Post-annealed Films Research Articles

UV-assisted room-temperature chemiresistive NO2 sensor based on TiO2 thin film

TiO2 thin film based, chemiresistive sensors for NO2 gas which operate at room temperature under ultraviolet (UV) illumination have been demonstrated in this work. The rf-sputter deposited and post-annealed TiO2 thin films have been characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to obtain surface morphology, chemical state, and crystal structure, respectively. UV–vis absorption spectroscopy and Tauc plots show the optical properties of the TiO2 films. Under UV illumination, the NO2 sensing performance of the TiO2 films shows a reversible change in resistance at room-temperature. The observed change in electrical resistivity can be explained by the modulation of surface-adsorbed oxygen. This work is the first demonstration of a facile TiO2 sensor for NO2 analyte that operates at room-temperature under UV illumination.

Atomistic aspects of carrier concentration variation in post-annealed indium tin oxide films

Post-annealing environment-dependent optical and electrical properties of indium tin oxide films grown on glass were examined. X-ray diffraction measurements revealed that all of the films exhibited poly-crystallinity after annealing at 400 °C for 10 min O2, in-air and N2. The optical property measurements yielded >80% transmittances for all the films except for the as-grown and O2-annealed films, even though there were no significant optical band-gap energy differences. In the Hall measurements, all of the films exhibited n-type characteristics. However, the film annealed under the N2 environment showed the best electrical properties (highest carrier concentration and conductivity). The physical origin of electrical property variations due to annealing environment differences was explained by examining the core-level x-ray photoelectron spectra.

Nanocrystalline Ferroelectric BiFeO3 Thin Films by Low-Temperature Atomic Layer Deposition

In this work, ferroelectricity is identified in nanocrystalline BiFeO3 (BFO) thin films prepared by low-temperature atomic layer deposition. A combination of X-ray diffraction, reflection high energy electron diffraction, and scanning transmission electron microscopy analysis indicates that the as-deposited films (250 °C) consist of BFO nanocrystals embedded in an amorphous matrix. Postannealing at 650 °C for 60 min converts the sample to a crystalline film on a SrTiO3 substrate. Piezoelectric force microscopy demonstrates the existence of ferroelectricity in both as-deposited and postannealed films. The ferroelectric behavior in the as-deposited stage is attributed to the presence of nanocrystals. Finally, a band gap of 2.7 eV was measured by spectroscopic ellipsometry. This study opens broad possibilities toward ferroelectric oxides on 3D substrates and also for the development of new ferroelectric perovskites prepared at low temperature.

Thickness and Grain Size Effects on Thermal Transport of Post-Annealed Antimony Telluride Thin Films

Thickness and Grain Size Effects on Thermal Transport of Post-Annealed Antimony Telluride Thin Films

Role of thermal annealing on SiGe thin films fabricated by PECVD

Amorphous Silicon Germanium (a-SiGe) thin films of 500nm thickness are deposited on silicon substrates using Plasma Enhanced Chemical Vapour Deposition (PECVD). To obtain polycrystalline nature of films, thermal annealing is done at various temperature (450–600°C) and time (1–10h). The surface morphology of the pre- and post-annealed films is investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The crystallographic structure of the film is obtained by X-ray diffraction method. Raman spectroscopy is carried out to quantify the Ge concentration and the degree of strain relaxation in the film. Nano-indentation is performed to obtain the mechanical properties of the film. It is found that annealing reduces the surface roughness of the film and increases the Ge concentration in the film. The grain size of the film increases with increase in annealing temperature. The grain size is found to decrease with increase in annealing time up to 5h and then increased. The results show that 550°C for 5h is the critical annealing condition for variation of structural and mechanical properties of the film. Recrystallization starts at this condition and results in finer grains. An increase in hardness value of 7–8GPa has been observed. Grain growth occurs above this critical annealing condition and degrades the mechanical properties of the film. The strain in the film is only relaxed to about 55% even for 10h of annealing at 600°C. Transmission Electron Microscopy (TEM) observations show that the strain relaxation occurs by forming misfit dislocations and these dislocations are confined to the SiGe/Si interface.

