Prof. Tapas Kumar Chini

The SINP CL-SEM Facility : Schematic & Actual Photo of the System          Specifications Manufacturer of HRSEM :      Carl Zeiss NTS GmbH, Germany Manufacturer of CL set up :   Gatan UK Model of HRSEM :                  Carl Zeiss Supra 40 Model of CL :                          Gatan MonoCL3 Installation and Location :      March, 2010 at the ground floor of Phase IV building Important features of the CL system :   * Direct optical coupling to chamber mounted monochromator  * Retractable, detachable diamond turned parabolid mirror  * Panchromatic and monochromatic mode of imaging  * Micrometer slits for controlling spectral resolution and band pass  * Peltier-cooled high sensitivity photomultiplier tube (HSPMT) sensitive in the range 165 nm to 930 nm wavelength of CL emission with integral pre-amplifier and 1200 lines/mm grating blazed at 500 nm  * LN2 cooled Ge detector sensitive in the range 800 nm to 1800 nm and an additioanl grating of 600 lines/mm blazed at 1000 nm  Important features of the HRSEM system : * High stability Schottky type field emitter  * Resolution : 1.0 nm at 20 kV; 1.3 nm at 15 kV; 2.1 nm at 1 kV  * Acceleration voltage : 100 V to 30 kV  * Annular In-lens SE detector and chamber SE detector  * High resolution BSD detector (retractable under vacuum)  * Ion getter pumped column and TMP with rotary backing having oil traps, oil mist filter to gurantee contamination free vacuum environment in the analysis chamber   How the CL measurements are performed : CL or electronbeam-induced radiation emission (EIRE) imaging/mapping on an isolated nanoparticle is performed in a ZEISS SUPRA40 SEM equipped with the Gatan MonoCL3 optical detection. The ZEISS SUPRA40 SEM has a hot Schottky field-emission gun and the attached MonoCL3 system uses a retractable paraboloidal light collection mirror. The parabolic mirror collects light that is emitted from the sample covering 1.42π sr of the full 2π of the upper half sphere and collimates it through a hollow aluminum tube to a 300 mm Czerny-Turner type optical monochromator with a spectral band-pass of approximately 11 nm and finally the signal is fed to a high-sensitivity photomultiplier tube (HSPMT). The electron beam is directed onto the sample surface through a 1 mm diameter opening in the mirror. To ensure maximum efficiency of light collection, the top surface of the sample is kept at the focal plane of the mirror, which lies approximately 1 mm below the bottom plane of the mirror. The CL system in conjunction with the SEM can be operated in two modes, namely, monochromatic and panchromatic. In the monochromatic mode of CL operation, the focused electron beam is either scanned over the sample or positioned on a desired spot while the emitted light from the sample passing through the monochromator allows the emission spectra to be recorded. Subsequently, the monochromatic photon map is built up at a selected peak wavelength of the EIRE spectrum by scanning the electron beam over the sample. In the panchromatic mode of CL operation, on the other hand, light skips the monochromator and all of the light is carried to the detection optics, so that light emission spectra cannot be obtained and all the wavelengths emitted from the sample contribute to the resulting panchromatic photon map. Each pixel in the monochromatic image corresponds to a different position of the electron beam, and the intensity of the pixel is proportional to the detected emission intensity of the spot. The contrast of the PanCL image is determined by the variation of the integrated photon counts at each pixel in the sensitivity range of the HSPMT detector.