Effects of methyl terminal and carbon bridging groups ratio on critical properties of porous organosilicate-glass films

Organosilicate glass-based porous low dielectic constant films with different ratios of terminal methyl to bridging organic (methylene, ethylene and 1,4-phenylene) groups are spin-on deposited by using a mixture of alkylenesiloxane with organic bridges and methyltrimethoxysilane, followed by soft baking at 120–200◦ C and curing at 430◦ C. The films’ porosity was controlled by using sacrificial template Brij® L4. Changes of the films’ refractive indices, mechanical properties, k-values, porosity and pore structure versus chemical composition of the film’s matrix are evaluated and compared with methyl-terminated low-k materials. The chemical resistance of the films to annealing in oxygen-containing atmosphere is evaluated by using density functional theory (DFT). It is found that the introduction of bridging groups changes their porosity and pore structure, increases Young’s modulus, but the improvement of mechanical properties happens simultaneously with the increase in the refractive index and k-value. The 1,4-phenylene bridging groups have the strongest impact on the films’ properties. Mechanisms of oxidative degradation of carbon bridges are studied and it is shown that 1,4-phenylene-bridged films have the highest stability. Methylene-and ethylene-bridged films are less stable but methylene-bridged films show slightly higher stability than ethylene-bridged films. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

The prospect of spray pyrolyzed pure, Mn-doped, and Zn-doped nickel oxide thin films as TCO material

Nickel Oxide films with Manganese (Mn) and Zinc (Zn) doping (NiO, Ni1-xMnxO, and Ni1-xZnxO; where x = 0, 0.02, 0.04, and 0.06) were fabricated using the spray pyrolysis technique on the glass substrates at 400 °C (673K) temperature. The XRD spectra revealed a polycrystalline nature of the films with cubic crystal structure and a favored growth orientation towards the (111) plane. The SEM micrographs revealed a smooth, homogeneous, and uniform surface, while the EDS spectra confirmed the presence of Ni, O, Zn, and Mn elements in the films. Optical analysis using UV–visible absorption spectroscopy demonstrated high transparency of the films in the visible region (400 nm–900 nm), and the transparency increased with higher Zn doping, reaching ∼85 % in Ni0.94Zn0.06O films. Conversely, Ni1-xMnxO films show a slight transmission decline with increasing Mn doping concentrations. The sheet resistance of the films was found to be decreased for low-concentration doping and again began to increase for highly doped Ni0.94Zn0.06O and Ni0.94Mn0.06O films. Among all the films, Ni0.98Zn0.02O exhibited the maximum figure of merit, showing the prospect for optoelectronic applications

UV-Excited Luminescence in Porous Organosilica Films with Various Organic Components

UV-induced photoluminescence of organosilica films with ethylene and benzene bridging groups in their matrix and terminal methyl groups on the pore wall surface was studied to reveal optically active defects and understand their origin and nature. The careful selection of the film’s precursors and conditions of deposition and curing and analysis of chemical and structural properties led to the conclusion that luminescence sources are not associated with the presence of oxygen-deficient centers, as in the case of pure SiO2. It is shown that the sources of luminescence are the carbon-containing components that are part of the low-k-matrix, as well as the carbon residues formed upon removal of the template and UV-induced destruction of organosilica samples. A good correlation between the energy of the photoluminescence peaks and the chemical composition is observed. This correlation is confirmed by the results obtained by the Density Functional theory. The photoluminescence intensity increases with porosity and internal surface area. The spectra become more complicated after annealing at 400 °C, although Fourier transform infrared spectroscopy does not show these changes. The appearance of additional bands is associated with the compaction of the low-k matrix and the segregation of template residues on the surface of the pore wall