Generation,growth, shrinkage,and dispersion of Au agglomerates in Si during the annealing of supersaturated substitutional Au

Si samples homogeneously pre-indiffused with Au atoms at a concentration 7.5 × 10¹⁶ atoms/cm³ were heat treated at 900 °C for 22.5, 90, 360, and 1,440 h to generate Au agglomerates during the out-diffusion process of supersaturated high-temperature substitutional Au. The number of Au atoms in all of the agglomerates in the regions 8–22, 22–36, 36–50, and 50–64 μm from the surface were measured by secondary ion mass spectrometry, and the change of their distributions during annealing was obtained. As a result, agglomerates containing (1–3) × 10⁵ Au atoms were initially generated with a concentration of 1.1 × 10¹⁰ agglomerates/cm³ at a short annealing time. The generated agglomerates grow, shrink, and disperse with the decrease of the supersaturation of the surrounding Au concentration, that is, with increase of annealing time. The boundary Au concentration for changing from growth to shrinkage of the agglomerates is (3–5) × 10¹⁵ atoms/cm³. The agglomerates grow and contain until about 2.3 × 10⁶ atoms. The agglomerates disperse and finally disappear as the surrounding Au concentration decreases to its thermal equilibrium value with continued annealing. It is difficult to explain the continuous generation, growth, shrinkage, and dispersion of the agglomerates during annealing using the usual theoretical treatment of agglomeration of supersaturated solutes in solids.     

SIMS measurement of nano-sized Au agglomerates in Si

The conditions required for SIMS measurement, namely the detection depth of the SIMS signal and an appropriate measurement cycle, to obtain a reliable shape, size and atom number of nano-sized agglomerates in Si have been investigated. Au agglomerates in Si generated during annealing at 900 °C for 360 h are measured by an appropriate SIMS method and it is found that the Au agglomerate has a spherical shape with a concentration of 5.4 × 10²¹ Au atoms/cm³. The SIMS results agree well with the calculation of spherical agglomerates. The size of agglomerates larger than 20 nm and the Au atom number in agglomerates larger than several nm can be measured in a usual SIMS experiment.     

Distribution of Au atom number in the Au agglomerates generated during the out-diffusion process of supersaturated high-temperature substitutional Au in Si at 900 °C

Au atom number in the Au agglomerates generated during the annealing of supersaturated high-temperature substitutional Au in Si at 900 °C are measured by SIMS and their distributions have been investigated. The annealing time is chosen as 22.5, 90 or 360 h, which corresponds to initial, middle or near final stage of the annealing. Many “initial agglomerates” containing about 2.0 × 10⁵ Au atoms are generated and the distributions show an abrupt one with the peak at the atom number in the initial and middle stages. The “initial agglomerates” have absorbed supersaturated Au atoms within 0.86 μm. The “initial agglomerates” are generated even in the near final stage and grow up to containing about 4 × 10⁶ Au atoms by absorbing the Au atoms within 2.3 μm, finally. As the consequence, many agglomerates contain 5 × 10⁴–1.3 × 10⁶ Au atoms resulting in a broad distribution at the near final stage. Schematic models of agglomerations corresponding to each stage are proposed.     

Defects and acceptor centers in ZnO introduced by C+-implantation

ZnO single crystals were implanted with 280 keV C⁺ to a dose of 6 × 10¹⁶ cm^?2. Positron annihilation measurements reveal a large number of vacancy clusters in the implanted sample. They further agglomerate into larger size or even microvoids after annealing up to 700 °C, and are fully removed at 1200 °C. X-ray diffraction, photoluminescence, and Raman scattering measurements all indicate severe damage introduced by implantation, and the damaged lattice is partially recovered after annealing above 500 °C. From room temperature photoluminescence measurements, an additional peak at around 3.235 eV appears in the implanted sample after annealing at 1100 °C, which is much stronger than that of the free exciton. From the analysis of low temperature photoluminescence spectra, this peak is mostly a free electron to acceptor (e,A⁰) line which is probably associated with C _O .     

