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The correlation between the crystal structure and valence band structure of a (GaxIn1-x)2O3 solid solution system was investigated by using combinatorial synthesis. At a low Ga content of (GaxIn1-x)2O3 with a single-phase cubic In2O3 crystal structure, a surface electron accumulation layer (SEAL), which is an important electrical phenomenon in In2O3, was confirmed. When the Ga content increased to approximately x = 0.4, mixed crystal structures of Ga2O3 and In2O3 were produced. Above x = 0.5, the dominant valence band structure was attributed to Ga2O3, the SEAL disappeared, and the sheet resistance increased greatly by 5 orders of magnitude or more. The in-gap state and valence band structure of the (GaxIn1-x)2O3 solid solution system were strongly affected by Ga2O3; however, the valence band maximum position shifted to a higher binding energy.

The absolute band position is a key parameter to design and optimize functionalities of photoelectrochemical cells. We determine the absolute band position of SrNbO2N using hard X-ray photoelectron spectroscopy on epitaxial SrNbO2N films. We reveal that the conduction band minimum lies 0.36 ± 0.07 eV negative than the water reduction energy and the valence band maximum lies 0.22 ± 0.07 eV positive than the water oxidation energy. In other words, the band edges lie in positions that straddle the redox potential of water.

Compound semiconductor-based power devices such as SiC and GaN require high-temperature operational passive devices such as a capacitor. SiC based active devices are capable of operating over 250°C. For module and system level advancement, the high-temperature operational passive should be developed urgently. In the case of capacitors, current available capacitors can efficiently function up to 175°C only. Therefore, a thin film capacitor that can be operated at high-temperatures and integrated monolithically in the proximity of active device should be developed. In this talk, I will introduce our achievements of development of high temperature operational dielectric film materials and its interface control of metal/oxide stacking structure mainly. By employing combinatorial method and the thermal diffusion theory, we found some candidates for the dielectric materials based on ferroelectric materials. The BaTiO3 based relaxor ferroelectrics with a high dielectric constant (> 200) and free of hazardous elements are promising candidates. Among the BaTiO3 based relaxor ferroelectrics, we have chosen x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] (BT-BMN). The permittivity of 400 and the stability 2, TiC, and TaC were selected as the electrode candidates to compare with the Pt electrode. To probe the interface structure and the band alignment non-destructively, we employed a combination of conventional x-ray PES using Al Kα light source (SXPES: hν= 1486.6 eV) and hard x-ray PES (HAXPES, hν= 5.95 keV). HAXPES is a powerful tool for investigating heterostructure interfaces due to its longer inelastic mean free path (IMFP) than that of SXPES. The IMFP of Pt 4f7/2, which was the heaviest element with the shortest IMFP in our measurement, was 4.68 nm, and HAXPES probed approximately 15 nm (probing depth: 3×IMFP) below the surface. For the Pt electrode, which is usually used as an electrode for Bi-contained oxides, the Bi diffusion into the electrode layer and the change of band alignment were clearly observed after annealing at 400°C. In contrast, the TiC electrode inhibited the Bi diffusion and did not show any change of the band alignment after annealing, meaning that the TiC electrode is a potential candidate for the electrode of Bi-contained oxide for high temperature operational devices. In the presentation, we also introduce the development of new high-k gate materials for GaN and Ge channels by combining the combinatorial method and HAXPES analysis. For a Ge channel, which has been attracting a lot of attention as a replacement for the Si channel used in current Si-based metal-oxide-semiconductor (CMOS) devices. This is because the Ge channel has high electron and hole mobility, which lead to a higher drive current, and Ge has a narrower band gap than Si thus allowing supply voltage scaling. However, Ge has the same issue as Si, namely an unintentionally oxidized layer with a low dielectric constant (~5.6) can form at an oxide/Ge interface. Furthermore, in contrast with SiO2, which is a good insulating layer for MOS devices, GeOx is thermodynamically unstable and water soluble. These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage characteristic. To overcome these issues, we have proposed the direct growth of (110) rutile TiO2 or non-oxide materials on (100) Ge substrates.

