Beams diameter

Besides phase identification XRD is also widely used for strain and particle size determination in thin films. Both produce peak broadenings, but they are distinguishable. Compared to TEM, XRD has poor area resolution capability, although by using synchrotron radiation beam diameters of a few pm can be obtained. Defect topography in epitaxial films can be determined at this resolution. 

Scanning Auger Electron Spectroscopy (SAM) and SIMS (in microprobe or microscope modes). SAM is the most widespread technique, but generally is considered to be of lesser sensitivity than SIMS, at least for spatial resolutions (defined by primary beam diameter d) of approximately 0.1 im. However, with a field emission electron source, SAM can achieve sensitivities tanging from 0.3% at. to 3% at. for Pranging from 1000 A to 300 A, respectively, which is competitive with the best ion microprobes. Even with competitive sensitivity, though, SAM can be very problematic for insulators and electron-sensitive materials. 

The basic instrumental set-up for dynamic SIMS is the same as for SSIMS (Sect. 3.1.2). Depending on the intensity, beam diameter, and ion species needed, dif ferent ion sources are used. Several mass analyzers with different characteristics enable a broad field of applications. 

The attainable particle current density per solid angle of the beam (ions pm s sr ) is an inherent property of the ion source, the so-called brightness. Because of this, reduction of the beam diameter is effected by reducing the beam current. 

In the scanning (or microprobe) mode the image is measured sequentially point-bypoint. Because the lateral resolution of the element mapping in scanning SIMS is dependent solely on the primary beam diameter, LMISs are usually used. Beam diameters down to 50 nm with high currents of 1 nA can be reached. 

The oxygen ion beam diameter is limited to 0.5 pm by the duoplasmatron source used. For mapping electropositive elements this drawback must be tolerated because of the chemical enhancement effect. 

Figure 16-44. Emission spectra of a vacuum-deposited thin (400 nm) film of Ooct-OPV3 after annealing at 70 °C for 30 min. Excitation energy (a) 7.3 pJ. (b) 43 pJ, (c) 46 pJ, (d) 48 p), (c) 210 pi excitation beam diameter 1.8 mm.

Figure 16-46. Integrated intensity of total ( ), broad (O). narrow (I 0, and lincwidlh of total ( ) and narrow (O) cmissioas as a function of excitation energy Tor an annealed thin (300 nm) film of Oocl-OPV5 excitation beam diameter % 1.8 mm.

Figure 16-47. Emission spectra of a melt-crystallized thin (300 nm) film of Oocl-OPV5. Excitation energy (a) I pJ, (b) 10 pj, (c) 50 pJ, (el) 70 pJ excitation beam diameter x 1 mm.

For this study, thin films were deposited onto glass substrates. The as-deposited films showed no spectral narrowing at any pump energy up to the damage threshold. Stimulated emission was observed only in annealed films. The spol-to-spot reproducibiliiy of the measured characteristics was good, and we could measure with excitation energies of up to 4 mJ (1.8 mm beam diameter) without visual damage of the illuminated spot. 

Ayy = (6.0 5.5) T, and A22 = (16.9 2.5) T (conventional dashed Unes). This again demonstrates the sensitivity of NFS for hyperfine interactions in nuclear ( Fe) scatterers. There can be no doubt that NFS benefits from experimental conditions such as polarization and time structure, and also from a beam diameter in the submillimeter range of the probing radiation. 

High spatial resolution (laser beam diameter 1 p,m)... 

Probe energy Beam diameter Beam current Analysis time Scattering angle Energy analyser... 

In conventional PIXE the beam diameter is a few millimetres, which gives detection limits of the order of 10 11g. With p-PIXE and a spatial resolution of about 1 pm, detection limits as low as 10 —16 g can be achieved. 

The sample environment was filled with He gas to prevent the argon X-ray emission from air. Beam scanning, data acquisition, evaluation and the generation of elemental maps were controlled by a computer. Micro-PIXE measurements were performed with a scanning 2.5MeVH+ microbeam accelerated by the 3 MV single-end accelerator. The beam diameter was 1-2 pm, so that individual particles could be analysed. The beam current was < 100 pA and the irradiation time was about 3(M0 min. 

When the electron beam enters the sample, it penetrates a small volume, typically about one cubic micron (10-18m3 ). X-rays are emitted from most of this volume, but Auger signals arise from much smaller volumes, down to about 3 x 10 25m3. The Auger analytical volume depends on the beam diameter and on the escape depth of the Auger electrons. The mean free paths of the electrons depend on their energies and on the sample material, with values up to 25 nm under practical analytical conditions. 

Technique Depth Depth resolution Depth profile Insulators Vacuum Composition maps Beam diameter... 

Nanobeam optics with beam diameters of several nanometers are presently developed at the ESRF. Using a Kirkpatrick-Baez optical system (cf. Fig. 4.9) beam diameters of 80 nm have been achieved. The Kirkpatrick-Baez system is made from two successively reflecting, orthogonal mirrors that are bent into elliptical shape by mechanical benders. The focused flux is strongly increased by deposition of a graded multilayer structure similar to that used with the parabolic Gobel mirror. 

Photothermal decomposition of palladium acetate by scanned cw Ar+ laser irradiation produces metal features that exhibit pronounced periodic structure as a function of laser power, scan speed, substrate and beam diameter, as shown in Figures 3 and 4. The periodic structure is a function of the rate at which the film is heated by absorption of the incident laser radiation coupled with the rate at which the heat of the decomposition reaction is liberated. This coupling generates a reaction front that outruns the scanning laser until quenched by thermal losses, the process to be repeated when the laser catches up and reaches unreacted material. Clearly, such a thermal process is also affected by the thermal conductivity of the substrate, the optical absorption of the substrate in those cases where the overlying film is not fully absorbing,... 

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