For preparation of reconstructed Si(hkl) substrates, we generally employ direct current (DC) heating method in ultra-high vacuum (UHV) condition. In this case, initially we degas the Si(hkl) substrates at ~ 600 0C for 12-15 hours. Thereafter, we perform repetitive 'flash heating' at ~ 1200 0C for 30 sec. It consequences formation of very large ( 1μm × 1μm), well-ordered and atomically smooth reconstructed template.
Can we use such methods (inside the molecular beam epitaxy (MBE) chamber) for preparation of reconstructed Ge(001), Ge(111) substrates ?
Dear Anjan,
This will be difficult in my opinion. I would recommend few cycles of Ar+ ion sputtering at 0.75 keV at a partial pressure of Ar of 1 10-5 mbar followed by annealing at 970 K at UHV by direct heating method after degas.
As an alternative way is wet etching using aggressive chemistry: see e.g. here: http://iopscience.iop.org/article/10.1088/0957-4484/22/14/145604/meta, however it was not worked properly in my case.
Best wishes
Wojtek
Direct Hearing is possible, but be careful with copper, it will alloy with Ge. Also the temperature has to be controlled very carefully. Wet chemical etching in advance is necessary as suggested by Wojciech.
Dear Mr. Wojciech Koczorowski and Mr. Christian Pettenkofer,
I agree with you about the conventional cleaning procedure of native GeOx layer from the Ge(hkl) substrates.
But what is the drawback for preparing an ultra-clean Ge(hkl) template using the 'flash heating' method at elevated temperature (~ 1200 deg C) ?
How it would affect the morphology and crystalline quality of the thin film for growth on it ?
With regards,
Anjan
I agree with Christian. The Ge crystal will be burned first, than cleaned ... .
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