High-throughput and combinatorial materials science methods were used to investigate the dependence of the work function in the Ni–Si system on the B content (0–30 at. %). Alloying of NiSi is used to adapt its properties to suit the needs as a gate electrode material. Thin-film materials libraries were fabricated and investigated with respect to their structural and electrical properties. Further the work function values of selected samples in the region of interest were analyzed. The results show that the work function can be adjusted between 4.86 eV (B = 4.2 at. %) and 5.16 eV (B = 29.2 at. %) for (NiSi)Bx.

This work reports on developments in the field of wide band gap Cu2ZnXY4 (with X = Sn, Si or Ge, and Y = S, Se) kesterite thin film solar cells. An overview on recent developments and the current understanding of wide band gap kesterite absorber layers, alternative buffer layers, and suitable transparent back contacts is presented. Cu2ZnGe(S,Se)(4) absorbers with absorber band gaps up to 1.7 eV have been successfully developed and integrated into solar cells. Combining a CdS buffer layer prepared by an optimized chemical bath deposition process with a 1.36 eV band gap absorber resulted in a record Cu2ZnGeSe4 cell efficiency of 7.6%, while the highest open-circuit voltage of 730 mV could be obtained for a 1.54 eV band gap absorber and a Zn(O,S) buffer layer. Employing InZnOx or TiO2 protective top layers on SnO2:In transparent back contacts yields 85-90% of the solar cell performance of reference cells (with Mo back contact). These advances show the potential as well as the challenges of wide band gap kesterites for future applications in high-efficiency and low-cost tandem photovoltaic devices. This project has received funding from the European Union's Horizon 2020 Research and Innovation Program under grant agreement No. 640868. The synchrotron radiation experiments were performed at the SPring-8 beamline BL15XU with the approval of the NIMS Synchrotron X-ray Station (Proposals 2016A4600, 2016B4601, and 2017A4600) and at BESSY II with the approval of HZB. B. Vermang has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 715027).

We present a data-driven approach to explore high-entropy alloys (HEAs). To overcome the challenges with numerous element-combination candidates, selecting appropriate descriptors, and the limitations and biased of existing data, we apply the evidence theory to develop a descriptor-free evidence-based recommender system (ERS) for recommending HEAs. The proposed system measures the similarities between element combinations and utilizes it to recommend potential HEAs. To evaluate the ERS, we compare its HEA-recommendation capability with those of matrix-factorization- and supervised-learning-based recommender systems on four widely known data sets, including binary and ternary alloys. The results of experiments using k-fold cross-validation on the data sets show that the ERS outperforms all competitors. Furthermore, the ERS shows excellent extrapolation capabilities in experiments of recommending quaternary and quinary HEAs. We experimentally validate the most strongly recommended Fe-Co-based magnetic HEA, viz. FeCoMnNi, and confirm that it shows a body-centered cubic structure and is stable at high temperatures.

The effects of reactive gas flow conditions on nonpolar AlN film growth on MnS/Si (100) substrates using reactive DC magnetron sputtering were investigated. During AlN deposition at a substrate temperature of 750 °C, the MnS surface can be unintentionally nitrided, resulting in a decrease in the crystallinity of the AlN. Low-temperature growth of the AlN layer at 300 °C prevents this nitridation and results in the crystallization of nonpolar AlN. A N2 flow equal to 30% of the Ar sputtering gas flow was found to improve the crystallinity of the nonpolar AlN and to reduce nitrogen defects, which play an important role in interfacial reactions. Nitrogen defects promote the formation of alloys such as AlMn and MnSi that degrade the interface and can significantly decompose the MnS. A higher proportion of N2 improves the nonpolar AlN crystallinity, reduces the concentration of defects and suppresses reactions at the AlN/MnS interface.

