I am looking at performing SQUID-VSM of doped-BTO thin films(400nm) on platinum substrates. With known thickness, width and length values, allowing me to calculate the volume, and from that, the mass using the mass density of bulk samples recorded in literature. However I am unaware if the density remains constant between bulk and thin film samples.
Is this an accurate technique for reporting mass, and if not, what is the correct way of reporting the mass of such thin films?
The simplest way is to measure the mass of the substrate before deposition and after depositing the film and the difference is the mass of the thin film. However you need a sensitive balance(micro gram).
If you are sure that your thin film is a pure known materiel you can calculate the area of the film and the thickness then you can determine the volume. So when you have the volume and the density then you can approximately estimate the mass taking into account that the density of the thin film usually is a bit less than bulk.
In my opinion, the density of thin films deposited on a substrate depends on many factors especially, the porosity of the film. The best option remains to measure the smoothness of the films through AFM to get the average thickness as the thickness measured from interferrometry or optical data may not be correct for such calculations. further, measure the XRD in thin film (grazing angle) mode and calculate the x-ray crystal density. The volume and density from such measurement should provide you a fairly good estimate of mass.
What you do will be correct if you can manage to find the volume of voids (porometry) in the thin film and take that out from the film volume. In other words, you can use bulk density and multiply it to the bulk parts of the film only to find mass.
Hi David,
up to now no real direct measurement technique was suggested that will give you for example the mass coverage of Ba on your BTO film.
At a first moment I thought on x-ray absorption spectroscopy around the Ba K-edge energy. From the jump of x-ray transmission at the Ba K-edge (~ 37,4keV) you are able to derive the mass coverage of Ba. But in your case (0,4µm film thickness) there is only less than 0,5% change in transmission, which is far too less in order to get reliable numbers ( in addition the Pt substrate will catch most of the x-rays).
But X-ray fluorescence may help at such small coverage. Catching Ba K-alpha will in contradiction to the x-ray absorption case not really suffer from the Pt substrate and will provide a sufficient number of photons.
However these experiments are not easily done. You have to calibrate your system, for example by a series of samples having well known Ba coverages.
I think here on x-ray induced fluorescence. Electron induced fluorescence will suffer from electron beam attenuation by Ti and O in your sample, although your sample is only around 400nm.
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