Metallic thin film on sige si substrates 7

Chapter Conclusions Chapter Conclusions 7.1 Conclusions We have studied the desorption of Ge from Si0.8Ge0.2 virtual substrate upon annealing and the behavior of Ni atoms deposited on both clean and H-terminated Si0.8Ge0.2(001) substrates by performing in-situ XPS and ex-situ AFM measurements The behaviors of Ni on H-Si(001) and H-Ge(001) were also similarly studied for a systematic comparison The results obtained are summarized as following: (1) We have identified two temperature regions The Si0.8Ge0.2 substrate remains stable in composition and unchanged in surface morphology between RT and 500oC (region-I) Above 500oC (region-II), Ge at surface region desorbed while Ge in the bulk diffused to surface region, which resulted in a decrease in Ge surface concentration and formation of three-types of holes Our model has suggested that the Ge behavior in region-II can be successfully described by the desorption and diffusion mechanism To avoid the degradation of underlying Si1-xGex substrate, temperatures used for metal deposition and subsequent processing steps should be in region I, i.e., not higher than 500oC (2) Ni reacted strongly with the Si, Ge and Si0.8Ge0.2 substrates to form thin, smooth and continuous NiSi-like, NiGe-like and NiSi0.8Ge0.2-like layers at room temperature on both clean and hydrogen terminated Si, Ge and Si0.8Ge0.2 surfaces, respectively Terminating the surface with hydrogen lead to a smoother morphology, but it did not suppress the reaction of Ni with Si, Ge and Si0.8Ge0.2 surfaces at RT 257 Chapter Conclusions (3) Ni growth on H-terminated Si, Ge, Si0.8Ge0.2 and clean Ge surfaces proceeded via a pseudo-layer-by-layer mode, while it changed to small close-packed island growth mode on the clean Si and Si0.8Ge0.2 surfaces XPS however can not distinguish between these two kinds of growth modes By controlling the growth time, we are able to grow smooth and continuous Ni thin films varying from NiSi-like layer to pure metallic Ni layer (4) At low Ni coverage (≤33%), Ni was protected from oxidation even after more than one year’s exposure to air This can be attributed to the formation of NiSilike and NiSi0.8Ge0.2-like layers, substantiating the existence of bonding between Ni and the Si, Ge & Si0.8Ge0.2 substrates even at the presence of hydrogen At high Ni coverage (≥41%), both Ni and the substrates (Si/Ge) were oxidized on all Si, Ge and Si0.8Ge0.2 substrates A power law can be used to fit the evolution of SiO2/Si and (GeO2+GeO)/Ge ratio as a function of oxidation time (5) Different phases were formed when the ultra-thin Ni film (~2-6Å) grown on hydrogen-terminated Si, Ge and Si0.8Ge0.2 surfaces were annealed from RT to 620oC Above 300oC, two time regions can be identified Region-I (annealing less than 30 minutes) is characterized by a sharp decrease in Ni%, which is attributed to Ni inward diffusion Region-II (annealing longer than 30 minutes) is represented by a steady state Ni/Si, Ni/Ge and Ni/Si0.8Ge0.2 intensity ratio at different temperatures The steady state value of Ni/Si, Ni/Ge and Ni/Si0.8Ge0.2 can be attributed to the formation of respective silicide and germanosilicide phase structures as well as clustering of formed 3D islands during annealing (6) Both rectangular and square islands were formed on Si(001), Ge(001) and Si0.8Ge0.2(001) substrates above 400oC These islands were elongated along the two 258 Chapter Conclusions perpendicular [ 110 ] and [110] directions They grew bigger and taller but decreased in density with temperature The formation of such islands may be explained by the diffusion anisotropy along and across the dimer row Although the crystallinity of silicide, germanide and germanosilicide improved after annealing, the morphology of these films has degraded from being smooth and continuous to one that is decorated with these 3D islands 7.2 Future work (1) We have monitored the Si, Ge and Si0.8Ge0.2 oxide intensity change as a function of time with/without the presence of Ni thin films in Chapter A crosssection TEM experiments would be helpful in identifying the structure of the Ni/HSi(Ge, Si0.8Ge0.2) after oxidation