The correlation between the crystal structure and valence band structure of a (Ga

A new heterostructured material is synthesized with lamellar arrangements in nanoscale precision through an innovative synthetic approach. The self-assembled Ni-based cyano-bridged coordination polymer flakes (Ni-CP) and graphene oxide (GO) nanosheets with a layered morphology (Ni-CP/GO) are used as precursors for the synthesis of multicomponent hybrid materials. Annealing of Ni-CP/GO in nitrogen at 450 °C allows the formation of Ni3 C/rGO nanocomposites. Grinding Ni-CP/GO and thiourea and annealing under the same conditions produces N,S-codoped reduced GO-wrapped NiS2 flakes (NiS2 /NS-rGO). Interestingly, further heating up to 550 °C allows the phase transformation of NiS2 into NiS accompanied by the formation of a face-centered cubic (FCC-Ni) metal phase between NS-rGO layers (FCC-Ni-NiS/NS-rGO). Among all the materials, the resulting FCC-Ni-NiS/NS-rGO exhibits good electrocatalytic activity and stability toward the oxygen evolution reaction (OER) owing to the synergistic effect of multiphases, the well-designed alternating layered structures on the nanoscale with abundant active sites.

A novel approach for hybridizing nanoporous NiCo oxide flakes with graphene sheets is reported. Positively charged cyano-bridged CoNi coordination polymer flakes (CoNi-CP) are mixed with graphene (G) suspension with negatively charged surface. Due to effective electrostatic interaction, both the materials are hybridized to form CoNi-CP/G composite. The as-prepared CoNi-CP/G composite is thermally treated in air, to remove the organic components without affecting the integrity of the parent G sheets. Through the thermal treatment, the CoNi-CP flakes wrapped into G sheets are converted to NiCo oxide, resulting in a new composite consisting of NiCo oxide flakes and G sheets. The NiCo-oxide/G composite shows the high specific capacitance (similar to 199 F g-1) at 5 mV/s, and features the good capacitance retention of similar to 68% at 100 mV(similar to 135 F g(-1)).

The chemical bonding state of Mn film on SiO 2 , which is expected to be applied as a bonding material for Si wafer, was investigated by x-ray photoelectron spectroscopy (XPS). The as deposited Mn film had unintentionally oxidized surface and interface layer, caused by an air exposure and a redox reaction with SiO x at the SiO 2 surface, respectively. Post deposition anneal (PDA) enhanced the redox reaction between MnO x and SiO 2 . The N 2 plasma treatment eliminates the redox reaction, and enhances the Si-Mn-O bonding formation, which should improve the tensile strength of wafer bonding.

The key concept behind this study is the use of “geometry engineering” to elucidate the carrier transport path and to control the device properties of organic antiambipolar transistors. Investigations of carrier transport properties with different device geometries, such as the pn-heterojunction length and the channel layer thickness, revealed that charge carriers transported through the lateral edge junction between p- and n-type channels. We also found that the peak voltage was effectively reduced from −49 to −39 V in a device with asymmetric channel lengths. These results suggest that device performance can be enhanced by taking advantage of the designability of the device geometry, which can employ the strong features of organic antiambipolar transistors.

Orthorhombic rare-earth trivalent manganites RMnO3 (R = Er-Lu) were self-doped with Mn to form (R0.667Mn0.333)MnO3 compositions, which were synthesized by a high-pressure, high-temperature method at 6 GPa and about 1670 K from R2O3 and Mn2O3. The average oxidation state of Mn is 3+ in (R0.667Mn0.333)MnO3. However, Mn enters the A site in the oxidation state of 2+, creating the average oxidation state of 3.333+ at the B site. The presence of Mn2+ was confirmed by hard X-ray photoelectron spectroscopy measurements. Crystal structures were studied by synchrotron powder X-ray diffraction. (R0.667Mn0.333)MnO3 crystallizes in space group Pnma with a = 5.50348(2) A, b = 7.37564(1) A, and c = 5.18686(1) A for (Lu0.667Mn0.333)MnO3 at 293 K, and they are isostructural with the parent RMnO3 manganites. Compared with RMnO3, (R0.667Mn0.333)MnO3 exhibits enhanced Neel temperatures of about TN1 = 106-110 K and ferrimagnetic or canted antiferromagnetic properties. Compounds with R = Er and Tm show additional magnetic transitions at about TN2 = 9-16 K. (Tm0.667Mn0.333)MnO3 exhibits a magnetization reversal or negative magnetization effect with a compensation temperature of about 16 K.

