The HfO2–Si valence and conduction band offsets (VBO and CBO, respectively) of technologically relevant HfO2/SiO2/Si film stacks have been measured by several methods, with several groups reporting values within a range of ∼1 eV for both quantities. In this study we have used a combination of x-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry to measure the HfO2–Si VBO and CBO of both as-deposited and annealed stacks. Unlike previous XPS based measurements of the HfO2–Si VBO, we have corrected for the effect of charging in the XPS measurement. We find that after correction for charging, the HfO2–Si VBOs are decreased from their typical XPS-measured values, and agree better with values measured by UV photoemission spectroscopy and internal photoemission. We also report values for the rarely reported HfO2–SiO2 and SiO2–Si VBOs and CBOs in HfO2/SiO2/Si stacks. In addition to the band offsets, XPS was used to measure the band bending in the Si substrate of HfO2/SiO2/Si film stacks. Unannealed HfO2 stacks showed downward Si band bending of 0.4–0.5 eV, while annealed HfO2 stacks showed negligible band bending. Finally, we investigated the composition of the SiO2 layer in SiO2/Si and HfO2/SiO2/Si. By decomposing the Si 2p spectra into the spin orbit partner lines of its five oxidation states we observed that the growth of the HfO2 films resulted in the growth of the SiO2 underlayer and an increase by a factor of ∼2.3 in the density of suboxide species of SiO2. Based on the relatively high binding energy of the Si 2p4+ level with respect to the Si 2p0 level and a survey of results from literature, we conclude that the SiO2 layer in the HfO2/SiO2/Si samples we measured does not undergo significant intermixing with HfO2.

With the replacement of SiO2 by high-k Hf-based dielectrics in complementary metal–oxide–semiconductor technology, the measurement of the high-k oxide bandgap is a high priority. Spectroscopic ellipsometry (SE) is one of the methods to measure the bandgap, but it is prone to ambiguity because there are several methods that can be used to extract a bandgap value. This paper describes seven methods of determining the bandgap of HfO2 using SE. Five of these methods are based on direct data inversion (point-by-point fitting) combined with a linear extrapolation, while two of the methods involve a dispersion model-based bandgap extraction. The authors performed all of these methods on a single set of data from a 40 Å HfO2 film, as well as on data from 20 and 30 Å HfO2 films. It was observed that the bandgap values for the 40 Å film vary by 0.69 eV. In comparing these methods, the reasons for this variation are discussed. The authors also observed that, for each of these methods, there was a trend of increasing bandgap with decreasing film thickness, which is attributed to quantum confinement. Finally, the authors observed a greater variation in bandgap values among the methods for the 40 Å films than among the methods for the 30 and 20 Å films. This is attributed to the larger tail in the extinction coefficient k curve for the 40 Å film.

Recent studies have shown that La 2 O 3 films can be used to adjust the threshold voltage ͑V t ͒ of NMOS Hf-based high-k/metal gate devices to desirable values, and a dipole at the high-k / SiO 2 interface has been proposed to explain the V t shifts. In order to investigate the mechanism of the V t shift further, we have measured the flatband voltage ͑V fb ͒ and Si band bending of technologically relevant TiN/ HfO 2 / La 2 O 3 / SiO 2 / p-Si stacks where the thickness and position of the La 2 O 3 layer have been systematically varied. We observed systematic changes in V fb , Si band bending and the HfO 2 -Si valence band offset as a function of La 2 O 3 layer thickness and position. These changes can be explained by a band alignment model that includes a dipole at the high-k / SiO 2 interface, thus supporting the work of previous authors. In addition, we have derived the theoretical relationship between V fb and Si band bending, which agrees well with our experimental measurements.

In this paper the surface of wood/polyethylene (PE) composites were treated by liquid oxidation, and the structure of surface for wood/polyethylene composites before and after treatment was characterized by contact angle, fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM); combined with bonding strength test, the effect of concentration for handling solution and addition of oxidant on bonding properties of wood/polyethylene composites was also investigated. The results showed that the contact angle of surface for wood/polyethylene composites reduced and the surface wettability had been improved after liquid oxidation; the -C-O- and C=O functional groups were formed on the treated surface and the surface roughness increased; meanwhile, the shear bonding strength for the treated sample increased significantly after treatment. And these changes would be more obvious when enhancing the concentration of handling solution and adding oxidant.

The surface of wood/polyethylene (PE) composites was treated by low-pressure glow discharge of air plasma to improve its adhesion properties. And the changes on the surface properties of the treated composites under different discharge time were studied by contact angle, AFM and FTIR analysis. To determine the effect of plasma treatment on the adhesion of the composites, shear bond strength tests were conducted. The results showed that the contact angle decreased gradually with the increasing of discharge time. The roughness of plasma treated samples increased. The FTIR analysis results showed that the polar groups such as -OH, -C=O and -O-C=O were formed on the surface of the composites treated under plasma. The data of shear bond strength analysis also showed that the adhesion strength of composites increased remarkably after plasma treatment, and the durability of bonding joint under water and heat environments also be improved.