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Formation of AlN on sapphire surfaces by high-temperature heating in a mixed flow of H2 and N2

Heat treatment of (0001) sapphire substrates in the temperature range 980–1480 °C was investigated in an atmospheric-pressure mixed flow of H2 and N2 for various molar fractions of H2 (F°=H2/(H2+N2)). At 1330 °C, AlN whiskers formed on the sapphire surfaces only when the heat treatment was performed in the presence of both H2 and N2 (0<F°<1). The amount of AlN that formed was a maximum for F°=0.750, whereas no AlN was formed at F°=0 (N2 flow) or 1.000 (H2 flow). When F°=0.750, AlN whiskers formed in the temperature range 1030–1430 °C, whereas no AlN was formed outside this temperature range. These experimental results are explained in terms of thermodynamic analysis.
Highlights
► Heat treatment of sapphire substrates in the range 980-1480 °C was investigated.
► AlN whiskers formed on sapphire by heat treatment in mixed flows of H2 and N2.
► Thermodynamic analysis of high-temperature heat treatment of sapphire was performed.
 
Fig. 1. 2θω XRD profiles of sapphire substrates after 60 min heat treatment at 1330 °C in gas flows with various values of F°.
 
Source: Journal of Crystal Growth
 
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