Au agglomerates observed in the out-diffusion process of supersaturated high-temperature substitutional Au in Si

Out-diffusion profiles of supersaturated substitutional Au in Si annealed at 900 °C for 90 h have been measured by SIMS and ICTS methods over a distance of 80 μm from the specimen surface. The tendency of the profile of total Au atoms measured by SIMS and that of electrically active substitutional Au measured by ICTS agrees well, but the very small regions containing high-concentration of Au atoms, 3 × 10²² cm⁻³, are observed sporadically at the distance deeper than 10 μm from the surface by SIMS method. The size of the high-concentration region is estimated to be about 20 nm and its density is about 2 × 10¹⁰ cm⁻³. The small agglomerates contain 10⁵–10⁷ Au atoms and many of them contain about 2 × 10⁵ atoms. The observed agglomerate is a new agglomeration of Au in Si. The state of the agglomeration (namely, precipitates of Au, agglomeration of substitutional Au in Si, or a new state) is not clear by SIMS measurement.     

Peculiarities in the formation of gold nanoparticles by ion implantation in stabilized zirconia

The investigation of bulk single crystals and sputter-deposited films of yttria-stabilized zirconia (YSZ) upon irradiation by gold (Au) ions with an average energy of 160 keV followed by postimplantation annealing revealed peculiarities in the formation of nanocrystalline metal (nc-M) particles in this matrix. In the case of irradiation to small doses (∼5 × 10¹⁵ cm⁻²), the optical absorption spectra of samples showed evidence of the formation of nanoclusters of matrix cations (nc-Zr). In these samples, postimplantation annealing at temperatures ∼700°C and above leads to the formation of nc-Au particles. Local elemental analysis of individual nc-M particles in the YSZ matrix irradiated to a dose of 4 × 10¹⁶ cm⁻² and annealed at 800°C showed the presence of metal nanoparticles with complex compositions including both implanted Au and matrix Zr atoms.     

Influence of rapid thermal annealing on the process of aluminum induced crystallization of amorphous Si

The effects of annealing methods on the crystallization process and microstructure of polycrystalline silicon (poly-Si) films obtained by aluminum-induced crystallization (AIC) of amorphous Si (a-Si) films were comparatively investigated. Glass/Al/a-Si structures were annealed by rapid thermal annealing (RTA) and conventional furnace at 500 °C for different times in Ar. As compared to furnace annealing, AIC of a-Si films annealed by RTA possesses a shorter period of nucleation time, a higher nucleation density and reduces the process time to form continuous poly-Si films. It is revealed that the continuous Si films obtained by both RTA and conventional furnace annealing are polycrystalline in nature, exhibiting good microstructures with Raman peaks at 518 cm^?1 and full-width at half-maximums of 6.43–6.48 cm^?1.     

Effect of rapid thermal annealing on Zn/ZnO layers

Zn/ZnO layers were deposited on SiO₂/Si substrate by magnetron sputtering at room temperature, and then these layers were annealed at various temperatures from 200 to 400 °C in nitrogen atmosphere for 1 min. The structural and electrical properties of the Zn/ZnO layers before and after annealing are systematically investigated by X-ray diffraction, scanning electron microscopy, current–voltage measurement system, and Auger electron spectroscopy. Current–voltage measurements show that the Zn/ZnO layers exhibit an Ohmic contact behavior. It is shown that, initially, the specific contact resistivity decreases with the increase of the annealing temperature and reaches a minimum value of 9.76 × 10^?5 Ω cm² at an annealing temperature of 300 °C. However, with a further increase of the annealing temperature, the Ohmic contact behavior degrades. This phenomenon can be explained by considering the diffusion of zinc interstitials and oxygen vacancies. It is also shown that Zn-rich ZnO thin films can be obtained by annealing Zn on the surface of ZnO film and that good Ohmic contact between Zn and ZnO layers can be observed when the annealing temperature was 300 °C.     

