I used to count the laser pulses and optimise accordingly.

say for  a 200 laser shots, measure the film thickness by preparing a well defined step, and measuring the thickness of the step using a thickness profilometer.

Remove the target, grind it and polish it to produce a fresh clean surface, Repeat the experiment for 400 shots, and see if the thickness is doubled.

Got a reasonable success.

Well reproducibility is an issue in PLD, because the target surface with its circular track can change after use. You should check the energy of the laser pulse, it should be constant, and secondly the target surface should be fresh, and you calculate the thickness being developed per laser shot pulse.

Putting thickness monitors etc is a complicated issue, because in my case I had a very high substrate temperature 800 deg C., and the space between the target and substrate was very congested to introduce the probe head of film thickness monitor. Moreover with complicated stoichiometry of oxide targets, it is very difficult to use film thickness monitors.

K. Sreenivas

I used to count the laser pulses and optimise accordingly.

say for  a 200 laser shots, measure the film thickness by preparing a well defined step, and measuring the thickness of the step using a thickness profilometer.

Remove the target, grind it and polish it to produce a fresh clean surface, Repeat the experiment for 400 shots, and see if the thickness is doubled.

Got a reasonable success.

Well reproducibility is an issue in PLD, because the target surface with its circular track can change after use. You should check the energy of the laser pulse, it should be constant, and secondly the target surface should be fresh, and you calculate the thickness being developed per laser shot pulse.

Putting thickness monitors etc is a complicated issue, because in my case I had a very high substrate temperature 800 deg C., and the space between the target and substrate was very congested to introduce the probe head of film thickness monitor. Moreover with complicated stoichiometry of oxide targets, it is very difficult to use film thickness monitors.

K. Sreenivas

Actually the thickness can be monitored with multiple methods.

If you grow epitaxial thin film on the single crystal substrate with high temp. like over 800 °C, using surface diffraction methode like surface x ray diffraction or electron diffraction is optimal.

If you grow at low temperature to get poly-crystalline thin film, then use either optical ellipsometer (either single wavelength or spectroscopic) or X-ray reflectivity measurements.

I haven't heard about neither theoretical, nor empirical formula for thickness calculations. Only calibration of the deposition system may be recommended (see Dr. Sreenivas above).

Thickness monitor (quartz oscillator) may be used if placed close enough to the target surface, but the relation between measurement and actual film thickness strongly depends on angular position of the monitor, pressure in chamber, beam energy density on target, etc. The reason is very directed spreading of the ablated cloud. Even small fluctuations of chamber geometry or gas pressure during deposition will result in wrong thickness estimations.

The ellipsometer measurements are working fine with transparent films, and even not transparent if the films are thin enough. Diffractional measurements are limited to certain films (single crystalline) and deposition conditions. Reflectivity measurements seem appropriate, though I never used such a technique myself :) If the film is conductive, measurements of conductance during the deposition may also provide information on thickness.

The simplest method is to measure the thickness profile by taking SEM images in cross-section of the fractured film on substrate. The method is suitable for films deposited by PLD as they are usually thin and is not dependent on material properties (refractive index, transparency). Once measured, the thickness will be proportional with the number of pulses, so you'll be able to obtain the desired thickness by adjusting the number of pulses for the same deposition conditions.

I measure the thickness of thin film by taking cross sectional SEM image

I feel the sem cross section image, is also a convenient option.

Alternately if you have a well performing chemical etchant, you can etch a

step in the grown film, and can do profilometry, or use the SEM imaging.

K. Sreenivas

An accepted model for thickness model in PLD is given by Anisimov in 1993 (Article Gas Dynamics and Film Profiles in Pulsed-Laser Deposition of Materials

Dear colleague Cyril Robinson Azariah John Chelliah

Have a nice time and good day.

Herein find three methods to calculate film thickness.

You can use one of the following according to condition of the film.

Film thickness can be checked by

1- An interferometric method, more details is available at: TOLANSKY S. Multiple beam interferometry of surfaces and films. London: Oxford University Press, 1988: 147.

2- Using mass of the film, m according to the next details::

W1 is the weight of cleaned substrate

W2 is the weight of cleaned substrate plus film

W2-W1= the weight of the film

ΔW=mg

m = ΔW/g

m=ρXV ; ρ, is the density of film material and V is the volume of the film

the Volume = (Width X Length X Thickness) of the film

3- SEM or AFM (film-substrate ) cross section

I wish this is useful and help you.

Yours

A. EL-Denglawey, Ph.d

Thank you respected scientists and professors for your valuable suggestions @K. Sreenivas @Wasna'a M. Abdulridha @A. Eldenglawey @Catalin Luculescu @Peter Borisovich Mozhaev @Chencheng Xu

Hello, I use reflectivity XRD measurements to calibrate the growth rate. For ultra-thin films the rate is not always linear - what thickness and what material do you aim for ?

@ K. Sreenivas : you do not preablate your targets to have reproducible depositions ?

I am agree with K. Sreenivas. Yes, you can count the laser pulses and optimise accordingly.

The simple way of the thikness measurement is the Newton ring method, or Fizeau fringe method.

The best accuracy method for the thckess measurement is the Ellipsometry Spectroscopy (SE) As for example: You can deposite a film of count 200 laser shots and 400 shots. After papared these films you can use SE readings and then you can fit these data with the data model and you can get more accuracy thickness of the films.

@Md. Kamruzzaman, Can you please tell me how thickness is measured using Newton ring method/ Fizeau fringe method? Is it easy one to do? Will this be approximate.

http://iopscience.iop.org/article/10.1088/1674-4926/36/4/044002/pdf

In this article, the thicknesses of the films are measured using Tolanky’s multiple mean interference method. Can anyone tell me what is this method?

@Laura Bégon-Lours: I use oxide based composites. I am aiming for less than 25 nm thickness.