Platinum-silicide formation during rapid thermal annealing: Dependence on substrate orientation and pre-implanted impurities

The kinetics of Pt-silicide formation during rapid thermal annealing has been studied as a function of silicon-substrate orientation ((111), (011), and (001)) and type of pre-implanted impurity in the silicon substrate (As, Kr, and Ge). Rutherford backscattering spectrometry, transmission electron microscopy, and four-point probe resistivity measurements were used for this investigation. In the case of Pt₂Si growth, both an orientation and impurity dependence was observed; the PtSi growth, however, was found to be independent of these parameters except in the case of As pre-implantation for which a retardation was found.     

Dependence of ligand fields in paramagnetic crystals on thermal changes in their structures

Paramagnetic behaviours of the salts of the iron group depend upon the asymmetric ligand fields acting upon the central paramagnetic ion, as also upon the structure and packing of the crystal lattice. A general picture of the energy levels of the paramagnetic ions is, available from the ligand field theory, based upon the coordinated data on X-ray structure, magnetic susceptibility and anisotropy, e.p.r and optical absorption spectra. When all these facts have been taken into account it is observed that there is an almost universal discrepancy between the observed thermal magnetic behaviours, particularly the anisotropy and those theoretically predicted on the assumption that the ligand fields are independent of temperature. The discrepancy cannot usually be covered by the change in the fields due to normal thermal expansion of the lattice. It is pointed out that these may be occasionally due to electric dipole ordering in the crystals at certain temperatures but more generally due to continuous types of transition in the crystal lattice with temperature, which change the lattice packing in an anomalous manner and thus cause a thermal variation in the asymmetric ligand fields.     

Formation of palladium silicide by rapid thermal annealing

The formation of palladium silicide Pd₂Si by rapid thermal annealing of Pd layers on silicon has been studied as a function of annealing time (1–60s) in the temperature range 350–500 °C. It is shown that the results found for conventional furnace annealing (long duration, low temperature) can be extrapolated for rapid thermal annealing (shorter time, higher temperature) when taking into account the exact time dependence of the short temperature cycle. The growth rate is essentially diffusion limited and the activation energy is close to 1.1±0.1 eV. Silicide resistivity of about 30–40 cm was obtained for 200–400 nm thick Pd₂Si layers formed at 400 °C for a few seconds.     

Rapid thermal annealing induced changes on the contact of Ni/Au to N-doped ZnO

N-doped p-type ZnO (p ∼ 10¹⁸cm^-3) was grown on sapphire(0 0 0 1) substrate by metal-organic chemical vapor deposition method. Ni/Au metal was evaporated on the ZnO film to form contacts. As-deposited contacts were rectifying while ohmic behavior was achieved after thermally annealing the contacts in nitrogen environment. Specific contact resistance was determined by circular transmission line method and a minimum specific contact resistance of 8 × 10⁻⁴ Ω cm² was obtained for the sample annealed at 650 °C for 30 s. However, Hall effect measurements indicate that, as the rapid thermal annealing temperature increased up to 550 °C or higher the samples’ conductive type have changed from p-type to n-type, which may be due to the instability nature of the present-day p-type N-doped ZnO or the dissociation of ZnO caused by annealing process in N₂ ambient. Evolution of the sample's electric characteristics and the increment of metal/semiconductor interface states induced by rapid thermal annealing process are supposed to be responsible for the improvement of electrical properties of Au/Ni/ZnO.     

Nanoscale thermal cloaking by in-situ annealing silicon membrane

With the advent of thermal metamaterials, many new thermal functionalities have been proposed, like thermal cloaking, concentrating, etc. However, these thermal functionalities are based on the transformation thermotics or scattering cancellation technique, which, derived from Fourier's law, cannot apply to the micro-/nanoscale counterparts. In this paper, we design a nanoscale thermal cloak based on a crystalline silicon (Si) membrane and investigate the in-plane phonon transport via non-equilibrium molecular dynamics (NEMD) simulation by in-situ tuning the thermal conductivity of the thermal cloak from crystalline Si to amorphous Si. The two-dimensional temperature profile is obtained, and the thermal cloaking effect is evaluated by the ratio of heat flux. By analyzing the phonon density of state (PDOS) and the mode participation ratio (MPR), the mechanism can be attributed to the phonon localization in the annealed cloaking region. The proposed nanoscale thermal cloak by in-situ tuned thermal conductivity, may trigger the development of nanoscale thermal functionalities and open avenues for and thermal management for nano-photonics and nano-electronics.     