and have a comparison with those observed by XPS The oxide/substrate ratio seemed to increase linearly with oxidation time in log scales, irregardless of Ni coverages Therefore, it would be interested if a model can be proposed in order to describe the power law dependence of the oxide/substrate ratio with time in order to substantiate the oxidation process we propose In addition, the two-gradient behaviour in Ge oxidation process can be further explored in order to provide evidence for the claimed hydrogen-termination breakdown mechanism A temperature-dependence mass spectroscopy experiment would be able to identify the hydrogen desorption temperature (and hence a bond strength of HGe) for a series of H-Ge(001) samples with various Ni coverages (2) In Chapter 6, the appearance of both rectangular and square islands with flat tops is unexpected because such structures not have the lowest surface energy 259 Chapter Conclusions Diffusion anisotropy along and across the dimer row is proposed to account for the formation of these islands However, there is no direct evidence to support this claim because all the morphology studies were done ex-situ after growth Therefore, experiments using in-situ STM should be employed to investigate and monitor the formation process of both rectangular and square islands as a function of annealing time and temperature at various Ni coverages Only then can we possibly address how a flat surface becomes island like in terms of diffusion of the species or inherent strain associated The 3D islands grew bigger and taller but decreased in density with temperature Therefore, a quantitative correlation between island density, annealing time and temperature through in-situ STM and some computation is clearly warranted as a future work in order to grow the 3D islands with not only the controlled density but also the desired size/height Such ability could be very promising for the future nano-device application 260 References References: M.E Levinshtein, S.L Rumyantsev, M.S Shur., Properties of advanced semiconductor materials GaN, AlN, InN, BN, SiC, SiGe New York, John Wiley, 2001 E Kasper and L Klara, Properties of Silicon Germanium and SiGe: Carbon London, INSPEC, 2000 F d'Heurle, C.S Petersson, J.E.E Baglin, S.J.L Placa, and C.Y Wong, J Appl Phys, 55 (1984), 4208 R.T Tung, Mater Chem Phys., 32 (1992), 107 D Mangelinck, J.Y Dai, J.S Pan, and S.K Lahiri, Appl Phys Lett., 75 (1999), 1736 S.L Cheng, H.M Lo, L.W Cheng, S.M Chang, and L.J Chen, Thin Solid Films, 424 (2003), 33 P Villars and L.D Calvert, Pearson’s Handbook of Crystallographic Data for Intermetallic Phases 1985, OH: American Society for Metals T.B Massalski, Binary Alloy Phase Diagrams 1986, OH: American Society for Metals Y.F Hsieh, L.J Chen, E.D Marshall, and S.S Lau, Thin Solid Films, 162 (1988), 287 10 S.-L Hsu, C.-H Chien, M.-J Yang, R.-H Huang, C.-C Leu, S.-W Shen, and T.-H Yang, Appl Phys Lett., 86 (2005), 251906 11 S Gaudet, C Detavernier, A.J Kellock, P Desjardins, and C Lavoie, Journal of Vacuum Science & Technology A, 24 (2006), 474 261 References 12 R Nath, C.W Soo, C.B Boothroyd, M Yeadon, D.Z Chi, H.P Sun, Y.B Chen, X.Q Pan, and Y.L Foo, Appl Phys Lett., 86 (2005), 201908 13 M Wittmer, M.-A Nicolet and J.W Mayer, Thin Solid Films, 42 (1977), 51 14 O Chamirian, A Lauwers, J.A Kittl, M.V Dal, M.D Potter, R Lindsay, and K Maex, Microelectron Eng., 76 (2004), 297 15 H.B Yao, M Bouville, D.Z Chi, H.P Sun, X.Q Pan, D.J Srolovitz, and D Mangelinck, Electrochemical and Solid State Letters, 10 (2007), H53 16 C.H Jang, D.O Shin, S.I Baik, Y.W Kim, Y.J Song, K.H Shim, and N.E Lee, Japanese Journal of Applied Physics, 44 (2005), 4805 17 S.L Zhang, Microelectron Eng., 70 (2003), 174 18 M Qin, V.M.C Poon and C.Y Yuen, Electronics Letters, 36 (2000), 1819 19 J Seger, S.L Zhang, D Mangelinck, and H.H Radamson, Applied Physics Letters, 81 (2002), 1978 20 K.L Pey, W.K Choi, S Chattopadhyay, H.B Zhao, E.A Fitzgerald, D.A Antoniadis, and P.S Lee, J Vac Sci Technol A, 20 (2002), 1903 21 C.Y Lin, W.J Chen, C.H Lai, A Chin, and J Liu, IEEE Electr Device L, 23 (2002), 464 22 Y.W Ok, S.H Kim, Y.J Song, K.H Shim, and T.Y