In recent years, experimental demonstration of ferroelectric tunnel junctions (FTJ) based on perovskite tunnel barriers has been reported. However, integrating these perovskite materials into conventional silicon memory technology remains challenging due to their lack of compatibility with the complementary metal oxide semiconductor process (CMOS). This communication reports the fabrication of an FTJ based on a CMOS-compatible tunnel barrier HfZrO (6 unit cells thick) on an equally CMOS-compatible TiN electrode. Analysis of the FTJ by grazing angle incidence X-ray diffraction confirmed the formation of the noncentrosymmetric orthorhombic phase (Pbc2, ferroelectric phase). The FTJ characterization is followed by the reconstruction of the electrostatic potential profile in the as-grown TiN/HfZrO/Pt heterostructure. A direct tunneling current model across a trapezoidal barrier was used to correlate the electronic and electrical properties of our FTJ devices. The good agreement between the experimental and theoretical model attests to the tunneling electroresistance effect (TER) in our FTJ device. A TER ratio of ∼15 was calculated for the present FTJ device at low read voltage (+0.2 V). This study suggests that HfZrO is a promising candidate for integration into conventional Si memory technology.

No abstract

The present work reports the fabrication of a ferroelectric tunnel junction based on a CMOS compatible 2.8 nm-thick Hf0.5Zr0.5O2 tunnel barrier. It presents a comprehensive study of the electronic properties of the Pt/Hf0.5Zr0.5O2/Pt system by X-ray photoelectron and UV-Visible spectroscopies. Furthermore, two different scanning probe techniques (Piezoresponse Force Microscopy and conductive-AFM) were used to demonstrate the ferroelectric behavior of the ultrathin Hf0.5Zr0.5O2 layer as well as the typical current-voltage characteristic of a ferroelectric tunnel junction device. Finally, a direct tunneling model across symmetric barriers was used to correlate electronic and electric transport properties of the ferroelectric tunnel junction system, demonstrating a large tunnel electroresistance effect with a tunneling electroresistance effect ratio of 20.

No abstract

No abstract

Different Li(4)SiO(4) solid solutions containing aluminum (Li(4+x)(Si(1-x)Al(x))O(4)) or vanadium (Li(4-x)(Si(1-x)V(x))O(4)) were prepared by solid state reactions. Samples were characterized by X-ray diffraction and solid state nuclear magnetic resonance. Then, samples were tested as CO(2) captors. Characterization results show that both, aluminum and vanadium ions, occupy silicon sites into the Li(4)SiO(4) lattice. Thus, the dissolution of aluminum is compensated by Li(1+) interstitials, while the dissolution of vanadium leads to lithium vacancies formation. Finally, the CO(2) capture evaluation shows that the aluminum presence into the Li(4)SiO(4) structure highly improves the CO(2) chemisorption, and on the contrary, vanadium addition inhibits it. The differences observed between the CO(2) chemisorption processes are mainly correlated to the different lithium secondary phases produced in each case and their corresponding diffusion properties.

Different Al-containing Li4SiO4 samples (Li4+x (Si1–x Al x )O4 solid solutions) were obtained by mechanosynthesis and then characterized structurally (X-ray diffraction (XRD) and solid-state NMR) and microstructurally (N2 adsorption and scanning electron microscopy (SEM)). While solid-state NMR results showed that the aluminum (silicon) presented some distortion after the milling process, the milling process tended to increase the Li4+x (Si1–x Al x )O4 surface areas. The samples were tested dynamically and isothermally in the CO2 chemisorption at high temperatures. In the second case, a complete kinetic analysis was produced. It was evidenced that aluminum addition and the new microstructural features produced during the milling process importantly increase the CO2 capture, in comparison to the Li4SiO4 phase and the Li4+x (Si1–x Al x )O4 solid solutions prepared by solid-state reaction.

The evaluation of the thermodynamic properties as well as the phase diagrams for the binary Na 2 O-SiO 2 , K 2 O-SiO 2 , and Li 2 O-SiO 2 systems are carried out with a structural model for silicate melts and glasses. This thermodynamic model is based on the assumption that each metallic oxide produces the depolymerization reaction of silica network with a characteristic free-energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analyzed and represented with a small number of parameters. The resulting equations represent the thermodynamic and phase diagram data for these alkali metal oxide-silica systems within experimental error limits. In particular, the measured limiting liquidus slope at X SiO2 ¼ 1 is well reproduced.