SPD/PN/089 Issue 1.0 June 2003 Product note from the Spectroscopy Products Division inVia Raman microscope Sample environment accessories Introduction Electrochemical cell Renishaw offers a wide range of sample stages that enables in situ dynamic Raman and photoluminescence experiments in a variety of environments. Renishaw's electrochemical cell is an ideal tool for researchers investigating electrochemistry. Electrochemical cell: for studying in situ corrosion, surface enhanced Raman scattering, etc. Humidity cell: for studying the effect of humidity on materials such as pharmaceuticals. High pressure cell: diamond anvil cell for compressing samples to 50 GPa (500 kbar) Temperature control stages: heating and cooling stages covering temperatures from 2.2 K (-271 °C) to over 1800 K (1500 °C) 0.1 V 0.6 V 500 1000 Raman shift / cm-1 1500 Spectra of corrosion inhibitors taken from inside an electrochemical cell with an electrochemically roughened silver working electrode and 0.05 Mol dm-3 solution of benzotriazole. The changes in the spectra are attributable to changes in molecular orientation in the region of the electrode surface. Data courtesy UK Atomic Energy Authority. It can be used for in situ corrosion studies, where Raman spectroscopy can be used to detect the chemical changes that occur during cyclic voltammagram studies, for the identification of electrochemically produced intermediates, and for investigations of catalysts. It can also be used to generate electrochemically roughened surfaces that use the phenomenon of surface enhanced Raman scattering (SERS) to give greatly enhanced Raman signals. Electrochemical cell and holder. The glass electrochemical cell is securely mounted in a metal holder that fits onto Renishaw's macro sampling set. This enables the user to use the standard microscope stage controls to focus accurately and easily into the cell. The cell features ports for easy filling of the cell with electrolye/reaction mixtures and for venting gaseous reaction products, and a side arm that contains the standard electrode (a calomel mercury/mercurous chloride electrode is normally supplied). The working electrode face is held vertically to allow gaseous reaction products to bubble away, and the distance between the working electrode and the window is adjustable to accommodate a range of working distance objectives. Use Raman spectroscopy to monitor the changes caused to samples by: • temperature • pressure • humidity • electrochemistry Humidity control cell VGI humidity control cell. The system is interfaced to a dedicated digital process controller allowing manual control and measurement of humidity in addition to programmed humidity profiles. PC based software allows greater programmable functionality, together with data acquisition and playback facilities. Changes in humidity can affect the structure and properties of many materials, from catalysts and semiconductors to microbiological cells and pharmaceuticals. Chemical and physical structure, as well as reaction rates and degradation processes, can all be influenced by changes in humidity. Raman spectroscopy is ideal for studying the reaction of samples with solvents and is especially suited to aqueous studies since water is a poor Raman scatterer and gives rise to only very weak Raman signals. The unrivalled sensitivity of Renishaw's Raman microscopes means that even very subtle changes can be monitored with ease. The VGI humidity cell (supplied to Renishaw by Surface Measurement Systems) allows users to control precisely the temperature and humidity environment of a microscopy sample. For example, the influence of humidity on chemical transformations in drug samples, the stability of drug delivery systems such as tablet coatings, the efficiency of catalysts, growth rates for micro biological samples, and electronic properties of semiconducting materials can be studied. B-05 high pressure (diamond anvil) cell. Temperature and pressure The cell is designed for use with ultra-long working distance objectives, using standard microscope slides as the sample mounting. Temperature and humidity around the sample are controlled using an integrated Peltier heat pump, circulating fluid pump, and water reservoir to ensure uniform temperature distribution and stable sample humidities (see Table 1 for specifications). The sample window is double-glazed to prevent condensation of moisture when working at temperatures above or below ambient. An organic option is available for working with solvents other than water. 