If you deposit many times it will dissolve all the material that you have deposited in the previous coating

The thickness is decided by the spin coating speed and concentration and the solvent that you used

Attention: I believe that quartz slides can crystallize above 900oC.

The parameters mentioned by "Suvankar Chakraborty" is right. In addition, thickness of the film is also depends on the viscosity of the precursor. The advisable annealing temperature for Quarts is 700 C. Beyond this, cracks will be developed in the thin layers. These are some basic parameters. Other parameters depend on apparatus and materials.

1. Multiple coating won't work as Srinivasa mentioned. It will just wash away previous layer.

2. Since film thickness changes with both rpm and solution concentration/viscosity, it will be difficult to predict by others who haven't made films of the same materials. As a preliminary study, you should make a series of films. You can either vary concentration of material in solution keeping rpm constant, or vary rpm (e.g. 500-3000 rpm) keeping solution concentration constant. Then measure the thickness of these films. This preliminary results will help you to predict what the best rpm/concentration is for a desired thickness. Also annealing reduces the thickness of the films and the extent of reduction in thickness has also to determined experimentally.

3. Polymer films are often blow dried with nitrogen/air to remove some solvents before putting the film in the vacuum oven for full drying and annealing.

4. You need to know if your material degrades at such a high temperature before you anneal.

-> choose proper solvent whose viscosity is low (not high).

-> In spin coating usually solutions of range 1 ml to 10 ml is taken depending on the thickness required.

-> Too much (or very high) spin speed (RPM) and spin time decreases the thickness of the film..

-> prefer low spin speed at first and then gradually increase the speed for next step.

-> after each coating u should allow it to dry..

-> after complete deposition process, keep the slides in oven for few mins (time depends on compound chosen) at optimum temperature (temp. depends on the solvent & compounds used) to remove any organic components in deposited films (do this if u donot want organic components in the film).

-> For quartz substrate, annealing above 800 0C leads to the appearance of additional peaks of SiO2 reflections, along with ur sample peaks. This is visible in XRD pattern..

Hi,

2. A result thickness of the thin film deposited by spin coating is a function of the solution viscosity, density, acceleration and final spin rotation and time. Be aware that the solvent used for a solution for spin coating may evaporate while spinning while it should be liquid up to the end of the whole process. Try to induce a saturated vapors of the solvent in the chamber of the spincaoater.

So according to my experience - the proper condition for spin coating of a particular system should be elaborated at the series of subsequent try-check processes.

BTW, the adhesion of the solvent and other components of the solution to the substrate play a critical role. If necessary use an adhesion promoter.

1. At the LCD technology usually a single layer is deposited . This is because application of a solution on a ready made original layer may induce their damage by solving/softening.

Best regards,

Wiktor

Hi, I absolutely agree that the thickness of your spin-coated samples is a function of rotation rate, concentration and viscosity of the solution, postdeposition temperature treatment and so on (maybe I missed something). We use spincoating for preparing Nb2O5 film from NbCl5. We deposited films with thickness 35-45 nm at a spin rate of 2500 - 3000 min-1 for 30 s. For increasing the thickness we run the spin-coating process few times. Prior to each deposition we dry the layer by hot air. Our experiments have shown that the films quality deteriorates at lower spinning rate. I am sending you one of our paper in the case if you are interested in more details about the spin-coating

Thanks to all for responding and for giving their valuable suggestions.

Dr. Babeva, thank u for attaching ur research paper.

Depends on the thickness, the coating should be made. I would rather have the RPM as from 4000 to 6000 for 5 or 6 secs to begin with. And definitely I would dry the slides after each coating. The mentioned data are not approximate, though average statistically.

To all these good advices I will add only one more: be aware of the lab conditions i.e. temperature and humidity in the room as it may influence the procedure

Most of the advise is good especially on the spinning parameters. A few details are needed like the shape and size of the quartz substrate. These parameters affect the spin conditions. Large plates need to spin more slowly. In the past I have used circular quartz plates (no corner effects). The Quartz anneal up to 1000C should be OK from the point of view of the Quartz itself (Quartz is used extensively in annealing furnaces), but the annealling proceedure is an art unto itself because you can have a differencial in expansion between the film and the substrate which can cause stress and cracking in the film. Film adhesion comes into play. A good rule is ramp up and ramp down the temperature slowly.to allow adequate stress relief.

1. It depends on how much thickness you do want. You have to calibrate first.

2. The RMP is generally 1000- 3000. It also depends on the viscous property of your solvent. Time is 10-20 seconds generally.

3. In case of multilayer deposition you have to pre-heat the film at some lower temperature for few minutes(10-15).

4. In case of quartz (or else) substrate do check the melting point. Do the post growth annealing at lower temperature than that. You can anneal quartz at 1100 C.

Best Wishes..

Parameters may be taken in the range like no of coatings (range 10-100 ), rpm (500-10000).

Every thing is trial - error method. Though the same material, just try it from 1 deposit to 2, 3 doposit one after other after drying. RPM and time of rotation start from 700 rpm step-by-step till 1500. fix time for 60 minutes. RPM depends upon the viscosity of ur solution. Annealing too try as 200, 400, etc with diff timings. Research is not as like learning and doing. Its most often do and learn method.

Dear Narang, according to my work in spin coating technique I want to answer your questions as following:

1. The number of layers that you want.

2. The RPM rate and time rotation are depend on the thickness you need. If you prepare thin layers the RPM should be 3500 and above and time rate should be 30s. You can change them according to the viscosity of the solution.

3. Yes, you should dry the film after each coating until you finish all layer. To get nice result you should heat the substrate before coating to make sure the film cover all the substrate.

4. you can annealing you film at 1100 but for 1 or 2 hours. long annealing time may affect the substrate.

Dear Narang,

From my experiments, I notice that the time between deposition and drying of thin films should be very short (few seconds) for a continuous and smoothly surface. So, be sure that near of your spin-coating apparatus is a source of drying.