ISSN 20751133, Inorganic Materials: Applied Research, 2014, Vol. 5, No. 2, pp. 133–137. © Pleiades Publishing, Ltd., 2014. Original Russian Text © N.N. Gerasimenko, A.N. Mikhailov, V.V. Kozlovskii, O.A. Zaporozhan, N.A. Medetov, D.I. Smirnov, D.A. Pavlov, A.I. Bobrov, 2013, published in Perspektivnye Materialy, 2013, No. 8, pp. 18–23.
MATERIALS OF ELECTRONIC
Structure and Luminescence of Silicon Irradiated by Protons N. N. Gerasimenkoa, b, A. N. Mikhailovc, V. V. Kozlovskiid, O. A. Zaporozhana, N. A. Medetove, D. I. Smirnova, b, D. A. Pavlovf, and A. I. Bobrov f a
National Research University of Electronic Technology, Moscow, Russia Lebedev Physical Institute, Russian Academy of Sciences, Moscow, Russia c Research PhysicalTechnical Institute (NIFTI), Nizhni Novgorod State University, Nizhni Novgorod, Russia d St. Petersburg State Polytechnical University, St. Petersburg, Russia e Kostanai PhysicalTechnical University, Kostanai, Kazakhstan f Nizhni Novgorod State University, Nizhni Novgorod, Russia email:
[email protected];
[email protected];
[email protected];
[email protected];
[email protected];
[email protected] b
Received March 19, 2013
Abstract—The temperature dependence of photoluminescence (PL) in the range 8–300 K is studied for sin gle crystalline silicon irradiated by protons at high temperatures. It is shown that the samples with ptype con ductivity display intense PL in contrast to the samples with ntype conductivity, which do not display photo luminescence. Studies using highresolution transmission electron microscopy (TEM) have shown that pho toluminescence exists until crack formation and splitting of the irradiated layer. The rodlike defects {113} formed during irradiation transform into residual fragments of dislocation structures. Keywords: rodlike defects {113}, proton irradiation, photoluminescence DOI: 10.1134/S2075113314020063
INTRODUCTION Interest in properties of single crystalline silicon irradiated by protons has risen in recent years because this material displays some effects which can serve as a basis for investigation of the origin of wellknown interstitial complexes in silicon referred to as rodlike defects [1, 2]. These extended interstitial complexes form in {113} planes consisting of intrinsic silicon atoms Siin (Fig. 1). These defects are present and are
easily distinguished in silicon samples implanted with boron ions [3]. Rodlike defects of interstitial type attract attention, first of all, in view of development of such an advanta geous direction as defect engineering, aimed at designing functional elements of electronic and elec tronoptical devices using structural defects. The configuration and structure of these defects are of interest to researchers and developers also in light of
0.4 µm
(а)
1.0 µm
(b)
+
Fig. 1. (a) Defects in silicon after irradiation by H 2 ions: irradiation dose D = 2 × 1016 cm–2, energy of implanted ions E = 500 keV, +
irradiation temperature Tirr = 450°C; (b) defects in Si at the depth of ≅3.5 μm after irradiation by H 2 : D = 10 × 17 cm–2, E = 500 keV, Tirr = 600°C.
133
134
GERASIMENKO et al. (a)
(b) 9K 24 K 42 K 61 K 81 K
120 100 80
101 K 121 K 151 K 200 K 250 K 300 K
60 40 20 0 1100
9K 24 K 42 K 61 K 81 K
40 PL intensity, arb. units
PL intensity, arb. units
140
30
101 K 121 K 151 K 200 K 250 K 300 K
20 10 0
1200
1300 1400 1500 Wavelength, nm
1600
1100
1200
1300 1400 1500 Wavelength, nm
1600
+
Fig. 2. Photoluminescence spectra of KDB10 sample: (a) after single irradiation (H 2 ions, 150 keV, Tirr = 500°C, j = 1 mA/cm2, D = 1 × 1017 cm–2); (b) after double irradiation at the temperature Tirr = 500°C ((1) H+ ions, 150 keV, j = 5 mA/cm2, D = 1 × +
1017 cm–2; (2) H 2 , 150 keV, j = 1 mA/cm2, D = 1 × 1017 cm–2) measured at different temperatures at laser excitation with the wavelength λexc = 488 nm.
