Hello, do you have any suggestions for cleaning a quartz tube used for hBN growth? The precursor I am using is borazane (H3BNH3). My precursor was placed outside the furnace and, following my initial run, brown residue was found where the precursor entered the furnace. I think this might be amorphous boron, but I am not sure. Additionally, white residue was next to where the precursor was stationed. I have tried heating these areas at 1000C to see if that would remove the residues but was unsuccessful. Would anyone have an acid or base washing method that might help successfully remove the residue? I have attached photos for reference. Thank you.
Try etching it with something that doesn't attack glass (so no HF, KOH or NaOH). You can start with a harmless acid such as acetic acid and see if that already fixes something and then "level up", maybe in the order HCl - H2SO4 - Aqua regia - Piranha etch.
Of course a heavily stuck boron contamination is hard to get off glass since SiO2 and B kinda like each other.
When I do hBN syntheses (from boric acid and urea), I'm able to clean the quartz tube fairly well just using water and ethanol, and soaking paper towels and rubbing them inside the tube (using a metal rod to push the paper towel inside the length of the tube). The physical abrasion works on what the water and ethanol can't just dissolve, with the exception of a few spots.
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