropriate sensitivity factors) to determine the composition of the materials surface. The shape of each peak and the binding energy can be slightly altered by the chemical state of the emitting atom. Hence XPS is able to provide chemical bonding information as well. The VG ESCALAB 220I-XL system in IMRE is a high-performance, imaging XPS system. It is capable of both high sensitivity XPS and XPS imaging.

Its main features are:

• High sensitivity spectroscopy for rapid small area analysis (down to 20 µm).
• ~ 2 µm spatial resolution imaging.
• Certainty of analysis location by combining spectroscopy and imaging.
• Choice of dual anode or monochromatic Al Ka X-rays for optimum selection of sensitivity and energy resolution with minimum sample damage.

Time-of-Flight Secondary Ion Mass Spectrometer

SIMS is a technique to determine elemental composition of samples, based on measurement of mass of atoms and molecules. The sample is bombarded by high energy ions, they sputter secondary ions from the surface, and the masses of the secondary ions are measured in the mass spectrometer. SIMS installed in IMRE has time-of-flight detector of secondary ions. It has high mass resolution above 7000, high sensitivity and unlimited mass range.

Modes of ToF SIMS operation:

• Surface spectroscopy. High sensitivity of ToF SIMS allows obtaining the mass spectrum after sputtering of less that one molecular layer.
• Surface imaging. By scanning a finely focussed ion beam over the surface, mass resolved secondary ion images can be obtained. Lateral resolution of 100 nm can be achieved.
• Depth profiling. Applying second ion beam for removing the sample material, depth profiles can be measured with resolution of 1 nm.

Variable Temperature Scanning Tunneling Microscopy

The scanning tunneling microscope consists basically of a conducting/semi-conducting sample and a sharp metal tip which acts as a local probe being brought within a distance of a few angstroms. This results in an overlap of electronic wave-functions. With an applied bias voltage, a tunneling current can flow from occupied electronic states near the Fermi level of one electrode to the unoccupied states of the other electrode. The STM is able to achieve vertical and lateral resolutions of about one angstrom, hence it is able to generate a real space image of the surface atomic topography of the sample being scanned.

Further spectroscopic operating modes of the STM also allow the probing of electronic structure of sample surfaces. Information such as localized tunneling barrier height, I-V characteristics and electronic states involved in specific reactions may also be gathered.

The variable temperature component allows the VT-STM to function in a temperature regime ranging from 25K to 1200K. This would allow thermal fluctuations and drift to be minimized at low temperature scanning as well as real time scanning of samples as a function of temperature.

Atomic Force Microscopy

Atomic force microscopy (AFM) falls into the Scanning Probe Microscopy (SPM) family of microscopy forms where a sharp probe is scanned across a surface and interactions between sample and probe are monitored. The MultiMode AFM in IMRE performs a full range of SPM techniques for surface characterization of properties like topography, elasticity, friction, adhesion, and magnetic fields: Tapping Mode, Contact Mode AFM, Phase Imaging, Lateral Force Microscopy (LFM), Magnetic Force Microscopy (MFM), Scanning Tunneling Microscopy (STM), Force Modulation & Force-Distance Measurements.

CHEMICAL ANALYSIS

• Differential Scanning Calorimeter (DSC)
• Thermogravimetric analyser (TGA)
• Fourier Transform Infrared Spectrometer (FTIR)
• Nuclear Magnetic Resonance (NMR)

Modulated Differential Scanning Calorimeter

Differential Scanning Calorimetry (DSC) is a thermal analysis technique used to measure changes in heat flows associated with material transitions. DSC measurements provide both qualitative and quantitative data on endothermic (heat absorbing) and exothermic (heat evolving) processes. DSC is commonly used to determine the glass transition temperature and crystalline melting point of polymeric materials.

MDSC is used to study the same material properties as conventional DSC including: transition temperatures, melting and crystallization, and heat capacity. However, MDSC also provides unique capabilities that increase the amount of information that can be obtained from a single DSC experiment, thereby improving the quality of interpretation.

