What is the best measurement method to determine bulk concentration, resistivity and mobility of thin films?
Dear Mostefa the best measurement method to determine bulk concentration, resistivity and mobility of thin films is by four probe technique or Hall measurement.
How can I determine exactly the film thickness of each layer in heterostructure
Dear Mostefa the best measurement method to determine bulk concentration, resistivity and mobility of thin films is by four probe technique or Hall measurement.
For thickness you can use some of these ideas:
a. X-ray reflectivity (XRR), but the more layers you have the more complex (and less reliable) is the interpretation and fitting of the data.
b. Ellipsometry and spectroscopic ellipsometry: would usually require prior knowledge of some of the coefficients of the materials (for common materials such as SiO2) they are known
c. Cross section transmission electron microscopy (TEM). Requires complex sample prep and allows measuring a relatively small region of the sample, but when done properly it can provide an abundance of information on the structure and chemistry.
d. For thick enough layers - cross section scanning electron microscope (SEM) could do fairly well. How thick depends on your microscope, modern SEMs have a nm-scale resolution. You'll need to assess whether your sample is suitable for getting enough contrast (i.e. are the densities of the layers different enough, is it not too insulating, etc).
As for mobilities/resistivities/carriers - this has been discussed here many times, try searching for it. In short, a combination of a 4 point measurement with a Hall measurements would answer most of your questions. The van der Pauw geometry allows you to perform both measurements using the same setup.
Good luck.
XRF can also provide information about layer thicknesses even for complex layer stacks
Hi Mostefa. For thickness of each layer in heterostructure: Spectroscopic Ellipsometry seems to be the most promising and precise Méthode.
For Bulk Concentration (of carriers i guess) Electrochemical CV gives you profiles of concentration.
For resistivity and mobility: like said by the elegant Neha Chaturvedi.
It depends on how thin is your film. In general, it is advisable to use multiple methods both contact and non-contact when ever possible and compare. For thickness, ellipsometry and profilometer will do. One can also use four point probe and infrared ellipsometry for resistivity. Carrier concentrations can then be determined directly from resistivity measurements or obtained from Hall measurements which is also a standard method for measuring carrier mobility.
... i'll recommend also to perform the resistivity and/or mobility measurements at different temperature if possible.
For thickness measurement, SEM with cross-section by focused-ion-beam milling is a simple method compared to the TEM preparation.
Hall effect, when your material is conductive, resistive materials are difficult to measure, what is your material?
zinc oxide, cadmium oxide, indium oxide, tin oxide are easy make electrical characterizacion, another oxides are very difficult like titanium oxide, cupper oxide
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