Comparison of secondary ion intensity enhancement from polymers on silicon and silver substrates by using Au-TOF-SIMS

The usefulness of the usage of cluster primary ion source together with an Ag substrate and detection of Ag cationized molecular ions was studied from the standpoint to realize high sensitivity TOF-SIMS analysis of organic materials. Although secondary ions from polymer thin films on a Si substrate can be detected in a higher sensitivity with Au₃⁺ cluster primary ion compared with Ga⁺ ion bombardment, it was clearly observed that the secondary ion intensities from samples on an Ag substrate showed quite a different tendency from that on Si. When monoatomic primary ions, e.g., Au⁺ and Ga⁺, were used for the measurement of the sample on an Ag substrate, [M+Ag]⁺ ions (M corresponds to polyethylene glycol molecule) were detected in a high sensitivity. On the contrary, when Au₃⁺ was used, no intensity enhancement of [M+Ag]⁺ ions was observed. The acceleration energy dependence of the detected secondary ions implies the different ionization mechanisms on the different substrates.     

Synthesis and properties of highly thermally stable ultrathin films of fluorine-containing hyperbranched polybenzoxazoles

In this paper, we aimed to develop ultrathin films of hyperbranched polybenzoxazole with a thickness in the range between 1 and 100 nm. They are expected to have great potential for various applications as functional materials due to their high thermal stability, good chemical resistance and mechanical strength. The synthesis of various hyperbranched poly(o-hydroxyamide)s as precursors of polybenzoxazole was examined by the polycondensation of 2,2-bis(3-amino-4-hydroxyphenyl)propane (AHP) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AHFP) with 1,3,5-benzenetricarbonyl trichloride (BCC), yielding the corresponding hyperbranched poly(o-hydroxyamide), poly(AHFP_m-co-AHP_n-co-BCC_2.0), with M_n in the range between 12,870 and 22,210 in satisfactory yields. Poly(AHFP_3.0-co-BCC_2.0), poly(AHFP_2.25-co-AHP_0.75-co-BCC_2.0), and poly(AHFP_1.50-co-AHP_1.50-co-BCC_2.0) showed good solubility and film-forming ability, and ultrathin films 8.9–88.6 nm thick were prepared on silicon wafers. Heating of the ultrathin films of poly(AHFP_m-co-AHP_n-co-BCC_2.0) on a hot plate at 350 °C for 1 h afforded the corresponding ultrathin films of hyperbranched polybenzoxazole, poly(AHFP_m-cyclo-AHP_n-cyclo-BCC_2.0), with a thickness of 5.3–82.4 nm. Double-layer thin films consisting of resist materials on top of hyperbranched polybenzoxazole were also prepared.