Surface preparation of MgO
What's the use of MgO
1) Good material for hight temperature processing 2800 C melting temperature
2) low dielectric constant ~10, low loss
Problem of MgO
1) surface reacts with H2O and CO2 after exposing to air
2) impurities like Ca
Preparation steps
1) Cleaving
Normally with charged surface, difficult for scanning
2)Polishing
sub-micron polishing is normally used.
3) Acid etching
This is to remove the additional material left from the polishing. So basically, the sample as received is already etched.
agent: phosphoric and nitric-acid
4) Annealing
Most important part. This is to solve problem 1) and to make atomically flat surface.
| Surface orientation | Duration | Temperature | Step height | Terrace width | Comments | Reference |
| (100) | 2 hours | Tanneal>1000 C, the surface changes remarkably The annealing is better for higher temperature until Tanneal>1350 C | 200-300 nm | Step comes from the Ca atoms diffuse to the surface | Ahmed1996 | |
| (100) | 12 hours | > 700 C can get rid of Mg(OH)2 and MgCO3 >1100C, one can get atomically smooth surface | 4 nm | 700 nm | Aswal2002 | |
| (100) 2 degree miscut | 360 min | 1000 | 3-7 nm | 120 nm | Benedetti2007 | |
| (110) | 10 min | 1000 in 10-7 torr | facet created because of liquid solid interface in the etching | Giese2000 | ||
| (111) | 30 min | 1700 to heal the facet | The surface may reorganize into (332) 1700 C to heal the facet |
Reference
[Ahmed1996] Ahmed F. et al J. of Low Temperature v105, p1343 (1996)
[Plass1998] Plass R. Surface Science, v414, p 268 (1998)
[Giese2000] Giese D.R. Surface Science, v 457, p 326 (2000)
[Aswal2002] Aswal D.K et al. Journal of Crystal Growth, v236, p.661. (2002)
