SiOx

SiOx refers to silicon oxide with a variable oxidation state, expressed as SiO_x, where x is between 1 and 2. The term covers non-stoichiometric silicon oxides that often contain silicon-rich regions or suboxide species embedded in a silicon oxide matrix.

Structure and properties: SiOx materials are typically amorphous and can range from silicon-rich oxide (lower x) to nearly stoichiometric silicon dioxide (x close to 2). Their electrical and optical properties depend on x and microstructure; they are generally insulating but can exhibit tunable dielectric behavior. The optical refractive index and bandgap increase with higher silicon content, while silicon-rich variants may harbor nanometer-scale silicon clusters that affect conductivity and photoluminescence. SiOx is commonly used as a diffusion barrier, passivation layer, or dielectric in electronic and optoelectronic devices.

Preparation and characterization: SiOx films and powders are produced by chemical vapor deposition, sputtering, plasma-enhanced methods, or thermal oxidation of silicon under controlled oxygen partial pressure. Post-deposition annealing can drive the material toward higher oxidation states (toward SiO2). Characterization methods include X-ray photoelectron spectroscopy to determine oxidation states, FTIR to identify Si–O–Si networks, and ellipsometry or spectroscopic techniques to measure thickness and optical constants.

Applications: SiOx serves as a protective coating, interfacial layer, or dielectric in semiconductors, solar cells, and microelectromechanical systems. It is also used as a precursor to silicon oxide in nanostructures and can participate in resistive switching in memory devices.

Notes: The properties of SiOx depend strongly on processing conditions and the exact x value, and the material tends to oxidize toward SiO2 with further exposure to oxygen.