Today cross-cutting approaches, where molecular engineering and clever processing are synergistically coupled, allow the chemist to tailor complex hybrid systems of various shapes with perfect mastery at different size scales, composition, functionality, and morphology. Hybrid materials with organic–inorganic or bio–inorganic character represent not only a new field of basic research but also, via their remarkable new properties and multifunctional nature, hybrids offer prospects for many new applications in extremely diverse fields. The description and discussion of the major applications of hybrid inorganic–organic (or biologic) materials are the major topic of this critical review. Indeed, today the very large set of accessible hybrid materials span a wide spectrum of properties which yield the emergence of innovative industrial applications in various domains such as optics, micro-electronics, transportation, health, energy, housing, and the environment among others (526 references).

Applications of advanced hybrid organic–inorganic nanomaterials: from laboratory to market

THE leading technology for flat, high-resolution computer and television screens is based on twisted nematic liquid-crystal displays1. The successful operation of these displays requires control of molecular alignment, which is currently achieved by confining the liquid crystal between mechanically rubbed surfaces2. But in addition to the practical difficulties associated with rubbing, the resulting displays suffer from restricted viewing angles arising from the uniaxial nature of the alignment process3,4. This latter problem can in principle be circumvented if molecular alignment is varied, in a controlled manner, within individual pixels5–9. Exposure of functionalized substrates to polarized light offers a means of achieving high-resolution patterns in the plane of the display10–12. But to ensure that the alignment pattern imposed on the liquid crystal is free of orientation defects, the tilt angle between the long molecular axes and the substrates must be precisely controlled13,14. Here we show how our earlier linear photoalignment strategy10,12 can be extended to obtain such control, and thereby fabricate stable, multi-domain pixel displays with markedly improved fields of view.

Optical patterning of multi-domain liquid-crystal displays with wide viewing angles

Preface. 1. Introduction to Semiconductor Lithography. 1.1 Basics of IC Fabrication. 1.2 Moore's Law and the Semiconductor Industry. 1.3 Lithography Processing. Problems. 2. Aerial Image Formation - The Basics. 2.1 Mathematical Description of Light. 2.2 Basic Imaging Theory. 2.3 Partial Coherence. 2.4 Some Imaging Examples. Problems. 3. Aerial Image Formation - The Details. 3.1 Aberrations. 3.2 Pupil Filters and Lens Apodization. 3.3 Flare. 3.4 Defocus. 3.5 Imaging with Scanners Versus Steppers. 3.6 Vector Nature of Light. 3.7 Immersion Lithography. 3.8 Image Quality. Problems. 4. Imaging in Resist: Standing Waves and Swing Curves. 4.1 Standing Waves. 4.2 Swing Curves. 4.3 Bottom Antirefl ection Coatings. 4.4 Top Antirefl ection Coatings. 4.5 Contrast Enhancement Layer. 4.6 Impact of the Phase of the Substrate Refl ectance. 4.7 Imaging in Resist. 4.8 Defi ning Intensity. Problems. 5. Conventional Resists: Exposure and Bake Chemistry. 5.1 Exposure. 5.2 Post-Apply Bake. 5.3 Post-exposure Bake Diffusion. 5.4 Detailed Bake Temperature Behavior. 5.5 Measuring the ABC Parameters. Problems. 6. Chemically Amplifi ed Resists: Exposure and Bake Chemistry. 6.1 Exposure Reaction. 6.2 Chemical Amplifi cation. 6.3 Measuring Chemically Amplifi ed Resist Parameters. 6.4 Stochastic Modeling of Resist Chemistry. Problems. 7. Photoresist Development. 7.1 Kinetics of Development. 7.2 The Development Contrast. 7.3 The Development Path. 7.4 Measuring Development Rates. Problems. 8. Lithographic Control in Semiconductor Manufacturing. 8.1 Defi ning Lithographic Quality. 8.2 Critical Dimension Control. 8.3 How to Characterize Critical Dimension Variations. 8.4 Overlay Control. 8.5 The Process Window. 8.6 H-V Bias. 8.7 Mask Error Enhancement Factor (MEEF). 8.8 Line-End Shortening. 8.9 Critical Shape and Edge Placement Errors. 8.10 Pattern Collapse. Problems. 9. Gradient-Based Lithographic Optimization: Using the Normalized Image Log-Slope. 9.1 Lithography as Information Transfer. 9.2 Aerial Image. 9.3 Image in Resist. 9.4 Exposure. 9.5 Post-exposure Bake. 9.6 Develop. 9.7 Resist Profi le Formation. 9.8 Line Edge Roughness. 9.9 Summary. Problems. 10. Resolution Enhancement Technologies. 10.1 Resolution. 10.2 Optical Proximity Correction (OPC). 10.3 Off-Axis Illumination (OAI). 10.4 Phase-Shifting Masks (PSM). 10.5 Natural Resolutions. Problems. Appendix A. Glossary of Microlithographic Terms. Appendix B. Curl, Divergence, Gradient, Laplacian. Appendix C. The Dirac Delta Function. Index.