We report a simple sol–gel method for the preparation of multilayered hybrid thin films composed of nanostructured SrTiO3 (STO) and BaTiO3 (BTO) layers. A nanoporous thin film of STO is prepared by the spin-coating method on Si/SiO2/Ti/Pt substrate. When the BTO is processed, the BTO is crystallized between STO crystal pores. A significant strain field is induced on the interface between the STO and BTO surfaces. The concave shape of the nanopores could enable the realization of a highly strained interfacial heterostructure composed of STO/BTO. Compared to nanostructured STO, BTO, and bilayer STO/BTO films, multilayered STO/BTO films show the highest dielectric constant and a high Curie temperature (Tc) at around 280 °C, which is suitable for electric capacitor applications.

The main purpose of this study is to establish a guideline for controlling the device properties of organic antiambipolar transistors. Our key strategy is to use interface engineering to promote carrier injection at channel/electrode interfaces and carrier accumulation at a channel/dielectric interface. The effective use of carrier injection interlayers and an insulator layer with a high dielectric constant (high-k) enabled the fine tuning of device parameters and, in particular, the onset (Von) and offset (Voff) voltages. A well-matched combination of the interlayers and a high-k dielectric layer achieved a low peak voltage (0.25 V) and a narrow on-state bias range (2.2 V), indicating that organic antiambipolar transistors have high potential as negative differential resistance devices for multivalued logic circuits.

Coordination polymers (CPs) have gained a great deal of attention over the years because of their beneficial uses in catalysis, drug-delivery, and energy storage and separation. Recent research efforts have been devoted to architecting CPs that satisfy the needs of applications that have recently been developed. Herein, we announce a survey of the latest developments in the synthesis of Prussian blue (PB) and Prussian blue analogues (PBAs) cyano-bridged CPs. The recent synthetic concepts and the modest control over the shape and size of particles are demonstrated to the present. Various ways have been taken to construct nanostructured inorganic materials from PB and PBAs. We surveyed one such example: the thermal decomposition of these materials in different environments. The regulated thermal treatment of their nanostructures as precursors, in air or inert atmosphere, yields nanoporous metal oxides and carbides or alloys, respectively. The resulting metal frameworks participate as metal sources, and the organic components, which can be removed by a simple process of calcination, produce pores. The original morphologies are almost retained, even after the thermal treatments. This strategy has proved to be a promising solid-state chemistry for the fabrication of nanoporous metal oxides and carbides or alloys with the similar morphology.

Research using X-ray diffraction (XRD) remains to be accelerated in spite of its importance in materials science. Automated noise separation or optimization of measurement time in XRD is beneficial for discovering materials. This study analyzes two-dimensional XRD (2D-XRD) with density-based clustering to accelerate XRD. This clustering technique can separate diffraction pattern signals from noises, even with low signal-to-noise ratio (S/N) 2D-XRD. Moreover, we found that the crystalline degree information in composition spreads is captured based on density. This information requires a long time to be captured with conventional one-dimensional detectors or scintillation counters. Therefore, these findings lead to dramatic reduction and optimization of measurement time to improve S/N. The proposed procedure is applicable with 2D detector measurements.

The effect of an Al buffer layer on the growth of AlN on a Si (111) substrate was investigated to develop an all-sputtered GaN film on a Si (111) template substrate. The X-ray diffraction method revealed an obvious improvement in the crystallinity of an AlN layer on the initial layer. At the interface structure, AlN film without the Al buffer layer exhibited surface nitridation of the Si surface, which degraded the AlN crystal growth. After investigating various growth conditions such as substrate temperature and layer thickness, we achieved the all-sputtered epitaxial growth of a GaN/AlN/Si substrate. The substrate temperature was below 650 °C, and the total thickness was less than 200 nm, which is beneficial as regards the cost efficiency of the template substrate for nitride semiconductors.