Purification of iron to low carbon and nitrogen contents by annealing

Purification of iron specimens to low levels of carbon and nitrogen by annealing in dry hydrogen below 1180 K was investigated. The magnetic after-effect and strain ageing were used for estimating the carbon and nitrogen contents. Decarburization of a few mm thick specimens was found to be controlled by both surface reactions and volume diffusion. The residual carbon content was found to depend not solely on the method of hydrogen purification but also on the type and state of the purification apparatus and on the annealing procedure. Carbon and nitrogen contents smaller than 1 at ppm were reproducibly obtained in a closed ZrH₂ purification system which was baked at 500 K during annealing of specimens.     

Effects of fluorine-based plasma treatment and thermal annealing on high-Al content AlGaN Schottky contact

Fluorine plasma treatment was used prior to the Schottky metal deposition on the undoped Al_(0.45)Ga_(0.55)N,which aimed at the solar-blind wavelength.After fluorine plasma treatment and before depositing the Ni/Au Schottky,the samples were thermal annealed in the N_2 gas at 400 ℃.The reverse leakage current density of Al_(0.45)Ga_(0.55)N Schottky diode was reduced by 2 orders of magnitude at-10 V.The reverse leakage current density was reduced by 3 orders of magnitude after thermal annealing.Further capacitance-frequency analysis revealed that the fluorine-based plasma treatment reduces the surface states of AlGaN by one order of magnitude at different surface state energies.The capacitance-frequency analysis also proved that the concentration of carriers in AlGaN top is reduced through fluorine plasma treatment.     

Effects of thermal annealing on titanium oxide films prepared by ion-assisted deposition

Titanium oxide thin films are prepared at a substrate temperature of 250 °C by electron-beam evaporation and ionassisted deposition. The effects of thermal annealing temperatures from 100 to 450 °C on the optical and mechanical properties are studied. The optical and mechanical properties include refractive indices, extinction coefficients, residual stress, surface roughness and crystallization. Experimental results show these properties of titanium oxide films clearly depend on the thermal annealing process.     

Extended defect removal in silicon by rapid thermal annealing

Summary Germanium, arsenic and krypton ions of 600 keV energy were implanted in <100> silicon substrate at 250°C. The hot implantation results in the formation of extended defects (dislocation loops and cluster of point defects) as residual damage. Rapid thermal annealing process at a temperature above 1000°C was used to remove the damage. Rutherford-backscattering channelling technique was used to measure the amount of defects and their annealing. In some cases the channelling results were correlated to transmission electron microscopy (TEM) analysis. The annealing process of the damage is governed by an activation energy of (4.4±0.2) eV for both germanium and arsenic implants. During RTA processes broadening of the As and Ge distributions is quite negligible. The Kr atoms interact instead with defects and the annealing even after a prolonged time at 1100°C is not complete, bubbles surrounded by extended defects are left The authors of this paper have agreed to not receive the proofs for correction.     

Dopant profile changes induced by pulsed laser annealing

A short review is given of recent experimental studies of helium in metals, emphasizing fundamental He behavior at low temperatures (room temperature and below), low He concentrations (～1 at.% He) and in the absence of radiation induced defects. Some of the main points are: (a) interstitial He is generally locally mobile at room temperature and below, (b) impurities behave as strong unsaturable traps which lose their identity with increasing numbers of trapped He atoms, and (c) the eventual microstructure of He charged metals appears qualitatively the same in pure undamaged materials as in radiation-damaged materials.     

