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Dry etching of InGaZnO (IGZO) thin films was performed in a capacitively coupled plasma-reactive ion etching (CCP-RIE) mode using hydrochloride (HCl) and argon (Ar) gases. Dry-etching characteristics and surface properties of IGZO films were then investigated according to gas mixture ratio, radio frequency power, and chamber working pressure. With an optimized ratio of HCl : Ar at 20 : 20 SCCM, the IGZO film showed good etch characteristics with a moderate etch rate of 6.0 nm/min and a low roughness of 0.19 nm. During the etching process of IGZO thin films, nonvolatile by-products such as GaClx, InClx, and ZnClx generated on the surface could be effectively removed by physical bombardment with Ar+ ions. As a result, we successfully conducted dry etching of IGZO thin films in the CCP-RIE system under HCl-Ar gas conditions, which demonstrated dry etching on IGZO without needing a fluorine-based etching gas. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) and electrical endurance characteristics of amorphous Sb2O5 films in Pt/Sb2O5/Pt and Sb/Sb2O5/Pt structures were examined. Although both structures showed unipolar RS characteristics with power consumption smaller than those of other various transition metal oxides by ∼ two orders of magnitude, enhanced electrical endurance was obtained when Sb was employed as the top electrode than when Pt was employed as the top electrode. This improvement was explained by the creation of Sb clusters in the Sb2O5 films through the diffusion of oxygen from Sb2O5 to the Sb layer and the suppression of excessive oxygen loss during conducting filament formation process by the Sb top electrode. Metallic Sb clusters in pristine Sb2O5 films were confirmed by X-ray photoelectron spectroscopy depth profiling measurements and Auger electron spectroscopy. From the results of current density variation as a function of sample area, it was confirmed that the RS properties of Sb2O5 were controlled by the localized conducting filament in Sb2O5; this finding was in agreement with the result of high resolution transmission electron microscopy. The RS properties of this pnictogen oxide material are discussed with the RS properties of other transition metal oxide materials. [ABSTRACT FROM AUTHOR]

Resonant elastic x-ray scattering has been widely employed for exploring complex electronic ordering phenomena, such as charge, spin, and orbital order, in particular, in strongly correlated electronic systems. In addition, recent developments in pump–probe x-ray scattering allow us to expand the investigation of the temporal dynamics of such orders. Here, we introduce a new time-resolved Resonant Soft X-ray Scattering (tr-RSXS) endstation developed at the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL). This endstation has an optical laser (wavelength of 800 nm plus harmonics) as the pump source. Based on the commissioning results, the tr-RSXS at PAL-XFEL can deliver a soft x-ray probe (400 eV–1300 eV) with a time resolution of ∼100 fs without jitter correction. As an example, the temporal dynamics of a charge density wave on a high-temperature cuprate superconductor is demonstrated. [ABSTRACT FROM AUTHOR]

Amorphous gallium indium zinc oxide (a-GIZO) thin films of different compositions (Ga2O3:In2O3:ZnO=1:1:1,2:2:1,3:2:1,4:2:1) on Si substrates were investigated by high-resolution x-ray photoelectron spectroscopy and x-ray absorption spectroscopy (XAS) using synchrotron radiation. The O 1s, Ga 3d, In 4d, Zn 3d core, and shallow-core levels as well as the valence band maxima and O K-edge XAS were investigated. Each O 1s spectrum could be deconvoluted by a main component (O1 in the text) representing the Ga–In–Zn–O quaternary system along with two other higher-binding energy (BE) components (O2 and O3 in the text). The O2+O3 intensity increased as the Ga2O3 content increased. For the as-prepared samples, the spectral peak separations between the Ga 3d (∼20 eV) and Zn 3d (∼11 eV) orbitals and between the In 4d (∼18 eV) and Zn 3d orbitals became larger, respectively, as the Ga2O3 content increased. For the surface-cleaned samples, this trend was the same but with smaller increases in their separations. The sputter-cleaning effectively reduced the Zn 3d intensity by ∼30% relative to those of Ga 3d and In 4d. The valence band maximum shifted toward higher BE, up to ∼0.5 eV for the as-prepared samples and ∼0.25 eV for the cleaned samples, and the conduction band minimum (measured at the O K-edge) was measured at photon energies ranging upwards to ∼0.2 eV as the Ga2O3 content increased, demonstrating that the band gap can be tailored by increasing the Ga2O3 content. The effects of increasing Ga2O3 contents on the local chemical states and the corresponding electrical conduction are discussed in this paper. [ABSTRACT FROM AUTHOR]

