Increase Of Annealing Time Research Articles

The evolution of Si-capped Ge islands on Si (1 0 0) by RF magnetron sputtering and rapid thermal processing: The role of annealing times

Germanium (Ge) nanocrystals were synthesized by rapid thermal processing (RTP) of radio frequency sputtered Ge on silicon (100) substrate. A Si capping layer of 185nm thickness was deposited onto the 225nm Ge layer. The layered samples subsequently underwent annealing during RTP at 900°C for 30, 45, and 60s to subsequently evolve into Ge islands. Scanning electron microscopy (SEM) showed that as the annealing time increased, the Ge islands’ size increased from 100nm to 500nm, and they became more uniform and dense. Atomic force microscopy (AFM) indicated that the increase in annealing time reduced the surface roughness by approximately 50%. Raman spectra showed that good crystalline nanostructures of the Ge peaks were obtained for all samples, with increased annealing time improving the crystallinity. A visible broad band photoluminescence was observed from UV to green with blue shift as nanocrystallite size decreases. High resolution X-ray diffraction (HR-XRD) revealed cubic and tetragonal Ge phases in the samples with low tensile strain around the Ge islands. The results indicated that both annealing ambient temperature and time do significantly influence the formation and evolution of the Ge islands on Si.

Investigation of local compositional uniformity in Cu2ZnSn(S,Se)4thin film solar cells prepared from nanoparticle inks

Cu2ZnSn(S,Se)4 (CZTSSe) is a promising material for low-cost photovoltaics (PV), however despite rapid improvements in recent years, the performance of CZTSSe based solar cells has yet to reach the level required for commercial relevance. In order to understand the sources of efficiency losses in CZTSSe thin film solar cells, a detailed analysis of a solution-processed CZTSSe solar cell with a power conversion efficiency of 8.6% was performed using transmission electron microscopy (TEM). The composition of the CZTSSe active absorber layer was found to be highly non-uniform laterally which contributed to efficiency losses due to band gap and potential fluctuations. To further understand how compositional non-uniformity develops during the annealing process, the microstructure and local composition of a series of CZTSSe thin films annealed for differing lengths of time were investigated using TEM. It was found that longer annealing times improved both the microstructure of the CZTSSe layer and the compositional uniformity across the thickness of the layer. However, the lateral grain-to-grain variation in composition increased with increasing annealing time. As a result, despite improvements in the short circuit current resulting from larger CZTSSe grains with increased annealing time, no significant net gain in efficiency was obtained due to a counterbalancing decrease in open circuit voltage as a result of the increased lateral CZTSSe composition non-uniformity. The results show a challenging need to improve the control of CZTSSe thin film compositional uniformity at all length scales in order to improve the PV device performance.

Recrystallization and Precipitation of β-Mg17Al12 Phase of the Cold-Rolled Mg-9Al-1Zn Alloy Strip during Isothermal Annealing

Effect of isothermal annealing on the microstructure evolution of the cold-rolled Mg-9Al-1Zn alloy strip was investigated. It is found that the competition between the precipitation of β-Mg17Al12 phase and recrystallization of α-Mg matrix occur under the conditions of various annealing temperature and time. At a low annealing temperature (523K), the β-Mg17Al12 particles precipitate preferentially at locally high deformation area and grow into the lamellar-cluster with an increase in the annealing time, retarding the recrystallization of α-Mg matrix. With raising the annealing temperature (573~623K), both the precipitation of β-Mg17Al12 particles and recrystallization of α-Mg matrix take place. Both recrystallization and grain growth are prone to proceed without precipitation of β-Mg17Al12 particles when the annealing temperature is 673K. A mechanism for the competitive behavior between the precipitation of β-Mg17Al12 phase and recrystallization of α-Mg matrix at various annealing conditions is discussed.