Surface morphology and thermal figure of merit of a new compound thin film

The third nonlinear optical properties of a new compound 4,4′-bis(3-methoxy benzylidene amino) biphenyl doped poly-methyl methacrylate (PMMA) have been studied using Z-scan technique. Experiments are performed using a continuous waveguide (cw) diode laser at 532 nm wavelength and 0.68 kW/cm² laser intensity. The optical power limiting behavior of sample doped PMMA was also investigated. It also shows a very good optical limiting behavior with a limiting threshold of 4.7 mW. We attribute the nonlinear absorption and optical limiting property of the sample film to two photon absorption effect at 532 nm. The experimental evidences of observing diffraction pattern in compound 4,4′-bis(3-methoxybenzylideneamino) biphenyl doped PMMA has been present. The refractive index change, Δn, and nonlinear refractive index, n ₂ determined from the number of observed ring. We obtained good values of Δn = 105.154 × 10^?4and n ₂ = 154.154 × 10^?7 cm²/W. Variation of refractive index with temperature, dn/dT, and figure of merit, H, are found to be 8.858 × 10^?6 1/°C and 5.316 × 10^?6, respectively. This large nonlinearity is attributed to a thermal effect resulting from linear absorption. Theoretical diffraction pattern that agree well with experimental one are generated using a wave theory.     

Multiple implantation of29Si+ in semi-insulating GaAs and its characterisation

Formation of a uniformn-layer by multiple²⁹Si⁺ implantation on LEC grown semi-insulating GaAs 〈100〉 substrate and its characterisation by differential Hall measurement at room temperature is reported. The implantation energies are 60, 160 and 260 keV with corresponding doses of 1 × 10¹², 2·55 × 10¹² and 3 × 10¹² cm⁻². Asimplanted, uncapped substrates were furnace-annealed with face-to-face configuration in an N₂ ambient at 850°C with arsenic overpressure. After annealing, the samples were subjected to Hall measurements using Van der Pauw configuration. Experimental and theoretical (LSS) profiles are compared. Electrical activation of the dopant atoms was found to range from 65–90% with average mobility values lying between 2000–2300 cm² V⁻¹ s⁻¹. Uniform concentration of then-layer ∼ 10¹⁷ cm⁻³ up to a depth of 0·3 μm has been achieved. These layers are used for the fabrication of power MESFETs.     

Understanding of post deposition annealing and substrate temperature effects on structural and electrical properties of Gd<Subscript>2</Subscript>O<Subscript>3</Subscript> MOS capacitor

The purpose of this study is to understand the effects of substrate temperature (ST) and post deposition annealing (PDA) on the structural-electrical properties of Gd₂O₃ film and to evaluate the electrical performances of the MOS based devices formed with this dielectric. The Gd₂O₃/Si structures were annealed at 500, 600, 700, and 800 °C under N₂ ambient after the films were grown on heated p-Si substrate at various temperatures ranged from 20 to 300 °C by RF magnetron sputtering. For any given ST, the crystallization/grain size increased with increasing PDA temperature. The bump in the accumulation region or continuous decrease in the capacitance values of the inversion region of the C–V curves for 800 °C PDA was not observed. The lowest effective oxide charge density (Q _eff ) value was obtained to be ??1.13?×?10¹¹ cm^?2 from the MOS capacitor with Gd₂O₃, which is grown on heated Si at 300 °C and annealed at 800 °C. The density of the interface states (D _it ) was found to be in the range of 0.84?×?10¹¹ to 1.50?×?10¹¹ eV^?1 cm^?2. The highest dielectric constant (ε) and barrier height \(({\Phi _B})\) values were found to be 14.46 and 3.68, which are obtained for 20 °C ST and 800 °C PDA. The results show that the negative charge trapping in the oxide layer is generally more than that of the positive, but, it is reverse of this situation at the interface. The leakage current density decreased after 20 °C ST, but no significant change was observed for other ST values.     

