"Front Matter". In: Organosilanes in Radical Chemistry - Index of

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Radical Chemistry on Silicon Surfaces 207 HO O O O H H oxidized silicon ?? Si O 2 Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si 48 49 50 oxygen insertion O O H H O H OH Si O 2 Si 1,2-Si shift Si Si Si 1,5-H shift Si OSi Si Si Si SiO Si Si SiO Si Si SiO Si Si SiO Si Si Si Si OSi Si Si Si 53 56 51 52 oxygen insertion 1,x-H shift H O 2 O O H H HO O OSi OSi Si Si OH Si SiO Si Si OSi Si O Si Si Si Si SiO Si Si Si 1,2-Si shift oxygen insertion Si Si Si Si SiO Si 54 59 OSi Si Si SiO 57 1,5-H shift 58 OH oxidized silicon 1,5-H shift OSi OSi Si O 2 SiO Si Si Si 55 Scheme 8.10 Proposed mechanism for the oxidation of silicon surfaces
208 Silyl Radicals in Polymers and Materials oxide growth rate. Indeed, infrared studies have shown that the half-life of the Si H stretch in air of an H Si(111) surface is humidity dependent. It was w w suggested that the oxidation of Si HtoSiOH by H2O is the rate-limiting w w step in the native oxide formation [51]. On the other hand, dissolved oxygen in 40 % aqueous ammonium fluoride solution initiates the formation of etch pits in the terraces of the otherwise ideal H Si(111) surface. Removal of oxygen from w the fluoride solution by sparging with argon substantially reduces the initiation of etch pits. It was suggested that oxygen molecules are reduced to superoxide radicals (O : 2 ) at the negative open-circuit potential of the silicon surface and that O : 2 abstracts hydrogen atoms from the H Si(111) terraces to form silicon w radicals [52]. Whatever the initial step of formation of surface silyl radicals, the mechanism for the oxidation of silicon surfaces by O2 is expected to be similar to the proposed Scheme 8.10. This proposal is also in agreement with the various spectroscopic measurements that provided evidence for a peroxyl radical species on the surface of silicon [53] during thermal oxidation (see also references cited in [50]). The reaction being a surface radical chain oxidation, it is obvious that temperature, efficiency of radical initiation, surface precursor and oxygen concentration will play important roles in the acceleration of the surface oxidation and outcome of oxidation. 8.5.2 HALOGENATION OF H w Si(111) The analogy drawn between radical reactions of organosilanes and those of H w Si(111) led to the exploration of halogenation reactions. Chlorine-terminated Si(111) surfaces, Cl w Si(111), were prepared by treating H w Si(111) with PCl5 in chlorobenzene under free-radical conditions using either thermal decomposition of dibenzoyl peroxide [54] or UV illumination under reflux [55]. Cl w Si(111) was also obtained by reaction of Cl2 gas with H w Si(111) activated either by heating at 80 8 C for 10 min or by irradiating with a 300 W tungsten lamp for 2 min at room temperature [56]. Analogously, H w Si(111) surfaces were brominated by reaction with N-bromosuccinimide or BrCCl3 to give Br w Si(111) using radical initiating conditions [57]. Halogen-terminated Si(111), X w Si(111), were characterized by several spectroscopic methods (XPS; AES; ATR-FTIR, HREELS, and NEXAFS) and have been further used in reactions with organolithium reagents (RLi) to obtain monolayer films R w Si(111) [54,55,57]. 8.5.3 ADDITION OF UNSATURATED COMPOUNDS ON H w Si(111) Wet chemical procedures for forming covalently bonded monolayer films on H w Si(111) are well developed. Among various methods, the radical approach is the most common one.