intense PL, which is displayed owing to their presence and manifests itself up to room temperature. The first studies of this emission were performed in light of ideas of their quantumdimensional character (quan tum wires) [4]. Thereafter, it was really shown that for mation of rodlike defects observed by TEM in samples of single crystalline silicon implanted with boron ions in some irradiation regimes resulted in intense lumi nescence. However, as the irradiation dose increases [3], i.e., as the concentration of interstitial boron atoms increases, these defects transforms into Frank dislocation loops, which is accompanied by extinction and elimination of luminescence. The subject of this work is study of PL and structure of crystalline silicon irradiated by protons. EXPERIMENTAL A series of experiments was performed on irradia tion of single crystalline silicon plates having ntype (KEF4) and ptype (KDB10) conductivity with pro tons of medium energies. Radiation treatment was carried out in the regimes of single and double irradiation. The single irradiation of the samples was performed in the following regime: + H 2 ions with the energy 150 keV were implanted at the temperature of irradiation Tirr = 500°C, the density of the beam was j = 1 mA/cm2, and the dose was D = 1 × 1017 cm–2. The double irradiation was applied since it was earlier discovered [7] that the structure of the irradiated layer in total displayed mutual impact of both treatments with independent result. The follow ing parameters were used for the first (1) and second (2) radiation treatments: Tirr = 500°C; (1) H+ ions,
150 keV, j = 5 mA/cm2, irradiation time tirr = 55 min, +
D = 1 × 1017 cm–2; (2) H 2 , 150 keV, j = 1 mA/cm2, tirr = 6 h 37 min, D = 1 × 1017 cm–2. The temperature was controlled via heating of a chip header. At the given parameters of a beam, irradiation did not lead to a considerable rise in temperature of the sample. The spectral optical characteristics of the irradiated samples in the near infrared (IR) range were studied by the PL method in a wide temperature range (9–300 K) at the laser excitation with the wavelength λexc = 488 nm. Structural faults and defects caused by integration of accelerated particles of the samples were analyzed in the specially prepared cross sections by highresolu tion TEM on a JEOL JEM2100F electron micro scope. RESULTS AND DISCUSSION In the case of a single irradiation of the single crys talline silicon by protons [5, 6], luminescence was observed in IR region of the spectrum with a dominant band at the wavelength of 1390 nm (Fig. 2a). The prin cipal feature of these results is the fact that intense luminescence manifested itself only on ptype con ductivity samples alloyed with boron (KDB10) and was not observed in the entire temperature range used in the studies of the ntype samples alloyed with phos phorus (KEF4). In the PL spectrum of the samples after double irradiation, several bands are distinguished, including those at 1300 and 1390 nm (Fig. 2b). A typical feature should be noted from comparison of the spectra in Figs. 2a and 2b. At the single irradiation, the intrinsic emission band of silicon (~1100 nm) was considerably weaker than after the double irradiation. This can
INORGANIC MATERIALS: APPLIED RESEARCH
Vol. 5
No. 2
2014
STRUCTURE AND LUMINESCENCE OF SILICON IRRADIATED BY PROTONS
135
777.61 nm
941.16 nm
200 nm
(а)
530.19 nm
(b)
200 nm
0.5 µm
(c)
Fig. 3. STEM images of cross sections of singularly irradiated samples: (a) KEF4; (b) KDB10; (c) STEM images of underlying silicon layers in singularly irradiated KDB10 sample.
