Phase transformation of Ni/Si thin films induced by nanoindentation and annealing

Thin Ni/Si films are prepared by depositing a Ni layer with a thickness of 100 nm on a Si (100) substrate. The as-deposited thin-film specimens are indented to a maximum depth of 500 nm using a nanoindentation technique and are then annealed at temperatures of 200°C, 300°C, 500°C and 800°C for 2 min. The microstructural changes and phases induced in the various specimens are observed using transmission electron microscopy (TEM) and micro-Raman scattering spectroscopy (RSS). Based on the load-displacement data obtained in the nanoindentation tests, the hardness and Young’s modulus of the as-deposited specimens are found to be 13 GPa and 177 GPa, respectively. The microstructural observations reveal that the nanoindentation process prompts the transformation of the indentation-affected zone of the silicon substrate from a diamond cubic structure to a mixed structure comprising amorphous phase and metastable Si III and Si XII phases. Following annealing at temperatures of 200∼500°C, the indented zone contains either a mixture of amorphous phase and Si III and Si XII phases, or Si III and Si XII phases only, depending on the annealing temperature. In addition, the annealing process prompts the formation of nickel silicide phases at the Ni/Si interface or within the indentation zone. The composition of these phases depends on the annealing temperature. Specifically, Ni₂Si is formed at a temperature of 200°C, NiSi is formed at a temperature of 300°C and 500°C, and NiSi₂ is formed at 800°C.     

Self-organization of the structure in the Cu60Fe40 composite during deformation-thermal treatment

The deformation-thermal stability of a clusterized amorphous-crystalline structure prepared from a Cu₆₀Fe₄₀ powder mixture at a logarithmic strain e = 4.6 and subjected to isochronous (40 min) annealings at T _a = 200–800°C has been investigated. Periodic changes (ΔT = 300°C) in the order and disorder with a maximum ordering at T _a = 300 and 600°C and a maximum disordering at T _a = 400 and 700°C have been observed. The periodicity of the dominant crystallographic order with a period ΔT = 400°C in the annealing temperature has been revealed for face-centered cubic copper phase planes separated by a singular point at T = 500°C characterized by the dominant body-centered cubic iron phase ordering. It has been shown that the sawtooth shape of the size distribution of strain clusters formed within the crystal structure of deformed samples slowly changes with increasing annealing temperature from exponential (T _a = 200–700°C) to linear (T _a = 800°C). This indicates a high density of internal local distortions in structural units.     

Temperature dependent surface and spectral modifications of nano V<Subscript>2</Subscript>O<Subscript>5</Subscript> films

Nanocrystalline V₂O₅ films have been deposited on glass substrates at 300°C substrate temperature using thermal evaporation technique and were subjected to thermal annealing at different temperatures 350, 400, and 550°C. X-ray diffraction (XRD) spectra exhibit sharper and broader characteristic peaks respectively indicating the rearrangement of nanocrystallite phases with annealing temperatures. Other phases of vanadium oxides started emerging with the rise in annealing temperature and the sample converted completely to VO₂ (B) phase at 550°C annealing. FESEM images showed an increase in crystallite size with 350 and 400°C annealing temperatures followed by a decrease in crystallite size for the sample annealed at 550°C. Transmission spectra showed an initial redshift of the fundamental band edge with 350 and 400°C while a blue shift for the sample annealed at 550°C, which was in agreement with XRD and SEM results. The films exhibited smart window properties as well as nanorod growth at specific annealing temperatures. Apart from showing the PL and defect related peaks, PL studies also supported the observations made in the transmission spectra.     

Effect of process parameters and post-deposition annealing on the microwave dielectric and optical properties of pulsed laser deposited Bi<Subscript>1.5</Subscript>Zn<Subscript>1.0</Subscript>Nb<Subscript>1.5</Subscript>O<Subscript>7</Subscript> thin films

Bismuth Zinc niobate (Bi_1.5Zn_1.0Nb_1.5O₇) thin films were deposited by pulsed laser deposition (PLD) method on fused silica substrates at different oxygen pressures. The structural, microwave dielectric and optical properties of these thin films were systematically studied for both the as-deposited and the annealed films at 600°C. The as-deposited films were all amorphous in nature but crystallized on annealing at 600°C in air. The surface morphology as studied by atomic force microscopy (AFM) reveals ultra-fine grains in the case of as-deposited thin films and cluster grain morphology on annealing. The as-deposited films exhibit refractive index in the range of 2.36–2.53 (at a wavelength of 750 nm) with an optical absorption edge value of 3.30–3.52 eV and a maximum dielectric constant of 11 at 12.15 GHz. On annealing the films at 600°C they crystallize to the cubic pyrochlore structure accompanied by an increase in band gap, refractive index and microwave dielectric constant.     

