Stress - mediated solid phase epitaxial re - growth of a-Si at annealing of Si:Mn
|Andrzej Misiuk 1, Adam Barcz 1, Artur Wnuk 2, Jadwiga Bak-Misiuk 3|
1. Institute of Electron Technology (ITE), al. Lotników 32/46, Warszawa 02-668, Poland
Ion-beam-induced formation of amorphous silicon (a-Si) and its solid phase epitaxial re-growth (SPER) during annealing of implanted single crystalline silicon (c-Si) have attracted significant interest because of their importance for fabrication of Si devices . SPER of a-Si depends, among others parameters, on processing temperature (HT) and pressure (HP) .
The structures prepared by implantation of Cz-Si with some metallic ions and annealed under HP have been reported to indicate interesting magnetic properties, of possible application in spintronics [3 - 5]. The HT - HP treatment of Si implanted with manganese (Si:Mn) affects its microstructure and magnetic ordering in a specific way [3, 5]. This motivated us to perform detailed investigation of the effect of HP applied at annealing of Si:Mn on its properties, related to SPER of a-Si.
Mn+ ions were implanted at room temperature with doses, D = 2x1015 – 1.2x1016 cm-2 and energy, E = 160 keV, into (001) oriented p–type Czochralski grown silicon (Cz-Si). The Si:Mn samples were processed in Ar atmosphere for up to 10 h at up to 1400 K under HP up to 1.2 GPa. The depth distribution of Mn was investigated by Secondary Ions Mass Spectrometry (SIMS). Photoluminescence (PL) and X-Ray measurements were applied to determine the sample microstructure.
Mn+ implantation produces a-Si near the implanted ions range (Rp = 140 nm), up to about 0.25 mm depth. The PL spectra of as-implanted samples are featureless confirming complete amorphisation of the near – surface layer of Si:Mn.
SPER of a-Si is strongly dependent on implanted dose, on HT, processing time (t) and HP. Processing of the Si:Mn samples (D = 2x1015 cm-2) for t = 1 h at 870 - 1000 K, both under 105 Pa and 1.2 GPa, results in the sharp minimum in Mn concentration at ~ 150 nm depth below the surface. SPER results in the movement of the a-c interface towards the surface. Since the solubility of Mn in c-Si is low, this re-crystallization expels Mn atoms from the re-growth region and the a-c interface moves toward the surface. The excess Mn atoms are accumulated at the a-c interface and so, depending also on the D value, the Mn concentration reach to a point, at which re-crystallization can not push longer excess Mn out of c-Si.
In the case of processing at 1070 – 1170 K, the a-Si is converted in part into polycrystalline material (as confirmed by X-Ray and PL measurements) while manganese silicides (such as Mn4Si7 ) are formed.
In Si:Mn prepared by high dose implantation (D ³ 1x1016 cm-2) and processed at ³ 1170 K, the effective out-diffusion of Mn to the Si:Mn surface increases with uniform stress applied; SPER and the Mn distribution are strongly dependent on p and t.
Our results help in understanding the mechanisms of SPER and, in the particular case of Si:Mn, suggest a new route to prepare, by the appropriate HT – HP treatment, the specific Si-Mn materials belonging to the Diluted Magnetic Semiconductor family.
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Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Andrzej Misiuk
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth
Submitted: 2007-01-09 10:23 Revised: 2009-06-07 00:44
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