Characterization of ohmic contacts to InP

The results of a study of the electrical and metallurgical properties of thin metallic layers deposited on InP for use as ohmic contacts are presented. The layers were heat treated at temperatures up to 550°C and were examined with Auger electron spectroscopy. For contact to n-type InP three thin film systems were investigated: gold, nickel and a composite Ni/Au/Ge layer. Nickel was found to produce ohmic behavior in the Ni/Au/Ge/InP system with a minimum specific contact resistance r_c of 3×10^?5 Ω cm² for a net doping of 3×10¹⁶ cm^?3. For contact to p-type InP a film consisting of Au/Mg was investigated. For heat treatment of the Au/Mg/InP system above 350°C, r_c decreased as the temperature of the heat treatment increased and the surface morphology exhibited increasing signs of alloying at higher temperatures. The smoothest surface was obtained at 446°C for 50 min with r_c≈1×10^?4Ω cm² for a net doping of 6×10¹⁷ cm^?3.     

Optimizing phase and microstructure of chemical solution-deposited bismuth ferrite (BiFeO3) thin films to reduce DC leakage

Polycrystalline bismuth ferrite (BiFeO₃ or BFO) thin films were prepared by chemical solution deposition to explore the impact of processing conditions including annealing temperature, percent excess bismuth, and gel drying temperature on film microstructure and properties. Incorporating 0–5 % excess Bi and annealing at 550 °C in air produced stoichiometric single-phase BiFeO₃ films. Deviation from this temperature yielded the bismuth-rich Bi₃₆Fe₂O₅₇ phase at temperatures below 550 °C or the bismuth-deficient Bi₂Fe₄O₉ phase at temperatures above 550 °C, both of which contributed to higher DC leakage. However, even single-phase BiFeO₃ films produced at 550 °C show high DC leakage (~1.2 × 10^?1 A/cm² at 140 kV/cm) due to a porous microstructure. We have thus investigated unconventional thermal treatments that significantly increase film densification while maintaining phase purity. Under these revised thermal treatment conditions, room temperature leakage current values are reduced by three orders of magnitude to ~1.0 × 10^?4 A/cm² at 140 kV/cm.     

Thermoelectric properties of zinc antimonide thin film deposited on flexible polyimide substrate by RF magnetron sputtering

Zinc-antimony binary system is one of the most promising P-type thermoelectric materials for low cost intermediate temperature thermoelectric application. In this work, zinc antimonide thin film was deposited on the flexible polyimide substrate using zinc antimonide alloy target. All the samples were annealed in argon atmosphere at different temperatures and the thermoelectric properties of all the samples were significantly boosted. X-ray diffraction results displayed that single ZnSb phase was obtained when the annealing temperature above 300 °C. The thin film annealed at 325 °C possessed the carrier concentration of 3.59 × 10¹⁹ cm^?3, which was the most optimum carrier concentration. The maximum Seebeck coefficient of 280 μV K^?1 and the maximum power factor of 2.35 × 10^?3 Wm^?1 K^?2 was obtained at 260 °C. The Seebeck coefficient and the power factor increase with the increasing of the testing temperature. The thermoelectric properties of thin film annealed at 325 °C were better than other samples.     

Effects of annealing process on microstructure and electrical properties of cold-drawn thin layer copper cladding steel wire

The microstructure, mechanical and electrical properties of cold-drawn thin layer copper cladding steel (CCS) wires annealed after different processes were studied by optical microscopy, electron omnipotent material experiment machine, micro hardness machine, SEM and electrical resistivity measurement system. The results indicated that the recovery and recrystallization of steel-core happened in the temperature range 550–750 °C for the holding period of 120 min. When the annealing temperature was higher than 750 °C, grains begun to grow and grain sizes increased gradually with increasing the annealing temperature. The tensile strength and micro hardness were declined with increasing annealing temperature and holding time. The distance of Cu–Fe atoms interfacial diffusion of thin layer CCS wires ranged from 4 µm of cold-drawn wire to 7.5 µm of annealed wire at 850 °C for 120 min. The higher the annealing temperature become, the larger the distance of Cu–Fe atoms interfacial diffusion is. When the annealing temperature was lower than 650 °C, the resistivity was slightly less than 71 × 10^?3 Ω mm² m^?1 which was the resistivity of cold-drawn wire. When the annealing temperature was higher than 650 °C, the resistivity increased with increasing the annealing temperature. Meanwhile, the variation of electrical property of thin layer CCS wires was analyzed and discussed based on microstructure and interfacial diffusion.     