Seong, Semicond Sci Technol., 19 (2004), 285 23 G.L Patton, J.H Comfort, B.S Meyerson, E.F Crabbe, G.J Scilla, E Defresart, J.M.C Stork, J.Y.C Sun, D.L Harame, and J.N Burghartz, IEEE Electr Device L, 11 (1990), 171 24 X Xiao, J.C Sturm, S.R Parihar, S.A Lyon, D Meyerhofer, S Palfrey, and F.V Shallcross, IEEE Electr Device L, 14 (1993), 199 262 References 25 K.L Pey, S Chattopadhyay, Y Miron, E.A Fitzgerald, D.A Antoniadis, and T Osipowicz, J Vac Sci Technol B, 22 (2004), 852 26 Y.S Li, P.S Lee and K.L Pey, Thin Solid Films, 462-463 (2004), 209 27 J.S Luo, W.T Lin, C.Y Chang, W.C Tsai, and S.J Wang, Mater Chem Phys., 48 (1997), 140 28 Z.H Wang, D.B Aldrich, Y.L Chen, D.E Sayers, and R.J Nemanich, Thin Solid Films, 270 (1995), 555 29 S.K Park, S Yamaguchi, N Sugii, K Nakagawa, and M Miyao, Applied Surface Science, 159-160 (2000), 116 30 B.I Boyanov, P.T Goeller, D.E Sayers, and R.J Nemanich, J Appl Phys, 86 (1999), 1355 31 R.E Weber and W.T Peria, J Appl Phys., 38 (1967), 4355 32 P.W Palmberg and T.N Rhodin, J Appl Phys., 39 (1968), 2425 33 T.E Gallon, Surf Sci., 17 (1969), 486 34 D.C Jackson, T.E Gallon and A Chambers, Surf Sci., 36 (1973), 381 35 E Bauer and H Poppa, Thin Solid Films, 12 (1972), 167 36 E Bauer, Zeitschrift fuer Kristallographie, 110 (1958), 372 37 C Argile and E Rhead, Surf Sci., 53 (1975), 659 38 G.E Rhead, Electronic Structure and Reactivity of Metal Surfaces 1976, New York: Plenum 39 C Argile and G.E Rhead, Surf Sci Rep., 10 (1989), 277 40 U Diebold, J.M Pan and T.E Madey, Phys Rev B, 47 (1993), 3868 41 P.S Lee, K.L Pey, D Mangelinck, J Ding, D.Z Chi, and L Chan, IEEE Electron Device Letters, 22 (2001), 568 263 References 42 T Ohguro, S Nakamura, M Koike, T Morimoto, A Nishiyama, Y Ushiku, T Yoshitomi, M Ono, M Saito, and H Iwai, IEEE Transactions on Electron Devices, 41 (1994), 2305 43 T Morimoto, T Ohguro, S Momose, T Iinuma, I Kunishima, K Suguro, I Katakabe, H Nakajima, M Tsuchiaki, M Ono, Y Katsumata, and H Iwai, IEEE Transactions on Electron Devices, 42 (1995), 915 44 R.T Tung and F Schrey, Appl Phys Lett., 55 (1989), 256 45 L Luo, G.A Smith, S Hashimoto, and W.M Gibson, Surface Science, 249 (1991), L338 46 E.J Van Loenen, J.F Van Der Veen and F.K LeGoues, Surface Science, 157 (1985), 47 T Nishimura, J Takeda, Y Asami, Y Hoshino, and Y Kido, Surface Science, 588 (2005), 71 48 R Kilper, S Teichert and P Oelhafen, Applied Surface Science, 123-124 (1998), 550 49 K Murano and K Ueda, Surface Science, 358 (1996), 910 50 J.F Wen, L.B Wang, C.H Liu, H.H Lee, J Hwang, C.P Ouyang, T.W Pi, J.W Hwang, and C.P Cheng, J Vac Sci Technol B, 23 (2005), 1659 51 K Hoummada, E Cadel, D Mangelinck, C Perrin-Pellegrino, D Blavette, and B Deconihout, Appl Phys Lett., 89 (2006), 181905 52 K Oura, V.G Lifshits, A.A Saranin, A.V Zotov, and M Katayama, Surface Science Reports, 35 (1999), 53 B Gergen, H Nienhaus, W.H Weinberg, and E.M McFarland, J Vac Sci Technol B, 18 (2000), 2401 264 References 54 M Gruyters, Surface Science, 515 (2002), 53 55 M Copel and R.M Tromp, Appl Phys Lett., 65 (1994), 3102 56 G Palasantzas, B Ilge, J de Nijs, and L.J Geerligs, Surface Science, 413 (1998), 509 57 J.S Pan, R.S Liu, Z Zhang, S.W Poon, W.J Ong, and E.S Tok, Surface Science, 600 (2006), 1308 58 K Hirose, A Hanta and M Uda, Applied Surface Science, 162-163 (2000), 25 59 T Emoto, K Akimoto, A Ichimiya, and K Hirose, Applied Surface Science, 190 (2002), 113 60 K Tatsumura, T Watanabe, K Hara, T Hoshino, and I Ohdomari, Physical Review B, 64 (2001), 115406 61 K Sumitomo, T Kobayashi, F Shoji, K Oura, and I Katayama, Physical Review Letters, 66 (1991), 1193 62 C Grupp and A Taleb-Ibrahimi, Physical Review B, 57 (1998), 6258 63 T.C Shen, C Wang and J.R Tucker, Physical Review Letters, 78 (1997), 1271 64 C Grupp and A Taleb-Ibrahimi, Journal of Vacuum Science & Technology A, 16 (1998), 2683 65 F.P Leisenberger, H Ofner, M.G Ramsey, and F.P Netzer, Surface Science, 383 (1997), 25 66 M Yoshimura, I Ono and K Ueda, Applied Physics a-Materials Science & Processing, 66 (1998), S1043 67 M Yoshimura, I Ono and K Ueda, Applied Surface Science, 130-132 (1998), 276 68 J Bardeen and W.H Brattain, Phys Rev., 74 (1948), 230 265 References 