Influence of vacuum annealing on structures and mechanical properties of Al–Ti–N films deposited by multi-arc ion plating

The Al–Ti–N films deposited by multi-arc ion plating have been annealed in vacuum within the range of 700–1100 °C. X-ray diffraction results showed that the structure of the films underwent the formation of coherent c-TiN and c-AlN for the annealing temperatures were up to 900 °C. A new phase AlTi_x (x = 0.50, 0.56, 3) was observed after annealing. The X-ray photoelectron spectroscopy results showed the intensity of Ti–Al bonds decreased as annealing temperatures increased, indicating the decomposition of (Al, Ti)N into c-TiN and c-AlN were at the expense of Ti–Al bonds. Differential scanning calorimetry experiments were used to investigate the dynamic behavior of the films during annealing process and the results showed that the N₂ formed as a consequence of the phase transformation process. The release of the N₂ resulted in the peeling of the films from the substrates. The film exhibited a maximum hardness of 39 GPa after 900 °C annealing due to the formation of coherent c-TiN and c-AlN phases. In addition, we also investigated the influence of vacuum annealing on adhesive strength.     

Die Verfestigungserholung von plastisch verformten Steinsalzeinkristallen

Cylindrical rock salt single crystals have been plastically deformed by compression in the [001]-direction at room temperature to shear stresser τ _E of 200 N/cm² and 350 N/cm², respectively. Isochronal annealing experiments reveal, that workhardening recovers at >300° C. The characteristic annealing temperature was found between 400° C and 450° C. At 600° C the residual workhardening still amounts to 15–20%. The isochronal reduction of screw dislocation density between 400 and 600° C shows qualitatively the same behaviour as recovery of workhardening. From the isothermal annealing curves of the samples deformed to 200 N/cm² the activation energy for recovery of workhardening was found to be about 1 eV. Assuming that the kinetics of recovery can be explained by processes distributed in activation energy, an approximate spectrum of activation energies (with a maximum arising at ～1 eV) has been evaluated. The results show that recovery of workhardening after low deformation (stage I of the stress strain curve) is mainly due to the dislocations.     

Further study on the influence of thermal treatments on the glow curve structure in LiF:Mg,Cu,P (GR-200A)

The influence of various annealing treatments with heating temperatures (T_A) from 240 to 700 °C, with re-annealing at 240 °C, and with a combined re-annealing procedure of 20 min at 270 °C followed by 10 min at 240 °C on LiF:Mg,Cu,P (GR-200A) was investigated. As the T_A increased, the intensity decreased rapidly to almost no signal at 340–380 °C then increased clearly and achieved a maximum at 540 °C. The position of the maximum intensity of the glow curve shifted basically in the direction of higher temperatures with an increase at T_A and achieved a maximum of 279 °C when annealed at 460 °C. The re-annealing influenced both the intensity and the glow curve structure at certain degree. The effect of re-annealing on the glow curve depended markedly on the T_A. With re-annealing at 240 °C, the intensity decreased as T_A increased up to 360 °C then increased and achieved a maximum at 540 °C. The intensity could be restored fully when annealed at above 500 °C, however, the glow curve couldn't be restored fully. With a combined annealing, the shape of glow curve of a sample annealed at above 540 °C or below 320 °C was similar to that of the standard glow curve of LiF:Mg,Cu,P and the intensity and glow curve could be restored completely when annealed in the range 620–660 °C. It seems that the main roles of the re-annealing at 240 °C are to restore partially the intensity of peak 4 and peak shape for LiF:Mg,Cu,P when annealed at above 260 °C, and restore fully the total TL intensity of LiF:Mg,Cu,P when annealed at above 500 °C and the main roles of the combined re-annealing are to reduce the intensity of peak 5 and the total TL intensity, increase the intensity of peak 4 and restore the glow curve shape.     

