Preface ...................................................... xiii
Acronyms and Symbols .......................................... xix
Introduction .................................................. xxv
1 Absorption and Reflection of Infrared Radiation by
Ultrathin Films ............................................ 1
1.1. Macroscopic Theory of Propagation of Electromagnetic
Waves in Infinite Medium ............................. 2
1.2. Modeling Optical Properties of a Material ........... 10
1.3. Classical Dispersion Models of Absorption ........... 13
1.4. Propagation of IR Radiation through Planar
Interface between Two Isotropic Media ............... 24
1.4.1. Transparent Media ........................... 26
1.4.2. General Case ................................ 29
1.5. Reflection of Radiation at Planar Interface
Covered by Single Layer ............................. 31
1.6. Transmission of Layer Located at Interface
between Two Isotropic Semi-infinite Media ........... 39
1.7. System of Plane-Parallel Layers: Matrix Method ...... 43
1.8. Energy Absorption in Layered Media .................. 49
1.8.1. External Reflection: Transparent
Substrates .................................. 50
1.8.2. External Reflection: Metallic Substrates .... 52
1.8.3. ATR ......................................... 55
1.9. Effective Medium Theory ............................. 60
1.10. Diffuse Reflection and Transmission ................. 65
Appendix ....................................................... 68
References ..................................................... 70
2 Optimum Conditions for Recording Infrared Spectra of
Ultrathin Films ........................................... 79
2.1. IR Transmission Spectra Obtained in Polarized
Radiation ........................................... 79
2.2. IRRAS Spectra of Layers on Metallic Surfaces
("Metallic" IRRAS) .................................. 84
2.3. IRRAS of Layers on Semiconductors and Dielectrics ... 87
2.3.1. Transparent and Weakly Absorbing Substrates
("Transparent" IRRAS) ....................... 87
2.3.2. Absorbing Substrates ........................ 90
2.3.3. Buried Metal Layer Substrates
(BML-IRRAS) ................................. 94
2.4. ATR Spectra ........................................ 100
2.5. IR Spectra of Layers Located at Interface .......... 102
2.5.1. Transmission ............................... 102
2.5.2. Metallic IRRAS ............................. 105
2.5.3. Transparent IRRAS .......................... 110
2.5.4. ATR ........................................ 111
2.6. Choosing Appropriate IR Spectroscopic Method for Layer
on Flat Surface .................................... 118
2.7. Coatings on Powders, Fibers, and Matte Surfaces .... 120
2.7.1. Transmission ............................... 120
2.7.2. Diffuse Transmittance and Diffuse
Reflectance ................................ 122
2.7.3. ATR ........................................ 128
2.7.4. Comparison of IR Spectroscopic Methods for
Studying Ultrathin Films on Powders ........ 130
References .................................................... 133
3 Interpretation of IR Spectra of Ultrathin Films ............. 140
3.1. Dependence of Transmission, ATR, and IRRAS Spectra
of Ultrathin Films on Polarization
(Berreman Effect) .................................. 141
3.2. Theory of Berreman Effect .......................... 146
3.2.1. Surface Modes .............................. 147
3.2.2. Modes in Ultrathin Films ................... 151
3.2.3. Identification of Berreman Effect in IR Spectra
of Ultrathin Films ......................... 157
3.3. Optical Effect: Film Thickness, Angle of
Incidence, and Immersion ........................... 159
3.3.1. Effect in "Metallic" IRRAS ................. 159
3.3.2. Effect in "Transparent" IRRAS .............. 164
3.3.3. Effect in ATR Spectra ...................... 167
3.3.4. Effect in Transmission Spectra ............. 169
3.4. Optical Effect: Band Shapes in IRRAS as Function of
Optical Properties of Substrate .................... 171
3.5. Optical Property Gradients at Substrate-Layer Interface:
Effect on Band Intensities in IRRAS ................ 175
3.6. Dipole-Dipole Coupling ............................. 179
3.7. Specific Features in Potential-Difference IR Spectra
of Electrode-Electrolyte Interfaces ................ 187
3.7.1. Absorption Due to Bulk Electrolyte ......... 189
3.7.2. (Re)organization of Electrolyte in DL ...... 190
3.7.3. Donation/Backdonation of Electrons ......... 202
3.7.4. Stark Effect ............................... 202
3.7.5. Bipolar Bands .............................. 203