69 A.I Kingon, J.P Maria and S.K Streiffer, Nature, 406 (2000), 1032 70 G.D Wilk, R.M Wallace and J.M Anthony, Journal of Applied Physics, 89 (2001), 5243 71 H.L Shang, K.L Lee, P Kozlowski, C D'Emic, I Babich, E Sikorski, M.K Ieong, H.S.P Wong, K Guarini, and N Haensch, IEEE Electron Device Letters, 25 (2004), 135 72 C Girardeaux, Z Tokei, G Clugnet, and A Rolland, Applied Surface Science, 162-163 (2000), 208 73 G.A Smith, L Luo and W.M Gibson, Journal of Vacuum Science & Technology A, (1991), 646 74 T Thundat, J Zegenhagen, K Thygesen, and W.M Gibson, Surface Science, 230 (1990), 205 75 T Thundat, L.A Nagahara and S.M Lindsay, Journal of Vacuum Science & Technology A, (1990), 539 76 Q.C Zhang, N Wu, T Osipowicz, L.K Bera, and C.X Zhu, Japanese Journal of Applied Physics, 44 (2005), L1389 77 S.Y Zhu and A Nakajima, Japanese Journal of Applied Physics Part 2, 44 (2005), L753 78 D Han, Y Wang, D Tian, W Wang, X Liu, J Kang, and R Han, Microelectronic Engineering, 82 (2005), 93 79 B Balakrisnan, C.C Tan, S.L Liew, P.C Lim, G.K.L Goh, Y.L Foo, and D.Z Chi, Applied Physics Letters, 87 (2005), 241922 80 S Gaudet, C Detavernier, C Lavoie, and P Desjardins, Journal of Applied Physics, 100 (2006), 034306 266 References 127 S.J Kilpatrick, R.J Jaccodine and P.E Thompson, J Appl Phys., 93 (2003), 4896 128 D.C Paine, C Caragianis and A.F Schwartzman, J Appl Phys., 70 (1991), 5076 129 L.S Riley and S Hall, J Appl Phys., 85 (1999), 6828 130 E.A Ogryzlo, L Zheng, B Heinrich, K Myrtle, and H Lafontaine, Thin Solid Films, 321 (1998), 196 131 J.M Madsen, Z.J Cui and C.G Takoudis, J Appl Phys, 87 (2000), 2046 132 Craciun, E.S Lambers, R.K Singh, and I.W Boyd, Appl Surf Sci., 186 (2002), 237 133 I.M Lee and C.G Takoudis, J Vac Sci Technol A, 15 (1997), 3154 134 K Prabhakaran, K Sumitomo and T Ogino, Surface Science, 429 (1999), 274 135 C Lavoie, F.M d'Heurle, C Detavernier, and C Cabral, Microelectron Eng., 70 (2003), 144 136 M Garcia-Mendez, N Elizondo-Villarreal, M.H Farias, G.A Hirata, and G Beamson, Surf Rev Lett, (2002), 1661 137 Y.L Jiang, G.P Ru, J.H Liu, X.P Qu, and B.Z Li, Journal of Electronic Materials, 33 (2004), 770 138 V Teodorescu, L Nistor, H Bender, A Steegen, A Lauwers, K Maex, and J Van Landuyt, Journal of Applied Physics, 90 (2001), 167 139 F d'Heurle, S Petersson, L Stolt, and B Strizker, Journal of Applied Physics, 53 (1982), 5678 140 B.S Kang, H.J Kang and S.K Oh, Surf Rev Lett., 10 (2003), 183 270 References 141 X Chen, Z Shi, S.K Banerjee, J.P Zhou, and L.K Rabenberg, Journal of Electronic Materials, 32 (2003), 1171 142 B.A Julies, D Knoesen, R Pretorius, and D Adams, Thin Solid Films, 347 (1999), 201 143 O Chamirian, J.A Kittl, A Lauwers, O Richard, M van Dal, and K Maex, Microelectron Eng., 70 (2003), 201 144 J.H Ko, C.H Jang, S.H Kim, Y.J Song, and N.E Lee, Journal of Vacuum Science & Technology A, 24 (2006), 1468 145 L.J Jin, K.L Pey, W.K Choi, E.A Fitzgerald, D.A Antoniadis, A.J Pitera, M.L Lee, D.Z Chi, M.A Rahman, T Osipowicz, and C.H Tung, Journal of Applied Physics, 98 (2005) 146 S.L Chiu, Y.C Chu, C.J Tsai, and H.Y Lee, J Electrochem Soc, 151 (2004), G452 147 Y He, X.L Liu, J.Y Feng, and Q.L Wu, J Appl Phys, 96 (2004), 6928 148 W Huang, L.C Zhang, Y.Z Gao, H.Y Jin, B.J Ning, and G.Q Zhang, J Vac Sci Technol B, 23 (2005), 2304 149 J.K Patterson, B.J Park, K Ritley, H.Z Xiao, L.H Allen, and A Rockett, Thin Solid Films, 253 (1994), 456 150 T.H Yang, G.L Luo, E.Y Chang, T.Y Yang, H.C Tseng, and C.Y Chang, Ieee Electron Device Letters, 24 (2003), 544 151 Q.T Zhao, D Buca, S Lenk, R Loo, M Caymax, and S Mantl, Microelectron Eng., 76 (2004), 285 152 K Do, D Lee, J Kim, H Kim, and D.H Ko, J Electrochem Soc, 153 (2006), J69 271 References 153 T Jarmar, F Ericson, U Smith, J Seger, and S.L Zhang, J Appl Phys, 98 (2005), 154 J Seger, T Jarmar, Z.B Zhang, H.H Radamson, F Ericson, U Smith, and S.L Zhang, J Appl Phys, 96 (2004), 1919 155 G S Higashi, Y J Chabal, G W Trucks, and K Raghavachari, Appl Phys Letts 56 (1990) 656 156 T Takahagi, I Nagai, I Ishitani, H Kuroda, and Y Nagasawa, J Appl Phys 64 (1988) 3516 157 M.J Almond, A.M Doncaster, P.N Noble, and R Walsh, J Am Chem Soc., 104 (1982), 4717 158 