Superconductivity of niobium nitride single crystals after implantation of carbon and nitrogen

Single crystals of δ-NbN_0.85 with a superconducting transition temperature T_c of 14.3 K were implanted with nitrogen and carbon ions at room temperature and subsequently annealed at high temperatures. Implantation was also performed at high substrate temperatures. After implantation at about 920°C maximum T_c-values of 16.5 and 17.8 K were obtained with N- and C-ions respectively. Disorder observed after room temperature implantation consisted of displaced Nb-atoms which could not be completely annealed in an isochromous annealing process up to 1000°C. For annealing temperatures above 1100°C nitrogen diffusion out of the implanted layers resulted in a reduction of T_c.     

Effect of hydrogen introduced by channelling implantation on the microstructures in silicon wafers

High-resolution transmission electron microscopy has been employed to study the platelet defects before annealing and the extended defects generated by annealing in the channelling-implanted silicon wafers. It has been found that there apparently appear platelet defects of quite great size and spacing at the maximum projected range of ions (R _max). Additionally, the cracks induced by annealing at 550 °C are generated around R _max instead of the average projected range of ions (R _p) as it is in the non-channelling-implanted samples. Moreover, after annealing at 1000 °C, cracks without branches and cavities arranging in a single array, different from the forked cracks and cavities arranged in several arrays in the non-channelling-implanted samples, are observed in the channelling-implanted silicon wafers. It is suggested that those special microstructure characteristics are ascribed to the channelling effect of implanted hydrogen ions.     

Raman spectroscopy of sol–gel derived titanium oxide thin films

Raman spectra of TiO₂ films prepared via the sol–gel process were studied by UV and visible Raman spectroscopy. The evolution of the phases of TiO₂ films during annealing was investigated, and the relative intensities of the Raman bands excited with 325 nm were found to be distinct from those of the bands excited with 514 nm. The transmittance and FTIR spectra of the films annealed at different temperatures were characterized. The crystallization process of the powders and thin films treated by different annealing methods were also studied with Raman spectroscopy. The results show that the change in the relative intensities is caused by the resonance Raman effect. The anatase to rutile transition of the powder occurs at 700 °C, while that of the thin film occurs at 800 °C. The analysis of Raman band shape (peak position and full width at half‐maximum) after conventional furnace annealing and rapid thermal annealing indicates the influence of the non‐stoichiometry and phonon confinement effect. Copyright © 2011 John Wiley & Sons, Ltd.     

Crystallization behaviour of PZT in multilayer heterostructures

Microstructural and electrical properties of PZT (lead zirconate titanate) thin films prepared by sol-gel techniques at annealing temperatures in the range from 550°C to 900°C are studied. Perovskite (Pe) grain nucleation in PZT film starts but not completes at 550°C. Along with formation of round Pe (111) grains on the Pt (111) interface, the film contains small Pe and pyrochlore (Py) grains. Films annealed at the temperatures higher than 600°C demonstrate column structure of Pe grains, the amount of Py inclusions reduces with the annealing temperature and practically disappears at 700°C. An increase of annealing temperature leads to enhancement of (100) Pe orientation as a result of Ti diffusion on the Pt surface. Polarization decreases with the annealing temperature (maximum at 600°C), whereas permittivity increases up to the annealing temperature of 750°C.     

Effects of annealing on the luminescent properties from defects formed in electron-irradiated GaN

The effects of annealing on the luminescence properties of electron-irradiated GaN were investigated by photoluminescence (PL), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Our results indicate that the yellow luminescence (YL) remains disappear after all annealing treatments and shows a non-linear dependence on the annealing temperature up to 800 °C. The annealing process can be divided into two main stages associated with irradiation defects. At annealing temperatures up to 600 °C, the behavior of YL can be attributed to the net effects of V_GaO_N complex formation caused by the migration of gallium vacancies (V_Ga) and V_GaO_N complex dissociation due to the disappearance of gallium vacancies. At annealing temperatures approaching 800 °C, the incorporation of carbon into the group-V sublattice becomes the dominant factor in the appearance of YL. In addition, experimental results of PL and SEM show that a small proportion of irradiation damage still exists in GaN after annealing at 800 °C.     