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Organosilanes in Radical Chemistry
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DEDICATION To my parents XrZstoB an
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viii Contents 3.6 Hydrogen Atom: An
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PREFACE A large number of papers de
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ACKNOWLEDGEMENTS I thank Keith U. I
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2 Formation and Structures of Silyl
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10 Formation and Structures of Sily
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2 Thermochemistry 2.1 GENERAL CONSI
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Bond Dissociation Enthalpies 21 Tab
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Bond Dissociation Enthalpies 23 2.2
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Ion Thermochemistry 25 Table 2.4 Re
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Ion Thermochemistry 27 Table 2.5 El
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References 29 3. Goumri, A., Yuan,
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32 Hydrogen Donor Abilities of Sili
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4 Reducing Agents 4.1 GENERAL ASPEC
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General Aspects of Radical Chain Re
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Tris(trimethylsilyl)silane 53 Therm
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Tris(trimethylsilyl)silane 55 4.3.1
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Tris(trimethylsilyl)silane 57 A goo
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Tris(trimethylsilyl)silane 59 C(O)C
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Tris(trimethylsilyl)silane 61 radic
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Tris(trimethylsilyl)silane 63 86% y
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Tris(trimethylsilyl)silane 65 RO RO
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Tris(trimethylsilyl)silane 67 O AcO
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Tris(trimethylsilyl)silane 69 Tris(
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Other Silicon Hydrides 71 The reduc
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Other Silicon Hydrides 73 The decre
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Other Silicon Hydrides 75 Ph MeS O
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Other Silicon Hydrides 77 Table 4.6
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Silicon Hydride / Thiol Mixture 79
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Silylated Cyclohexadienes 81 and (4
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References 83 34. Kawashima, E., Uc
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References 85 104. Gimisis, T., Bal
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88 Addition to Unsaturated Bonds te
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90 Addition to Unsaturated Bonds ap
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92 Addition to Unsaturated Bonds 5.
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94 Addition to Unsaturated Bonds R
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96 Addition to Unsaturated Bonds Ph
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98 Addition to Unsaturated Bonds EP
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100 Addition to Unsaturated Bonds 5
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102 Addition to Unsaturated Bonds T
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104 Addition to Unsaturated Bonds R
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106 Addition to Unsaturated Bonds a
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110 Addition to Unsaturated Bonds S
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112 Addition to Unsaturated Bonds T
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114 Addition to Unsaturated Bonds I
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120 Unimolecular Reactions 1 Si(H)M
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122 Unimolecular Reactions t-Bu t-B
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124 Unimolecular Reactions MeO Si O
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126 Unimolecular Reactions t-Bu t-B
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128 Unimolecular Reactions R 1 R 2
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130 Unimolecular Reactions From the
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132 Unimolecular Reactions rearrang
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134 Unimolecular Reactions H 3 C +
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136 Unimolecular Reactions Br O Si(
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138 Unimolecular Reactions R3Si C C
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140 Unimolecular Reactions Me3Si O
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142 Unimolecular Reactions 43. Albe
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144 Consecutive Radical Reactions c
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146 Consecutive Radical Reactions O
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148 Consecutive Radical Reactions a
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150 Consecutive Radical Reactions d
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152 Consecutive Radical Reactions T
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154 Consecutive Radical Reactions M
Page 161 and 162: 156 Consecutive Radical Reactions F
Page 163 and 164: 158 Consecutive Radical Reactions O
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Page 169 and 170: 164 Consecutive Radical Reactions A
Page 173 and 174: 168 Consecutive Radical Reactions r
Page 175 and 176: 170 Consecutive Radical Reactions E
Page 179 and 180: 174 Consecutive Radical Reactions A
Page 181 and 182: 176 Consecutive Radical Reactions P
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Page 187 and 188: 182 Consecutive Radical Reactions 1
Page 189 and 190: 184 Consecutive Radical Reactions 8
Page 191 and 192: 186 Silyl Radicals in Polymers and
Page 211: 206 Silyl Radicals in Polymers and
Page 225 and 226: 220 List of Abbreviations PED photo
Page 227 and 228: 222 Index Carbonyl sulfide 111 Carb
Page 229 and 230: 224 Index Organosilicon boranes 2,
Page 231 and 232: 226 Index Triethylsilane as mediato
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