Indium Oxide Systems

The list of precursors for indium contains indium trichloride (InCfi) [96-109], indium trifluoride (InFj) [110], indium acetate (In(ac)2(OH)) [111], indium acetylace-tonate (In(acac)j) [112-115], tris-2,2,6,6-tetramethyl-3,5-heptanedionate indium (In(thd)3) [116, 117], trimethyl indium (ln(CH3)3) [116, 118], trimethyl indium diethyletherate ((CH3)3ln(0(CH2CH3)2)) [119], indium 2-ethylhexanoate 

A different deposition technique, termed chemical transport, was studied by Enloe and Wirtz [123]. They used In20, pellets as starting material and brought this into the gas phase at sufficiently high temperatures by transformation into In20 and In in a reducing atmosphere. Those species were decomposed in a reaction chamber under oxidizing conditions. 

The kinetics of the deposition of In20i films have not been investigated by many groups, since most of them concentrate on the physical properties and possible applications. The published results are listed in Table 3-8. In addition, there are only two remarks about decomposition pathways. Maruyama andTabata [111] state that indium acetate needs no oxygen as reactant to form indium oxide, i.e., some of the metal-oxygen bonds are not broken during the deposition. Also, as proposed by Nomura and coworkers [122], the butylindium thiolate decomposes via formation of indium sulfides  

Indium trichloride is a very common precursor for spray pyrolysis. The compound was dissolved in different solvents such as water [103], methanol [103], ethanol [101], isopropanol [98], butyl acetate [96, 97] and mixtures of them [99, 100, 102,103]. There are no reports on the kinetic behavior of the deposition. 

As shown in Table 3-9, doped In203 films are frequently a-axis orineted. However, Ishida et al. [103] showed that the preferred orientation depends on the growth parameters and can be intentionally changed from [100] to [111] direction. 

---

Alloys suitable for castings that ate to be bonded to porcelain must have expansion coefficients matching those of porcelain as well as soHdus temperatures above that at which the ceramic is fired. These ate composed of gold and palladium and small quantities of other constituents silver, calcium, iron, indium, tin, iridium, rhenium, and rhodium. The readily oxidi2able components increase the bond strength with the porcelain by chemical interaction of the oxidi2ed species with the oxide system of the enamel (see Dental materials). 

OSHA PEL TWA 0.1 mg(In)/m3 ACGIH TLV TWA 0.1 mg(In)/m3 SAFETY PROFILE A poison by subcutaneous route. It affects the liver, heart, kidneys, and the blood. Teratogenic effects. Inhalation of indium compounds may cause damage to the respiratory system. Hydrated indium oxide is a poison by... 

Another limiting case is an alloy, AB, neither component of which initially reacts to form an external scale and in which component A has a much greater affinity for oxygen than B. A classical example is the silver-indium alloy system. Silver doesn t form an oxide at elevated temperatures, but it does dissolve oxygen. Small amounts of indium will therefore form an oxide within the alloy metal, a so-called subscale or internal oxide. The process is diffusion controlled and the diffusion of oxygen in the alloy is rate limiting. Such systems have been studied extensively by R. A. Rapp, especially the transition from only internal oxidation to the formation of an external scale (22),... 

The system consists of five functional layers, which are located between two glass or plastic substrates. Each plate is coated with a thin transparent conductive electrode (TCE), usually a doped form of tin oxide e.g., fluorine doped tin oxide (FTO Sn02 F) or Sn-doped indium oxide (ITO In203 Sn). One ofthe TCE is coated with an electrochromic coating (EC-layer), the other with a coimter electrode (CE layer). Both layer systems are separated by an ionic conductive electrolyte with very low electronic conductivity. In order to have high diffusion coefficients and fast kinetics, the ions should be small, therefore protons (H" ) or lithium (Li ) are preferred. The electrical contacts are attached at the TCE coatings. 

INDIUM OXIDE. In20j. Mol. wt. 277.64 sp. gr. 7.179 m.p. 1910°C. An n-type semiconductor finding use as a resistive element in integrated circuits. Resistivity values from 100 ohm/sq to megohms per square can he tailored. The screen printed mix consists of high-purity indium oxide, dopants and borosihcate glass flux. Piling temperature 900-1000°C. Temperature coefficients of resistivity of such systems have been measured at <500 ppm/C from room temperature to 100°C. 

For polymer solar cells, as described above, typically, conjugated low band gap polymer (electron donor) is blended with an electron acceptor to achieve a BHJ layer and fabricated on a transparent conducting oxide (TCO)-coated glass substrate (i.e., tin-doped indium oxide (ITO)). In this system, photons are absorbed by the electron donor, then excitons are generated, diffuse to the interface of the two bulk components, and dissociate. The acceptor receives the electron and transfers to the electrode, while the hole remains within the donor as shown in Fig. 6.4. 

Dyes for Color Filters. Colorhquid crystal display systems consist of LSI drivers, glass plates, polarizers, electrodes (indium—tin oxide), and microcolor filters. The iadependent microcolor filter containing dyes is placed on each Hquid crystal pixel addressed electrically and acts as an iadividual light switch. All colors can be expressed by the light transmitted through each filter layer of the three primary colors, ie, red, green, and blue (Fig. 12). 

Fig. 12. General stmcture of LCD. A, polarizer plate B, glass plate C, electrodes (indium—tin oxide) D, Hquid crystal E, common electrode (ITO) F, overcoated layer G, colored pixel H, back light. In an improved color LCD system today, retardation films are placed between A and B.

NB. Mixed solvent systems are shown as e.g. acn-aq (0.01 M) where the number in parentheses indicates the concentration of the lesser constituent ITO-Indium/tin oxide-coated glass, Ar- Solutions purged with argon, Ar atm - Experiment performed under an argon atmosphere, N2 atm - Experiment performed under a nitrogen atmosphere b All potentials are measured vs. SCE unless otherwise stated ... 

---