Fabrication and magnetic properties of highly ordered Co16Ag84 alloy nanowire array

Highly ordered Co-Ag alloy nanowire arrays embedded in the nanochannels of anodic alumina membranes (AAMs) were successfully fabricated using electrodeposition. Scanning electron microscopy and transmission electron microscopy observations revealed that the ordered Co-Ag alloy nanowires were uniformly assembled into the hexagonally ordered nanochannels of the AAMs. Magnetic measurements showed that the perpendicular coercivity (H_c⊥) of the ordered nanowire arrays increased dramatically as the annealing temperature (T_a) rose from 300 °C, reached its maximum (183 Oe) at 400 °C and then decreased sharply as T_a further increased beyond 400 °C. However, there was little change in the parallel coercivity (H_c∥) of the nanowire arrays during the annealing process. The mechanism of this phenomenon was attributed to the special structure of the AAMs and nanowires. Received: 27 November 2000 / Accepted: 3 May 2001 / Published online: 25 July 2001     

Effect of annealing on the opto-electronic properties of Cu0.9In1.0Se2.0 films

The influence of annealing on the structure and opto-electronic properties of Cu_0.9In_1.0Se_2.0 films prepared by solution growth technique has been studied. The films annealed at 500–520°C in air, vacuum (10^?4 torr), In-vapour and Se-vapour show polycrystalline chalcopyrite structure with orientation perpendicular to the (220) plane. Films annealed in Se-vapour at 500°C for 30 min have maximum grain size (560 Å), minimum optical energy gap, maximum absorption coefficient, lowest resistivity, maximum photosensitivity and thus are suitable for photovoltaic applications. Annealing in In-vapour or in vacuum changesp-type CuInSe₂ inton-type which possibly arises due to the increase in Se vacancies.     

Oxidizing effects of high temperature annealing in reducing atmosphere in Ca-doped YIG films

The existence of an oxidation mechanism is reported in Ca-doped YIG films, when high temperature annealing is carried out in N₂ atmosphere. The annealing were performed at successively increasing temperatures, and optical absorption, lattice parameter and thermoelectric power were measured at each step. Optical absorption was observed going down to a minimum (T = 450°C in one cycle of annealing, T = 400°C in a different cycle) and then rise again. The minimum in absorption corresponds to a maximum of the lattice parameter, while the thermoelectric power is always p-type. Analysis of the data leads to the conclusion that we are observing a reoxidation process, triggered both by temperature and oxygen vacancy concentration. This process is subject to exhaustion. Previous annealing experiments are analyzed in the light of these results.     

Recrystallization of amorphous nanotracks and uniform layers generated by swift-ion-beam irradiation in lithium niobate

The thermal annealing of amorphous tracks of nanometer-size diameter generated in lithium niobate (LiNbO₃) by Bromine ions at 45 MeV, i.e., in the electronic stopping regime, has been investigated by RBS/C spectrometry in the temperature range from 250°C to 350°C. Relatively low fluences have been used (<10¹² cm⁻²) to produce isolated tracks. However, the possible effect of track overlapping has been investigated by varying the fluence between 3×10¹¹ cm⁻² and 10¹² cm⁻². The annealing process follows a two-step kinetics. In a first stage (I) the track radius decreases linearly with the annealing time. It obeys an Arrhenius-type dependence on annealing temperature with activation energy around 1.5 eV. The second stage (II) operates after the track radius has decreased down to around 2.5 nm and shows a much lower radial velocity. The data for stage I appear consistent with a solid-phase epitaxial process that yields a constant recrystallization rate at the amorphous-crystalline boundary. HRTEM has been used to monitor the existence and the size of the annealed isolated tracks in the second stage. On the other hand, the thermal annealing of homogeneous (buried) amorphous layers has been investigated within the same temperature range, on samples irradiated with Fluorine at 20 MeV and fluences of ∼10¹⁴ cm⁻². Optical techniques are very suitable for this case and have been used to monitor the recrystallization of the layers. The annealing process induces a displacement of the crystalline-amorphous boundary that is also linear with annealing time, and the recrystallization rates are consistent with those measured for tracks. The comparison of these data with those previously obtained for the heavily damaged (amorphous) layers produced by elastic nuclear collisions is summarily discussed.     