Structural characterization of SiGe nanoclusters formed by rapid thermal annealing

This work presents the structural characterization of nanoclusters formed from a-Si:H/Ge heterostructures processed by rapid thermal annealing (RTA) at 1000 °C for annealing times varying between 30 s and 70 s. The a-Si:H layers were grown on electron cyclotron resonance (ECR) using SiH₄ and Ar precursor gases. The Ge layer was grown in an e-beam evaporation system. The structural characterizations were performed by high-resolution X-ray diffractometer (HRXRD) on grazing incidence X-ray reflection mode (GIXRR) and micro-Raman measurements. The average grain size, Ge concentration (x_Ge) and strain were estimated from Lorentzian GIXRR peak fit. The average grain size varied from 3 nm to 7.5 nm and decreased with annealing time. The x_Ge increase with annealing time and varied from 8% to 19%, approximately. The strain calculated for (1 1 1), (2 2 0) and (3 1 1) peaks at 40 s, 50 s, 60 s and 70 s annealing time suggest the geometrical changes in nanoclusters according to process time.     

Rapid thermal annealing of ITO films

Tin-doped indium oxide (ITO) films with 200 nm thickness were deposited on glass substrates by DC magnetron sputtering at room temperature. And they were annealed by rapid thermal annealing (RTA) method in vacuum ambient at different temperature for 60 s. The effect of annealing temperature on the structural, electrical and optical properties of ITO films was investigated. As the RTA temperature increases, the resistivity of ITO films decreases dramatically, and the transmittance in the visible region increases obviously. The ITO film annealed at 600 °C by RTA in vacuum shows a resistivity of 1.6 × 10⁻⁴ Ω cm and a transmittance of 92%.     

Conductivity increase of ZnO:Ga films by rapid thermal annealing

Due to a constant increase in demands for transparent electronic devices the search for alternative transparent conducting oxides (TCO) is a major field of research now. New materials should be low-cost and have comparable or better optical and electrical characteristics in comparison to ITO. The use of n-type ZnO was proposed many years ago, but until now the best n-type dopant and its optimal concentration is still under discussion. Ga was proposed as the best dopant for ZnO due to similar atomic radius of Ga³⁺ compared to Zn²⁺ and its lower reactivity with oxygen. The resistivity ρ of ZnO:Ga/Si (100) films grown by PEMOCVD was found to be 3×10⁻² Ω cm. Rapid thermal annealing (RTA) was applied to increase the conductivity of ZnO:Ga (1 wt%) films and the optimal regime was determined to be 800  C in oxygen media for 35 s. The resistivity ratio before and after the annealing and the corresponding surface morphologies were investigated. The resistivity reduction () was observed after annealing at optimal regime and the final film resistivity was approximately ≈4×10⁻⁴ Ω cm, due to effective Ga dopant activation. The route mean square roughness (R_q) of the films was found to decrease with increasing annealing time and the grain size has been found to increase slightly for all annealed samples. These results allow us to prove that highly conductive ZnO films can be obtained by simple post-growth RTA in oxygen using only 1% of Ga precursor in the precursor mix.     

Electron microscopy studies of void swelling and annealing of voids in aluminium irradiated with aluminium ions

Abstract

MgO single crystals implanted with Au⁺ ions (180 keV, 6 10¹⁶-10¹⁷ ions cm^?2) and annealed at temperatures between 25°C and 1100°C, have been analysed—by optical spectrophotometry—by Rutherford back-scattering (to confirm the effective presence and to study the distribution profile of Au atoms), and by TEM and X-ray diffraction (to identify the phases precipitated by thermal treatment).

Thermal annealing between 550°C and 1100°C produced an optical absorption band located between 565 nm and 600 nm. This band can be attributed to a fee Au precipitate with diameter varying from 50 to 200 Å. Larger metallic colloids 1000 Å are in simple orientation with the matrix.

Annealing at temperatures higher than 500°C produces a supplementary optical absorption located at 425 nm. This band can be attributed to Au plasma resonance.

After annealing for 15 min at 1100°C, a new phase is detected by X-ray diffraction and TEM and identified as Au₃Mg alloy with hexagonal structure.     