Bonding characteristics of low-dielectric-constant (low-k) fluorine-incorporated silicon oxide (SiOF) and carbon-incorporated silicon oxide (SiOC) films prepared by plasma enhanced chemical vapor deposition were investigated by Fourier transform infrared spectroscopy (FTIR). The frequency of Si–O stretching vibration mode in SiOF film shifted to higher wave number (blueshift) with the increase of fluorine incorporation, while that in SiOC film shifted to lower wave number (redshift) as the carbon content increased. In N[sub 2]-annealed SiOC film, the Si–O stretching frequency slightly shifted to lower wave number. To elucidate these phenomena, we have developed the “bonding structure model” based on the electronegativity of an atom. The frequency shifts observed in the FTIR spectra of SiOF and SiOC films were well explained by this model. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A flexible vertical-channel thin-film transistor (VTFT) with a channel length of 400 nm was fabricated on a poly(ethylene naphthalate) substrate. The vertical gate-stack composed of gate electrode/gate insulator/active channel was prepared by a conformal atomic layer deposition and a dry etching process of an organic polyimide spacer. The transfer characteristics of the fabricated flexible VTFT were well confirmed after the postannealing process at 200 °C, in which the on/off ratio was obtained to be 1.8 × 102. The threshold voltage shifts were estimated to be +6.1 and −4.5 V under the positive and negative bias-stress conditions for 104 s, respectively. The device characteristics showed no remarkable degradation when delaminating from the carrier glass substrate. Furthermore, there were no marked changes in transfer curves even when the device was bent with a radius of curvature of 10 mm. A suitable choice of spacer material, optimization of the dry etching process, and employment of ultra-thin flexible film substrate were suggested to appropriate solutions for enhancing the device performance of the proposed flexible VTFTs. [ABSTRACT FROM AUTHOR]

Deals with a study which investigated stress-temperature behaviors of RuO[sub2] thin films on (100) silicon by measuring the deflection of film-coated substrates in situ during thermal cycling. Experimental methods; Results and discussion; Conclusion.

Presents a study that investigated the solid state reactions of bilayer systems with a silicon substrate. Method of the study; Results and discussion; Conclusion.

Presents a study which investigated the thickness dependence of the preferred orientation of Mn-Zn ferrite thin films deposited by ion-beam sputtering. Theories of preferred orientation; Examination of the thickness dependence of magnetic properties of the ferrite films; Importance preferred orientation of thin films.

Describes a technique for the formation of titanium (Ti)-nitrogen (N) film with large grain size from TiN layer deposited by sputtering in argon and nitrogen. Overview of the film properties and electromigration; Epitaxial continuity at the aluminum/TiN interface; Structural properties of the TiN mutilayered aluminum interconnection and its EM characteristics.

Describes the epitaxial nature of the cobalt (Co)-silicon (Si) formed on the Si substrates as a result of annealing of Co/tantalum (Ta) bilayer in nitrogen atmosphere. Cause of the improvement of the epitaxiality of CoSi[sub2]; Investigation of microstructure using x-ray diffraction; Degradation of the eptaxial nature due to the loss of Ta diffusion barrier function.

Presents a study that investigated the epitaxial growth of cobalt silicide on silicon water using cobalt/tantalum bilayer. Experimental procedures; Results; Discussion.

