Quantitative Analysis（Ian Pearce).pptVIP

Quantitative AnalysisbyIan PearceCustomer Support Manager for East Asia Select the menu option Point and ID Options Select the Duane Hunt tab Click on Enabled This will give a warning in the quantitative results if the spectrum high energy cut off is less than the accelerating voltage as recorded in INCA Quantitative Analysis – The sample Sample Charging – What can I do Coating with C, Au or other element – but not too thick Reduce probe current / spot size Reduce accelerating voltage - but remember you need to efficiently excite all the elements in your sample Scan the beam rather than spot – but only if you are analyzing bulk areas – not particles Quantitative Analysis – The sample Sample Charging – What can I do to reduce it Use Low Vacuum – but remember this will cause beam spreading so you will get x-rays from a larger area and you will get absorption of x-rays in the gas Tilting the sample Ideally our samples would be flat But in practice this is often not possible For rough samples we always have to have in mind the direction of the detector relative to the sample Roughness of a few microns is ok but fracture surface morphologies could give problems Quantitative Analysis – The sample What other sample factors can affect analysis? Rough Sample Electron beam Surface roughness Shadowing from the detector can occur where The whole x-ray signal from a spot or area will be absorbed Or preferential absorption may occur where the lower energies / lighter elements will be absorbed giving us an unrepresentative spectrum Quantitative Analysis – The sample What other sample factors can affect analysis? Rough Sample Electron beam Flat surface Increased exit path Surface roughness Check and compare spectra in valleys and on peaks Rotate and / or tilt sample so that absorption paths are reduced Quantitative Analysis – The sample What other sample factors can affect analysis? The heating effect of the electron beam can cause problems for some