Metal oxides such as zirconia and hafnia are being investigated as new materials for application as gate dielectrics in future complementary metal-oxide-semiconductor devices. In this paper, we present results on oxidation of metal films such as Zr, Hf, and Al by the ultraviolet ͑UV͒ ozone oxidation method. A nuclear reaction analysis technique, the 16 O͑d,␣) 14 N nuclear reaction, was used to quantify the oxygen concentration in the dielectric stacks. The method was found to be sensitive to monolayer levels of oxygen. It was found that the oxidation kinetics of the metals increased significantly due to the presence of UV light. The oxidation rate was also found to depend on the oxygen partial pressure. The oxidation rate of Zr was greater than that of Hf, while Al oxidized more slowly than Hf for the UV-ozone oxidation conditions investigated. Possible reasons for the observed oxidation behavior are discussed in detail.
a b s t r a c tExposure of polytetrafluoroethylene (PTFE) to a-radiation was investigated to determine the physical and chemical effects, as well as to compare and contrast the damage mechanisms with other radiation types (b, g, or thermal neutron). A number of techniques were used to investigate the chemical and physical changes in PTFE after exposure to a-radiation. These techniques include: Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and fluorescence spectroscopy. Similar to other radiation types at low doses, the primary damage mechanism for the exposure of PTFE to a-radiation appears to be chain scission. Increased doses result in a change-over of the damage mechanism to cross-linking. This result is not observed for any radiation type other than a when irradiation is performed at room temperature. Finally, at high doses, PTFE undergoes mass-loss (via small-fluorocarbon species evolution) and defluorination. The amount and type of damage versus sample depth was also investigated. Other types of radiation yield damage at depths on the order of mm to cm into PTFE due to low linear energy transfer (LET) and the correspondingly large penetration depths. By contrast, the a-radiation employed in this study was shown to only induce damage to a depth of approximately 26 mm, except at very high doses.
The microstructural changes and associated effects on thermal conductivity were examined in UO 2 after irradiation using 3.9 MeV He 2+ ions. Lattice expansion of UO 2 was observed in x-ray diffraction after ion irradiation up to 5×10 16 He 2+ /cm 2 at low-temperature (< 200 °C). Transmission electron microscopy (TEM) showed homogenous irradiation damage across an 8 µm thick plateau region, which consisted of small dislocation loops accompanied by dislocation segments. Dome-shaped blisters were observed at the peak damage region (depth around 8.5 µm) in the sample subjected to 5×10 16 He 2+ /cm 2 , the highest fluence reached, while similar features were not detected at 9×10 15 He 2+ /cm 2. Laser-based thermo-reflectance measurements showed that the thermal conductivity for the irradiated layer decreased about 55 % for the high fluence sample and 35% for the low fluence sample as compared to an un-irradiated reference sample. Detailed analysis for the thermal conductivity indicated that the conductivity reduction was caused by the irradiation induced point defects.
Bulk austenitic stainless steels (SS) have a face-centered cubic (fcc) structure. However, sputter deposited films synthesized using austenitic stainless steel targets usually exhibit body-centered cubic (bcc) structure or a mixture of fcc and bcc phases. This paper presents studies on the effect of processing parameters on the phase stability of 304 and 330 SS thin films. The 304 SS thin films with in-plane, biaxial residual stresses in the range of approximately 1 GPa (tensile) to approximately 300 MPa (compressive) exhibited only bcc structure. The retention of bcc 304 SS after high-temperature annealing followed by slow furnace cooling indicates depletion of Ni in as-sputtered 304 SS films. The 330 SS films sputtered at room temperature possess pure fcc phase. The Ni content and the substrate temperature during deposition are crucial factors in determining the phase stability in sputter deposited austenitic SS films.
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