Influence of Hetero Grain Boundaries on Oxygen Exchange Activity: Investigation of Two-Phase (La,Sr)CoO3-δ / (La,Sr)2CoO4+δ Cathode Materials

Recent investigations indicated that oxygen reduction is accelerated at hetero-contacts between perovskite (La,Sr)CoO3- d (LSC) and Ruddlesden-Popper phase (La,Sr)2CoO4+ d(LSC-RP) [1-3]. In the present study, we want to quantify the activity of triple phase boundaries (TPB) and distinguish it from the activity of the pure LSC and LSC-RP phases, and evaluate under which conditions LSC/LSC-RP composites could be more active cathode materials compared to pure LSC. Dense thin films of LSC/LSC-RP composites on single crystalline YSZ were prepared by a single PLD run from a two-phase PLD target with overall Sr content z=nSr/(nLa+nSr) of 0.3 and phase ratio w=nLSC-RP/(nLSC+nLSC-RP) of 0.25-0.75. On the heated substrate, the incoming material from the plasma plume crystallizes into a two-phase mixture (miscibility gap between LSC and LSC-RP). The resulting dense films are a nanocomposite of LSC and LSC-RP phases. For comparison, films of pure LSC and LSC-RP only were deposited under identical conditions. Furthermore, composite samples were deposited as amorphous films on unheated substrates, and crystallized by subsequent annealing. XRD shows crystalline LSC and/or LSC-RP phases in the single-phase and composite films deposited at 770 °C. The amorphous films developed crystal-like morphology (SEM) at annealing temperatures >500 °C. The SEM images in Fig. 1 show a crystallite size of 50-100 nm for films deposited at 770 °C, and 5-10 nm for amorphously deposited, post-annealed films. The area specific resistance of oxygen reduction (ASR, measured by impedance spectroscopy on microelectrodes) of single phase samples and composites is shown as a function of the volumetric LSC-RP content. The lines show the expected behavior of the ASR under the assumption that TPB effects are negligible. The grey line assumes a Sr content of 30% in both phases, the red curve takes into account that LSC and LSC-RP phases in thermodynamic equilibrium exhibit different Sr content (Sr accumulation in LSC-RP, for overall Sr content up to 40%). This Sr distribution can happen during the PLD films growth, and was evidenced by TEM. Its quantification by XRD on powder samples (glycine-nitrate process, annealed at 1200 °C) is shown in Fig. 2. Since the oxygen exchange activity of LSC decreases more steeply with decreasing Sr content than the activity of LSC-RP increases [4,5], the expected overall ASR of composite films is higher considering this distribution. The post-annealed sample with high TPB length (about 106 cm/cm2) showed the lowest ASR of all composites, but also deactivated most quickly (under morphological changes such as coarsening). The composites deposited at high T with shorter TPB lengths (105 cm/cm2 or less) exhibit a higher ASR, and after initial deactivation most of them are situated at or above the red curve. XRD/TEM indicated formation of a higher-order Ruddlesden-Popper phase at expense of LSC in some samples, which could explain an activity below the red curve. Taking the red curve as reference ASR (absence of TPB effects) for the two most active composites, their length specific resistance was in the range of 1-2 MΩ∙cm. At 500-600 °C their ASR is lower than the values obtained in [3] for a slightly larger overall Sr content. To summarize: dense composite films can be deposited in a single PLD run, with crystallite sizes down to 5-10 nm. The effects of Sr distribution increase the overall ASR compared to single phases with same overall Sr content, and unless very high TPB lengths are achieved (or high overall Sr/La ratios are used which diminish this effect) this effect prevails over the small activity enhancement which is specifically caused by the LSC/LSC-RP hetero-contacts. [1] M. Sase, K. Yashiro, K. Sato, J. Mizusaki, T. Kawada, N. Sakai, K. Yamaji, T. Horita, H. Yokokawa, Solid State Ionics 178 (2008) 1843. [2] E.J. Crumlin, E. Mutoro, S.-J. Ahn, G. Jose la O', D.N. Leonard, A. Borisevich, M.D. Biegalski, H.M. Christen, Y. Shao-Horn, J. Phys. Chem. Lett. 1 (2010) 3149. [3] W. Ma, J.J. Kim, N. Tsvetkov, T. Daio, Y. Kuru, Z. Cai, Y. Chen, K. Sasaki, H.L. Tuller, B. Yildiz, J. Mater. Chem. A 3 (2015) 207 [4] A.V. Berenov, A. Atkinson, J.A. Kilner, E. Bucher, W. Sitte, Solid State Ionics 181 (2010) 819 [5] F. Zhao, X. Wang, Z. Wang, R. Peng, C. Xia, Solid State Ionics 179 (2008) 1450 Figure 1

Molecular Beam Epitaxy Growth and Scanning Tunneling Microscopy Study of Pyrite CuSe2 Films on SrTiO3**Supported by the National Natural Science Foundation of China under Grant Nos 11374336 and 61176078.