M.P Develyn, S.M Cohen, E Rouchouze, and Y.L Yang, J Chem Phys., 98 (1993), 3560 159 J.H Scofield, Journal of Electron Spectroscopy and Related Phenomena, (1976), 129 160 T Walther, C.J Humphreys and A.G Cullis, Applied Physics Letters, 809, 71 (1997) 161 P.C Zalm, G.F.A.v.d Walle, D.J Gravesteijn, and A.A.v Gorkum, Applied Physics Letters, 2520, 55 (1989) 162 P.C Kelires and J Tersoff, Phys Rev Lett, 1164–1167, 63 (1989) 163 K Sumitomo, Y Kobayashi, T Ito, and T Ogino, Thin Solid Films,76,357 (1999) 164 Y.J Zheng, A.M Lam and J.R Engstrom, Applied Physics Letters,817,75 (1999) 272 References 165 S Fukatsu, K Fujita, H Yaguchi, Y Shiraki, and R Ito, Appl Phys Lett, 2103, 59 (1991) 166 J.E Rowe, D.M Riffe, G.K Wertheim, and J.C Bean, J Appl Phys,4915,76 (1994) 167 D.J Godbey, J.V Lill, J Deppe, and K.D Hobart, Applied Physics Letters, 711, 65 (1994) 168 D.J Godbey and M.G Ancona, J Vac Sci Technol A, 976, 15 (1997) 169 D.J Godbey and M.G Ancona, Surface Science, 60, 395 (1998) 170 E.S Tok, N.J Woods and J Zhang, Journal of Crystal Growth,321,209 (2000) 171 J L Gray, R Hull and J A Floro, Applied Physics Letters, 85, 3253 (2004) 172 C Tetelin, X Wallart, D Stievenard, J.P Nys, and D.J Gravesteijn, J Vac Sci Technol B 137, 16 (1998) 173 X Deng and M Krishnamurthy,Phys Rev Lett,1473,81 (1998) 174 D.E Jesson, K.M Chen, S.J Pennycook, T Thundat, and R.J Warmack,Phys Rev Lett,1330,77 (1996) 175 M A Gosalvez and R M Nieminen, New Journal of Physics, 100.1, (2003) 176 J Werner, K Lyutovich and C.P Parry, European Physical Journal-Applied Physics, 367, 27 (2004) 177 K.M Chen, D.E Jesson, S.J Pennycook, T Thundat, and R.J Warmack,Appl Phys Lett,34,66 (1995) 178 J.W.P Hsu, E.A Fitzgerald, Y.H Xie, P.J Silverman, and M.J Cardillo,Appl Phys Lett,1293,61 (1992) 179 J.A Kerr, “CRC Handbook of Chemistry and Physics”, David R Lide (Editor), CRC Press, Boca Raton, Florida, USA, 81st edition, 2000 273 References 180 A Fritsch and P Legare, Surf Sci 162 (1985) 742 181 Q Ma and R A Rosenberg, Surf Sci 391 (1997) L1224-L1229 182 D Q Yang and E Sacher, Surf Sci 504 (2002) 125 183 U Diebold, J M Pan, and T E Madey, Phys Rev B 47 (1993) 3868 184 M G Mason, Phy Rev B 27 (1983) 748 185 G.K Wertheim and S.B Dicenzo, Physical Review B, 37 (1988),844 186 F Arnaud, D Avitaya, J A Chroboczek, C D Anterroches, G Glastre, Y Campidelli, and E Rosencher, J Cryst Growth 81 (1987) 463 187 M Iwami, T Terada, M Kubota, H Tochihara, and Y Murata, Surf Sci 194 (1988) 115 188 K N Tu, Appl Phys Lett 27 (1975) 221 189 S Higai and T Ohno, Physical Review B, 62 (2000), R7711 190 S Higai, T Ohno and T Sasaki, Applied Surface Science, 169-170 (2001), 16 191 A Franciosi, J.H Weaver and F.A Schmidt, Physical Review B, 26 (1982), 546 192 D.H Galvan, A.P Amarillas, J.C.S Reyna, M Garcia-Mendez, and M.H Farias, Phys Status Solidi B-Basic Res., 241 (2004), 2905 193 A Hiraki, J Electrochem Soc., 127 (1980), 2662 194 Y Hoshino, T Nishimura, Y Taki, Y Asami, K Sumitomo, and Y Kido, Surface Science, 511 (2002), 112 195 M.G Barthes and A Rolland, Thin Solid Films, 76 (1981), 45 196 VG Scientific Technical Document 197 M P Seah and W A Dench, Surf Interface Anal (1979) 274 References 198 K Hirose, T Saitoh, A Hanta, and M Uda, Surface Science, 433-435 (1999), 581 199 I Abbati, G Rossi, L Braicovich, I Lindau, and W.E Spicer, Applications of Surface Science, (1981), 243 200 L.J Jin, K.L Pey, W.K Choi, E.A Fitzgerald, D.A Antoniadis, A.J Pitera, M.L Lee, D.Z Chi, and C.H Tung, Thin Solid Films, 462-463 (2004), 151 201 D Iotova, N Kioussis and S.P Lim, Physical Review B, 54 (1996), 14413 202 G Rossi, I Abbati, L Braicovich, I Lindau, and W.E Spicer, Physical Review B, 25 (1982), 3619 203 H.I Starnberg, P Soukiassian, S.T Kim, A Papageorgopoulos, and S Kapoor, Surface Science, 270 (1992), 934 204 S Higai and T Ohno, Phys Rev B, 65 (2002), 165309 205 J.M Hill, D.G Royce, C.S Fadley, L.F Wagner, and F.J Grunthaner, Chemical Physics Letters, 44 (1976), 225 206 D.F Mitchell, K.B Clark, J.A Bardwell, W.N Lennard, G.R Massoumi, and I.V Mitchell, Surf Interface Anal., 21 (1994), 44 207 D.A Cole, J.R Shallenberger, S.W Novak, R.L Moore, M.J Edgell, S.P Smith, C.J Hitzman, J.F