Aluminium nitride

AIN (Table 5.3) has recently been introduced as a substrate because it combines a high thermal conductivity with a thermal expansion coefficient close to that of silicon. Its resistivity is somewhat lower than that of BeO and A1203 but is sufficient for most substrate applications. 

AIN dissociates into its elements at 2500 °C. It is formed by the reaction of aluminium powder with nitrogen and can be sintered in a nitrogen atmosphere. 

AIN replaces BeO in many applications since it is competitive in price and does not present the problems of toxicity in manufacture. It may replace A1203 as a substrate for silicon chips because of its better heat conductivity and its closer match in thermal expansion. 

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Aluminium nitride can also be prepared by heating a mixture of aluminium oxide and carbon in nitrogen in an electric arc furnace ... 

It is stable up to 2000 K and melts under pressure at 2500 K. The crystal structure of aluminium nitride resembles that of boron nitride and diamond, but unlike both of these it is rapidly and exothermically hydrolysed by cold water ... 

Aluminium borohydride Aluminium chloride Aluminium chlorate Ammonium tetrachloroaluminate Aluminium fluoride Aluminium trihydroxide Aluminium ammonium sulphate Aluminium potassium sulphate Aluminium nitride Aluminium nitrate Sodium aluminate Aluminium sodium aluminate Aluminium phosphate Aluminium phosphide Aluminium borate Aluminium oxychloride Aluminium fluorosilicate Aluminium magnesium silicate Aluminium sulphate... 

When controlled nitridation of surface layers is required, as for example in the modification of the chemical properties of the surface of a support, the atomic layer deposition (ALD) technique can be applied." This technique is based upon repeated separate saturating reactions of at least two different reactants with the surface, which leads to the controlled build-up of thin films via reaction of the second component with the chemisorbed residues of the first reactant. Aluminium nitride surfaces have been prepared on both alumina and silica supports by this method wherein reaction cycles of trimethylaluminium and ammonia have been performed with the respective supports, retaining their high surface areas." This method has been applied to the modification of the support composition for chromium catalysts supported on alumina." ... 

Hydrazoic acid is a weak acid like acetic acid. Mendeleyev [40] noted its acidic properties. It reacts with zinc, iron, magnesium and aluminium, to form azides with evolution of hydrogen (Curtius and Rissom [41] Curtius and Darapsky [42], A small amount of ammonia is also produced, due to the reduction of hydrazoic acid. According to Sofianopoulos [43] heated A1 dust reacts with HN3 to form aluminium nitride... 

The gas volume is 502 l./kg and calculated explosion temperature 5400°C. It is also possible that aluminium reacts with nitrogen to form aluminium nitride (A12N2). The reaction is also exothermic (—ztff=80 kcal). (The work was done at the Chem-isch-Technische Reichsanstalt in Germany in the period between the two World Wars [61].)... 

The carbides and nitrides are well known for their hardness and strength, and this section will briefly compare a number of these properties with those of the pure metals. Concentration will be placed here on the first row compounds, since these constitute a complete series, and Mo and W, since these are the most commonly studied metals. As will be shown, the physical and mechanical properties of carbides and nitrides resemble those of ceramics not those of metals. Comparisons will be made with boron carbide (B4C), silicon carbide (SiC), aluminium nitride (AIN), silicon nitride (Si3N4), aluminium oxide (A1203), and diamond, as representative ceramic materials. 

Fig. 14.—Diagrammatic Representation of O. Serpek s Aluminium Nitride Process.

Schober R, Richter HJ (1999) Composite ceramics based on silicon nitride or aluminium nitride. In Krams J (ed) Proceedings Biennial Worldwide Congress UNITECR 99, Verlag Stahleisen, Diisseldorf, p 198... 

Christensen, N.E. and Gorczyca, I. (1993), Calculated structural phase-transitions of aluminium nitride underpressure , Physics Review B, 47, 4307 1314. 

Delavignette, P, Kirkpatrick, H.B. and Amelinckx, S. (1961), Dislocations and stacking faults in aluminium nitride , Journal of Applied Physics, 32, 1098-1100. 

Nieto, M.I., Martinez, R., Mazerolles, L., Baudin, C. (2004), Improvement in the thermal shock resistance of alumina through the addition of submicron-sized aluminium nitride particles , J. Eur. Ceram. Soc., 24, 2293-2301. 

Hossain et al [15] measured die cathodoluminescence in undoped aluminium nitride (AIN) thin films at 300, 77 and 4.2 K. These films were grown on sapphire and SiC substrates by LP-MOCVD at 1473 K. As shown in FIGURE 1, two distinct peaks were observed at about 6.1 and 5.9 eV, respectively. The energy position of these peaks increases and the linewidth becomes narrower, as the temperature is decreased. They believed that these two peaks are due to exciton recombination. Recently, MacMillan et al measured cathodoluminescence in AlN-GaN superlattices [16],... 

The five distinguishable second-order elastic moduli in a hexagonal crystal are Cn, Cn, Ci3, C33 and C44. There are reports of neither measured nor calculated values but, since each depends principally on the lattice constants [21] which vary by only about 10% across the nitrides, values for AIN (q.v.) may be used as a first approximation. The comparability of bulk moduli in indium, gallium and aluminium nitrides supports this approach. Estimates of the principal transverse and longitudinal elastic constants Ct and Ci are given in TABLE 2. 

In the case of aluminium nitride, the decomposition is into liquid aluminium and nitrogen gas. This decomposition is the impediment to the growth of AIN bulk crystals using conventional melt growth processes. 

One technique that addresses both container reaction and impurity inclusions is a high pressure, RF, melt growth process. With this process, the material is inductively heated by RF energy, oscillating at frequencies between 450 kHz and 4 MHz. Power levels up to 100 kW are available to produce melt temperatures of the order of 2600°C. To prevent decomposition, the chaige is contained in a nitrogen over-pressure of 10 to 100 atm. The liquid aluminium nitride is self-contained in a water-cooled skin, which prevents both container reaction and deleterious inclusions. 

TABLE 2 Thermochemical Data of Selected Chemical Compounds Aluminium Nitride (AIN), crystal, mol. wt. = 40.98824... 

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