Chemical Oxide Films Research Articles

Corrosion Behavior of Chemical Oxidation Film of Magnesium Alloy in NaCl Solution

Magnesium alloy chemical oxidation is a commonly used conductive anti-corrosion treatment method for aerospace. In order to study the corrosion resistance of its chemical oxide film in the coastal launch site and evaluate the impact of the marine environment on its surface film performance, the corrosion properties of magnesium specimens were studied in 3.5% NaCl solution. The corrosion characteristics with different immersion time were characterized by using scanning electron microscopy, energy spectroscopy and electrochemical methods. The corrosion mechanism was discussed. The results showed that as the immersion time increases, corrosion starts from pitting. The pit spreads to the morphology of multi-pronged extension cracks and then continues to deepen and widen, gradually covers the entire surface of the specimen. The corrosion products are mainly composed of magnesium and oxygen. The electrochemical results show that as the corrosion time increases, the corrosion rate increases from 0h to 12h, which the Icorr increases and the reaction resistance decreases. However, as the corrosion products cover the surface which prevents the corrosion expanding, the Vcorr trends to forward shift and reaction resistance increases.

Effect of the Interfacial SiO2 Layer on High-k Gate Stacks

Interfacial oxide (IL) /high-k (HK) gate dielectric stack is widely used in 45nm logic technology and beyond nodes. Interfacial oxide, which is buffer layer between silicon substrate and HK dielectric, is a crucial factor to control Silicon/IL, IL/high-k interface charge and high-k film quality. In this work, atom layer deposition (ALD) Hf based HK film is deposited on two classes of IL by thermal oxidation (process A or B) and chemical oxidation (process C or D), respectively. XPS is used to characterize the film bonding energy, while non contact CV and spectroscopic ellipsometry (SE) are used to characterize the interface trap. The electric properties of the film stacks are characterized by C-V and I-V curves. The results reveal that interface trap of chemical oxide film has positive surface voltage and less dense SiOx, as compared with that of thermal oxide. With the same interfacial oxide thickness and HK deposition process, the chemical oxide/HK stack got 3.4A thick EOT, which is about two orders lower leakage than that of thermal oxide/HfO2. It can be explained by the fact that chemical oxide had plenty of O-H bonds, which is good for ALD Hf based HK film nucleation and growth and resulted in good film quality. However, due to the high Si/chemical oxide interfacial charge, the chemical oxide/HfO2 dielectric stack has a disadvantage of the larger C-V hysteresis.

Interaction of liquid tin and zinc with AISI 304 stainless steel after passivation in air and nitric acid

The reaction of liquid Sn and Zn with passivated AISI 304 stainless steel has been investigated by analyzing the growth of interfacial intermetallic layers. Both Sn and Zn are prone to metallurgically react with ground stainless steel by the formation of interfacial (Fe, Cr)Sn2 and ζ-(Fe, Cr)Zn13, δ-(Fe, Cr)Zn10 intermetallics, respectively. The native oxide film grown in air has retarded the growth of (Fe, Cr)Sn2 layer. The chemical oxide film grown in nitric acid has prevented the formation of (Fe, Cr)Sn2 layer and changed the metallurgical combination to physical attachment. In the liquid Zn, both native and chemical oxide films become unstable and slightly decrease the growth of intermetallic layer. It is supposed that the composition and structure differences in those two oxide films and the fast diffusion of zinc at relatively high temperature are responsible for the instability of oxide film and the growth of the intermetallic Fe–Zn compound.