Electrical characteristics of self-aligned coplanar amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) were investigated for different annealing temperatures. The field-effect mobility of the a-IGZO TFTs increased with the annealing temperature, in particular, for a small channel length. The effective channel length (Leff) of the a-IGZO TFTs was extracted using the transmission line method. The decrease in Leff significantly depended on the annealing temperature, due to the hydrogen diffusion into the a-IGZO channel region. The intrinsic mobility calculated from the channel resistance of the a-IGZO TFTs was in good agreement with the mobility corrected by Leff. [ABSTRACT FROM AUTHOR]

We report an overview of soft X-ray scientific instruments and X-ray optics at the free electron laser (FEL) of the Pohang Accelerator Laboratory, with selected first-commissioning results. The FEL exhibited a pulse energy of 200 μJ/pulse, a pulse width of <50 fs full width at half maximum, and an energy bandwidth of 0.44% at a photon energy of 850 eV. Monochromator resolving power of 10 500 was achieved. The estimated total time resolution between optical laser and X-ray pulses was <270 fs. A resonant inelastic X-ray scattering spectrometer was set up; its commissioning results are also reported. [ABSTRACT FROM AUTHOR]

Explores the development of magnetic anisotropy in NiFe/Cu/Co trilayers. Alignment of easy axes; Magnetic resonance ratio; Suitability for memory application.

Al2O3 thin films were deposited using tri-methyl aluminum and ozone by spatially separated atomic layer deposition (SALD). A large gap was kept between the reactor and substrates in an attempt to enhance the process gas flow. According to simulation data and deposition results, strong edge pumping for the dominantly lateral flow improved the gas isolation and deposition was very effective, with a resulting gap height of 5 mm. To compare this SALD process with conventional atomic layer deposition (ALD), the authors examined how the amount of source supplied, the deposition temperature, and the number of rotations affected the growth rate. The growth rate per rotation was saturated at ∼0.12 nm/rotation at a deposition temperature of 250 °C, which is comparable to the saturated growth rate of the same film using conventional ALD. The dielectric constant of the films was ∼8 and the film with a capacitance equivalent thickness of 3.2 nm had a leakage level of 9.8 × 10-8 A/cm2 (at -1 V). X-ray photoelectron spectroscopy peak area analysis indicates that the films deposited by SALD consist of Al2O3. This indicates that SALD is a viable option for several mass-production applications that require high throughput. [ABSTRACT FROM AUTHOR]

This study examined the effects of the indium fraction in indium zinc oxide (IZO) on the performance and stability of IZO thin film transistors (TFTs). The field-effect mobility and sub-threshold swing were much improved with increasing In fraction; 41.0 cm2/Vs and 0.2 V/decade, respectively, at 85 at. % In, compared to 1.1 cm2/Vs and 2.4 V/decade of ZnO TFTs. In contrast, a local minimum negative bias illumination stress instability was observed near 73-77 at. % In. This behavior was explained by a poly-crystalline to amorphous phase transition in IZO thin films. [ABSTRACT FROM AUTHOR]

Effects of Ti top electrode on unipolar resistive switching characteristics are investigated for NiO based resistive switching memory with Ni-inserting layer, compared with those for Pt-electrode. Current-voltage curves for forming process are almost identical for Ti-Ni-NiO-Pt and Pt-Ni-NiO-Pt structure, which may suggest that Ti does not chemically react with NiO. However, I-V curves for reset and set operation with Ti top electrode show improved resistive switching behaviors, such as reduction of reset current and less variation of both high and low resistance states. In order to understand the mechanism for improved resistive switching properties, electro-thermal simulation is performed, which shows that improvement in resistive switching characteristics is ascribed to reduced heat flow through top electrode resulting from lower thermal conductivity of Ti as compared to Pt. [ABSTRACT FROM AUTHOR]

Threshold-switching (TS) and selector performances of Si-As-Te thin films for crossbar resistive memory were studied. Composition of the film was the major factor determining the emergence of TS. On-state conduction was found to occur at localized regions. The change of threshold voltage and off-state current by varying composition was observed, which were explained by the change in the concentration of defects and generation efficiency of carriers. The serially connected TiO2 unipolar switching memory and Si-As-Te threshold switch showed the resistance switching of the memory layer with the leakage current lowered by ∼120 times at 0.5 V. [ABSTRACT FROM AUTHOR]