We perform molecular beam epitaxy growth and scanning tunneling microscopy study of copper diselenide (CuSe2) films on SrTiO3(001). Using a Se-rich condition, the single-phase pyrite CuSe2 grows in the Stranski—Krastanov (layer-plus-island) mode with a preferential orientation of (111). Our careful inspection of both the as-grown and post-annealed CuSe2 films at various temperatures invariably shows a Cu-terminated surface, which, depending on the annealing temperature, reconstructs into two distinct structures and . The Cu termination is supported by the depressed density of states near the Fermi level, measured by in-situ low temperature scanning tunneling spectroscopy. Our study helps understand the preparation and surface chemistry of transition metal pyrite dichalcogenides thin films.

Colloidal Crystallization and Ionic Liquid Induced Partial β-Phase Transformation of Poly(vinylidene fluoride) Nanoparticles

Colloidal crystallization of poly(vinylidene fluoride) (PVDF) nanoparticles (NPs) and its β-phase transformation were studied. The pristine PVDF NPs with an average diameter of 230 nm consist of 46% α-phase and 54% amorphous PVDF. The PVDF NPs were assembled on a quartz substrate by means of vertical deposition method from a tetrahydrofuran dispersion of PVDF NPs with a few volume percentage of n-alkane. The resultant colloidal thin films displayed a pale-greenish structural color with the selective reflection at around 550 nm wavelength due to closely packed PVDF NPs. The colloidal thin films were immersed into an acetonitrile solution containing 2 wt % ionic liquid, subsequently air-dried, and thermally annealed at 140 °C, just below the melting point of the PVDF–IL blends. After annealing, the PVDF NPs partially transformed into its β-phase with the volume percentages of α-, β-, and amorphous phases of 22, 32, and 46%, respectively. The postannealed colloidal films still maintained the face-centered-cubic assembling structure of PVDF NPs, thus displaying the greenish structural color and selective reflection.

Influence of addition of indium and of post-annealing on structural, electrical and optical properties of gallium-doped zinc oxide thin films deposited by direct-current magnetron sputtering

Abstract In this study, both gallium-doped zinc oxide (GZO) and indium-added gallium-doped zinc oxide (IGZO) thin films were deposited on commercial glasses by magnetron dc-sputtering in argon atmosphere. The crystal structure, electrical conductivity and optical transmission of as-deposited as well as post-annealed thin films of both GZO and IGZO were investigated for comparison. A small amount of indium introduced into GZO thin films had improved their polycrystalline structure and increased their electrical conductivity by over 29%. All obtained GZO and IGZO thin films have strong [002] crystalline direction, a characteristic orientation of ZnO thin films. Although post-annealed in air at high temperatures up to 500 °C, IGZO thin films still had very low sheet resistance of 6.6 Ω/□. Furthermore, they had very high optical transmission of over 80% in both visible and near-infrared regions.

Low-frequency alternative-current magnetic susceptibility, photoelectric properties, and adhesive properties of Ni80Fe20 (XÅ)/ZnO(500Å) and ZnO(500Å)/Ni80Fe20(YÅ) on glass substrate