Thermogravimetric Analysis

Thermogravimetric Analysis (TGA) is a thermal analysis technique used to measure changes in the weight (mass) of a sample as a function of temperature and/or time. TGA is commonly used to determine polymer degradation temperatures, residual solvent levels, absorbed moisture content, and the amount of inorganic (noncombustible) filler in polymer or composite material compositions. The evolved gas analysis of the degradation products from materials with a hyphenated system (TGA coupled with FTIR) is known as TG-IR.

Fourier transform infrared spectrometer and IR microscope

Infrared microscope is useful for physically small samples and smaller areas of a larger sample (eg. Contamination, inclusion etc.). Our system consists of auto-image microscope with Mercury-Cadmium-Telluride (MCT) detector coupled to spectrum 2000 FTIR spectrometer. The system allows different measurement modes such as transmission, reflection, attenuated total internal reflection (ATR).

Nuclear Magnetic Resonance

NMR Spectroscopy is powerful analytical chemistry techniques used for identify the unknown materials, determining the content and purity of a sample as well as its molecular structure especially in polymer and protein structure elucidation.

The NMR facility at IMRE is equipped with both liquid and solid-state probes that enable the study of organic and inorganic materials either in liquid or solid state respectively. The magnetic field strength of our system is 9.4 Tesla, which corresponds to an energy gap between the two states of the 1H Nuclei of 400MHz. It has a multinuclear probe head capable of acquiring a wide range of one- and two- dimensional NMR experiments.

MICROSTRUCTURAL CHARACTERISATION

• Electron Microscopy
• X-ray Scattering/Diffraction

Electron Microscopy

The Philips CM300 is a high-resolution TEM equipped with a field emission gun (FEG) and an “ultratwin” objective lens. It is capable of resolving atomic columns and can be used to determine crystal structure using high resolution images, bright-field images, dark-field images and diffraction patterns. An attached energy dispersive X-ray spectrometer (EDS) allows chemical composition to be determined at nanometer resolution. A Gatan Image Filter (GIF) has recently been added, giving electron energy-loss spectroscopy (EELS) and energy filtered TEM (EF-TEM) capabilities on the microscope.

The JSM-6700F is an ultra-high vacuum FE-SEM. It has a conical cold cathode FEG and a semi-in-lens objective lens, which makes the system capable of both high-resolution imaging and high quality real time image display. The JSM-5600 is our backup SEM that is based on W filament. Both the JSM-6700F and 5600 are equipped with EDS detectors. Typical use of these SEMs includes observation of surface structure, failure analysis and chemical identification, at nanometer resolution. Our JSM-6360LV can be operated at lower vacuum, which allows examination of non-conducting samples such as plastics, ceramics, fibers and biological samples in their natural state without any sample preparation.

X-ray Scattering/Diffraction

Our X-ray facility is equipped with four X-ray instruments: Bruker Nanostar SAXS, Bruker D8 Discover GADDS, Philips X'pert MPD, and PANalytical X'pert Pro HR-XRD.

The Bruker Nanostar SAXS is used for probing large length scale structures such as polymers, biological macromolecules, meso- and nano-porous materials, nano-powders, fibres, and molecular self-assemblies. The information we can gather includes size distributions, shapes and orientation distributions in liquids, powders or bulk samples.

The Bruker D8 Discover GADDS, based on 2D area detector, is used for fast data acquisition in microdiffraction, phase identification, stress and texture analysis. The GADDS detector allows for simultaneous data collection of a large 2Θ range without sample or detector movement. The Philips X'pert MPD is a powder diffractometer, which is used primarily for phase analysis and determination of crystal structure by Rietveld analysis of powder samples.

Our new PANalytical X'pert Pro HR-XRD has multi-modular primary and secondary optics in order to account for requirements of primary x-ray beam divergence and detector angular acceptance.

It can be configured for:

• high-resolution rocking curve measurement of epitaxial layer
• high-resolution reciprocal space mapping of epitaxial layer
• texture analysis
• residual stress analysis
• phase analysis
• X-ray reflectivity and thin film thickness analysis
• grazing incidence X-ray diffraction (in-plane diffraction)