In-Situ TOF-SIMS and SFM Measurements Providing True 3D Chemical Characterization of Inorganic and Organic Nanostructures

Abstract

Information on the chemical composition, physical properties and the three dimensional structure of materials and devices at the nanometer scale is of major importance in nanoscience and nanotechnology. Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is known to be an extremely sensitive surface imaging technique which provides elemental as well as comprehensive molecular information on all types of solid surfaces. Depth profiling of multilayers with high depth resolution as well as threedimensional analysis is performed in the so-called dual beam mode. In this mode the pulsed analysis beam is combined with a low energy sputter ion beam for the removal of material providing chemical 3D information of the sample. However, the topography of the initial sample surface as well as the subsequent evolution of the topography due to different erosion rates of the compounds cannot be identified by the technique and lead to distortions of the detected depth distribution. In order to get a true image of the 3D volume, the time scale of the TOF-SIMS 3D depth profiles needs to be converted into a depth scale. Scanning Force Microscopy (SFM) provides the required complementary information on the surface topography with a resolution on the nanometer level. Beyond that SFM can provide valuable information about the physical properties of the sample if the cantilever is operated in the different dynamic operation modes.We have combined the techniques ToF-SIMS and SFM in one UHV analysis chamber. This instrument was conjointly developed within the framework of a FP7 research project (www.3dnanochemiscope.eu). One of the key components of the new instrument is a piezo driven XYZRT-stage which moves the sample between the TOF-SIMS and the SFM analysis site with sub-μm precision and high speed. This allows analyzing exactly the same surface area with both techniques. The TOF-SIMS analysis is performed using a new bismuth liquid metal cluster ion gun that can achieve a beam size for Bi 3 cluster primary ions down to 20 nm [1]. These heavy projectiles exhibit very high secondary ion yields in particular for organic materials. For the sputtering of inorganic materials the instrument is equipped with an oxygen and cesium beam. At low sputter energies of a few hundred eV a depth resolution of about 1 nm is achieved for inorganic thin films. Although this beam energy is rather low, the sputtering of organic materials would lead to strong radiation damage and a rapid loss of the molecular ion signals. This is avoided by the use of large gas clusters with energies per atom in the range from 1 -10 eV [2] allowing high quality molecular depth profiles of organic multilayers with a depth resolution of 5 nm [3] as well as 3D analysis of organic nanostructures [4]. The SFM unit with a beam deflection design is mounted on a 3-axis high precision flexure stage scanner. This linearized scanner with a very small out-of-plane motion yields very accurate information on the surface topography and has a scan range of 40 x 40 x 6 µm 3 . The SFM...

High Sensitivity of Fluorine Gas-Assisted FIB-TOF-SIMS for Chemical Characterization of Buried Sublayers in Thin Films

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“…The depth of the FIB-sputtered crater can be measured using SEM or AFM. However, the latter one demands time-consuming and demanding protocols to assess thicknesses of individual thin films in the case of multilayer systems. − Figure S3 shows Al 2 O 3 /Ni/Al 2 O 3 /Au/Al 2 O 3 /Cu/Al 2 O 3 depth profiles. The generation of 28 Si + , 58 Ni + ,, 63 Cu + and 197 Au + ions was significantly increased (up to over 2 orders of magnitude) due to the presence of fluorine gas.…”

Depth Correction of 3D NanoSIMS Images Shows Intracellular Lipid and Cholesterol Distributions while Capturing the Effects of Differential Sputter Rate

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Analysis and imaging of biocidal agrochemicals using ToF-SIMS

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