In my opinion glass and SnO2 are two materials with an acidic character, this results in poor adhesion. Try to modify glass surface prior to SnO2 coating with 3-aminipropyltriethoxysilane, to add an basic character to the glass surface. This is very popular coupling agent.

According to me, you need to heated the substrate from 300-400C° during deposition for better adhesion.@anabil Dey

Related to the two. answers, I would expect that thorough cleaning is crucial. My personal favourite (but this comes from metal evaporation on glass): Mechanical cleaning with soap/water and wiping with as much force as possible; ultrasound with the usual sequence of solvents (directly poured from their container, as pure as possible), e.g. dichloromethane, then acetone, then isopropanol, then water - maybe acetone and water suffice. Then chemical oxidation, i.e. nochromix in H2SO4 (please not H2O2+H2SO4!), or oxygen plasma, or ozone. I would guess the last step can be replaced by heating in air, as suggested by Noor Mohammad Khan

Very important is keeping everything as clean as possible, the usual contaminants are dust particles or organic molecules/layers.

One of the most common issues is insufficient substrate cleaning. Make sure your glass substrate is thoroughly cleaned with solvents (e.g., acetone, ethanol, deionized water) and possibly plasma or UV-ozone treatment to remove organic contaminants and improve surface energy.

Glass is chemically inert and may require surface activation (e.g., silanization or treatment with a surfactant) to enhance adhesion of SnO₂ nanoparticles.

Without proper nucleation sites, SnO₂ may prefer to grow in the solution rather than on the surface. You might try applying a seed layer or modifying the surface roughness.

Some types of glass have coatings (e.g., hydrophobic layers) that may hinder adhesion. Make sure the glass is plain and uncoated.

Yana Suchikova , I have often experienced that even ultrasound cleaning, and even starting with chlorinated solvents before moving to acetone, was insufficient due to strongly adhering "stuff" (I guess thick organic layers). Hence I recommend to use soap+water+very strong rubbing as a first step.

I have experienced when everything had been done correctly i.e. after cleaning glass, properly mixed precursors, at optimised conditions, the SnO₂ films can still did not stick if the surface isn’t treated rightly. So I suggest starting with serious cleaning, use soap first, then rinse with water, you should do real hard scrubbing. Then continue with your usual solvent steps. As for the hydrothermal part, adjust your temp to around 150–200 °C, increase its timing to between (6–12 hours), and make sure that the glass is placed face-down in the solution. After you've done that, you should rinse the glass gently, and allow it to dry slowly (no rushing), and anneal carefully at 400–500 °C to really grow the film in.

Quick Troubleshooting Steps:**

✔ **Check cleanliness** of the substrate.

✔ **Optimize deposition parameters** (temp, pressure, power).

✔ **Post-anneal** the film (if not already done).

✔ **Test different pre-treatment methods** (plasma, chemical).

Clean the glass thoroughly using a standard cleaning procedure:

• Rinse with deionized (DI) water.
• Ultrasonic cleaning in acetone and isopropanol.
• Dry with nitrogen or hot air.
• Optionally, use UV-ozone or plasma cleaning to remove organic residues.

Causes of Poor SnO₂ Adhesion on Glass & Solutions

1.Surface Contamination:

Residual oils or particles on the glass surface can hinder adhesion.

• Solution: Clean the substrate using solvents like acetone and ethanol, followed by deionized water. Techniques such as plasma treatment or UV-Ozone can further enhance surface wettability and adhesion. 2. Thermal Expansion Mismatch: Differences in thermal expansion coefficients between glass and SnO₂ can induce mechanical stress during cooling, leading to film delamination.
• Solution: Implement a slow cooling rate post-annealing or minimize temperature differentials during processing. 3.Inadequate Processing Temperature:Too low temperatures may result in poor crystallinity, while excessively high temperatures can produce brittle or cracked films.
• Solution: Optimize annealing or deposition temperatures, typically within the 400–600°C range for SnO₂, depending on the specific method employed. 4.Chemically Inert Glass Surface:Glass surfaces may lack sufficient hydroxyl (-OH) groups, reducing chemical bonding with SnO₂.
• Solution: Activate the glass surface using plasma treatment or strong acids (e.g., H₂SO₄/H₂O₂) to introduce hydroxyl groups and enhance chemical interaction. 5.Absence of a Seed Layer:Without a seed or buffer layer, SnO₂ crystals may not adhere well to the glass substrate.
• Solution: Apply a thin initial layer of SnO₂, TiO₂, or ZnO to promote nucleation and improve film adhesion.