Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Reaction Products of Co Catalysts in Ethanol-Chemical-Vapor-Deposition Ambient at Low-Pressure Studied by in situ X-Ray Photoelectron Spectroscopy

Abstract: We succeeded in growing carbon nanotubes in a photoelectron spectroscopy analysis system using thermal chemical vapor deposition and analyzed the chemical states of the Co catalysts by in situ X-ray photoelectron spectroscopy before and after the growth. The carbon nanotubes were grown in an ethanol ambient at about 4×10-2 Torr, a relatively low pressure that was used because we needed to subsequently measure photoelectrons under ultrahigh vacuum. We found that almost all of the Co particles are metallic after the growth. This shows that the metallic state is stable for Co under low-pressure ethanol ambient in our growth condition for carbon nanotubes.

Effect of nitrogen doping on the microstructure and thermal stability of diamond-like carbon coatings containing silicon and oxygen

Abstract: Using hexamethyldisiloxane, acetylene, and N2 as the precursors, binary Si/O and ternary Si/O/N co-doped diamond-like carbon (DLC) coatings were deposited on 316 L stainless steel and single-crystal Si wafer substrates via high-bias voltage plasma-enhanced chemical deposition. The coated specimen was annealed in the temperature range 200–650 °C in a chamber maintained at 5 Pa vacuum. The microstructure and chemical bonds were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The mechanical properties were investigated using a residual stress tester and a nano-indenter. It was found that approximately 50% of the Si in the binary Si/O co-doped coating were present as Si O bonds. Notably, N doping reduced the sp3 C C fraction, hindered the formation of O-containing bonds, and enhanced the Si C bonds in the as-deposited ternary Si/O/N co-doped coatings; however, the dominant chemical state of the N atom remained in the form of C N bonds. Furthermore, N doping was beneficial toward the stabilization of the Si C and Si O bonds and hindered graphitization during annealing. The thermal stability of the microstructure and mechanical performance of the ternary co-doped DLC coatings were superior to those of the binary Si/O-co-doped DLC coatings. After annealing at 500 °C, the ternary coatings retained a hardness of 16.5 GPa.

Interface properties of thin oxide layers grown on strained SiGe layers at low temperatures

Abstract: The chemical state and the electrical properties of the interfaces of thin oxide films grown on strained layers using plasma and thermal oxidation have been studied in detail. X-ray photoelectron spectroscopy studies show no Ge pile-up at the oxide/substrate interface. In the case of plasma oxidation, Ge at the oxide surface is found to be in a fully oxidized state, while the formation of an intermediate oxidized state is observed in the case of low-temperature thermal oxidation. High-frequency (1 MHz) capacitance - voltage (C - V) and conductance - voltage (G - V) measurements have indicated the growth of good quality gate oxides. The fixed oxide charge and interface state densities are comparable to those of low-temperature-grown metal - oxide - semiconductor capacitors on Si with aluminium gates.