point to the fact that, during the single irradiation, a great amount of nonradiative recombination centers were introduced, which disappeared after the double irradiation. To interpret the obtained data, structural faults and defects were studied in the irradiated samples. Com parison of the images obtained in the scanning TEM (STEM) regime for the samples containing boron and phosphorous impurities (the first one demonstrated intense emission, while there was no emission from the second one) showed that, in both types of samples, there was a distinct boundary separating a damaged layer (dark contrast) from the main substrate. The thickness of the main damaged layer in the samples was ~780 nm, which corresponded to the projected track length of protons with a given energy. The smart cut effect of the damaged layer was observed in all sam ples alloyed with boron or phosphorous. The main dif ference of the irradiated KDB10 from KEF4 sam ples is that the contrast of the damaged layer is less uni form, the propagation depth and the number of extended defects in the lower crystalline layer are higher, and the second defect layer is more distin guished at a depth of ~1.8 μm (Fig. 3). According to [8], the processes of formation and restructuring of rodlike defects display a distinguished temperature dependence. Thus, for the chosen irradi ation conditions, the highresolution TEM images INORGANIC MATERIALS: APPLIED RESEARCH
Vol. 5
shown in Fig. 4 contain defects typical of the processes of restructuring observed in [8] for the irradiation tem perature of 600°C associated with implantation of protons with the energy of 5 keV, and in [9] in the experiments on studies of radiationenhanced diffu sion of boron under irradiation with the energy of 40 keV and the following annealing at 815°C. The rod like defects in the KEF4 sample were more extended than in the KDB10 sample. The observed defects had greater transverse dimension in the KDB10 sample. Preliminary experiments on microdiffraction of electrons on similar samples [5, 6] showed that the structure of the found defects can be interpreted as hexagonal. In this view, it should be noted that the hexagonal structure was observed not for the first time on silicon subjected to severe impacts. In particular, this structure was formed at the front of crystallization of a silicon layer amorphized by ion bombardment during its recrystallization under continuous irradia tion (“effect of great doses”) [10]. In order to continue the detailed studies of the physical reasons for intense luminescence arising in silicon irradiated by protons, it is necessary to consider some special features of interaction of the implanted hydrogen atoms with the matrix atoms (silicon atoms) in the framework of the obtained results. These special features, in our opinion, reduce to the follows. No. 2
2014
136
GERASIMENKO et al. (а)
(b)
(–111)
(–110)
(–113) (001) (–11–3)
(–11–1)
5 nm
5 nm
(001)
(–110)
Fig. 4. Highresolution TEM image after Fourier processing of rodlike defects in singularly irradiated samples: (a) KEF4; (b) KDB10 in comparison with the image of rodlike defect (in inset [9]) in the silicon sample ionimplanted with Si+ ions and annealed at 815°C. Arrows point to directions of atomic rows belonging to respective planes.
1. Hydrogen atoms form chemical bonds with sili con atoms, both with broken bonds on atoms in equi librium positions in sites of the crystal lattice and with knockedout atoms, i.e., with Siin interstitial atoms. In the first case, the known vacancy defects, in particular, bivacancies, are decorated, which is observed by the drop in intensity of the absorption band in the IR spec trum of silicon irradiated at the wavelength 1.6 μm [11]. The same decoration was found after annealing of multivacancy complexes (VV centers) implanted by ion bombardment in silicon. Decorated multivacancy defects can be reduced by additional irradiation by protons in the regimes when VV centers are not integrated directly by proton bom bardment [12]. In other words, the multivacancy com plexes formed in the initial samples under bombard ment by B+ and heavier ions are decorated by hydro gen atoms at the first irradiation by protons and are eliminated from observation; however, during the repeated irradiation by protons at room temperature, the vacancy complexes appear again [13]. 2. Interstitial Siin atoms (components of Frenkel pairs formed during irradiation) also form chemical compounds with hydrogen atoms, which appear as resonance bands in the absorption IR spectrum of sil icon irradiated by protons in the range of 4.5–5.5 μm. The spectral distribution of these bands can be com pared with IR absorption spectral bands of gaseous silanes [14]. Probably, these compounds are responsi ble, first of all, for realization of the smartcut effect, which was described for the first time in [15]. 3. The smartcut effect is observed only during ion implantation of hydrogen (or helium) atoms, but it is not observed during implantation of oxygen and nitro gen, i.e., at formation of buried layers of silicon oxide and nitride. Probably, it is associated with the fact that in the latter case no gaseous components form which could congregate in the area of maximum stresses of the plate and cause its chipping.
CONCLUSIONS Irradiation with protons or ions of molecular hydrogen is, in our opinion, the best way of integration of rodlike defects, which are associated with intense PL of the samples. Asserting unambiguously that the sources of luminescence are rodlike defects is possible only if their generation in the boroncontaining sam ples is reliably proved. However, it should be noted that, during formation of such defects up to smart cut ting, other defect complexes form, which in some cases demonstrate hexagonal structure. This allows consideration of these defective precipitates as sources of intense PL, provided that in this case (for hexagonal phase) another energy zone structure of silicon can form and, probably, provide direct emission transi tions. Undoubtedly, the future works on use of rodlike defects for formation of intense PL sources in silicon + will be most efficient for H 2 proton irradiation. How ever, the mechanism of formation of emitting centers, their origin, and optimal conditions of their formation should be studied additionally. ACKNOWLEDGMENTS We are grateful to D.I. Tetelbaum for discussion of the materials in this article. REFERENCES 1. Kalinin, V.V., Aseyev, A.L., Gerasimenko, N.N., Obodnikov, V.I., and Stenin, S.I., The formation of defects in Si under the radiation enhanced diffusion conditions, Radiation Effects, 1980, vol. 48, pp. 13–18. 2. Eaglesham, D.J., Stolk, P.A., Grossmann, H.J., Haynes, T.E., and Poate, J.M., Implant damage and transient enhanced diffusion in Si, Nucl. Instr. Meth. Phys. Res. B, 1995, vol. 106, pp. 191–197. 3. Pan, G.Z., Ostroumov, R.P., Ren, L.P., Lian, Y.G., and Wang, K.L., Silicon light emissions from boron
INORGANIC MATERIALS: APPLIED RESEARCH
Vol. 5
No. 2
2014
STRUCTURE AND LUMINESCENCE OF SILICON IRRADIATED BY PROTONS
4.