Annealing time dependent 1.53 µm fluorescence enhancement in Er3+-doped tellurite glasses containing silver NPs

Silver nanoparticles (NPs) were introduced into the Er3+-doped tellurite glasses (TeO2–Bi2O3–TiO2) and their effects on the 1.53µm band fluorescence of Er3+ and thermal stability of glass host were investigated. It was found that the presence of silver NPs nucleated and grown during the heat annealing process, could improve the thermal stability and the 1.53µm band fluorescence. Maximum enhancement in the 1.53µm band fluorescence was obtained in sample heat-treated for 48h. However, further increase in the heat annealing time (~72h) reduces the fluorescence intensity. Enhancement in the 1.53µm band fluorescence is attributed to the increased local electric field induced by silver NPs whereas the quenching is ascribed to the energy transfer from Er3+ ions to silver NPs.

The Effect of Dy-Additive on Phase Transformation and Magnetic Properties of Fe-Pt Alloy Films

A series of Fe-Pt based alloy films were deposited on glass substrates by DC magnetron sputtering. It is found that the Fe3Pt and FePt3 phases appear in Dy-addition films at first and then a composition reaction Fe3Pt + FePt3 FePt occurs at 500°C as annealing time increase. It suggested that Dy element can restrain the fct phase forming but help to form Fe3Pt and FePt3 phases. Coercivity and remanence ratio of DyxFe50-xPt50 alloy films annealed at 500°C for 200 h achieve the maximum 11kOe and 0.89 as x =1.5, respectively.

A generalized method for alignment of block copolymer films: solvent vapor annealing with soft shear.

One of the key issues associated with the utilization of block copolymer (BCP) thin films in nanoscience and nanotechnology is control of their alignment and orientation over macroscopic dimensions. We have recently reported a method, solvent vapor annealing with soft shear (SVA-SS), for fabricating unidirectional alignment of cylindrical nanostructures. This method is a simple extension of the common SVA process by adhering a flat, crosslinked poly(dimethylsiloxane) (PDMS) pad to the BCP thin film. The impact of processing parameters, including annealing time, solvent removal rate and the physical properties of the PDMS pad, on the quality of alignment quantified by the Herman's orientational factor (S) is systematically examined for a model system of polystyrene-block-polyisoprene-block-polystyrene (SIS). As annealing time increases, the SIS morphology transitions from isotropic rods to highly aligned cylinders. Decreasing the rate of solvent removal, which impacts the shear rate imposed by the contraction of the PDMS, improves the orientation factor of the cylindrical domains; this suggests the nanostructure alignment is primarily induced by contraction of PDMS during solvent removal. Moreover, the physical properties of the PDMS controlled by the crosslink density impact the orientation factor by tuning its swelling extent during SVA-SS and elastic modulus. Decreasing the PDMS crosslink density increases S; this effect appears to be primarily driven by the changes in the solubility of the SVA-SS solvent in the PDMS. With this understanding of the critical processing parameters, SVA-SS has been successfully applied to align a wide variety of BCPs including polystyrene-block-polybutadiene-block-polystyrene (SBS), polystyrene-block-poly(N,N-dimethyl-n-octadecylammonium p-styrenesulfonate) (PS-b-PSS-DMODA), polystyrene-block-polydimethylsiloxane (PS-b-PDMS) and polystyrene-block-poly(2-vinlypyridine) (PS-b-P2VP). These results suggest that SVA-SS is a generalizable method for the alignment of BCP thin films.

Precipitates Caused in Silicon Wafers by Prolonged High-Temperature Annealing in Nitrogen Atmosphere

ABSTRACTThe precipitate behavior in a floating zone silicon crystal produced from a Czochralski single-crystal ingot has been studied. Large precipitates of α-Si3N4 crystal, having a dimension of about 2 μm, were formed at the mid-depth in the wafer by means of annealing at a high temperature in an ambient N2 (70%) + O2 (30%) atmosphere. The precipitate number detected by cross-sectional X-ray topography increased with the increasing annealing time. Interstitial silicon is expected to eliminate the precipitate origins.

Effect of Annealing Temperature on the Optical Properties of ZnO Nanoparticles

In this work, ZnO films were prepared by drop casting technique. The films were deposited on quartz substrates under different annealing time (15, 30, 45 and 60 min.) at a constant temperature (800 °C). The optical properties were achieved by measuring the absorbance and transmittance spectra in the wavelength range (200-900) nm. It was found that the absorbance decreases while transmission increases as the annealing time increases, while the reflectance decreases as the annealing time increases. The optical measurements indicate the kind of transition which was a direct allowed with an average band gap energies lie between 3.3 eV and 3.54 eV with the change of annealing time.