90% RH 80% RH 70% RH 0% RH to 60% RH TIme / s 300 200 100 0 820 840 860 Raman shift / cm-1 880 Temperature and pressure control cells are therefore widely used for the study of phase transitions (such as polymer melting, crystallisation, and conformational changes in proteins), and for the study of degradation/oxidation in the pharmaceutical, adhesive, polymer, and paints fields. They are also used by materials scientists for studies of photoluminescence in semiconductors and other materials, and by chemists for studies of catalysts and reaction kinetics. Renishaw's Raman microscopes are valuable tools in this work as Raman spectra are sensitive to molecular arrangement and can differentiate different structures. The microscopes' ability to acquire photoluminescence spectra also enables them to reveal detailed information about defects and the effect of pressure and temperature on them; these data are especially useful in the semiconductor and materials science fields. 95% RH 800 Changes in temperature and pressure can cause changes to the phase, morphology, and structure of materials, can cause chemical degradation, and can modify the mechanical, electrical, and catalytic behaviour of materials. 900 Effect of humidity on an pharmaceutical tablet (ibuprofen meltlet). Dramatic changes occur at 80% RH as the sucrose component deliquesces. (Excitation: 830 nm) High pressure cell Temperature control cells The high pressure cell operates by forcing two diamond anvils together, and can produce hydrostatic or nonhydrostatic pressures. Customer's requirements are normally satisfied by one or more of four cell types: • hot cell (ambient to 1500 °C) (Linkam Scientific Instrument’s TS1500) • hot-cold cell (-196 °C to 600 °C) (Linkam Scientific Instrument’s THMS600) For hydrostatic pressures the sample is immersed in a pressure transmitting material surrounded by a metal gasket with a central hole, with the confinement being created by the vertical walls of the gasket hole and the two anvil faces. This configuration is useful for high precision pressure measurements. Non-hydrostatic pressures are generated if the gasket is omitted. This gives a pressure gradient, with the pressure gradually dropping from the centre of the cell towards its periphery, and is useful for visualizing pressure induced phase changes. • liquid nitrogen cell (77 K to 500 K) (Oxford Instruments Superconductivity’s MicrostatLN) • liquid helium cell (2.2 K to 500 K) (Oxford Instruments Superconductivity’s MicrostatHe) TS1500 hot cell supports temperatures from ambient to 1500 °C. Details of the cells are given in Table 2. Please contact Renishaw if you require further information, or have a requirement for a custom temperature control cell. The B-05 high pressure cell (supplied to Renishaw by Diacell Products Ltd.) can support pressures up to 50 GPa (500 kBar). It normally operates at ambient temperatures, but the addition of a ring heater allows use to about 600 ºC. THMS 600 hot-cold cell supports temperatures from –196 °C to 600 °C. (A0,X)-LO (D0,X)-LO X-LO The anvils can be adjusted for tilt to ensure anvil faces are parallel. For convenience, all adjustments necessary for alignment can be made under the microscope. GaN/Al2O3 T = 4.2 K d = 200 µm 3.7 GPa 675 700 ×100 A1 (LO) MicrostatHe supports temperatures from 2.2 K to 500 K 725 875 Raman shift / cm-1 (A0,X) ×5 0 GPa 650 X DAP 6.3 GPa E2 (high) (D0,X) X-2LO 9.7 GPa 900 925 950 Raman spectra of the (0001) face of AlN, as a function of hydrostatic pressure. Data courtesy M. Kuball, University of Bristol, and D.J. Dunstan, Queen Mary, University of London. 3.1 3.2 3.3 Energy / eV 3.4 3.5 325 nm excitation photoluminescence spectrum of a 200 µm GaN layer on sapphire, taken at 4.2 K. Data courtesy of H. Siegle et al., Technical University, Berlin, Germany. MicrostatN supports temperatures from 77 K to 500 K. Renishaw plc Spectroscopy Products Division Old Town, Wotton-under-Edge, Gloucestershire GL12 7DW United Kingdom T +44 (0) 1453 844302 F +44 (0) 1453 844236 E [email protected] www.renishaw.com Table 1: Humidity control stage Temperature stabilitya ± 0.1 °C Temperature Rangeb +10 °C to +40 °C Humidity stability ± 1.5% RH Humidity Range: 0% RH to 95% RH Notes: a Where difference between ambient and programmed temperature > ±2 °C b Assuming ambient temperature of 25 °C. Table 2: Temperature control stages Temperature range Maximum sample size Diameter Height Hot Hot/cold Liquid nitrogen Liquid helium ambient to 1500 °C -196 °C to 600 °C 77 K to 500 K 2.2 K to 500 K 8 mm 2.5 mm (6 mm deep also available) 22 mm 3 mm (lid extension also available) 20 mm 2 mm 23 mm 8 mm Light aperture (diameter) 1.7 mm 2.4 mm 20 mm 10 mm Window thickness Variousa 0.17 mm Typicallya 0.5 mm Typicallya 0.5 mm Objective lens working distance > 6 mm 0.1 mm to 4.5 mm > 2 mm > 3 mm 104 mm 95 mm 29 mm 137 mm 92 mm 22 mm 90 mm 190 mm 24 mm 110 mm 440 mm 44 mm Stage body size Length Width Height Notes: a A variety of window thicknesses are available. Please contact Renishaw for more details. Renishaw is continually improving its products and reserves the right to change specifications without notice. © 2003 Renishaw plc