Abstract
Time-of-flight secondary ion mass spectrometer (ToF-SIMS) is an analytical technique that can be used to characterize the surface and near surface region of solids and the surface of some liquids. ToF-SIMS could distingulish analytes with mass resolution different by 10000 at ppma to ppba sensitivity. Top monolayer atomic or molecular information could be determined by adjusting primary ion current density. Chemical images with lateral resolution 100 nm or less can be obtained by using Ga+ gun. ToF-SIMS extend its applicability to broad fields such as microelectronics, nano-technology, polymer science, life science technology, environmental analysis and medical technology. ToF-SIMS could simultaneously provide critical chemical information and is a multi functional state-of-the art instrument. In chapter 2, a single hair sample preparation protocol modified from reported method was developed and used to prepare longitudinally sectioned hair for ToF-SIMS analysis. Preliminary results demonstrate that ToF-SIMS is capable of providing molecular distribution of fragment ions from intrinsic constituents as well as external chemicals like the hair dye ingredients used in this study. The observation of pPDA and HPO4- penetrating into the internal region of hair might initiate a renewed interest in exposure study. In chapter 3, A model organic light-emitting diodes (OLEDs) with structure of tris(8-hydroxyquinoline) aluminum (Alq3)/N,N’-diphenyl-N,N’-bis[1-naphthy- (1,1’-diphenyl)]-4,4’-diamine (NPB)/indium tin oxide (ITO)-coated glass was fabricated for diffusion study by ToF-SIMS. The results demonstrate that ToF-SIMS is capable of delineating the structure of multi-organic layers in OLEDs and providing specific molecular information to aid deciphering the diffusion phenomena. Upon heat treatment, the solidity or hardness of the device was reduced. Complicated chemical reaction might occur at the NPB/ITO interface and results in the formation of a buffer layer, which terminates the upper diffusion of ions from underlying ITO. In chapter 4, all-nanoparticle multilayer films were prepared by layer-by-layer deposition of SiO2 and Al2O3 nanoparticles onto polyester (PE) substrate. The top-most SiO2 (and Al2O3) layer was characterized using ToF-SIMS and SEM. An element-specific homogeneity index obtained by ToF-SIMS measurement provides clue to the formation mechanism. Experimental results from ToF-SIMS and SEM accord well with molecular dynamics simulation results, demonstrating the potential of using ToF-SIMS to study all-nanoparticle multilayer films. In chapter 5, we have investigated the growth behavior in all-nanoparticle multilayer films using a novel indicator layer by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) detection. The all-nanoparticle multilayer films were prepared by dipping the polyester substrate with electrostatic charges alternatively into solutions containing three different types of nanoparticles (TiO2, Al2O3, and SiO2). Upon the deposition of each layer, ToF-SIMS was employed to determine the surface chemical composition of intermediate products. The intermixing extent of TiO2 indicator layer was used to reveal the stratification of each layer. Combining with zeta-potential measurements, the solvation and deposition of the under-layer species in the aqueous environment during fresh layer formation was proposed as a plausible cause for mutilayers not stratified into well-defined layers but displaying a nonlinear growth behavior.