MNCL Instrumentation
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The experimental UHV ESCALAB system:
The listed instrumentation allow to perform electron spectroscopy investigations like XPS, UPS, EELS and Auger) |
 Picture of the UHV STM system available in the Micro-Nano-Carbon Lab.
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Modified VG ESCALAB
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RT-STM
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EXPERIMENTAL TECHNIQUES
In the MNC lab several techniques for surface preparation and characterization are available:SAMPLE PREPARATION
The insitu preparation of metal surfaces is carried on by means of well established and standardized procedure in UHV. Ion bombardment (sputtering) with Ar+ ions roughen the surface and mechanically remove the first layers, while the annealing at high temperature produce a smoothing at the atomic level.
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SURFACE CHARACTERIZATION
Electron Spectroscopies and Scanning Tunneling Microscopy are the main experimental techniques available in the MNC lab. As a general view they allow to extract information on the surface chemical state (electronic configuration of the surfacial atomic species) as well as the sample topography (constant density of states profile) at the atomic level.
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EXPERIMENTAL TECHNIQUES
Carbon nanostructures growth apparatus (CVD)
The experimental chamber vaccum apparatus consists of two turbo-molecular pumps, back-pumped with a membrane and a scroll respectively. Two valves can exclude the pumps from the chamber, so it is possible to fill the chamber with gasses without shutting them down. There are two connections to gas bottles, in our case hydrogen and acetylene. The acetylene bottle is not directly joint to the main chamber, it is possible to fill a pre-chamber with the gas and then open instantly the shutter between pre-chamber and main chamber. The sudden break in of the gas is useful for the growth.
Photograph of the growth setup
Connected to the chamber there is a Pirani gauge, to measure pressures in the range [103,10−3]mbar and a cold cathode vacuum gauge for lower pressures [10−2,10−11]mbar. The samples are mounted on a custom-made heater. Tungsten filaments are sandwiched by two Molybdenum plates (40 × 80 × 1mm), in between boron nitride foils were placed to isolate the filaments from the grounded plates. A photo and a schematic view of the heater is shown in the figures below.
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The heater has been tested up to 400 W corresponding to approximately 1000◦C. Although it is built with a high thermal capacity, the power applicable is enough to reach high temperatures in a few minutes. The temperature is controlled with two K-type thermocouples. One is in contact with the sample, while the second one, placed in an other point of the heater, is useful to observe if the molybdenum plates heats homogeneously.
Electrochemical growth metodology
Within the laboratory it has been developed an Electrochemical cell working with two electrodes for the growth of different ZnO nanostructures from common chemical reagents. The results and analysis of the morphologyof the produced samples have demonstrate the ease and flexibility of this cell to grow diverse nanostructures based on semiconducting compounds on conductive substrates from electrolytic solution. C.Castellarin et al. AIP Advances 1, 032147 (2011) and B.A.Taleatu et al. Current Applied Physics 13(1), 97-102 (2013).
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cartoon of the e-cell |
This experimental work has been supported also by the Abdus Salam ICTP/IAEA and in collaboration with dr. B. Taleatu, Materials Science division, CERD-OAU Ile-Ife, Nigeria.
