Abstract
Plasma nitridation of an amorphous SiO2 layer on Si (110) substrate can form well-aligned α-Si3N4 crystallites in fibrous morphology. Nitriding is performed at a temperature in the range of 800–1000 °C by using microwave plasma with a gas mixture of N2 and H2. Raman spectroscopy shows the characteristics of an α-Si3N4 phase without other crystalline nitrides. As shown by scanning electron microscopy, the formed α-Si3N4 microfibers on the Si substrate can be in a dense and straight array nearly along with Si <11¯0>, and can have a length over 2 mm with a diameter in the range of 5–10 μm. Structural characterization of scanning transmission electron microscopy in cross section view reveals that the elongated α-Si3N4 crystallites are formed on the surface of the nitrided SiO2/Si (110) substrate without any interlayers between Si3N4 and Si, and the longitudinal direction of α-Si3N4 appears mainly along <112¯0>, which is approximately parallel to Si <11¯0>.
Highlights
Silicon nitride (Si3 N4 ) has been used in many structural applications for a long time due to its excellent properties, such as high hardness and high-temperature stability, resistance to thermal shock, and wear resistance
Plasma nitridation of SiO2 and Si for the formation of Si3 N4 have been studied in previous reports by using thermal and radio frequency plasma processes with gases containing nitrogen [9,10,11] in which hydrogen may be necessary for the oxide reduction, and nitrogen reaction with Si formed nitride
We have shown that microwave plasma can be effectively applied for nitridation of c-plane and m-sapphires to form epitaxial AlN
Summary
Silicon nitride (Si3 N4 ) has been used in many structural applications for a long time due to its excellent properties, such as high hardness and high-temperature stability, resistance to thermal shock, and wear resistance. Si3 N4 has many different crystal structures, among which α-Si3 N4 , β-Si3 N4 , and γ-Si3 N4 are common phases. Both α-Si3 N4 and β-Si3 N4 can be formed under ambient conditions at high temperatures, while γ-Si3 N4 exists under high temperature and high pressure [3,4,5]. Si3 N4 synthesis, generally in polycrystalline microstructure, has been widely conducted by nitridation of Si and SiO2 powders at high temperature. We have shown that microwave plasma can be effectively applied for nitridation of c-plane and m-sapphires to form epitaxial AlN. Epitaxial TiN can obtain plasma nitridation of rutile TiO2 [12,13,14]
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