Kirchhoff, E Principe, W Nieveen, F.K Huang, S Biswas, R.J Bleiler, and K Jones, Journal of Vacuum Science & Technology B, 18 (2000), 440 208 A.T Fromhold, Theory of metal oxidation 1980, Amsterdam ; New York: North Holland Pub Co American Elsevier Pub Co 209 M Garcia-Mendez, D.H Galvan, A Posada-Amarillas, and M.H Farias, Applied Surface Science, 230 (2004), 386 275 References 210 O.L Alerhand, A.N Berker, J.D Joannopoulos, D Vanderbilt, R.J Hamers, and J.E Demuth, Physical Review Letters, 64 (1990), 2406 211 R.J Hamers, R.M Tromp and J.E Demuth, Phys Rev B, 34 (1986), 5343 212 J Tersoff and R.M Tromp, Physical Review Letters, 70 (1993), 2782 213 B.E Deal and A.S Grove, Journal of Applied Physics, 36 (1965), 3770 214 H.I Starnberg, P Soukiassian, M.H Bakshi, and Z Hurych, Surface Science, 224 (1989), 13 215 P Thanikasalam, T.K Whidden and D.K Ferry, J Vac Sci Technol B, 14 (1996), 2840 216 S Dimitrijev and H.B Harrison, Journal of Applied Physics, 80 (1996), 2467 217 D.R Wolters and A.T.A Zegersvanduynhoven, Journal of Applied Physics, 65 (1989), 5126 218 D.R Wolters and A.T.A Zegersvanduynhoven, Journal of Applied Physics, 65 (1989), 5134 219 Do, K., et al., J Electrochem Soc, 153, (2006) J69 220 Nath, R and M Yeadon, Electrochemical and Solid State Letters, 7, (2004) G231 221 Gao, H.J and W.D Nix, Annu Rev Mater Sci, 29, (1999) 173 222 Seng, H.L., et al., Appl Phys Lett, 80, (2002) 2940 223 Surface analysis by Auger and x-ray photoelectron spectroscopy, ed by D Briggs and J.T Grant 2003, Chichester: IM 224 D.A.Shirley, Phys Rev B (1972) 4709 225 Nanoscale characterization of surfaces and interfaces, ed by N.J DiNardo 1994, Weinheim: VCH 276 Appendices Using existing model to fit oxide/substrate intensity change with oxidation time It is of technical importance to grow SiO2 layer with the desired thickness As such, a large amount of theoretical calculations have been dedicated to simulate and model the growth mechanism in order to predict growth rate of SiO2 A linearparabolic law (Equ A.1) has been proposed by Deal and Grove to estimate the film thickness The kinetics of the process is governed primarily by the transport of oxygen through the oxide layer and it is given by the following expression213: D2/kp + D/kl = t + constant, (A.1) where D is the oxide thickness, t is the time, kp and kl are the parabolic and linear rate constants, respectively This “linear-parabolic” rate law, or Deal-Grove model, is so far the most successful model in predicting the thickness of thick SiO2 (hundreds of nanometers) grown on Si substrates in both wet and dry oxygen ambient at high temperatures213 However, significant deviation from this linear-parabolic occurs when oxide thickness is less than 20nm The term “thin oxidation regime” is therefore often used to define growth of films up to several nanometers thickness214 Within this “thin oxide” regime, significantly higher oxidation rate were observed than what is predicted by the DealGrove mode, which is also known as initial enhanced oxidation89,215-216 As the shrinkage in device dimensions require a thinner SiO2 thickness ranging from 3nm to 100nm215, it raise imminent needs for models capable of precisely predicating oxidation rates and hence the oxide thickness in this thin regime As such, extensive efforts have been put in to modify the Deal-Grove model88,90,215-216 or to propose new models89 in order to explain initial enhanced oxidation 277 Appendices In Chapter 5, it has been observed that the presence of Ni accelerates the oxidation of Si, Ge and Si0.8Ge0.2 substrates It is interesting to note that the oxidation process follows a power-law dependence with oxidation time on Si, Ge and Si0.8Ge0.2 surfaces rather than following the Deal-Grove model The oxide films we grow in our work are all very thin and hence fall in this “thin oxide” regime, which can be described by a power law: y=a*xb (A.2) log y= log a + b* log x (A.3) where y can be SiO2/Si or (GeO+GeO2)/Ge, x is the oxidation time in unit of days, a and b are the pre-exponential factor and power order, respectively A.1 Fitting of SiO2/Si intensity change in Ni/H-Si as a function of oxidation time In