The electrical properties of thermally grown and atomic-layer-deposition (ALD) oxides, followed by nitridation treatment, on 4H-SiC substrate were compared. The nitridation treatment was performed with post oxidation annealing in NO atmosphere (NO POA). The best electrical characteristics of the thermally grown and ALD oxides were observed at 120 and 180 min NO POA, respectively. The NO POA treated ALD oxide showed extremely low interface trap density (Dit), less than 1011 eV-1 cm-1. A metal-oxide-semiconductor field-effect-transistor with the ALD oxide showed high field effect mobility, especially in the high electric field region. The reasons for these superior results were also discussed. [ABSTRACT FROM AUTHOR]

Silicon oxide thin film grown at low temperatures (<300-500 °C) is essential for a range of applications in semiconductor devices. In this study, silicon oxide films were deposited at a substrate temperature of ∼300 °C by an atomic layer deposition (ALD) process using Bis(ethyl-methyl-amino)silane (BEMAS). BEMAS precursors adsorbed on the growing surface reacted with ozone but not with H2O. This suggests that the Si-H bonds in the BEMAS precursors adsorbed on the surface are robust and could be cleaved only by ozone. The reaction using BEMAS and ozone exhibited ALD saturation behavior. The dielectric constant of the ALD-SiO2 was measured to be ∼9, which is 2.3 times higher than that (∼3.9) of normal amorphous SiO2. This was attributed to the existence of the ∼10% OH species in the film. [ABSTRACT FROM AUTHOR]

TiO2 and its nanopattern fabrication have been studied intensively because of its wide band gap and photocatalystic nature. TiO2 nanopatterns can be made by conventional patterning techniques, consisting of deposition, photolithography, and etching processes. However, these processes include complicated and expensive process steps, such as photolithography. Therefore, a simpler and more economic process is needed. In this work, TiO2 nanopatterns were fabricated using reverse-imprint lithography and the sol-gel method. Ethanol based TiO2 sol was prepared using tetrabuthylorthotitanate (C16H36O4Ti) and diethanolamine (C4H11NO2). TiO2 sol was then coated on the surface of the replicated polymer mold of hard-polydimethylsiloxane and polydimethylsiloxane by spin coating and transferred to the substrate by the reverse imprinting process at 200 °C. A postimprint annealing process was subsequently carried out to form the TiO2 polycrystalline phase. The x-ray diffraction and x-ray photoelectron spectroscopy results confirmed that the transferred TiO2 nanopattern was chemically pure polycrystalline TiO2. [ABSTRACT FROM AUTHOR]

Thin film transistors (TFTs) with In and Ga-free multicomponent Zn-Sn-Zr-O (ZTZO) channel layers were fabricated using the cosputtering approach. The incorporation of ZrO2 into the Zn-Sn-O (ZTO) films increased the contact resistance, which led to the degradation of the transport properties. In contrast, the threshold voltage shift under negative bias illumination stress (NBIS) was largely improved from -12.5 V (ZTO device) to -4.2 V (ZTZO device). This improvement was attributed to the reduction in the oxygen vacancy defects in the ZTZO film, suggesting that the photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability. [ABSTRACT FROM AUTHOR]

The concurrent presence of unipolar resistive switching (URS) and bipolar resistive switching (BRS) characteristics of the Sb/Sb2O5/Pt structure were examined. It was discovered that the BRS phenomenon was driven by the abnormal reset process during URS cycles which was induced by the rupture and recovery of the conducting filament (CF) in the localized region near the anode. The electrical conduction behavior in the high resistance state of URS and BRS was explained by the Schottky emission and space-charge-limited current mechanism, meaning that the URS and BRS phenomena are induced by the extent of reoxidaton and reduction regarding the local CF-ruptured region. [ABSTRACT FROM AUTHOR]

The authors measured magnetization hysteresis curves and used magneto-optical imaging to visualize the flux distributions in superconducting MgB2 films in order to study dendritic flux avalanches. The flux avalanches are found to disappear above some upper threshold field that is typically ∼1 kOe, but strongly depends on the film width. If the film is made wider, this threshold field first increases and then tends to saturate. This behavior is quantitatively explained using a thermomagnetic model for the dendritic avalanches and taking into account the field dependence of Jc. The results demonstrate that patterning superconducting films into narrow strips substantially increases the range of magnetic fields for which they can be used for applications. [ABSTRACT FROM AUTHOR]