Thin film growth of Zn x Mn1−x S on a Si (100) substrate by sputtering was investigated for nonpolar AlN film growth on Si (100) substrate. The Zn x Mn1−x S buffer layer reduces the large differences in thermal expansion coefficient and lattice constants between AlN and Si. Although the solubility of ZnS in MnS is less than 5% at 800 °C in bulk form, the insertion of a room-temperature MnS layer between Zn x Mn1−x S and Si enabled (100)-oriented cubic-Zn x Mn1−x S film growth even at x = 9.5%, which is a metastable phase and a phase separation region in bulk form. On the (100)-oriented cubic Zn x Mn1−x S film, nonpolar AlN growth was achieved by sputtering. Furthermore, X-ray photoelectron spectroscopy measurements revealed that the Zn x Mn1−x S film improved the stability of the AlN/Zn x Mn1−x S interface. Zn x Mn1−x S has the potential to enable nonpolar AlN growth on large-diameter Si (100) substrates.

Herein, the rule of using a controlling agent, trisodium citrate dihydrate (TSCD), as a co-reactant in the crystal growth process of Mn–Ru coordination polymer (Mn–Ru CP) nanocubes has been reported. The size and shape of the final product is tuned by increasing the amount of TSCD. Random and aggregated particles were obtained in the absence of TSCD. The shape of the Mn–Ru CP nanocubes was improved using small amounts of TSCD. On further increasing the initial amounts of TSCD, regular and large nanocubes were obtained. In the presence of TSCD, the reaction was slow since the complex appeared to be more stable; thus led to controlled crystal growth. After mixing Mn(CH3COO)2 with TSCD, a Mn-citrate complex was formed. By dropwise addition of a K4[Ru(CN)6] aqueous solution, few Mn2+ ions were slowly released from the complex to react with [Ru(CN)6]4−. Subsequently, the nuclei were generated and further grew to form fine Mn–Ru CP nanocubes. After regular aerobic thermal treatment, synergetic nanoporous Mn–Ru mixed oxides were obtained. The Mn–Ru oxides are promising catalysts for oxygen reduction reactions through an exact four-electron pathway. We speculate that the high catalytic activity of these oxides can be attributed to the fine cubic structure, synergetic composition between Ru and Mn, and intrinsic high electrochemical activity of the ruthenium metal.

We report a controlled crystal growth process that enables the design of monocrystalline cyanide bridged coordination polymer (NiCNNi CP) nanoflakes using trisodium citrate dihydrate (TSCD) to control the nucleation rate. TSCD reacted with Ni2+ in the first stage of the reaction to form Ni–TSCD complex. The formed complex enabled few ions of Ni to release steadily and slowly in the reaction solution to interact with [Ni(CN)4]2− ions, thus resulting in the formation of fine NiCNNi CP nanoflakes (an orthorhombic crystal structure). A controlled thermal treatment at 420 °C under nitrogen yielded a trigonal nickel carbide (Ni3C) with similar flake-like morphology. On further heating, a phase transformation occurred and led to the formation of cubic Ni nanoparticles (fcc-type). Both Ni3C and fcc-Ni showed quite good electrocatalytic activity toward the reduction reaction of oxygen (ORR) with strong durability, but fcc-Ni showed better efficacy than Ni3C. The high activity of fcc-Ni nanoparticles could be attributed to the high intrinsic electrochemical activity, corrosion resistance, and chemical stability of Ni metal.

Quantum molecular devices have a potential for the construction of new data processing architectures that cannot be achieved using current complementary metal–oxide–semiconductor (CMOS) technology. The relevant basic quantum transport properties have been examined by specific methods such as scanning probe and break-junction techniques. However, these methodologies are not compatible with current CMOS applications, and the development of practical molecular devices remains a persistent challenge. Here, we demonstrate a new vertical resonant tunneling transistor for large-scale integration. The transistor channel is comprised of a MOS structure with C60 molecules as quantum dots, and the structure behaves like a double tunnel junction. Notably, the transistors enabled the observation of stepwise drain currents, which originated from resonant tunneling via the discrete molecular orbitals. Applying side-gate voltages produced depletion layers in Si substrates, to achieve effective modulation of the drain currents and obvious peak shifts in the differential conductance curves. Our device configuration thus provides a promising means of integrating molecular functions into future CMOS applications.

