A. Mathew

Reactivity and morphology of vapor-deposited Al/polymer interfaces for organic semiconductor devices

The chemistry and the morphology of metal-deposited organic semiconductor interfaces play a significant role in determining the performance and reliability of organic semiconductor devices. We investigated the aluminum metallization of poly(2-methoxy-5,2′-ethyl-hexyloxy-phenylene vinylene) (MEH-PPV), polystyrene, and ozone-treated polystyrene surfaces by chemical (x-ray and ultraviolet photoelectron spectroscopy) and microscopic [atomic force microscopy, scanning electron microscopy (SEM), focused ion beam (FIB)] analyses. Photoelectron spectroscopy showed the degree of chemical interaction between Al and each polymer; for MEH-PPV, the chemical interactions were mainly through the C–O present in the side chain of the polymer structure. The chemical interaction of aluminum with polystyrene was less significant, but it showed a dramatic increase after ozone treatment of the polystyrene surface (due to the formation of exposed oxygen sites). Results showed a strong relationship between the surface reactivity...

Oxygen pressure dependence of copper ion transport in SiO2 dielectrics

Electrical bias-temperature stress measurements were performed on copper oxide/SiO2/silicon metal-oxide-semiconductor capacitors to measure the oxygen partial pressure dependence of the copper ion transport rates through the SiO2 layer. Both copper(I) oxides (Cu2O) and copper(II) oxides (CuO) were investigated, and copper oxide film stoichiometry was characterized by glancing incidence x-ray diffraction and x-ray photoelectron spectroscopy. At relatively high oxygen pressures, copper ion transport is observed for both Cu2O∕SiO2∕Si and CuO∕SiO2∕Si, and the activation energies are comparable. Under reduced oxygen pressures and vacuum, the copper ion flux is reduced for both copper oxides. In vacuum, the activation energy for copper transport from CuO layers is reduced by approximately 0.7eV compared to the apparent activation barrier at high oxygen pressures, and the copper transport signals for Cu2O are below the detection limit of the experiment. A study of copper transport rates for both CuO and Cu2O ele...

X‐ray Photoelectron Spectroscopy of High‐κ Dielectrics

Photoelectron spectroscopy is a powerful technique for the analysis of gate dielectrics because it can determine the elemental composition, the chemical states, and the compositional depth profiles non‐destructively. The sampling depth, determined by the escape depth of the photoelectrons, is comparable to the thickness of current gate oxides. A maximum entropy algorithm was used to convert photoelectron collection angle dependence of the spectra to compositional depth profiles. A nitrided hafnium silicate film is used to demonstrate the utility of the technique. The algorithm balances deviations from a simple assumed depth profile against a calculated depth profile that best fits the angular dependence of the photoelectron spectra. A flow chart of the program is included in this paper. The development of the profile is also shown as the program is iterated. Limitations of the technique include the electron escape depths and elemental sensitivity factors used to calculate the profile. The technique is als...