Growth mechanism and characterization of chemical oxide films produced in peroxide mixtures on Si(100) surfaces

The growth kinetics of silicon chemical oxides in H 2O 2-containing solutions at various pH values and temperatures was studied by electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy. Infrared (IR) spectroscopy was also used to investigate the evolution of the surface chemistry from the initial hydrogen coverage as Si–H bonds to the subsequent oxidation states by analysing the Si–O–Si stretching vibration modes. Successive EIS diagrams obtained as a function of time constituted a series of semicircles indicating that the semiconductor/oxide/electrolyte junction can be modelled as a resistance-capacity (RC) circuit. It was then observed that the resistance term increased with time to almost 1 MΩ cm 2 after 3 h in SC1 solution. It is generally known that, in alkaline solutions such as SC1, the oxidation rate reaches rapidly a steady regime controlled by the interfacial charge transfer reaction and the subsequent dissolution of the generated oxide. Accordingly, a mechanism involving a diffusion process of reactants through the oxide barrier followed by a simultaneous dissolution of the layer is proposed. Likewise, in acidic media such as SC2, even though the solubility is extremely low, we have extended our model based on the competition between the oxidation rate at the surface and the dissolution of the built-up oxide, and thus it was possible to evidence oxide solubility at the nanoscopic scale. In addition, thickness measurements by ellipsometry together with the observed gradual change in the IR spectrum of the Si–O–Si vibration mode were interesting parameters revealing that the oxide growth proceeds simultaneously with an evolution of the structure leading to a more compact and insulating dielectric layer. The whole of the results lead to a model for the oxidation process accounting for the observed structure and complex impedance properties under various conditions of chemical treatment.

Determination of the electrical properties of 2.5 nm thick silicon-based dielectric films: thermally grown SiO x

Ultra-thin (<5 nm thick) thermal oxide and oxynitride films with different compositions are candidates for complementary metal/oxide/semiconductor technology in ultra-large-scale integration (ULSI) applications. The latter are expected to offer the best compromise between nitrides and oxides. The aim of this work is to measure the electrical properties of a leaky 2.5 nm thick thermally grown oxide film using the high frequency capacitance–voltage (HF C( V)) measurements. The cleanliness and the surface roughness of the Si(1 0 0) surface were measured prior to in situ oxidation by means of, respectively, Auger electron spectroscopy (AES) and atomic force microscopy (AFM). The physical–chemical properties of the thermal oxide film were measured by AES (film thickness, composition), Fourier transform infrared spectroscopy (FTIR) (composition, vibration modes), cross-sectional transmission electron microscopy (TEM) (film thickness, homogeneity) and electron energy loss spectroscopy (EELS) (gap width determination). The results are compared to those obtained for the native oxide film and a chemical oxide film. The latter was first grown on the silicon substrate to prevent contamination and surface disorder after flash heating in vacuum prior to oxide growth. The substrate Si(1 0 0) surface cleaned in ultra-high vacuum (UHV) was then oxidized in a 10 −3 mbar oxygen (O 2) gas pressure at 900°C to get the 2.5 nm thick oxide film. The grafting of a self-assembled insulating monolayer (SAM) of organic molecules on the grown oxide film permits us to obtain analysable capacitance as a function of voltage data. Indeed, this monolayer made up of octadecyltrichlorosilane molecules leads to a reduction of the leakage current through the aluminium/self-assembled monolayer/oxide/silicon heterostructure. The resulting current as a function of voltage data were compared to those of a standard 2.5 nm thick oxide film. The method proposed here to extract the electrical parameters of the thermal oxide film is demonstrated to be valid. We show mainly that the reduction of the leakage current through the aluminium/self-assembled monolayer/thermal oxide/silicon heterostructure is seven orders of magnitude bigger than in the case of the native oxide film.

Roughening of the Si/SiO2 interface during SC1-chemical treatment studied by scanning tunneling microscopy

The Si/SiO2 interface morphology is observed with subnanometer resolution by an ultrahigh vacuum scanning tunneling microscope (STM). We analyze the roughness of the Si/SiO2 interface for a chemical oxide film formed by a wet chemical process (NH4OH/H2O2/H2O treatment). The oxide film is selectively removed by irradiating a field emission electron beam extracted from a STM tip at a temperature of 300–350 °C. We find that during the chemical process the roughness of the Si/SiO2 interface increases with the treatment time.