5.
6.
7.
8.
9.
implantinduced defect engineering, J. NonCrystal. Solids, 2006, vol. 352, pp. 2506–2509. Gerasimenko, N.N., Dzhamanbalin, K.B., and Medetov, N.A., Samoorganizovannye nanorazmernye struktury na poverkhnosti i v ob”eme poluprovodnikov (SelfOrganized NanoSized Structures on the Surface and in Volume of Semiconductors), Almaty: LEM, 2002. Gerasimenko, N.N., Kozlovskii, V.V., and Mikhay lov, A.N., Radiation defects as nanocrystals in bulk crystalline silicon, Proc. 25th Int. Conf. on Defects in Semiconductors (ICDS25), St. Petersburg, 2009. Gerasimenko, N.N., Ionic synthesis of silicon nano structures, Tezisy IV Vserossiiskoi konferentsii “Fizicheskie i fizikokhimicheskie osnovy ionnoi implantatsii” (Proc. 4th AllRuss. Conf. “Physical and PhysicoChemical Foundations of Ionic Implantation), Novosibirsk, 2012. David, M.L., Oliviero, E., Ratchenkova, A., Gerasi menko, N.N., Declemy, A., Barton, J.F., van Veen, A., and Beaufort, M.F., Defects created by helium implan tation at different temperatures in silicon, Solid State Phenom., 2002, vol. 82–84, pp. 285–290. Arakawa, K., Saitoh, K., Mori, H., and Ono, R., Com parison among the formation processes of extended defects in Si under irradiation with lowenergy H+, He+ ions and high energy electrons, Nucl. Instr. Meth. Phys. Res. B, 2003, vol. 206, pp. 76–80. Eaglesham, D.J., Stolk, P.A., Gossmann, H.J., and Poate, J.M., Implantation and transient B diffusion in
INORGANIC MATERIALS: APPLIED RESEARCH
Vol. 5
10.
11.
12.
13.
14.
15.
137
Si: The source of the interstitials, Appl. Phys. Lett., 1994, vol. 65, pp. 2305–2307. Gerasimenko, N.N., Dvurechenskii, A.V., Romanov, S.I., and Smirnov, L.S., On effects of large doses of injected into semiconductor iones, Fiz. Tekhn. Poluprovod., 1973, vol. 7, pp. 2195–2199. Gerasimenko, N.N. and Tynyshtykbaev, K.B., Forma tion of radiation defects in silicon contained hydrogen atoms, Fiz. Tekhn. Poluprovod., 1980, vol. 14, pp. 1673– 1676. Fizicheskie protsessy v obluchennykh poluprovodnikakh (Physical Processes in Irradiated Semiconductors), Smirnov, L.S, Ed., Novosibirsk: Nauka, 1977. Vikhrev, B.I., Gerasimenko, N.N., Dvurechenskii, A.V., and Smirnov, L.S., Interaction of hydrogen atoms in silicon with defects, injected by ionic bombardment, Fiz. Tekhn. Poluprovod., 1974, vol. 8, pp. 1345–1348. Korshunov, F.P., Larionova, T.P., Mudryi, A.V., et al., Luminescence of silicon films, irradiated by high energy particles, on sapphire, Trudy IV mezhdunarod noi konferentsii “Vzaimodeistvie izluchenii s tverdym telom” (Proc. 4th Int. Conf. “Interaction of Radiation with Solid”), Minsk: Belor. Gos. Univ., 2001. Gerasimenko, N.N., Rolle, M., Cheng, LiJen., Lee, Y.H., Corelli, J.C., and Corbett, J.W., Infrared absorption of silicon irradiated by protons, Phys. Stat. Sol. (B), 1978, vol. 90, pp. 689–695.
Translated by E. Borisenko
No. 2
2014