Bulk Heterojunction Nanomorphology of Fluorenyl Hexa-peri-hexabenzocoronene–Fullerene Blend Films

In this study, the nanomorphology of fluorenyl hexa-peri-hexabenzocoronene:[6,6]-phenyl C61-butyric acid methyl ester (FHBC:PC61BM) absorber layers of organic solar cells was investigated. Different electron microscopical techniques, atomic force microscopy, and grazing incidence wide-angle X-ray scattering were applied for a comprehensive nanomorphology analysis. The development of the nanomorphology upon sample annealing and the associated change of the device performance were investigated. It was shown that the annealing process enhances the phase separation and therefore the bulk heterojunction structure. Due to π-π stacking, the FHBC molecules assemble into columnar stacks, which are already present before annealing. While the nonannealed sample consists of a mixture of homogeneously distributed PC61BM molecules and FHBC stacks with a preferential in-plane stack orientation, crystalline FHBC precipitates occur in the annealed samples. These crystals, which consist of hexagonal arranged FHBC stacks, grow with increased annealing time. They are distributed homogeneously over the whole volume of the absorber layer as revealed by electron tomography. The FHBC stacks, whether in the two phase mixture or in the pure crystalline precipitates, exhibit an edge-on orientation, according to results from grazing incidence wide-angle X-ray scattering (GIWAXS), dark-field transmission electron microscopy (DF TEM) imaging and selective area electron diffraction (SAED). The best solar cell efficiencies were obtained after 20 or 40 s sample annealing. These annealing times induce an optimized degree of phase separation between donor and acceptor material.

Effect of Annealing Temperature on the Optical Properties of ZnO Nanoparticles

In this work, ZnO films were prepared by drop casting technique. The films were deposited on quartz substrates under different annealing time (15, 30, 45 and 60 min.) at a constant temperature (800 °C). The optical properties were achieved by measuring the absorbance and transmittance spectra in the wavelength range (200-900) nm. It was found that the absorbance decreases while transmission increases as the annealing time increases, while the reflectance decreases as the annealing time increases. The optical measurements indicate the kind of transition which was a direct allowed with an average band gap energies lie between 3.3 eV and 3.54 eV with the change of annealing time.

Structural and optical properties and photoluminescence mechanism of fluorine-doped SnO2 films during the annealing process

F-doped SnO2 (SnOx:F) films deposited on a glass substrate by atmospheric pressure chemical vapor deposition (APCVD) were annealed at 600°C for different times. The effects of annealing time on the structural, optical and photoluminescence (PL) properties of SnOx:F films were investigated. The results show that all the films have a polycrystalline cassiterite tetragonal crystal structure and exhibit obviously preferred orientations with (200) and (310) planes. The films annealed for 15min possess the smallest particle sizes, of 94.95nm, and a minimum root mean square roughness of 15.74nm. The transmittances of all the films in the visible range can reach ∼80%. When the annealing time increases from 0 to 60min, the optical band gap of SnOx:F films decreases from 3.91 to 3.87eV. The room temperature PL spectra show weak UV emission, intense violet emission and broad and weak blue emission. The violet emission related to F substitutions and oxygen vacancies is composed of three PL subbands centered at 3.22, 3.03 and 2.81eV. The photoemission position is observed to be independent of annealing time.

Structural and photoluminescence properties of SnO2 obtained by thermal oxidation of evaporated Sn thin films

Tin oxide films have been prepared by oxidation of Sn thin films deposited by thermal evaporation method onto glass substrates. The oxidation of films was done, in air at a temperature of 500 °C, from 20 to 120 min. The oxidized films were characterized by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), photoluminescence spectroscopy (PL) and surface profilometer. The XRD patterns show that the crystalline structure of the oxidized Sn films improves with the annealing time. The tetragonal SnO2 phase (cassiterite) was obtained after 120 min of annealing with grains sizes between 15 and 20 nm. The thickness of oxide films, as function of the annealing time, follows a parabolic law. The O/Sn atomic ratio increases with the annealing time indicating an improvement of the films quality. Tin interstitials defects density, calculated from PL spectra using Smakula's formula, was found to decrease with the increasing annealing time. Tin interstitials defects density was found proportional to the increasing oxygen density (deduced from RBS). A fit of this proportionality allowed us to quantify the tin cations and oxygen anions diffused through the oxide films.