3.7.6. Effect of Coadsorption ..................... 205
3.7.7. Electronic Absorption ...................... 206
3.7.8. Optical Effects ............................ 210
3.8. Interpretation of Dynamic IR Spectra:
Two-Dimensional Correlation Analysis ............... 212
3.9. IR Spectra of Inhomogeneous Films and Films
on Powders and Rough Surfaces. Surface
Enhancement ........................................ 219
3.9.1. Manifestation of Particle Shape in IR
Spectra .................................... 220
3.9.2. Coated Particles ........................... 223
3.9.3. Composite, Porous, and Discontinuous
Films ...................................... 225
3.9.4. Interpretation of IR Surface-Enhanced
Spectra .................................... 232
3.9.5. Rough Surfaces ............................. 241
3.10. Determination of Optical Constants of Isotropic
Ultrathin Films: Experimental Errors in
Reflectivity Measurements .......................... 243
3.11. Determination of Molecular Packing and
Orientation in Ultrathin Films: Anisotropic
Optical Constants of Ultrathin Films ............... 252
3.11.1. Order-Disorder Transition ................. 253
3.11.2. Packing and Symmetry of Ultrathin Films ... 257
3.11.3. Orientation .............................. 266
3.11.4. Surface Selection Rule for Dielectrics ... 280
3.11.5. Optimum Conditions for MO Studies ........ 282
References .................................................... 284
4 Equipment and Techniques .................................. 307
4.1. Techniques for Recording IR Spectra of Ultrathin
Films on Bulk Samples .............................. 308
4.1.1. Transmission and Multiple Transmission .... 308
4.1.2. IRRAS ..................................... 313
4.1.3. ATR ....................................... 317
4.1.4. DRIFTS .................................... 327
4.2. Techniques for Ultrathin Films on Powders
and Fibers ......................................... 328
4.2.1. Transmission .............................. 329
4.2.2. Diffuse Transmission ...................... 331
4.2.3. Diffuse Reflectance ....................... 334
4.2.4. ATR ....................................... 342
4.3. High-Resolution FTIR Microspectroscopy of Thin
Films .............................................. 343
4.3.1. Transmission .............................. 345
4.3.2. IRRAS ..................................... 346
4.3.3. DRIFTS and DTIFTS ......................... 347
4.3.4. ATR ....................................... 348
4.3.5. Spatial Resolution and Smallest Sampling
Area ...................................... 350
4.3.6. Comparison of u,-FTIR Methods ............. 351
4.4. Mapping, Imaging, and Photon Scanning Tunneling
Microscopy ......................................... 352
4.5. Temperature-and-Environment Programmed Chambers
for In Situ Studies of Ultrathin Films on Bulk
and Powdered Supports .............................. 356
4.6. Technical Aspects of In Situ IR Spectroscopy of
Ultrathin Films at Solid-Liquid and Solid-Solid
Interfaces ......................................... 360
4.6.1. Transmission .............................. 361
4.6.2. In Situ IRRAS ............................. 363
4.6.3. ATR ....................................... 369
4.6.4. Measurement Protocols for SEC
Experiments ............................... 374
4.7. Polarization Modulation Spectroscopy ............... 376
4.8. IRRAS of Air-Water Interface ....................... 381
4.9. Dynamic IR Spectroscopy ............................ 383
4.9.1. Time Domain ............................... 383
4.9.2. Frequency Domain: Potential-Modulation
Spectroscopy .............................. 387
4.10. Preparation of Substrates .......................... 389
4.10.1. Cleaning of IREs ......................... 389
4.10.2. Metal Electrode and SEIRA Surfaces ....... 391
4.10.3. BML Substrate ............................ 393
References ................................................... 393
5 Infrared Spectroscopy of Thin Layers in Silicon
Microelectronics .......................................... 416
5.1. Thermal SiO2 Layers ................................ 416
5.2. Low-Temperature SiO2 Layers ........................ 421
5.3. Ultrathin SiO2 Layers .............................. 427
5.4. Silicon Nitride, Oxynitride, and Carbon
Nitride Layers ..................................... 434
5.5. Amorphous Hydrogenated Films ....................... 439
5.5.1. a-Si:H Films .............................. 439
5.5.2. a-SiGe:H .................................. 444
5.5.3. a-SiC:H Films ............................. 445