Fig A.1, the increase of SiO2/Si ratio with oxidation time can generally be fitted well with a linear fit in log scales, which implies that the growth of SiO2 abides by power law The fitting results of a and b as a function of Ni% were shown in Fig A.2 Generally the bigger “a” and smaller “b” value yield a faster oxidation rate The power order in the oxidation of pure H-Si is 0.62±0.05, within the range of typical power value of 0.25~1 for other metal systems217 However, the powder order is 0.09±0.04 for the samples with Ni coverage from 10% to 75%, which is much smaller than the typical reported value214,217-218 278 Appendices H-Si(001) 10% Ni/H-Si(001) 20% Ni/H-Si(001) 33% Ni/H-Si(001) 41% Ni/H-Si(001) 50% Ni/H-Si(001) 60% Ni/H-Si(001) 75% Ni/H-Si(001) Linear fit of H-Si(001) Linear fit of 10% Ni/H-Si(001) Linear fit of 20% Ni/H-Si(001) Linear fit of 33% Ni/H-Si(001) Linear fit of 41% Ni/H-Si(001) Linear fit of 50% Ni/H-Si(001) Linear fit of 60% Ni/H-Si(001) Linear fit of 75% Ni/H-Si(001) SiO2/Si 0.1 0.01 1E-3 1E-3 0.01 0.1 10 100 1000 Oxidation Time (days) Fig A.1 The linear dependence of SiO2/Si ratio on oxidation time in a log scale indicates SiO2 grows in a power law with oxidation time 0.0 0.7 0.6 -0.5 0.5 -1.0 a b 0.4 0.3 -1.5 0.2 0.1 -2.0 0.0 10 20 30 40 Ni% 50 60 70 80 10 20 30 40 50 60 70 80 Ni% (b) (a) Fig A.2 Fitting results of a and b as a function of Ni% on H-Si(001) surfaces A.2 Fitting of (GeO2+GeO)/Ge intensity change in Ni/H-Ge as a function of oxidation time In Fig A.3, the increase of (GeO+GeO2)/Ge ratio with oxidation time can generally be fitted well with a linear line in log scales in both regimes, which implies 279 Appendices that the growth of Ge oxides abides by power law as well The resulting a and b values are plotted in Fig A.4 with the subscript of and representing the first and second regimes, respectively It can be seen that a1 was generally bigger than a2 over the whole Ni coverage Meanwhile, both a1 and a2 increased with Ni coverages till 38% before they started to decrease when Ni coverages further increased from 38% to 68% As for the power order, b1 was consistent at ~0.14±0.03 for all the samples, while b2 varied from 0.84±0.09 to 1.92±0.16 among the samples b1 was generally much smaller than b2 over the whole Ni coverages H-Ge(001) 10% Ni/H-Ge(001) 20% Ni/H-Ge(001) 29% Ni/H-Ge(001) 38% Ni/H-Ge(001) 47% Ni/H-Ge(001) 60% Ni/H-Ge(001) 68% Ni/H-Ge(001) Line fit for H-Ge(001) Line fit for 10% Ni/H-Ge(001) Line fit for 20% Ni/H-Ge(001) Line fit for 29% Ni/H-Ge(001) Line fit for 38% Ni/H-Ge(001) Line fit for 47% Ni/H-Ge(001) Line fit for 60% Ni/H-Ge(001) Line fit for 68% Ni/H-Ge(001) 100 (GeO2+GeO)/Ge Regime-II 10 Regime-I 0.1 1E-4 1E-3 0.01 0.1 10 100 1000 Oxidation Time (days) (a) H-Ge(001) 10% Ni/H-Ge(001) 20% Ni/H-Ge(001) 29% Ni/H-Ge(001) 38% Ni/H-Ge(001) 47% Ni/H-Ge(001) 60% Ni/H-Ge(001) 68% Ni/H-Ge(001) Line fit for H-Ge(001) Line fit for 10% Ni/H-Ge(001) Line fit for 20% Ni/H-Ge(001) Line fit for 29% Ni/H-Ge(001) Line fit for 38% Ni/H-Ge(001) Line fit for 47% Ni/H-Ge(001) Line fit for 60% Ni/H-Ge(001) Line fit for 68% Ni/H-Ge(001) 100 (GeO2+GeO)/Ge Regime-II 10 Regime-I 0.1 1E-4 1E-3 0.01 0.1 10 100 1000 Oxidation Time (days) (b) Fig A.3 The linear dependence of (GeO+GeO2)/Ge ratio on oxidation time in a log scale for (a) regime-I and (b) regime-II They indicate Ge oxide grows in a power law with oxidation time in both regimes 280 Appendices 2.8 2.0 2.6 2.4 1.8 2.2 2.0 b1 b2 1.6 1.8 1.4 1.6 a 1.2 b a1 a2 1.4 1.2 1.0 1.0 0.8 0.6 0.8 0.4 0.2 0.2 0.0 0.0 10 20 30 40 50 Ni% 60 70 10 20 30 40 50 60 70 Ni% (a) (b) Fig A.4 Curve-fitting results of (a) a1 & a2 and (b) b1 & b2 as a function of Ni coverage The subscript of and represent the first and second regimes, respectively A.3 Fitting of SiO2/Si and (GeO2+GeO)/Ge intensity change in Ni/H-Si0.8Ge0.2 as a function of oxidation time In Fig A.5, the increase of SiO2/Si and (GeO+GeO2)/Ge ratio with oxidation time can generally be fitted well with linear lines in log scales, which implies that the growth of both Si and Ge oxides in Si0.8Ge0.2 follow the power law as well The resulting a and b values are plotted in Fig A.6 For