High-temperature diamond-like Si-based ferromagnet with self-organized superlattice distribution of Mn impurity

Abstract

Crystal structure of Si:Mn diluted magnetic semiconductor with Curie temperature 500К, deposited from laser plasma on GaAs(100) substrates, was investigated by high-resolution transmission electronic microscopy and diffraction. This laser technology allows to reach of solid solution of 15%Mn in silicon with high electrical and full magnetic activity, conservation of diamondlike crystal structure and epitaxy growth of Si:Mn. The self-organized formation of superlattice structures takes place with period equal to trebled distance between nearest atomic layers (110) and interval between layers (110) which are doped by Mn atoms and oriented along direction of growth of 50 nm Si:Mn film.To necessity to fill a gap between microelectronics and magnetic electronics J. K. Furdyna 1 had paid attention in 1988. The first ferromagnetic so-called diluted magnetic semiconductors (DMS) on basis of compounds II-VI 2,3 and III-V 4 were synthesized in 90s of last century. Now there are a lot of publications devoted to epitaxy layers of DMS Ga 1-x Mn x As with atomic fraction of Mn impurity x≈0.05 and perfect crystal structure grown up at low temperatures ≈250°С by molecular beam epitaxy (MBE). However maximum attained Curie point of this ferromagnetic Ga 1-x Mn x As 170К is below room temperature 5. Especially interesting DMS are on basis of elementary silicon semiconductor because of their compatibility with the most widespread silicon technology. Numerous attempts of synthesis ferromagnetic DMS on basis of silicon, doped by 3d -impurities, were undertaken [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . The problem of synthesis such DMS is even more difficult than in case of III-V compounds because of the close to equilibrium solubility of middle 3d -iron group elements impurities in Si is about 10 16 cm -3 on two order more low, these impurities mainly occupy position of interstitials and show donor properties 23,24 . Though, according to regularities in recharge levels of such impurities in diamond like semiconductors, the most preferable analogue of manganese in compounds III-V in silicon is iron 18,25 , the greatest successes have been reached by doping of Si also by manganese. Encouraging preconditions have appeared still in 1993 6 . The ferromagnetic behavior up to 320К according to field dependence of magnetization was observed for periodic structure of 20 nm layers of Si and Mn fabricated by electron beam vacuum evaporation (EBVE). The layers of DMS Si:Mn with about 5% Mn and T c =70К, according to abnormal Hall effect (AHE), were produced on silicon substrates (Si:Mn/Si) at 300°С by MBE technology as well as in case of DMS on basis of compounds III-V 7 . The single crystal layers of Si:5%Mn/Si were made by EBVE method 9,10 with ferromagnetism on magnetization data up to 400К. However DMS's rather high resistivity (0.25-2.5) Ohm·cm with semiconductor dependence ρ=ρ 0 exp(E a /kT) means absence of degeneration of semiconductor. The degeneration is necessary for realization of the most probable in DMS fe...

Electron diffraction study of a high-temperature diamond-like silicon ferromagnet with the self-organized superlattice distribution of manganese impurity

“…The Mn impurity in it has the high electric and magnetic activity. The direct evidence of the ordered structure of the layers of the diluted magnetic semiconductor Si:Mn/GaAs was presented earlier [3], which was obtained using high resolution transmis sion electron microscopy and local electron diffrac tion. The self organized formation of the superlattice structure with the period of the triple distance between the nearest atomic layers (110) and the interval between layers (110) doped with Mn atoms and ori ented along the growth direction of the Si:Mn film was found.…”

“…There were repeated attempts to synthesize the ferro magnetic diluted magnetic semiconductor on the basis of silicon doped with 3d impurities [3]. The highest temperature diluted magnetic semiconductors on the basis of diamond like semiconductors were synthe sized in our laboratory by pulse deposition from a laser plasma [3][4][5][6]. It was demonstrated that such strongly nonequilibrium technology can be used to synthesize thin (30-200 nm) GaSb:Mn and InSb:Mn layers with the Curie temperature T C above 500 K and Ge:Mn, Si:Mn, and Si:Fe layers with the Curie temperatures of 400, 500, and 250 K, respectively, on single crystal GaAs, Si, and sapphire (Al 2 O 3 ) substrates.…”

“…DOI: 10.1134/S0021364014230027 the same 500 nm Si:Mn layers on GaAs(100) thinned out in the layer plane. We also applied the technology of the deposition from laser plasma of layers of the diluted magnetic semiconductor Si:Mn with 15% Mn on single crystal GaAs substrates with the orientation (100) described in [3][4][5][6]. High resolution transmission electron microscopy and local electron diffraction measure ments of the (110) cross section or thinning of (100) Si:Mn layers in the 〈110〉 and 〈100〉 directions were performed on a JEM 2100F device (JEOL).…”

“…The hole concentration p ≥ 7.5 × 10 20 cm -3 corresponds to the explicitly degenerate semimetal state of silicon and means that no less than 10% of impurity manganese atoms are electrically active at 293 K. As in [3][4][5][6], the ferromagnetic resonance spectrum at room tempera ture consists of several resonance absorption peaks, which merge into a single relatively narrow peak at a decrease in the temperature. According to the ferro magnetic resonance data at 93 K, under the assump tion that the manganese spin is 5/2, the value N Mn = 8 × 10 21 cm -3 almost coincides with the X ray spectral value of 15% Mn (N Mn = 7.5 × 10 21 cm -3 ); i.e., the entire amount of manganese is magnetoactive.…”

“…Diluted magnetic semiconductors on the basis of the diamond like silicon semiconductor are of particular interest for applications because of the com patibility with the most widespread silicon technology. There were repeated attempts to synthesize the ferro magnetic diluted magnetic semiconductor on the basis of silicon doped with 3d impurities [3]. The highest temperature diluted magnetic semiconductors on the basis of diamond like semiconductors were synthe sized in our laboratory by pulse deposition from a laser plasma [3][4][5][6].…”