Effects of annealing on ion-implanted Si for interdigitated back contact solar cell

Effects of annealing on the properties of P- and B-implanted Si for interdigitated back contact (IBC) solar cells were investigated with annealing temperature of from 950 to 1050 °C. P-implanted samples annealed at 950 °C were enough to activate dopants and recover the damage by implantation. As the annealing temperature was increased, the diode properties of P-implanted samples were degraded, while that of B-implanted samples were improved. However, in order to activate an implanted B ion, B-implanted samples needed an annealing of above 1000 °C. The implied V_oc of lifetime samples by quasi-steady-state photoconductance decay followed the trend of diode properties on annealing temperature. Finally, IBC cell was fabricated with a two-step annealing at 1050 °C for B of the emitter and 950 °C for P of the front and back surface fields. The IBC cell had V_oc of 618 mV, J_sc of 35.1 mA/cm², FF of 78.8%, and the efficiency of 17.1% without surface texturing.     

The charge states’ conversion of the activator ions in CaF2:Eu nanophosphors

According to stationary X-ray-excited luminescence spectra and thermally stimulated luminescence spectra of CaF₂:Eu nanophosphors, it was found that Eu³⁺?→?Eu²⁺ conversion can occur during thermal annealing of fine-grained (d?=?25?nm) nanoparticles in the 200–800°C range, which is accompanied by an increase in their size within 40–189?nm. An important role of the exciton mechanism of Eu²⁺ luminescence excitation was revealed according to the temperature dependence of X-ray-excited luminescence spectra of CaF₂:Eu nanoparticles of 114?nm size. The maximum of the X-ray-excited luminescence light output of CaF₂:Eu nanophosphors in the Eu²⁺ ions’ emission band was traced out at 400–500°C annealing temperature and at the size of nanoparticles of 114–180?nm. The subsequent growth of the annealing temperatures, particularly in the 800–1000°C range, causes the reduction of X-ray-excited luminescence light output because of the increment of lattice defects’ concentration due to a sharp increase in the size of nanoparticles and their agglomeration.     

The annealing of damage in ion implanted gallium arsenide

Photoluminescence measurements at 77°K and Rutherford scattering of 450 keV protons were used to study radiation damage and annealing in ion implanted GaAs. The characteristic band edge luminescence (8225 Å) in GaAs is completely quenched by ion implantation. Photoluminescence measurements on samples which were isochronally annealed show a single annealing stage at 600°C. A luminescence peak at 9140 Å is introduced into the spectra of all implanted and annealed samples. This peak is attributed to an acceptor level created by As vacancies. The intensity of the peak is greatly reduced by protecting the surface of implanted layers with SiO₂ during annealing. Rutherford scattering measurements on isochronally annealed samples reveal two annealing stages. A 300°C annealing stage is observed on samples which have an initial aligned yield less than random while a 650°C stage is observed on samples which have an initial aligned yield equal to random.     

Microdisperse Iron Silicide Structures Produced by Implantation of Iron Ions in Silicon

Iron implanted and subsequently annealed n-type Si(111) was studied by conversion electron Mössbauer spectroscopy for phase analysis and Auger electron spectroscopy for sputter depth profiling and element mapping. During implantation (200 keV, 3 × 10¹⁷ cm^?2, 350°C) a mixture of β- and α-FeSi₂ is firmed and after the subsequent annealing (900°C for 18 h and 1150°C for 1 h) a complete transition to the β- and the α-phase can be detected. The as-implanted profile has Gaussian shape and is broadening during annealing at 900°C to a plateau-like profile and shows only a slight broadening and depth depending fluctuations of the iron concentration after the 1150°C annealing. With scanning Auger electron spectroscopy the lateral iron and silicon distribution were investigated and show for the sample annealed at 900°C large separated β-FeSi₂ precipitates which grow due to the process of Ostwald ripening. At 1150°C additionally coalescence of the precipitates occur and a wide extended penetration α-FeSi₂ network structure is formed.