Photoinduced reactivity of titanium dioxide

Novel information processing techniques are being actively explored to overcome fundamental limitations associated with CMOS scaling. A new paradigm of adaptive electronic devices is emerging that may reshape the frontiers of electronics and enable new modalities. Creating systems that can learn and adapt to various inputs has generally been a complex algorithm problem in information science, albeit with wide-ranging and powerful applications from medical diagnosis to control systems. Recent work in oxide electronics suggests that it may be plausible to implement such systems at the device level, thereby drastically increasing computational density and power efficiency and expanding the potential for electronics beyond Boolean computation. Intriguing possibilities of adaptive electronics include fabrication of devices that mimic human brain functionality: the strengthening and weakening of synapses emulated by electrically, magnetically, thermally, or optically tunable properties of materials.In this review, we detail materials and device physics studies on functional metal oxides that may be utilized for adaptive electronics. It has been shown that properties, such as resistivity, polarization, and magnetization, of many oxides can be modified electrically in a non-volatile manner, suggesting that these materials respond to electrical stimulus similarly as a neural synapse. We discuss what device characteristics will likely be relevant for integration into adaptive platforms and then survey a variety of oxides with respect to these properties, such as, but not limited to, TaOx, SrTiO3, and Bi4-xLaxTi3O12. The physical mechanisms in each case are detailed and analyzed within the framework of adaptive electronics. We then review theoretically formulated and current experimentally realized adaptive devices with functional oxides, such as self-programmable logic and neuromorphic circuits. Finally, we speculate on what advances in materials physics and engineering may be needed to realize the full potential of adaptive oxide electronics.

Adaptive oxide electronics: A review

Preparation and physical properties of transparent conducting oxide films

A review of recent and current work on microwave FET's and amplifiers is presented, and an extensive bibliography of recent articles is appended (250 references). First, the various FET structures (MRSFET's, JFET's, and IGFET's) and their performances are reviewed. Second, the principle of operation is outlined for Si- and GaAs-MESFET's; the basic device physics, equivalent circuit, high-frequency limitations, and noise behavior are treated. Third, the design principles and performance of microwave MESFET amplifiers are summarized.

Microwave Field-Effect Transistors--1976

Polycrystalline BiFeO3 (BFO), Ti-doped BFO, Mn-doped BFO, and (Mn, Ti)-codoped BFO (BFMT) thin films were fabricated on Pt/SrTiO3 (100) substrate by pulsed laser deposition. Observed leakage current behavior in those ion-doped BFO films indicated the dominance of space-charge-limited current in the high electric field region. The leakage current of the BFMT film was much reduced in relation to the other films due to the formation of deep traps. In the BFMT film, well saturated P-E hysteresis curves were observed. Remanent polarization and coercive field for maximum electric field of 2100 kV/cm were 75 μC/cm2 and 310 kV/cm, respectively.

Improved leakage and ferroelectric properties of Mn and Ti codoped BiFeO3 thin films

As semiconductor device geometries continue to shrink, trace volatile organic contamination adsorbing on silicon surfaces has an increasingly detrimental impact on product performance and yield. Therefore, it becomes important to identify the origin of the organic contaminants and to eliminate them from the wafer. When wafers are stored in a plastic box in order to protect them from airborne contaminants, volatile organics from the polymeric construction material adsorb onto the wafer surfaces. A very small quantity of additives in the plastic material are apt to adsorb onto the wafers more easily than the unpolymerized monomers and oligomers outgassing in large quantities. As a result of the evaluation of various wet cleaning solutions in terms of their ability to remove these trace organic contaminants, dilute HF as well as ozonized ultrapure water has been found to completely remove these organic contaminants adsorbing on the silicon surfaces. After wet cleaning, organic contaminants adsorb more easily on the ozonized water‐treated silicon surface than on the dilute HF‐treated surface. Adsorption of the organic additives on the silicon surfaces can be inhibited by preventing the native oxide growth in a nitrogen atmosphere after dilute HF cleaning. Possible explanations for these phenomena are considered.

Identification and Removal of Trace Organic Contamination on Silicon Wafers Stared in Plastic Boxes

The electronic structure of multiferroic BiFeO{sub 3} has been studied using soft-X-ray emission spectroscopy. The fluorescence spectra exhibit that the valence band is mainly composed of O 2p state hybridized with Fe 3d state. The band gap corresponding to the energy separation between the top of the O 2p valence band and the bottom of the Fe 3d conduction band is 1.3 eV. The soft-X-ray Raman scattering reflects the features due to charge transfer transition from O 2p valence band to Fe 3d conduction band. These findings are similar to the result of electronic structure calculation by density functional theory within the local spin-density approximation that included the effect of Coulomb repulsion between localized d states.

/pdf/electronic-structure-of-multiferroic-bifeo3-by-resonant-soft-2jygva078c.pdf

Electronic structure of multiferroic BiFeO3 by resonant soft-x-ray emission spectroscopy

A method of cleaning the surface of a substrate, wherein the first step of the process of cleaning the substrate including a step of cleaning the surface of the substrate by an acidic solution, oxidizing solution, or alkaline solution, comprises a step of removing the natural oxide film formed on the surface of the substrate.

Method of cleaning substrate

Growth of TiO2 thin film by reactive RF magnetron sputtering using oxygen radical

The valence state of Mn-doped BiFeO3–BaTiO3 ceramics has been probed by soft X-ray absorption spectroscopy (XAS). Mn-doped BiFeO3–BaTiO3 has valence states of Fe3+ and Ti4+, although BiFeO3 and Mn-doped BiFeO3 have mixed valence states of Fe2+ and Fe3+. The Mn 2p-XAS peak of Mn-doped BiFeO3–BaTiO3 locates at a lower energy side than that of Mn-doped BiFeO3 that corresponds to the Mn3+ valence state. These findings may indicate that the Fe3+ valence state of Mn-doped BiFeO3–BaTiO3 is stabilized by charge transfer from the Mn 3d state to the Fe 3d state through the Ti 3d state in BaTiO3.

https://iopscience.iop.org/article/10.1143/APEX.1.011502/pdf

Takeshi Hattori

Papers

Identification and Removal of Trace Organic Contamination on Silicon Wafers Stared in Plastic Boxes

Electronic structure of multiferroic BiFeO3 by resonant soft-x-ray emission spectroscopy

Method of cleaning substrate

Growth of TiO2 thin film by reactive RF magnetron sputtering using oxygen radical

Valence State of Mn-Doped BiFeO3–BaTiO3 Ceramics Probed by Soft X-ray Absorption Spectroscopy