Preparation of rare earth CeO<Subscript>2</Subscript> thin films using metal organic decomposition method for metal-oxide–semiconductor capacitors

Investigation of metal organic decomposed rare earth cerium oxide thin films deposited on Si substrate by sol–gel spin coating technique was carried out. The structural properties have been examined by using XRD, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The XRD confirms the cubic phase of CeO₂ thin films with (111) plane observed at 28.54°. The FTIR and EDAX spectra confirm the formation of CeO₂ films with atomic percentage of 19.39 and 54.82% of Ce and O₂, respectively. Thickness of 60.11 nm of CeO₂ film measured by cross sectional FESEM image, the average roughness of ~0.6 nm of 400?°C annealed CeO₂ films were observed from AFM micrograph. The MOS capacitors were fabricated by using Ti/Au bilayer metal contact depositing by E-beam evaporator on CeO₂/Si thin film for electrical measurements. Capacitance and conductance voltage measurement was carried out to determine the effective oxide charges (Q_eff), interface trap density (D_it) and dielectric constant (k) and are 2.48?×?10¹² cm^?2, 1.26?×?10¹² eV^?1cm^?2 and ~39, respectively. The effective metal work function of 5.68 for Ti/Au bilayer is observed to be higher than the work function of Ti or Au metals in vacuum.     

Effect of annealing time on the structural,optical and electrical characteristics of DC sputtered ITO thin films

Using an Indium tin oxide (ITO) ceramic target (In₂O₃:SnO₂, 90:10 wt%), ITO thin films were deposited by conventional direct current magnetron sputtering technique onto glass substrates at room temperature. The obtained ITO films were annealed at 400 °C for different annealing times (1, 2, 5, 7, and 9 h). The effect of annealing time on their structural, optical and electrical properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microcopy (AFM), ultra violet–visible (UV–Vis) spectrometer, and temperature dependence Hall measurements. XRD data of obtained ITO films reveal that the films were polycrystalline with cubic structure and exhibit (222), (400) and (440) crystallographic planes of In₂O₃. AFM and Scanning Electron Microscopy SEM have been used to probe the surface roughness and the morphology of the films. The refractive index (n), thickness and porosity (%) of the films were evaluated from transmittance spectra obtained in the range 350–700 nm by UV–Vis. The optical band gap of ITO film was found to be varying from 3.35 to 3.47 eV with the annealing time. The annealing time dependence of resistivity, carrier concentration, carrier mobility, sheet resistance, and figure of merit values of the films at room temperature were discussed. The carrier concentration of the films increased from 1.21 × 10²⁰ to 1.90 × 10²⁰ cm^?3, the Hall mobility increased from 11.38 to 18 cm² V^?1 s^?1 and electrical resistivity decreased from 3.97 × 10^?3 to 2.13 × 10^?3 Ω cm with the increase of annealing time from 1 to 9 h. Additionally, the temperature dependence of the carrier concentration, and carrier mobility for the as-deposited and 400 °C annealed ITO films for 2 and 9 h were analysed in the temperature range of 80–350 K.     