We investigate the introduction of oxygen vacancies by the interaction of Pt with CeO2(111) (ceria) thin epitaxial film grown on Cu(111) and the influence of the vacancies on resistive switching behavior. For this purpose, we used X-ray photoelectron spectroscopy and conductive atomic force microscopy. We found out that after Pt deposition, the ceria film was partially reduced. By our estimation, the reduction occurs not only at the Pt/CeO2 interface, but also on the surface of the ceria film which is not covered by Pt, after Pt deposition and annealing. A different distribution of oxygen vacancies in the film proves to have an influence on the resistance switching process of the film. Finally, the proper balance between the reduced and the unreduced species in order to obtain relatively stable repeatable resistance switch with clear resistance window is discussed.

This paper describes the adhesive interface between a conducting polymer/metal composite and a polytetrafluoroethylene (PTFE) substrate. Strong adhesion was observed from using a Ag/polypyrrole (Ag/PPy) composite on a fluoropolymer substrate, which in most cases has a very low adhesion to different materials. To clarify the adhesion mechanism between the Ag/PPy composite and the PTFE substrate, the interfacial structure was studied by the use of transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Our results show that Ag/PPy composite is absorbed inside the nano-sized pores of PTFE and the composite mechanically interlocks after solidifying, which causes the nanocomposite to stick strongly to the substrate. The use of Ag/PPy coating could be a novel technique for developing electrodes, antennae or other high performance applications as this metal/conductive polymer composite has excellent adhesion properties on various plastics.

This work reports on developments in the field of wide band gap Cu2ZnXY4(with X = Sn, Si or Ge, and Y = S, Se) kesterite thin film solar cells. An overview on recent developments and the current understanding of wide band gap kesterite absorber layers, alternative buffer layers, and suitable transparent back contacts is presented. Cu2ZnGe(S,Se)4absorbers with absorber band gaps up to 1.7 eV have been successfully developed and integrated into solar cells. Combining a CdS buffer layer prepared by an optimized chemical bath deposition process with a 1.36 eV band gap absorber resulted in a record Cu2ZnGeSe4cell efficiency of 7.6%, while the highest open-circuit voltage of 730 mV could be obtained for a 1.54 eV band gap absorber and a Zn(O,S) buffer layer. Employing InZnOxor TiO2protective top layers on SnO2:In transparent back contacts yields 85–90% of the solar cell performance of reference cells (with Mo back contact). These advances show the potential as well as the challenges of wide band gap kesterites for future applications in high-efficiency and low-cost tandem photovoltaic devices.

Closed-loop optimization of epitaxial titanium nitride (TiN) thin-film growth was accomplished using metal-organic molecular beam epitaxy (MO-MBE) combined with a Bayesian machine-learning technique and reduced the required number of thin-film growth experiments. Epitaxial TiN thin films grown under the process conditions optimized by the Bayesian approach exhibited abrupt metal–superconductor transitions above 5 K, demonstrating a new approach to the efficient development of less-studied materials, such as transition metal nitrides. The combination of the thin-film growth technique and Bayesian approach is expected to pave the way toward accelerating the development of the automated operation of thin-film growth apparatuses.