Ge oxide, subscripts of and are similarly used to represent the first and second regimes, respectively 281 Appendices H-Si0.8Ge0.2 10 10% Ni/ H-Si0.8Ge0.2 20% Ni/ H-Si0.8Ge0.2 42% Ni/ H-Si0.8Ge0.2 52% Ni/ H-Si0.8Ge0.2 SiO2/Si 84% Ni/ H-Si0.8Ge0.2 Linear fit of H-Si0.8Ge0.2 Linear fit of 10% Ni/H-Si0.8Ge0.2 0.1 Linear fit of 20% Ni/H-Si0.8Ge0.2 Linear fit of 42% Ni/H-Si0.8Ge0.2 Linear fit of 52% Ni/H-Si0.8Ge0.2 0.01 Linear fit of 84% Ni/H-Si0.8Ge0.2 1E-3 0.01 0.1 10 100 1000 Oxidation time (days) (a) H-Si0.8Ge0.2 10 (GeO2+GeO)/Ge 10% Ni/ H-Si0.8Ge0.2 II 20% Ni/ H-Si0.8Ge0.2 42% Ni/ H-Si0.8Ge0.2 52% Ni/ H-Si0.8Ge0.2 I 84% Ni/ H-Si0.8Ge0.2 Linear fit of H-Si0.8Ge0.2 Linear fit of 10% Ni/H-Si0.8Ge0.2 0.1 Linear fit of 20% Ni/H-Si0.8Ge0.2 Linear fit of 42% Ni/H-Si0.8Ge0.2 Linear fit of 52% Ni/H-Si0.8Ge0.2 0.01 Linear fit of 84% Ni/H-Si0.8Ge0.2 1E-3 0.01 0.1 10 100 1000 Oxidation time (days) (b) H-Si0.8Ge0.2 10 (GeO2+GeO)/Ge 10% Ni/ H-Si0.8Ge0.2 II 20% Ni/ H-Si0.8Ge0.2 42% Ni/ H-Si0.8Ge0.2 52% Ni/ H-Si0.8Ge0.2 I 84% Ni/ H-Si0.8Ge0.2 Linear fit of H-Si0.8Ge0.2 Linear fit of 10% Ni/H-Si0.8Ge0.2 0.1 Linear fit of 20% Ni/H-Si0.8Ge0.2 Linear fit of 42% Ni/H-Si0.8Ge0.2 Linear fit of 52% Ni/H-Si0.8Ge0.2 0.01 Linear fit of 84% Ni/H-Si0.8Ge0.2 1E-3 0.01 0.1 10 100 1000 Oxidation time (days) (c) Fig A.5 The linear dependence of (a) SiO2/Si and (GeO+GeO2)/Ge ratio on oxidation time in a log scale for (b) regime-I and (c) regime-II They indicate both Si andGe oxides grow in a power law with oxidation time throughout 282 Appendices 0.4 0.5 0.2 0.0 0.4 -0.4 b a -0.2 0.3 -0.6 -0.8 0.2 -1.0 -1.2 0.1 -1.4 -1.6 10 20 30 40 50 60 70 80 90 0.0 10 20 30 40 50 60 70 80 90 Ni% Ni% (a) (b) 0.7 -0.2 -0.4 b2 0.6 -0.6 b1 0.5 -0.8 a b -1.0 -1.2 -1.4 a2 0.4 a1 -1.6 0.3 0.2 -1.8 0.1 -2.0 -2.2 0.0 10 20 30 40 50 60 70 80 90 Ni% 10 20 30 40 50 60 70 80 90 Ni% (c) (d) Fig A.6 Curve-fitting results of (a) a and (b) b for SiO2/Si and (c) a and (d) b for (GeO+GeO2)/Ge as a function of Ni coverage The subscripts of and represent the first and second regimes, respectively The average power order (b) is 0.2 for SiO2/Si during oxidation of Ni/HSi0.8Ge0.2, which is larger than the average power order (b) of 0.1 in Ni/H-Si system It thus implies that Si in Ni/H-Si0.8Ge0.2 is much heavily oxidized than the Si in Ni/H-Si system The average order of power (b) is fitted to be 0.11 and 0.36 for regime-I and regime-II for (GeO+GeO2)/Ge in Ni/H-Si0.8Ge0.2 system, while they are 0.13 and 1.26 283 Appendices for regime-I and regime-II in Ni/H-Ge system Hence, it indicates Ge was less oxidized in Ni/H-Si0.8Ge0.2 system than in Ni/H-Ge system It appears that the power law can be used to fit the SiO2/Si and (GeO2+GeO)/Ge very well in Si, Ge and Si0.8Ge0.2 substrates, irregardless of Ni coverage and presence of 2nd oxidation regime D.R Wolters217-218 has given a review of various power laws and concluded that the Deal-Grove’s model appears to be an approximation to a power law Power law dependence has been derived after taking into account the effect of coupled ionic and electronic currents in growing oxides, or in some cases the field disproportionation due to high densities of space charge present in the oxide, in addition to considering the oxygen diffusion We have not attempted to derive the power law dependence based on these approaches It will certainly be of interest to study this as a future work in order to carefully resolve this oxidation behavior and its dependence on Ni coverage as illustrated by the examples shown for Si, Ge and Si0.8Ge0.2 surfaces 284 ... semiconductor materials GaN, AlN, InN, BN, SiC, SiGe New York, John Wiley, 2001 E Kasper and L Klara, Properties of Silicon Germanium and SiGe: Carbon London, INSPEC, 2000 F d''Heurle, C.S Petersson,... and the substrates (Si/ Ge) were oxidized on all Si, Ge and Si0 .8Ge0.2 substrates A power law can be used to fit the evolution of SiO2 /Si and (GeO2+GeO)/Ge ratio as a function of oxidation time... Lett,1330 ,77 (1996) 175 M A Gosalvez and R M Nieminen, New Journal of Physics, 100.1, (2003) 176 J Werner, K Lyutovich and C.P Parry, European Physical Journal-Applied Physics, 3 67, 27 (2004) 177 K.M