Hello
I have fabricated interdigitated electrodes on thin films and measured in plane capacitance. Now I want to calculate the dielectric constant of thin film. How can I do that?
Inter-digitated electrodes are usually used for sensing purposes and not so much for dielectric constant measurement. It can be easily calibrated, however, on samples with known dielectric constant. You can select polymer films and determine their dielectric properties in a standard parallel plate arrangement, then measure the same films with comb-electrodes, and from this you can easily calculate the geometrical capacitance of the latter one.
I am attaching the following articles that you can go through to determine whether you will go for analytical equations based dielectric constant determination or using diagnostic measurement method through instruments used in academia and companies. If you do not have access to buy the instrument reported in one of these articles for dielectric constant measurement, go for the other two papers as they provide analytical equations to extract dielectric constant.
Please recommend my answer if it is helpful to your query.
Sincerely,
Dr. Nabil Shovon Ashraf.
Inter-digitated electrodes are usually used for sensing purposes and not so much for dielectric constant measurement. It can be easily calibrated, however, on samples with known dielectric constant. You can select polymer films and determine their dielectric properties in a standard parallel plate arrangement, then measure the same films with comb-electrodes, and from this you can easily calculate the geometrical capacitance of the latter one.
which thin film material are you trying to grown, and want to measure its dielectric constant. If you can tell then it is easy to solve the problem.
K. Sreenivas
To to calculate the dielectric constant of thin films there are two ways;
Optically and electrically. You prefer to measure the dielectric constant of thin film electrically, you fabricated interdigitated electrodes so need to measure the total conductivity, σ(ω)total ( σac (ω) and σdc);
σ(ω)total = σac (ω) + σdc (1)
σac (ω) = σ(ω)total - σdc
where σdc is the dc conductivity, which is independent of frequency.
Its value can be obtained by extrapolating the experimental data of σ(ω)total at low frequency down to zero value, and σac (ω) is the frequency-dependent conductivity. σac (ω) can be calculated as follows
σ(ω)total = d/ZA ------ (2)
where d is the film thickness, A is the cross-sectional area, and Z is the impedance
ε1 = Cd/ ε0A -------- (3)
where ε1 is the permittivity of free space, C is the capacity.
ε2 = ε1 tanδ
ε1 and ε2 are the real and imaginary part of dielectric constant.
More details are available in the attached paper.
I wish this is useful and help you.
Yours
A. El-Denglawey
Dear Dr. Kashmir
For dielectric measurements, you have to make sandwich geometry and measure parallel capacitance to calculate dielectric constant of the film. Kindly make sure that barrier capacitance is negligible. You can use standard formula for calculation. Stray capacitance has to be avoided using three terminal measurements by mounting the sample in a metallic sample holder having a good vacuum.
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