5.6. Films of Amorphous Carbon, Boron Nitride, and Boron
Carbide ........................................... 446
5.6.1. Diamondlike Carbon ........................ 446
5.6.2. Boron Nitride and Carbide Films ........... 448
5.7. Porous Silicon Layers .............................. 450
5.8. Other Dielectric Layers Used in Microelectronics ... 454
5.8.1. CaF2, BaF2, and SrF2 Layers ............... 454
5.8.2. GeO2 Film ................................. 456
5.8.3. Metal Silicides ........................... 457
5.8.4. Amorphous Ta2O5 Films ..................... 458
5.8.5. SrTiO3 Film ............................... 458
5.8.6. Metal Nitrides ............................ 459
5.9. Multi- and Inhomogeneous Dielectric Layers:
Layer-by-Layer Etching ............................. 460
References .................................................... 465
6 Application of Infrared Spectroscopy to Analysis of
Interfaces and Thin Dielectric Layers in
Semiconductor Technology ............................... 476
6.1. Ultrathin Oxide Layers in Silicon Schottky-Type
Solar Cells ........................................ 476
6.2. Control of Thin Oxide Layers in Silicon MOS
Devices ............................................ 481
6.2.1. CVD Oxide Layers in Al-SiOx-Si Devices .... 482
6.2.2. Monitoring of Aluminum Corrosion Processes
in Al-PSG Interface ....................... 484
6.2.3. Determination of Metal Film and Oxide Layer
Thicknesses in MOS Devices ................ 486
6.3. Modification of Oxides in Metal-Same-Metal
Oxide-InP Devices .................................. 488
6.4. Dielectric Layers in Sandwiched Semiconductor
Structures ......................................... 492
6.4.1. Silicon-on-Insulator ...................... 492
6.4.2. Polycrystalline Silicon-c-Si Interface .... 493
6.4.3. SiO2 Films in Bonded Si Wafers ............ 494
6.4.4. Quantum Wells ............................. 495
6.5. IR Spectroscopy of Surface States at SiO2-Si
Interface .......................................... 497
6.6. In Situ Infrared Characterization of Si and
SiO2 Surfaces ...................................... 502
6.6.1. Monitoring of CVD of SiO2 ................. 502
6.6.2. Cleaning and Etching of Si Surfaces ....... 504
6.6.3. Initial Stages of Oxidation of
H-Terminated Si Surface ................... 506
References .................................................... 508
7 Ultrathin Films at Gas-Solid, Gas-Liquid, and
Solid-Liquid Interfaces ................................ 514
7.1. IR Spectroscopic Study of Adsorption from Gaseous
Phase: Catalysis ................................... 514
7.1.1. Adsorption on Powders ..................... 515
7.1.2. Adsorption on Bulk Metals ................. 527
7.2. Native Oxides: Atmospheric Corrosion and Corrosion
Inhibition ......................................... 532
7.3. Adsorption on Flat Surfaces of Dielectrics and
Semiconductors ..................................... 542
7.4. Adsorption on Minerals: Comparison of Data Obtained
In Situ and Ex Situ ................................ 547
7.4.1. Characterization of Mineral Surface
after Grinding: Adsorption of Inorganic
Species ................................... 547
7.4.2. Adsorption of Oleate on Calcium
Minerals .................................. 551
7.4.3. Structure of Adsorbed Films of
Long-Chain Amines on Silicates ............ 554
7.4.4. Interaction of Xanthate with Sulfides ..... 561
7.5. Electrochemical Reactions at Semiconducting
Electrodes: Comparison of Different In Situ
Techniques ......................................... 570
7.5.1. Anodic Oxidation of Semiconductors ........ 571
7.5.2. Anodic Reactions at Sulfide Electrodes
in Presence of Xanthate ................... 583
7.6. Static and Dynamic Studies of Metal
Electrode-Electrolyte Interface: Structure of
Double Layer ....................................... 595
7.7. Thin Polymer Films, Polymer Surfaces, and
Polymer-Substrate Interface ........................ 600
7.8. Interfacial Behavior of Biomolecules and
Bacteria ........................................... 613
7.8.1. Adsorption of Proteins and Model
Molecules at Different Interfaces ......... 614
7.8.2. Membranes ................................. 624
7.8.3. Adsorption of Biofilms .................... 626
References ................................................... 629
Appendix ...................................................... 669
References .................................................... 687
Index ......................................................... 691
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