Radiative thermal neutron capture by natural sulfur

A high precision study of the gamma ray spectrum following neutron capture by a target of natural sulfur is reported. The energy precision obtained has permitted construction of decay schemes for³³S and³⁵S. In the case of the former isotope a total of 22 levels have been identified while for the latter and much weaker reaction 7 states have been observed. While some transitions attributable to capture by³³S are observed, their weakness prohibited detailed analysis. The neutron separation energies, based upon the¹⁴N(n, γ)¹⁵N standard are found to be 8,641.60 (3) keV and 6,985.84 (5) keV for³³S and³⁵S respectively.     

Structure changes caused by strain annealing of nylon 6 fibers

Experiments are described in which nylon 6 fibers are annealed while subjected to a constant stretch (or slack). Subsequent mechanical and structural measurements are described and analyzed. A paracrystalline structure model is proposed in which folded chains, fully extended chains, partially folded, and partially extended chains coexist in the highly drawn high strength fiber. An explanation of structural changes occurring during the thermal-mechanical treatment is that the folded and partially folded chains are arranged randomly in staggered fashion in small units throughout the structure. During slack annealing, the chains become more folded and shrinkage occurs. Some of the chain refolding will be permanent and may act as new defect sites thereby reducing fracture stress. During annealing in the presence of comparatively high tensile stresses the folded chains are unfolded to some extent, but not completely, and the load-carrying chains in the structure are more uniformly loaded. At the higher applied strains during annealing, chains are broken and may snap back into folds. The tension annealing increases the overall chain orientation, the strained segment uniformity, and the number of load-bearing chains. These factors may contribute to an increased fracture stress.     

Dependence of thermal conductivity on electrical resistivity in Bismuth-Tellurides

The p-type (Bi_0.25Sb_0.75)₂Te₃ doped with 3-12 wt% excess Te alone and n-type Bi₂(Te_0.94Se_0.06)₃ codoped with 0.017-0.026 wt% Te and 0.068-0.102 wt% I were prepared by the Bridgman method, to produce intentionally polycrystalline. Some of the as-grown specimens were annealed, in order to prepare specimens with much different ρ. These polycrystalline specimens have almost the same degree of alignment of the c plane parallel to the freezing direction. The electrical rersistivity ρ and thermal conductivity κ were measured at 298 K along the freezing direction and κ was plotted as a function of ρ. As a result, the lattice components κ_ph obtained by subtracting the electronic component κ_el from the observed κ were found to decrease almost linearly with a decrease of ρ in both p- and n-type specimens, where κ_el was calculated using Wiedemann-Franz law. This tendency is consistent with the conventional result that κ_ph becomes negligible small in metals. The significant decrease in κ_ph with decrease in ρ is considered to be caused predominantly by the phonon scattering due to dopants. The relationship between κ_ph and ρ was first clarified in the intermediate region between the metal and insulator.     

Effect of thermal annealing on ZnO:Al thin films grown by spray pyrolysis

We report the effect of thermal annealing in air on the structural and optical properties of undoped and aluminium-doped (1%–4%) zinc oxide (AZO) thin films, grown by the spray pyrolysis technique on quartz substrates. Films were characterized by X-ray diffraction, low-temperature photoluminescence, electrical resistivity, and Raman spectroscopy after annealing at temperatures between 500 and 900 C. Annealing in air improves the long-range order crystalline quality of the bulk crystals, but promotes a number of point defects in the surface affecting both the resistivity and the photoluminescence.     

Nucleation of epitaxial graphene on SiC substrate by thermal annealing and chemical vapor deposition

Growth of epitaxial graphene (EG) on silicon carbide (SiC) is regarded as one of the most effective routes to high-quality graphene towards practical applicability. We try to build up a model to illuminate the nucleation process of EG on SiC by thermal decomposition. The model is derived from some experimental results and discloses that surface diffusion plays an important role in the nucleation. For the chemical vapor deposition process used, the organic gas as carbon precursor enables carbon deposition quickly for supporting the growth of high-quality graphene via vapor transformation, so that the nucleated and final graphene becomes almost stress-free and mimics the free-standing graphene. Our findings have a potential in preparing high-quality graphene by controlling the nucleation conditions.