Materials for Electronics

We introduced the basic principles of semiconduction in Section 5.3. Many semiconductors have the cubic sphalerite (zinc blende) structure (Fig. 4.12), which is the same as the diamond lattice (Fig. 3.1) if all the atoms are the same, as in Si or Ge. Inorganic semiconductors generally have four valence electrons per atom, as is the case for Si and Ge. They can be classified according to the number of valence electrons of the participating atoms  

As noted in Sections 5.3-5.5, vacancies in the anion or cation array can exist in equilibrium with the vapor of the depleted element. If the enthalpy of formation of a vacancy in the anion array is markedly greater than that of one in the cation sublattice—for example, in ZnTe, where it is about 1 electron volt (1 eV = 96.5 kJ mol ) higher—the heated solid will tend to develop an excess of cuiions and so will become a p-type semiconductor. The enthalpies of vacancy formation correlate with the anion-cation radius ratios thus, very large anions such as Te matched with relatively small cations such as Zn + favor doping with vapor of the anionic element for 

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Electronic. Diamonds have been used as thermistors and radiation detectors, but inhomogeneities within the crystals have seriously limited these appHcations where diamond is an active device. This situation is rapidly changing with the availabiHty of mote perfect stones of controUed chemistry from modem synthesis methods. The defect stmcture also affects thermal conductivity, but cost and size are more serious limitations on the use of diamond as a heat sink material for electronic devices. 

To achieve low stress embedding material, low modulus material such as siUcones (elastomers or gels) and polyurethanes are usually used. Soft-domain elastomeric particles are usually incorporated into the hard (high modulus) materials such as epoxies and polyimides to reduce the stress of embedding materials. With the addition of the perfect particle size, distribution, and loading of soft domain particles, low stress epoxy mol ding compounds have been developed as excellent embedding materials for electronic appHcations. 

C. P. Wong, Improved Eoom-Temperature Wulconicyed Silicone Elastomers as Integrated Circuit Encapsulants, Polymer Materials for Electronics Applications, American Chemical Society Symposium Series, Washington, D.C., Nos. 184, 171, 1982. 

Heat-sink substrates and packaging materials for electronic devices (major application). 

Experimental high-power and high-temperature material for electronic and optoelectronic devices especially in the UV region of the spectrum. 

Considerable work is in progress in the development of silicide materials for electronic applications. These compounds are used increasingly as conductive thin films and are replacing... 

Controlled/living radical polymerisation (CRP) is currently a fast developing area in polymer synthesis and it allows preparation of many advanced polymeric materials, including thermoplastic elastomers, surfactants, gels, coatings, biomaterials, materials for electronics and many others. 

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

The wide use of p-block and early transition metal chalcogenide materials for electronics applications (semiconductors, semi-metals, battery materials, etc.) has resulted in a large amount of work concerned with CVD using mixtures of metal halides and chalcogenoethers as dual source precursors and preformed complexes as single sources.166... 

Wu J, Pisula W, Mullen K (2007) Graphene molecules as potential material for electronics. Chem Rev 107 718... 

Licari, J. J. 2003. Coating Materials for Electronic Applications Polymers, Processes, Reliability, Testing. Noyes Publications, William Andrew Publishing, New York. 

GaN as a semi-conducting material for electronics is about to be launched on the market, especially for the use in blue- and UV-emitting LEDs and laser diodes [2]. The material is deposited on crystalline substrates like sapphire using thin-film epitactical techniques. Often, metal-organic chemical vapor deposition (MOCVD) is used. The necessity for such technologies limits the production rate and pushes up costs. 

Silicon is a model for the fundamental electronic and mechanical properties of Group IV crystals and the basic material for electronic device technology. Coherent optical phonons in Si revealed the ultrafast formation of renormalized quasiparticles in time-frequency space [47]. The anisotropic transient reflectivity of n-doped Si(001) featured the coherent optical phonon oscillation with a frequency of 15.3 THz, when the [110] crystalline axis was parallel to the pump polarization (Fig. 2.11). Rotation of the sample by 45° led to disappearance of the coherent oscillation, which confirmed the ISRS generation,... 

As already mentioned, unsubstituted PT is an insoluble and infusible material. Once the polymer is prepared, it is difficult (if not impossible) to further process it as a material for electronic applications. The solubility can be greatly enhanced by the introduction of side chains at position 3 (or at both, 3 and 4). The most widely studied side chains are n-alkyl substituents that can be easily introduced into the thiophene core by reaction of 3-bromothio-phene with alkyl-Grignard reagents [464]. 

Y. Shirota, Organic materials for electronic and optoelectronic devices, J. Mater. Chem., 10 1-25 (2000). 

Varieties of polymers are also employed as sensitive material for electronic nose applications, and the operating temperature may reach about 100 ° C. In the case of quartz microbalance-based sensors a large role is played by the chemically interactive material (CIM) on which it is deposited. A rather efficient room temperature operating CIM is the metal-porphirin, by which it is possible to construct varieties of nostrils, just changing the type of coordinated metal. Interesting metals success-... 

Reichmanis,E. Wilkens,C.W. In Polymer Materials for Electronic Applications American Chemical Society Symposium Series Washington, DC, 1983 Vol.184, p.30. 

Cold cure silicone rubbers and available as pastes. These pastes are mixed with an organometallic catalyst and silicate and cured at room temperature. These are used as adhesives, and as encapsulating materials for electronic components. They are also used for textile coating and in moulds. 

To assess the effect of elastomer degradation on composite performance, additional composites were fabricated with the same 121°C cure epoxy without any addition of the elastomer (211. The expansion behavior of the modified epoxy composite was similar to the toughened material. For electron doses less than 10 rads the CTE of the toughened and untoughened composites were essentially the same which suggests that the epoxy matrix and not the elastomeric component controls the thermal expansion behavior. 

Preparation of biological material for electron microscopy still required fixation, dehydration, and ultrathin sections. Araldite and other resins were used in place of paraffin wax for blocking. At first, specially sharpened steel knives were employed to cut the sections, but from 1950 glass or diamond knives were used which could cut slices 100-200 nm thick. By 1952, Palade and others were obtaining sections... 

Lupinski JH, Moore RS (eds) (1989) Polymeric materials for electronic packaging and interconnection. ACS Symposium Series 407... 

E.R. Howells (Ed.), Technology of Chemicals and Materials for Electronics, EUis Horwood, Chichester, 1984. 

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