Copper sulfide – Preparation of precursor solutions

Copper sulfide – Preparation of precursor solutions
Chemical solutions for CuS deposition

During my postdoctoral stay at the Physics Institute of BUAP one of my duties is the deposition of thin-film semiconductors. At this laboratory IFUAP-205, I have been doing chemistry activities like the preparation of precursors solutions. In Fig.1, I want to show you three vials with solutions of different molar concentrations used for copper sulfide thin-film deposition: Copper chloride (CuCl2), Sodium hydroxide (NaOH) and Thiourea (NH2CSNH2). These solutions were dissolved in deionized water and stirred using a magnetic plate.

What I have learned here is that solutions should be prepared one day before or in the moment of the chemical deposition. I think this methodology has the advantage of saving precursor material (salt) but its disadvantage is that the chemical deposition of copper sulfide takes more than 1 hour in preparation.

Look inside the vial (Fig. 1) you will see a little magnet which spin to mix the solution.

Fig.1 Precursors solutions for CuS chemical deposition

In Fig. 2, I show you copper chloride salt inside the analytic balance. The easy way to prepare a solution of a certain concentration is to use a volumetric flask (100 ml, 250 ml or up to 1000 ml). Here we will add the corresponding amount of salt and dissolve it in deionized water (some salts are not soluble in water ). Let me be more specific:

How to prepare 100 ml of 1M Copper Chloride?

Fig.2 Weight the Salt of copper CuCl2 using balance.

Material:

  • Equipment:
    • Analytical balance (Calibrated)
    • Magnetic stirrer (You can mix the solution by hand )
  • Chemical:
    • Copper chloride: CuCl2
    • Deionized water: H2O
  • Accessories
    • Spatula
    • White plastic container (Chalupa)
    • Volumetric flask of 100 ml

Methodology

When you look at the supplier’s datasheet of copper chloride (Click this link) you will find the molecular weight of the CuCl2 salt: 134.45 g/mol. This is the value you will need to prepare the solution. If you dissolve 1 mol of CuCl2 in water then you get a 1 M concentration solution. In other words, if you dissolve 134.45 grams in 1 liter of water (solvent) then 1M concentration solution is achieved. Here, we can use the following relation to calculate the amount of CuCl2 salt for 100 ml of solution.

  • 1 M = 1000ml = 134.45 g of CuCl2
  • 1 M = 100 ml = 13.4 g of CuCl2

Using the following relation. I will need to weigh 13.4 g of CuCl2 on the analytical balance, this salt is put on the volumetric flask (100 ml) and finally, add deionized water up to the mark of 100 ml. This solution will be stirred using the stirrer plate to get the most homogeneous possible solution, during the required time.

Do you have any doubts about this procedure? Please comment below if you have any.

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