There are (at least) two principal questions to be answered before. Firstly, how precisely characterized are your substrates (e.g. substrate roughness, …)? And the second - do You know, if your sub nanometer thin film prepared by sputtering is really continuous film or it has rather island-like structure?
In dependence on given answers and properties of substrate and ”thin film”, several possible techniques arise. From direct methods the mechanic probe microscopies (Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)) should be mentioned. And from indirect methods e.g. Spectroscopic Ellipsometry may help.
Also You can find inspiration of growth monitoring equipment of Molecular Beam Epitaxy (MBE) or Atomic Layer Deposition (ALD) techniques like X-Ray Reflectivity measurement (XRR). (You should tagged your question also by these tags, in my opinion).
And finally, several techniques may be adjusted to estimate or even measure of thickness. These techniques are usually used for elemental analysis – like UV or X-Ray Photoelectron Spectroscopy (UPS, XPS), X-Ray Fluorescence (XRF), …
There are (at least) two principal questions to be answered before. Firstly, how precisely characterized are your substrates (e.g. substrate roughness, …)? And the second - do You know, if your sub nanometer thin film prepared by sputtering is really continuous film or it has rather island-like structure?
In dependence on given answers and properties of substrate and ”thin film”, several possible techniques arise. From direct methods the mechanic probe microscopies (Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)) should be mentioned. And from indirect methods e.g. Spectroscopic Ellipsometry may help.
Also You can find inspiration of growth monitoring equipment of Molecular Beam Epitaxy (MBE) or Atomic Layer Deposition (ALD) techniques like X-Ray Reflectivity measurement (XRR). (You should tagged your question also by these tags, in my opinion).
And finally, several techniques may be adjusted to estimate or even measure of thickness. These techniques are usually used for elemental analysis – like UV or X-Ray Photoelectron Spectroscopy (UPS, XPS), X-Ray Fluorescence (XRF), …
Efectivamente lo mas recomendable es caracterizar por reflectividad de rayos x, de prefereccia usa sustrato de silicio para que tengas menos rugosidad que en vidrio, en vidrio es mas dificil
I would say that X ray diffraction will be tough for films below 1 nm in thickness (this is what Gerard states in his question): a very high quality of the interfaces and the crystallinity of the deposited film, and a very low surface roughness will be needed to see the interference fringes with sufficient accuracy.
Probably the cheapest and most convenient method is to do a good in-situ calibration within the sputter deposition chamber using a quartz microbalance: grow a series of films with different thicknesses, measure them ex-situ with a profilometer or x-rays, or any other method, and then extrapolate. An extremely accurate but technically more complex method, and valid only for materials growing in a layer-by-layer mode, is to use an electron gun and a phosphor screen to measure the oscillations in the intensities of the RHEED diffraction spots. When this method is applicable you can routinely get precisions of the order of 1/10 of a monolayer, or about 0.2 angstroms.
It is a tough problem. We have done such measurements down to about 0.4 micron using EDXRF technique. The calibrations involved SRM of NIST, USA as well as the use of sensitive micro-balance. Publications have been reported in 1980's in Nuclear Instruments and Methods or Journal of Thin Films. Please contact for exact reference and preprint if available.
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