Silicon oxynitride
Encyclopedia
Silicon oxynitride is a ceramic
material with the chemical formula SiOxNy. While in amorphous forms its composition can continuously vary between SiO2 (silica) and Si3N4 (silicon nitride
), the only known intermediate crystalline phase is Si2N2O. It is found in nature as the rare mineral sinoite
in some meteorites and can be synthesized in the laboratory.
and resistance to heating and oxidation up to temperatures of about 1600 °C.
and silicon nitride
with the advantages of low leakage currents and high thermal stability. These films have an amorphous structure and therefore their chemical composition can widely deviate from Si2N2O. By changing the nitrogen/oxygen ratio in these films, their refractive index can be continously tuned between the value of ~1.45 for silicon dioxide and ~2.0 for silicon nitride. This property is useful for gradient-index optics components such as graded-index fiber
s.
Silicon oxynitrides can be doped with metal atoms. The most common example is sialon
, a family of quaternary SiAlON compound. Quaternary silicon oxynitrides containing a lanthanide
element, such as La, Eu or/and Ce are used as phosphor
s.
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
material with the chemical formula SiOxNy. While in amorphous forms its composition can continuously vary between SiO2 (silica) and Si3N4 (silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
), the only known intermediate crystalline phase is Si2N2O. It is found in nature as the rare mineral sinoite
Sinoite
Sinoite is rare mineral with the chemical formula Si2N2O. It was first found in 1905 in chondrite meteorites and identified as a disntict mineral in 1965. Sinoite crystallizes upon meteorite impact as grains smaller than 0.2 mm surrounded by Fe-Ni alloys and the mineral enstatite...
in some meteorites and can be synthesized in the laboratory.
Properties
The crystalline structure of silicon oxynitride is built by SiN3O tetrahedra connected through oxygen atoms along the c axis and through nitrogen atoms perpendicular to it. The strong covalent bonding of this structure results in high flexural strengthFlexural strength
Flexural strength, also known as modulus of rupture, bend strength, or fracture strength, a mechanical parameter for brittle material, is defined as a material's ability to resist deformation under load...
and resistance to heating and oxidation up to temperatures of about 1600 °C.
Synthesis
Polycrystalline silicon oxynitride ceramics are produced by nitridation of a mixture of Si and silicon dioxide at a temperature above melting point of silicon (1414 °C), in the range 1420–1500 °C:- 3 Si + SiO2 + 2 N2 → 2 Si2N2O
Applications
Thin films of silicon oxynitride can be grown on silicon using a variety of plasma deposition techniques and used in microelectronics as a dielectric layer alternative to silicon dioxideSilicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
and silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
with the advantages of low leakage currents and high thermal stability. These films have an amorphous structure and therefore their chemical composition can widely deviate from Si2N2O. By changing the nitrogen/oxygen ratio in these films, their refractive index can be continously tuned between the value of ~1.45 for silicon dioxide and ~2.0 for silicon nitride. This property is useful for gradient-index optics components such as graded-index fiber
Graded-index fiber
In fiber optics, a graded-index or gradient-index fiber is an optical fiber whose core has a refractive index that decreases with increasing radial distance from the fiber axis ....
s.
Silicon oxynitrides can be doped with metal atoms. The most common example is sialon
Sialon
Sialon ceramics are a specialist class of high temperature refractory materials, with high strength , good thermal shock resistance and exceptional resistance to wetting or corrosion by molten non-ferrous metals, compared to other refractory materials such as, for example, alumina. A typical use...
, a family of quaternary SiAlON compound. Quaternary silicon oxynitrides containing a lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
element, such as La, Eu or/and Ce are used as phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s.