Dear Jen Wang , at first glance your AFM image of the Al substrate shows that it is not a single crystal, domains are clearly visible. So the first thing would be to check the reference of your substrate to be sure it really was Al(100) single crystal.

I have had a look to Goodfellow site and they sell Al(100) single crystals with two conditions: unpolished and polished to 1um (nominal).

Your z-range in the image is 134.8nm so the sample looks like polished.

Unfortunately there is no information in the reference article you cited about the appearance of their substrate to make some comparations. The article also lacks the origin of their Al substrate or any previous polishing treatment.

Al gets oxidised very fast when exposed to air, forming a crust of usually around 2.5-4nm thick and then becomes impermeable to oxigen and stops growing. May be this Al2O3 layer is still on your sample, causing the appearance of polycrystalline domains in the AFM image, and being the source of your problems. It could be also the source of O in your measures and the reason it cost to remove (C can be organic dirt on the surface).

Terraces is what one will expect to see on a clean sample.

If the Al2O3 is there you will have to remove it .

In any case, you could contact directly with the paper´s authors for any extra information, just use the contact email and request politely.

Hope it helps.

Hello Manuel,

indeed, it is a hard work to prepare high quality surfaces.

Sputtering is a very rough tool. To prepare fine surfaces you must select a very flat sputter angle. This attacks especially steps and so on. You only must overcome the binding energy of the atoms. To get flat faces a tender preparation is necessary.

Furthermore, I would use sublimation pumps. A cooled surface (77 K) removes oxygen from the rest gas.

If you don't have a thermocouple, you can build one yourself. Two wires of different metals whatever you have and rough calibration within a boiling liquid seems to be sufficient.

To get a well reconstruction of the surface the annealing temperature must be 10 to 20% below the liquidation.

(I remember to earlier experiments where the sputter to annealing process was repeated daily over 2 month! it is a work for patient people).

With Regard

R. Mitdank

Hello Manuel,

indeed, it is a hard work to prepare high quality surfaces.

Sputtering is a very rough tool. To prepare fine surfaces you must select a very flat sputter angle. This attacks especially steps and so on. You only must overcome the binding energy of the atoms. To get flat faces a tender preparation is necessary.

Furthermore, I would use sublimation pumps. A cooled surface (77 K) removes oxygen from the rest gas.

If you don't have a thermocouple, you can build one yourself. Two wires of different metals whatever you have and rough calibration within a boiling liquid seems to be sufficient.

To get a well reconstruction of the surface the annealing temperature must be 10 to 20% below the liquidation.

(I remember to earlier experiments where the sputter to annealing process was repeated daily over 2 month! it is a work for patient people).

With Regard

R. Mitdank