Influence of diffusion-annealing temperature on physical and mechanical properties of Cu-diffused bulk MgB2 superconductor

This study reports not only the effect of Cu diffusion on physical and mechanical properties of bulk MgB₂ superconductors with the aid of Vickers microhardness (H_v) measurements but also the diffusion coefficient and the activation energy of copper (Cu) in the MgB₂ system using the resistivity measurements for the first time. Cu diffusion is examined over the different annealing temperature such as 650, 700, 750, 800 and 850 °C via the successive removal of thin layers and resistivity measurement of the sample. Further, Vickers microhardness, elastic modulus, yield strength, fracture toughness and brittleness index values of the samples studied are evaluated from microhardness measurements. It is found that all the results obtained depend strongly on the diffusion annealing temperature and applied load. The microhardness values increase with ascending the annealing temperature up to 850 °C owing to the increment in the strength of the bonds between grains but decreasing with the enhancement in the applied load due to Indentation Size Effect behaviour of the bulk samples. Moreover, the diffusion coefficient is observed to enhance from 2.84 × 10^?8 to 3.22 × 10^?7 cm² s^?1 with the increase of the diffusion-annealing temperature, confirming that the Cu diffusion is more dominant at higher temperatures compared to lower ones. Besides, temperature dependence of the Cu diffusion coefficient is described by the Arrhenius relation D = 2.66 × 10^?3 exp(?1.09 ± 0.05 eV/k_BT) and the related activation energy of the Cu ions in the MgB₂ system is obtained to be about 1.09 eV. Based on the relatively low value of activation energy, the migration of the Cu ions primarily proceeds through defects such as pore surfaces and grain boundaries in the polycrystalline structure, resulting in the improvement of the physical and mechanical properties of the bulk MgB₂ samples.     

Grain boundary self-diffusion in evaporated Au films at low temperatures

Direct self-diffusion measurements in vapor-deposited polycrystalline Au films have been made using ¹⁹⁵Au radioactive tracer and an r.f. back-sputtering technique for serial sectioning. A temperature range of 117°–177°C was investigated. It has been demonstrated that self-diffusion in thin Au films at these low temperatures takes place by rapid transport of the tracer atoms along the grain boundaries. The grain boundary self-diffusion parameters are Q_b=1.0±0.1 eV and δD_b⁰ = 9 × 10^?10 cm³/sec, which compare well with those in bulk polycrystalline Au.     

Structural relaxation and electrical conductivity of molybdovanadate glass

⁵⁷Fe Mössbauer spectrum of conductive barium iron vanadate glass with a composition of 20BaO·10Fe₂O₃·70V₂O₅ (in mol%) showed paramagnetic doublet peak due to distorted Fe^IIIO₄ tetrahedra with isomer shift (δ) value of 0.37 (±?0.01) mm s^?1. Mössbauer spectra of 20BaO·10Fe₂O₃·xMoO₃·(70???x)V₂O₅ glasses (x?=?20–50) showed paramagnetic doublet peaks due to distorted Fe^IIIO₆ octahedra with δ’s of 0.40–0.41 (±?0.01) mm s^?1. These results evidently show a composition-dependent change of the 3D-skeleton structure from “vanadate glass” phase, composed of distorted VO₄ tetrahedra and VO₅ pyramids, to “molybdate glass” composed of distorted MoO₆ octahedra. After isothermal annealing at 500 °C for 60 min, Mössbauer spectra also showed a marked decrease in the quadrupole splitting (Δ) of Fe^III from 0.70 to 0.77 to 0.58–0.62 (±?0.02) mm s^?1, which proved “structural relaxation” of distorted VO₄ tetrahedra which were randomly connected to FeO₄, VO₅, MoO₆, FeO₆ and MoO₄ units by sharing corner oxygen atoms or edges. DC-conductivity (σ) of barium iron vanadate glass (x?=?0) measured at room temperature was 3.2?×?10^?6 S cm^?1, which increased to 3.4?×?10^?1 S cm^?1 after the annealing at 500 °C for 60 min. The σ’s of as-cast molybdovanadate glasses with x’s of 20–50 were ca. 1.1?×?10^?7 or 1.2?×?10^?7S cm^?1, which increased to 2.1?×?10^?2 (x?=?20), 6.7?×?10^?3 (x?=?35) and 1.9?×?10^?4 S cm^?1 (x?=?50) after the annealing at 500 °C for 60 min. It was concluded that the structural relaxation of distorted VO₄ tetrahedra was directly related to the marked increase in the σ, as generally observed in several vanadate glasses.