Thermal characteristics, chemical composition and polyphenol contents of date-pits powder

Polyphenol contents in date-pits varied from 21–62mg gallic acid equivalents (GAE)/g date-pits when acetone–water, ethanol–water, methanol–water and water alone were used as solvents for extraction at temperatures 22, 45, and 60°C. The BET and GAB monolayer values of date-pits were estimated as 4.3 and 4.1g/100g dry-solids. The DSC thermogram of freeze-dried date-pits showed an endothermic peak due to the melting of oil, and a second endothermic peak for solids-melting (i.e. non-fat). The first shift indicated the glass transition (i.e. Tg) while the second exothermic shift after solids-melting indicated the interactions of the components in melted solids. The melting peak temperature was decreased due to the plasticization of solids with water and the melting enthalpy was increased with the increasing water content due to the formation of more order in the amorphous, semi-crystallites and crystallites parts. The Flory–Huggins modelling of peak temperature estimated the water–solids interaction parameter as 0.0068. The melting peak temperature increased exponentially with increasing heating rate and the data was fitted with Mehl–Johnson–Avrami and Kissinger models. Annealing close to the onset of melting indicated that melting peak temperature increased exponentially with increasing annealing time, while melting enthalpy decreased with the increasing annealing time.

Ferromagnetic Tetragonal ${\rm L}1_{0}$-Type MnGa Isotropic Nanocrystalline Microparticles

This paper reports the structure and magnetic properties of ferromagnetic face-centered tetragonal L10-type MnGa isotropic nanocrystalline microparticles prepared by high energy ball milling and subsequent annealing. The L10-type microparticles with a nominal composition of Mn56Ga44 size mainly in the range of 10-50 μm, an average crystallite size in the range of 40-62 nm and a Curie temperature of 356°C. Post-annealing had little effect on the particle size and morphology but dramatically increased the hard magnetic properties. As the annealing temperature increased, coercivity iHc first increased from 4.8 kOe after annealing at 400°C for 20 min, to a maximum value of 6.2 kOe after annealing at 600°C for 20 min, and then decreased after annealing at 650°C. The increase in iHc is attributed to an improvement of crystallinity and chemical ordering of fct δ-MnGa phase while the decrease may be due to a too coarse crystallite size. Remanence Mr remained almost the same, in the range of 41-42 emu/g, for the samples annealed from 400 to 650°C for 20 min. These magnetic properties are comparable to the highest ones reported so far for ferromagnetic fct MnGa films grown by molecular beam epitaxy. After annealing at 700°C for 20 min, iHc decreased to 2.3 kOe and Mr to 10.9 emu/g due to both, an excessive grain growth, and re-precipitation of a nonmagnetic ζ - Mn8Ga5 phase. Annealing time increase from 10 to 90 min has little effect (within ~10%) on the magnetic properties for the samples annealed at 550°C.

Growth and electrical properties of spin coated ultrathin ZrO2 films on silicon

Ultrathin (<50 nm) zirconium oxide (ZrO2) films are being intensively studied as high-k dielectrics for future metal-oxide-semiconductor (MOS) technology. In this paper, ultrathin ZrO2 films are deposited on silicon substrates by spin on deposition technique and annealed at 700 °C for different duration. The phase formation and morphological study have been performed by x-ray diffraction and scanning electron microscopy, respectively. Electrical properties of the films are investigated. The threshold voltages of the MOS structure were found to vary from −1.5 V to −2.5 V as the annealing time increases. The dielectric constants of the films are found to be 7.2–7.67 at 1 KHz. Leakage current of the films is found to increase with the annealing time. The dielectric breakdown field of the film is found to be 6.29–8.15 MV/cm.