For the interface states at the SiO2/SiC interface, the energy distribution of interface states in the whole-gap region of SiC cannot be obtained from electrical method such as capacitance-voltage and conductance-voltage methods because deep interface states cannot respond to the electrical signal due to their extremely large time constants. Thus interface states at the SiO2/SiC interface in the SiC whole-gap region have not been obtained even though the observation of the energy distribution of interface states is indispensable for further improvement of the electrical properties. We have recently developed a spectroscopic method to observe the energy distribution of interface states based on photoelectron spectroscopic measurements under bias voltage (PES-BA) [1,2]. In the present study, we have investigated the energy distribution of interface states at the SiO2/4H-SiC interface using PES-BA. A Pt(10nm)/SiO2(8nm)/4H-SiC(0001) was used in the present study. The PES-BA measurements were performed using BL15XU at SPring-8. For PES-BA measurements, the incident photon energy was 5.95 keV, while the total energy resolution was set to 240 meV. Applying a positive bias voltage of 2.0V to SiC with respect to the Pt overlayer shifted the Si 1s substrate peak toward a higher binding energy by 0.61 eV. On the other hand, applying a -2.4 V voltage shifted the Si 1s peak toward a lower binding energy by 0.68 eV. These bias-induced shifts were completely reversible; that is, the shift diminished upon removing the bias voltage. Therefore, these shifts were not due to a bias-induced chemical reaction, but were caused by the accumulation or release of charge in the electronic states by the bias. Thus, by analyzing the these shifts as a function of bias voltage, we obtained the energy distribution of the interface states for the SiO2/4H-SiC(0001) interface. Note that the principle for the determination of interface states was described in our previous papers [1-3] For the observed interface states, uniform interface states in the whole gap existed while high density interface states were present near the CBM. By referencing previous theoretical calculations, the observed interface states were assigned. The sharp interface states observed below CBM may be attributed to Si2-C-O states at the interface. For the uniform interface states, two dimensional graphitic carbon and/or chemical disorder may be responsible for the uniform interface states because of the spectrum shape. The synchrotron measurements were performed under the approval of NIMS Beamline Station (Proposal No. 2013B4600 and No. 2014B4602). This study is collaboration with Prof. R. Hasunuma at Tsukuba University References: [1] Y. Yamashita, H. Yoshikawa, T. Chikyow, and K. Kobayashi, J. Appl. Phys. 113, 16370 (2013). [2]Y. Yamashita, K. Ohmori, S. Ueda, H. Yoshikawa, T. Chikyow, and K. Kobayashi, e-J. Surf. Sci. Nanotech. 8, 81 (2010). [3] Y. Yamashita, A. Asano, Y. Nishioka, and H. Kobayashi, Phys. Rev. B59, 15872 (1999).

We studied characteristic of Metal-Insulator-Metal capacitors with ZrO2/high-k/ZrO2 (Z/high-k/Z)-nanolaminate dielectric layers and TiN electrodes. Amorphous Al2O3, (Ta/Nb)Ox (TN) and (Ta/Nb)Ox-Al2O3 (TNA) as high-k interlayer were prepared by atomic layer deposition and post-deposition annealing. The dielectric constant (k) of ZrO2 thin film exhibited about 28 because of tetragonal, orthorhombic and cubic phases. The k value of Z/high-k/Z-nanolaminate dielectric layer is high in order of ZTNZ > ZTNAZ > ZAZ due to the dependence of each k value of Al2O3 (~ 9) and TN (~29). The ZTNAZ layer exhibited lowest leakage current density of 10-8 ~ 10-7 A/cm2 at 0.6 V compared to those of ZAZ and ZTNZ in CET ~ 1.1 nm. We found that the leakage current property of Z/high-k/Z layer is influenced by not only amorphous structure but also band gap width (conduction band offset of ZrO2) of high-k interlayer. We conclude that the TNA material is one of the candidate material as high-k interlayer for future DRAM.