The following conditions are deposited: (a) glass/Ni80Fe20(XÅ)/ZnO(500Å) and (b) glass/ZnO(500Å)/Ni80Fe20(YÅ), where each of X and Y is 1000Å, 1500Å, 2000Å or 2500Å. The substrate temperature was maintained at room temperature (RT), and post-annealing was performed with heating at (TA)=150°C for 1h or (TA)=250°C for 1h. The sputtering sequence and the thickness of the NiFe film were varied to study the effects of these factors on the low-frequency alternative-current magnetic susceptibility (χac), maximum χac with corresponding optimal resonance frequency (fres), transmission, electrical resistivity (ρ), and surface energy of the multilayered glass/Ni80Fe20(XÅ)/ZnO(500Å) and glass/ZnO(500Å)/Ni80Fe20(YÅ). Experimental results demonstrate that ZnO(500Å)/Ni80Fe20(YÅ) is superior to Ni80Fe20/ZnO(500Å) because diffraction from the ZnO (002) crystals at the bottom of ZnO(500Å)/Ni80Fe20(YÅ) improves the magneto crystalline anisotropy of Ni80Fe20, improving its magnetic and photoelectrical properties. X-ray diffraction patterns (XRD) reveal that the ZnO (002), ZnO (220), and NiFe (111) peaks of ZnO(500Å)/Ni80Fe20(YÅ) are more intense than those of Ni80Fe20/ZnO(500Å) under three substrate conditions, indicating the ZnO (002) peak reflects magneto crystalline anisotropy in the crystalline NiFe layer of ZnO(500Å)/Ni80Fe20(YÅ), yielding the highest χac of approximately 3.16 with an fres of 250Hz upon post-annealing TA=250°C for 1h. The (111) diffracted intensity and grain size of the thicker and post-annealed Ni80Fe20 thin films exceeded those of the thinner and as-deposited Ni80Fe20 thin films. A spectral analyzer was used to measure transmittance through NiFe of various thicknesses. The transmittance declined slightly as the thickness and grain size increased, because increasing thickness reduced penetration. Post-annealing promoted grain growth, increased the average size of the grains and reduced transmittance. Both as-deposited glass/Ni80Fe20(XÅ)/ZnO(500Å) and as-deposited glass/ZnO(500Å)/Ni80Fe20(YÅ) had the highest penetration, when X, Y=1000Å, and the highest transmittances of 87% and 93%, respectively. The highest transmittance of glass/ZnO(500Å)/Ni80Fe20(YÅ) exceeded that of glass/Ni80Fe20(XÅ)/ZnO(500Å) owing to ZnO (002) crystallization. Furthermore, ρ decreased as the Ni80Fe20 thickness increased, because grain boundaries and the surface of thin films scattered the electrons, so thinner films had greater resistance. Electrical measurements revealed that the maximum resistivities of glass/Ni80Fe20(1000Å)/ZnO(500Å) and glass/ZnO(500Å)/Ni80Fe20(1000Å) were 292μΩcm and 288μΩcm, and the resistivity declined as the thickness of the film increased. The surface energy of the as-deposited and thinner NiFe layers exceeded that of post-annealed and thicker NiFe layers, revealing that the adhesion of the as-deposited and thinner NiFe films was stronger than that of the post-annealed and thicker films, on account of the degrees of crystallinity. Glass/Ni80Fe20(1000Å)/ZnO(500Å) and glass/ZnO(500Å)/Ni80Fe20(1000Å) had the highest surface energies of 64mJ/mm2 and 59mJ/mm2; the surface energy worsened as the temperature increased, suggesting that the adhesion of the as-deposited and thinner NiFe films in glass/Ni80Fe20(XÅ)/ZnO(500Å) was stronger than in glass/ZnO(500Å)/Ni80Fe20(YÅ). The results indicate that the magnetic and photoelectric properties of glass/ZnO(500Å)/Ni80Fe20(YÅ) were better than those of glass/Ni80Fe20(XÅ)/ZnO(500Å) because the strong ZnO (002) crystallization in ZnO(500Å)/Ni80Fe20(YÅ) increased the magneto crystalline anisotropy NiFe (111) and importantly affected the magnetic and photoelectrical properties.

Effect of excess ZnO on structure and dielectric properties of Bi1.5Zn1.0Nb1.5O7 thin films grown at room temperature by RF magnetron sputtering

Bismuth zinc niobate (BZN) thin films with excess Zn contents were deposited from the ceramic targets containing various excess amounts of ZnO (0–20mol%) on Pt/TiO2/SiO2/Si substrate by RF magnetron sputtering at room temperature. As-deposited thin films were post-annealed at a temperature ≤200°C, which is compatible with PCB substrates. The effect of Zn deficiency and Zn excess on the microstructure, dielectric, and electrical properties of BZN thin films was studied. As-deposited and post-annealed BZN thin films at a temperature ≤200°C were amorphous in nature. An appropriate amount of excess zinc improves the dielectric and electrical properties of BZN thin films, while too much excess zinc leads to deteriorate the properties. BZN thin film with 5mol% excess Zn content exhibits the maximum dielectric constant of 64 with a very low loss of 0.6%, measured at 10kHz and the leakage current of less than 1µA at an applied electric field of 200kV/cm.