Current conduction mechanisms of an atomic-layer-deposited Al2O3 gate on n-type 4H SiC have been systematically investigated, analyzed, and reported in this letter. It has been revealed that space charge limited, Poole-Frenkel (PF) emission, combination of PF emission and Fowler-Nordheim tunneling are the dominate current conduction mechanisms in the dielectric. Besides, Schottky emission has also been proposed as a possible leakage path at temperature beyond the investigated range. A relationship among the conduction mechanism, temperature, and applied electric field has been presented. [ABSTRACT FROM AUTHOR]

The effects of the isoelectronic Al doping of epitaxial GaN films grown by metalorganic chemical vapor deposition on a (0001) Al2O3 single crystal substrate were investigated. It was found that the threading screw and edge dislocation densities of the GaN film decreased to less than half of that of the undoped GaN film up to Al doping concentration of 0.45%. The in-plane and out-of-plane strains were simultaneously reduced with the decrease in dislocation density as a result of the solution hardening effect. Accordingly, the electron mobility of the 0.45% Al-doped GaN film (524 cm2/Vs) was greatly improved compared to that of the undoped GaN film (178 cm2/Vs). However, the threading dislocation densities and strains were increased at a 0.64% Al concentration, and the electron mobility decreased accordingly. Therefore, the improvement in the electron mobility by Al doping up to 0.45% is the result of a decrease in the threading dislocation density and not a decrease in the number of point defects (Ga-site vacancy) as suggested earlier [Lee et al., Appl. Phys. Lett. 83, 917 (2003)]. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We measured the superconducting critical current densities (J[sub c]) from the magnetization hysteresis (M–H) loop for Au-coated MgB[sub 2] thin films. The purpose of this experiment was to determine whether the vortex avalanche phenomenon which suppresses the J[sub c] for low temperature (T<15 K) and low field (H≤1000 Oe) could be cured by gold deposition. This avalanche, called flux noise, has been a headache in applications of MgB[sub 2] thin films. Fortunately, the flux noise in the M–H loop is suppressed with increasing Au-film thickness and finally disappears when the thickness of the gold becomes 2.55 μm. We found a way to remove one obstacle for applications of MgB[sub 2] thin films as an superconducting device. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The minority carrier (electron) capture process and the interface trap density of a TiN/Al[sub 2]O[sub 3]/p-Si metal-oxide-semiconductor capacitor were examined by deep level transient spectroscopy (DLTS). It was found that the activation energies of the large peaks detected at higher temperatures with gate bias voltages of 1.8, 1.5, 1.3, and 1.1 V were 0.19, 0.24, 0.29, and 0.37 eV, respectively. These energies were related to the electron-capture process from the conduction band by interface states in the upper half of the Si band gap. The interface state passivation effect of postannealing in a hydrogen ambient was studied from the minority carrier capture process and the usual DLTS signals. The D[sub it] at an energy of 0.35 eV from the valence bandedge decreased from 1 × 10[sup 12] cm[sup -2] eV[sup -1] at the as-fabricated state to 4 × 10[sup 11] cm[sup -2] eV[sup - 1] after H[sub 2] annealing at 450 °C. It was also found that the D[sub it] at an energy of 0.3 eV from the conduction bandedge decreased to the same amount by the same annealing process. [ABSTRACT FROM AUTHOR]

Pb(Zr, Ti)O[sub 3] (PZT) thin films were deposited on Pt/Ti and Pt/IrO[sub 2] electrode stacks with various Pt thicknesses (30-200 nm) by a sol-gel process. The sputter-deposited Pt films showed a (111)-preferred texture irrespective of the thickness. However, a high-resolution x-ray diffraction study of the Pt films showed that the films were composed of three kinds of grains with slightly different lattice parameters. The grains with a bulk-like lattice parameter grew with increasing Pt thickness, which was accompanied with an improvement in the crystalline quality. Accordingly, the crystallization and ferroelectric behavior of the 100-nm-thick PZT films improved with increasing Pt film thickness. However, the PZT films on the Pt/IrO[sub 2] electrode showed a deteriorated ferroelectric performance due to the outward diffusion of the Ir (O) onto the Pt surface, which increases the depolarizing field and amount of charge injection by the formation of a conducting phase. [ABSTRACT FROM AUTHOR]