Introduction InOx-based thin film transistors (TFTs) such as In-Ga-Zn-O, In-Ti-O, In-W-O, and In-Si-O have been widely investigated. We also reported carbon doped In-Si-O (In1-xSixOC) as channel material because of the highest bond dissociation energy of 1076 kJ/mol between carbon and oxygen. The turn on voltage shift (ΔV on) of In0.80Si0.20OC (C: 0.9 at. %) and In0.79Si0.21O TFT were 0 V and -0.2 V, respectively. The ΔV on of the In0.80Si0.20OC (C: 0.9 at. %) TFT was improved 0.2 V compared to that of In0.79Si0.21O TFT under positive gate bias stress (PBS) due to excess electron trapping reduction. Although In0.80Si0.20OC showed a good stability, the base In0.79Si0.21O TFT shows a low mobility of 7.7 cm2/Vs. To archive both high mobility and reliability, we investigated carbon doped In-W-O (In1-xWxOC) TFT because the In0.98W0.02O has a high mobility (> 39.0 cm2/Vs). In this paper, we studied transistor properties of In1-xWxOC TFT. We also discuss effect of carbon in In-W-O by comparing the stability between In1-xWxO and In1-xWxOC TFTs. Experiment The In1-xWxOC TFTs were fabricated on p++-Si (0.00099 Ω·cm) with 300-nm-thick thermal-oxide layers. 10-nm-thick In1-xWxOC films were formed on the substrates through a stencil shadow mask at room temperature by co-sputtering using In2O3 and WC targets under an Ar/O2 atmosphere at 0.2 Pa with PO 2 = 0.08 Pa. The XW of In1-xWxOC films were controlled in the range of 0.02 ~ 0.06 by changing the sputtering power for each target. Then, the post deposition annealing (PDA) was performed at 300 °C for 60 min in air. Finally, Au (100 nm)/Ti (10 nm) layer as source and drain electrodes were deposited by thermal evaporation method. The channel length and width of the TFT used in this study were 350 and 1000 μm, respectively. Results and Discussion The carbon content and chemical bond state of In1-xWxOCfilms were examined by X-ray photoelectron spectroscopy (XPS) measurements. The atomic ratio of carbon in In0.98W0.02OC, In0.96W0.04OC, and In0.94W0.06OC films were 0.3, 0.4, and 1.2 at. %, respectively. Moreover, the C1s peaks at 285 and 290 eV are observed after PDA, and attribute to W-C and O-C=O bonds in the In1-xWxOC films, respectively. Figure 1 (a) and (b) show comparison of the ΔV on of the In0.96W0.04OC and the In0.98W0.02O TFTs as a function of stress time under PBS and NBS conditions, respectively. The subthreshold swing (S.S.), on/off current ratio (I on/I off), threshold voltage (V th) and saturation field-effect-mobility (μ sat) values of In0.96W0.04OC TFT were 0.52 V/decade, 1.0×109, 0.4 V and 5.6 cm2/Vs, respectively at the initial state. The ΔV on in the In0.96W0.04OC TFT was 4.4 V after the PBS application of 10800 s (Fig. 1(a)). The ΔV on of the In0.96W0.04OC TFT was always smaller than that of In0. 98W0. 02O film under PBS. This indicates that trap state in In1-xWxOC channel were suppressed by introducing carbon. On the other hand, it is clear that the ΔV on (~ 0 V) of In0.96W0.04OC TFT was improved significantly compared to that (-0.5 V) of In0.98W0.02O TFT under the NBS of 5000 s. It was reported that the large ΔV on under NBS is due to the abnormal VO formation in oxide channel for GIZO TFT [7]. Therefore, this indicates that excess abnormal VO formation in In1-xWxOC channel is suppressed by introducing carbon. Conclusions We succeeded to introduce carbon (0.3-1.2 at. %) into In-W-O by co-sputtering WC and In2O3 targets. The S.S., I on/I off, V th and μ sat values of In0.96W0.04OC TFT were 0.52 V/decade, 1.0×109, 0.4 V and 5.6 cm2/Vs, respectively. The ΔV on of In0.96W0.04OC TFT was suppressed compared to that of In0. 98W0. 02O film under PBS. The ΔV on of In0.96W0.04OC TFT was not changed stress time up to 5000 s. The In0.96W0.04OC TFT is useful to reduce ΔV on under both the PBS and the NBS. References [1] S. Aikawa et al., Appl. Phys. Lett. 103, 172105 (2013). [2] S. Aikawa et al., Appl. Phys. Lett. 102, 102101 (2013). [3] T. Kizu et al., Appl. Phys. Lett. 104, 152103 (2014). [4] N. Mitoma et al., Appl. Phys. Lett. 104, 102103 (2014). [5] Y. R. Luo, “Bond dissociation energies,” in CRC Handbook of Chemistry and Physics, 90th ed.,edited by D. R. Lide (CRC Press/Taylor and Francis, Boca Raton, 2009). [6] K. Kurishima et al.,46th IEEE Semiconductor Interface Specialists Conference, Arlington, USA , December (2015). [7] J.-H. Park et al., Appl. Mater. Interface. 6, 21363 (2014). Figure 1