Structural, optical and electrical properties of Cu2FeSnX4 (X = S, Se) thin films prepared by chemical spray pyrolysis

We report on fabrication of polycrystalline Cu2FeSnX4 (X=S, Se) thin films by chemical spray pyrolysis subsequent with post-sulfurization and selenization. The post-annealing of as-sprayed Cu2FeSnS4 (CFTS) films in sulfur and selenium ambient demonstrated drastically improved surface texture as well as crystallinity. The crystal lattice parameters calculated from X-ray diffraction patterns for post-annealed films were found to be consistent with stannite structure. The fabricated Cu2FeSnS4 (CFTS) and Cu2FeSnSe4 (CFTSe) films showed p-type conductivity with carrier concentration in the range of 1021cm−3 and mobility ∼1–5cm2V−1s−1. The band gap energies of post-sulfurized CFTS and post-selenized CFTSe films were estimated to be ∼1.37eV and ∼1.11eV with an error of ±0.02eV by UV–Vis absorption, respectively, which are promising for photovoltaic application.

Growth and Surface Properties of Cuprous Oxide Films on Au(111)

Reactive Cu deposition in an O2 ambience is used to prepare homogeneous copper oxide films on an Au(111) support. X-ray photoelectron spectroscopy reveals a predominant Cu2O stoichiometry of the ad-layers. Their growth morphology and atomic structure is determined with scanning tunneling microscopy (STM) and low-energy electron diffraction. The films grow in a layer-by-layer fashion and expose different terminations depending on the preparation conditions. While as-prepared films develop a variety of surface reconstructions, the structure of postannealed films is similar to the one of bulk-cut Cu2O(111). STM conductance spectroscopy is used to probe the local electronic structure and work function of the material. Apart from the ∼2.0 eV band gap of Cu2O, an unoccupied surface state is identified for annealed films. The high crystallographic quality of the cuprous oxide films renders them suitable for further investigations of the defect landscape and the optical properties of this reference material for p...

Antireflective downconversion ZnO:Er3+,Yb3+ thin film for Si solar cell applications

Hexagonal wurtzite phased ZnO:Er3+/Yb3+ thin films with various Yb concentrations were deposited on Si(111) substrate by Aerosol Assisted Chemical Vapor Deposition process. Post-annealed films at 1000 °C in air atmosphere showed a crystallinity enhancement. Yb3+ (4F7/2 → 4F5/2) 1000 nm emission increased with the increase of Yb3+ concentration emanating from an Er-Yb energy transfer. The reflectance percentage of 12% was achieved in the [250–1000 nm] range, and the refractive index of 1.97 was obtained for 632 nm wavelength. These results suggest that the (3 mol. % Er, 9 mol. % Yb) codoped film is a highly efficient antireflective downconversion layer for enhancing Si solar cell efficiency.

Post-annealing effect on the room-temperature ferromagnetism in Cu-doped ZnO thin films

In this work, we investigated the structural and magnetic properties of both as-deposited and post-annealed Cu-doped ZnO thin films for better understanding the possible mechanisms of room-temperature ferromagnetism (RT-FM) in ZnO-based diluted magnetic oxides. All of the films have a c-axis-oriented wurtzite structure and display RT-FM. X-ray photoelectron spectroscopy results showed that the incorporated Cu ions in as-deposited films are in 1+ valence state merely, while an additional 2+ valence state occurs in post-annealed films. The presence of Cu2+ state in post-annealed film accompanies a higher magnetization value than that of as-deposited film and, in particular, the magnetization curves at 10 K and 300 K of the post-annealed film separate distinctly. Since Cu1+ ion has a filled 3d band, the RT-FM in as-deposited Cu-doped ZnO thin films may stem solely from intrinsic defects, while that in post-annealed films is enhanced due to the presence of CuO crystallites.

Temperature dependence of ferroelectric properties and the activation energy of polarization reversal in (Pr,Mn)‐codoped BiFeO3 thin films

We applied Vopsaroiu's model to (Bi,Pr)(Fe,Mn)O3 (BPFM) and Pb(Zr,Ti)O3 (PZT) ferroelectric thin films fabricated by chemical solution deposition. The temperature dependences of the saturation polarization and the coercive field were measured in a low‐temperature region from 100 to 200 K. The saturation polarizations of BPFM thin films decreased on decreasing the measurement temperature due to the polarization pinning effect, while that of PZT thin film was almost unchanged over the temperature region. The coercive fields of all the thin films were increased linearly on decreasing the measurement temperature. The activation energies for polarization reversal in as‐grown BPFM, postannealed BPFM, and PZT thin films were 1.18, 1.25, and 0.95 eV, respectively. These results indicate that BPFM thin films have large activation energies for polarization reversal compared with PZT thin films. In addition, the postannealed BPFM thin film has a larger activation energy than the as‐grown BPFM thin film.