The electrical conduction behavior of sputter-grown (Ba, Sr)TiO[sub 3](BST) thin films having IrO[sub 2] electrodes were studied under the assumption of a fully accumulated film. In the film-thickness range studied (40-80 nm), the dielectric constants and their electric field dependencies were found to be independent of the film thickness. Contrary to similar BST films grown on Pt electrodes, the leakage current density decreased with increasing film thickness at a given field. The phenomena were explained from the electric-field depression effect inside the film due to the accumulated negative space charges in the films. The leakage current conductions were controlled by the Poole-Frenkel mechanism in the low field whereas it changed to thermionic field emission in the high-field region. The dielectric constant obtained from the Poole-Frenkel fitting was approximately 300, which was in a qualitative agreement with the value obtained from the low-frequency capacitance measurement. The calculated interfacial potential-barrier height at zero volt and effective mass of electrons were 1.03 eV and 0.06m[sub 0], respectively, from the thermionic field emission fittings. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Dielectric properties of carbon-incorporated silicon oxide (SiOC) films deposited by plasma enhanced chemical vapor deposition (PECVD), using a bis-trimethylsilylmethane precursor, were compared with the dielectric properties of silicon oxide thermally grown in a furnace (thermal oxide) and also with oxide deposited by PECVD using a tetraethoxysilane (TEOS) precursor (PE-TEOS oxide). The electronic contribution to the dielectric constant of the three oxide films was calculated from their refractive indices measured at 632.8 nm by ellipsometry. Ionic contributions were computed from their IR reflection spectra, measured at 650–4000 cm-1, by using the Kramers–Kronig relation. The dipolar contribution was qualitatively analyzed from temperature dependence of the polarizability, on a per unit volume basis. The dielectric constant of the SiOC films, which was measured at 1 MHz, decreased from 4.2 to 2.3 as the carbon content increased from 0 to 19.6 at. %. Although there was a significant reduction of the dielectric constant, the electronic contribution was only slightly changed from 2.10 to 1.90, whereas the ionic polarization noticeably changed from 1.86 to 0.25. SiOC films showed considerable dipolar contribution when compared to thermal oxide and PE-TEOS oxide films, but the dipolar contribution in the SiOC films became negligible as the carbon content was increased. The variation of each contribution with the carbon content shows that carbon incorporation leads to a decrease in the electronic and ionic contributions. The reduction of the ionic contribution was the predominant factor leading to a decrease in the overall dielectric constant. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

SrVO[sub 3] films were grown by laser molecular beam epitaxy on LaAlO[sub 3] substrates. For a 10-nm-thick film, its resistivity could be reduced by a factor of 4 by inserting a single La-O atomic layer on an oxygen-annealed LaAlO[sub 3] substrate. X-ray diffraction and x-ray photoelectron spectroscopy measurements revealed that oxygen defect concentrations could be varied significantly by controlling the substrate terminations, i.e., interface chemistry. It was suggested that the interface chemistry could influence formation of extended defects and result in changes in electrical properties. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A non-toxic and non-flammable organosilicon source having alternate Si–C bonding structure, bis-trimethylsilylmethane [C7H20Si2], was first used to deposit epitaxial β-SiC films at low growth temperature by chemical vapor deposition. Epitaxial β-SiC films were successfully grown on carburized Si(100) substrates at temperatures as low as 1100 °C, although the carburized buffer layer was a well-oriented, (100) polycrystalline film. Transmission electron microscopy analysis revealed that the films contain twins, stacking faults, and antiphase boundaries. Without the carburized buffer layer, highly (111) preferred oriented β-SiC films were grown by increasing the growth temperature. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]