Assessing analytical convolution effects in diffusion studies: Applications to experimental and natural diffusion profiles
Fig 5
Deconvoluting Ti profiles in quartz determined by SEM-CL.
Images were acquired using a Zeiss Gemini 1530 field emission gun scanning electron microscope equipped with an ellipsoidal mirror and an ASK SEM-CL View VIS (250–900 nm) imaging spectrometer. The SEM was operated at 7 kV, 10 nA with a working distance of 14.2 mm. (a) CL image of an un-annealed high Ti quartz-low Ti quartz couple, with an extracted greyscale profile in (c). (b), same sample as in (a), after annealing at 1600°C, 20 kbar for 89.5 h, showing a wider transition zone, with the extracted profile in (d). (c) assuming that the gradient in (a) is purely convolution (i.e. (a) is a step function) and the beam-sample interaction is Gaussian, the FWHM is determined by fitting a curve with the form erf(x/(√2σ)) to the data, giving FWHM = 322 nm. (d) extracted profile from (b), deconvoluted using PACE and the FWHM from (c). The ‘Ti-rich’ section contains ~3000 wt. ppm Ti, versus <0.2 wt ppm for the ‘Ti-poor’ section.