Fundamental principles of optical lithography : the science of microfabrication

The spin coating of thin (> 200 nm thick) and ultrathin (< 200 nm thick) polymer films is examined in several solvents of varying volatility over a broad range of polymer solution concentrations and spin speeds. Experimentally measured film thicknesses are compared with a simple model proposed by Bornside, Macosko, and Scriven, which predicts film thickness based on the initial properties of the polymer solution, solvent, and spin speed. This model is found to predict film thickness values within 10% over the entire range of conditions explored, which gave film thicknesses from 10 nm to 33 μ:m. The model underpredicts film thickness for cases in which a very volatile solvent is used or the initial concentration of polymer is high, while overpredicting film thickness for cases in which a low volatility solvent is used or the initial polymer concentration is very low. These deviations are a consequence of how the model decouples fluid flow and solvent evaporation.

Spin coating of thin and ultrathin polymer films

Dip coating is a simple old way of depositing onto a substrate, especially small slabs and cylinders, a uniform thin film of liquid for solidification into a coating. The basic flow is steady, and in it film thickness is set by the competition among viscous force, capillary (surface tension) force and gravity. Thickness and uniformity can be sensitive to flow conditions in the liquid bath and gas overhead. The faster the substrate is withdrawn, the thicker the film deposited. This can be countered by using volatile solutes and combining rapid enough drying with the basic liquid flow. Then the physics grows more complicated, theoretical prediction of process performance more difficult, and control of the process more demanding. Outside product RD actually it is often modified.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400485180

Physics and Applications of DIP Coating and Spin Coating

A model is presented for the description of thin films prepared from solution by spinning. Using only the centrifugal force, linear shear forces, and uniform evaporation of the solvent, the thickness of the film and the time of drying can be calculated as functions of the various processing parameters. The model is compared with experimental results obtained on positive photoresists and excellent agreement is obtained. When adequate care are is taken, the liquid forms a level surface during spinning, and the film thickness becomes uniform and independent of the size of the substrate. The film thickness h shows the following dependence on spin speed f, initial viscosity ν0, and evaporation rate e:h∝f−2/3νo1/3e1/3, and e is proportional to f1/2.

Characteristics of resist films produced by spinning

This paper describes a study of current flow through very thin insulating films. Several possible conduction mechanisms are presented and their properties are discussed. The dominant conduction process in the layers studied is quantum‐mechanical tunneling. Previous work on this mechanism is extended by an exact calculation which shows the current‐voltage characteristic to be divided into three regions of different logarithmic curvature. The dielectric constant of the insulator is found to have a large effect, via the image force, on the tunneling current. The theoretical results are fitted to measurements made on insulating layers less than 100 A thick, sandwiched between metal electrodes. For Al2O3 layers the fit is excellent, resulting in barrier heights of 2.0–2.5 eV and thicknesses approximately 25 A less than the values determined from capacitance, as expected. In contrast the conduction characteristics of BeO layers can be explained by tunneling only in the low‐voltage region; barrier height and thickness are similar to the Al2O3 case. At intermediate voltages the currents are lower than predicted and at high voltages reproducible hysteresis effects are observed with time constants of the order of minutes. These effects are only weakly temperature dependent. They appear to be due to tunneling from one of the metals into trap states in the forbidden gap of the insulator, creating space charge which distorts the barrier for tunneling.

Current Flow in Very Thin Films of Al2O3 and BeO

The dielectric constants and two elastic constants were measured for a series of mixtures of two nematic liquid crystals, MBBA and PEBAB. The materials covered the range from 0 to 10% PEBAB. The parameters were calculated from the measured voltage dependence of capacitance. The dielectric constants vary linearly with PEBAB concentration and the anisotropy changes from negative to positive at 1.7%. The elastic constants remain fixed over most of the range, but are reduced in mixtures of small anisotropy. The results differ significantly from recent measurements of Michel and Smith, the probable reason being that we take any nonideal alignment at the surface explicitly into account in the calculations.

Elastic and dielectric constants in mixtures of nematic liquid crystals

The relationships between the optical transfer characteristics of twisted‐nematic liquid‐crystal devices and the material and cell parameters were investigated. The dependence of transmission on wavelength, birefringence, cell thickness, and surface alignment was measured as functions of light direction and operating conditions. The experimental results were confirmed by calculations of the transmission using Berreman’s numerical procedure for anisotropic media. The angle over which good contrast is observed increases with increasing wavelength and decreasing cell thickness and birefringence. This is accompanied by a decreasing value of optical threshold. The most uniform response and widest viewing angle is obtained with materials of small birefringence in cells with near‐planar alignment.

Dietrich Meyerhofer

Papers

Characteristics of resist films produced by spinning

Current Flow in Very Thin Films of Al2O3 and BeO

Elastic and dielectric constants in mixtures of nematic liquid crystals

Optical transmission of liquid‐crystal field‐effect cells