3차원 적층 패키지를 위한 Cu/Ni/Au/Sn-Ag/Cu 미세 범프 구조의 열처리에 따른 금속간 화합물 성장 거동 분석

In-situ annealing tests of Cu/Ni/Au/Sn-Ag/Cu micro-bump for 3D IC package were performed in an scanning electron microscope chamber at in order to investigate the growth kinetics of intermetallic compound (IMC). The IMC growth behaviors of both and follow linear relationship with the square root of the annealing time, which could be understood by the dominant diffusion mechanism. Two IMC phases with slightly different compositions, that is, and formed at Cu/solder interface after bonding and grew with increased annealing time. By the way, and phases formed at the interfaces between and Ni/Sn, respectively, and both grew with increased annealing time. The activation energies for and IMC growths during annealing were 0.69 and 0.84 eV, respectively, where Ni layer seems to serve as diffusion barrier for extensive Cu-Sn IMC formation which is expected to contribute to the improvement of electrical reliability of micro-bump.

Effect of ordering kinetics on the degree of far atomic order in Pd3Fe alloy

The parameters of far atomic order η in Pd3Fe alloy were determined during X-ray diffraction analysis under stepped and isothermal annealing in a two-phase field (A1 + L12) at T = 600°C for 175 and 350 h. An increase in the isothermal annealing time was accompanied by a drop in the degree of far atomic order.

Effects of annealing on structural and electrical properties of sub-micron thick CIGS films

In this study, we have investigated the electrical and structural properties of sub-micron thick Cu(In,Ga)Se2 (CIGS) films with various in-situ post annealing times. Sub-micron thick CIGS films were deposited on Mo/soda-lime glass (SLG) substrates by single-stage co-evaporation. We decreased the deposition time to 700 s for sub-micron thick CIGS films (≈0.85 μm thickness). After deposition, the CIGS films were annealed under a constant Se rate by a SiC heater for 500–3000 s in a co-evaporator. Increased annealing time led to improved surface morphology and grain size. In the XRD patterns, the CIGS films also showed improved crystal quality for the (112) plane. We suggest that post annealing of sub-micron thick CIGS films at optimized time can be applied for improving device efficiency. The open circuit voltage (Voc) and the fill factor (FF) were increased by 15% and 10%, respectively. The total cell efficiency was increased by more than 35%.

Spectral modulation through controlling anions in nanocaged phosphors

A new approach has been proposed and validated to modulate the emission spectra of europium-doped 12CaO·7Al2O3 phosphors by tuning the nonradiative and radiative transition rates, realized by controlling the sort and amount of the encaged anions. A single wavelength at 255 nm can excite simultaneously Eu2+ and Eu3+ centres to yield blue and red emissions, respectively. The amount of the anions in the nanocages, like OH− and H−, can be controlled by heat treatment processes. The existence of encaged OH− accelerates the nonradiative process of the emission centres, while the presence of encaged H− induces a higher symmetry that decreases the radiative transition rate, confirmed by the analysis of decay processes. It is demonstrated that the emission colour is tuned finely from red to blue with the CIE chromaticity coordinates from (0.630, 0.352) to (0.216, 0.086) when the annealing time increases. This strategy can be readily extended to similar systems with other rare earth active centres.

High Dielectric and Piezoelectric Properties Observed in Annealed Pb0.88Sr0.12Zr0.54Ti0.44Sb0.02O3 Ceramics

The dielectric, ferroelectric, and piezoelectric properties of ceramics from the Pb0.88Sr0.12 Zr0.54Ti0.44Sb0.02O3 system were investigated as a function of annealing time after being prepared via the solid-state method. Following the annealing process, a shift in the ferroelectric to paraelectric transition temperature (Tm) was observed. In addition, a high relative permittivity >24300 at Tm was recorded for the 64 h annealed sample which was 52% higher than that of the as-sintered samples. The increased annealing time produced an enhancement in the ferroelectric properties and a high piezoelectric coefficient (d33) of 670 pC/N was also observed for the 64 h annealed sample.