Microscopic Study on Artificial Metal-Semiconductor Nano-Materials

    The experimental data are shown in the following four parts:

    1.   Surface topography Images;
    2.   Cross-section Images;           
    3.   X-ray spectrum;                       
    4.   X-ray mapping;                        

  3.  X-ray spectrum

    Besides secondary electrons and backscattered electrons, a third most useful signal produced by the interaction of the electron beam with the specimen in a SEM is the x-ray, since the energy of the X-ray is equal to the energy difference between the two electron orbitals, and therefore can be used to determine the material composition of the sample. The present SEM system has a energy dispersive spectrometer to analyze the X-ray signals.

    X-ray spectrum is taken for samples #1, #4 and #6 with accelerating voltage of 20kV. The spectrums are shown in Figs. 4.11-4.13, respectively, and the result is quite as expected since the samples are fabricated purposely. It should be noted that the expected gold peaks are missing in the spectrum of sample #4. which is against normal expectation. This abnormality is probably because the size (and the volume) of the gold nano-particles is too small that there are hardly any X-ray generated from the interaction between gold and electrons. This issue will be studied further later in the analysis section.

Fig. 4.11 X-ray spectrum from sample #1 (Ag on porous InP)

Fig. 4.12 X-ray spectrum from sample #4 (Au nano-particles on bulk InP)

Fig. 4.13 X-ray spectrum from sample #6 (Au nano-particles on porous InP)