Effect of vacuum annealing on structural, morphological and optical properties of Sn2Sb2S5thin films with different thicknesses

Sn2Sb2S5 thin films in thickness of 100–900 nm were deposited on unheated glass substrates using thermal evaporation method and annealed in vacuum at temperature of 200 °C for 2 h. X-ray diffraction spectra indicated that all the Sn2Sb2S5 samples are polycrystalline in nature having orthorhombic structure. The various structural parameters, such as, crystalline size, dislocation density, strain and texture coefficient were calculated and the surface morphology of the films was also analyzed. The optical constants, i.e., refractive index, absorption coefficient and optical band gap of the as-deposited and post-annealed films have been determined from the analysis of the transmittance and reflectance spectral data over the wavelength range 300–1800 nm. All the Sn2Sb2S5 thin films before and after annealing have relatively high absorption coefficient between 104 and 105 cm−1 in the visible spectral range. The optical band gap was found to decrease, from 1.72 to 1.5 eV for samples before annealing and from 172 to 1.46 eV for samples annealed in vacuum, with increasing films thickness in the 100–900 nm range.

High <inline-formula> <tex-math notation="LaTeX">$K_{{{u}}}$ </tex-math></inline-formula> and Low Intergranular Exchange Coupling of Postannealed CoPt-WO<sub>3</sub> Granular Film

Magnetic properties and microstructure of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80</sub> Pt <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> -30 vol.% (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , WO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) and Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">82.4</sub> Pt <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17.6</sub> -27.7 vol.% SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> granular films postannealed at various temperatures in a heat-treating furnace were investigated. In this paper, it is found that among these granular films, CoPt-WO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> granular film shows the highest coercivity (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) because of low intergranular exchange coupling of well-isolated magnetic grains. Furthermore, the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> is enhanced with postannealing because of the increase of the magnetic anisotropy field (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sup> ) and uniaxial magnetocrystalline anisotropy (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sup> ) of the columnar growth magnetic grains. The increase of K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sup> for the postannealed granular film primarily originates from the reduction of the stacking faults as well as the lattice constant ratio.

RF 마그네트론 스퍼터링법으로 상온 증착된 비정질 ITZO 산화물의 전기적 및 광학적 특성

The electrical and optical properties of amorphous In-Tin-Zinc-Oxide(ITZO) deposited at room temperature using rf-magnetron sputtering were investigated. The amorphous ITZO thin films were obtained at the composition of In:Sn:Zn = 6:2:2, 4:3:3, and 2:4:4, but the ITZO (8:1:1) showed a crystalline phase of bixbyite structure of In2O3. The resistivity of ITZO could be controlled by oxygen pressure in the sputtering ambient. The resistivity of post-annealed ITZO thin films exhibited the dependence on the amount of Indium. Optical energy band gap and transmittance increased as the amount of indium in ITZO increased. For the device application with ITZO, the bottom-gated thin-film transistor using ITZO as a active channel layer was fabricated. It showed a threshold voltage of 1.42V and an on/off ratio of operated with saturation field-effect mobility of .

Two different mechanisms on UV emission enhancement in Ag-doped ZnO thin films

Ag-doped ZnO thin films were prepared by a sol–gel method. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis and photoluminescence spectra. The results show that the Ag in the ZnO thin films annealed at 500°C for 1h substitutes for Zn and exists in the form of Ag+ ion (AgZn) while the Ag in the ZnO thin films without a post-annealing mainly exists in the form of simple substance (Ag0). The incorporation of Ag indeed can improve the ultraviolet emission of ZnO thin films and suppress the visible emissions at the same time. However, the mechanisms on the ultraviolet emission enhancement in the annealed and unannealed Ag-doped ZnO thin films are very different. As for the post-annealed Ag-doped ZnO thin films, the UV emission enhancement maybe mainly results from more electron–hole pairs (excitons) due to Ag-doping while for the unannealed Ag-doped ZnO thin films; the UV emission enhancement is attributed to the resonant coupling between exciton emission in ZnO and localized surface plasmon in Ag nanoparticles.