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Rapid thermal anneal (RTA) at high temperatures can be employed to introduce vacancies to control oxygen precipitation (OP) behavior in Czochralski (CZ) silicon. Such excessive vacancies survive from the recombination of silicon-interstitials and vacancies (V-I recombination) during the RTA. In this work, we aim to elucidate the carbon effect on the survival of vacancies in CZ silicon during the high temperature RTA by means of gold diffusion in combination with deep-level transient spectroscopy. It is revealed that the existence of ∼1017 cm−3 carbon atoms significantly increases the amount of survival vacancies in the form of vacancy-oxygen (VOm, m ≥ 2) complexes in CZ silicon when subjected to the 1250 °C/60 s RTA. Moreover, such an increase in the number of vacancies becomes more significant with the increase in the cooling rate of RTA. The density functional theory calculations suggest that the V-I recombination is to some extent unfavorable as a carbon atom is close to the silicon-interstitial. Alternatively, it is believed that the substitutional carbon (Cs) atoms tend to trap the silicon-interstitials, thus forming Ci complexes (Cs + I → Ci) in CZ silicon during the RTA. In this context, the V-I recombination is suppressed in a manner, leading to the survival of more vacancies, thus generating more VOm complexes. Furthermore, after the 1250 °C/60 s RTA, the oxide precipitate nucleation based on the VOm complexes is more significant in carbon-rich CZ (CCZ) silicon than in the conventional CZ counterpart. Hence, when subjected to the same OP anneal consisting of the nucleation anneal at 650 or 800 °C for 4 h and the subsequent growth anneal at 1000 °C for 16 h, CCZ silicon possesses a higher density of bulk microdefects and therefore stronger internal gettering capability than CZ silicon. However, the nucleation temperature for OP should be carefully selected as 650 °C for CCZ silicon in order to form an oxide precipitate-free denuded zone. [ABSTRACT FROM AUTHOR]

We present the first-principles calculations of vibrational and thermal properties for wurtzite and zinc-blende zinc oxide (ZnO) within DFT and quasi-harmonic approximation, especially for their negative thermal expansion (NTE) behavior. For the wurtzite and zinc-blende phases, negative thermal expansions are obtained at T < 95 K and T < 84 K, respectively. For the wurtzite structure, calculated phonon frequencies and mode Grüneisen parameters of low-energy modes are in good agreement with that determined experimentally. And the thermal expansion coefficient is found to be in good agreement with the experimental results. Like many other NTE semiconductors, detailed study of both phases shows that maximum contribution to NTE comes from low-frequency transverse acoustic modes, while for the wurtzite structure the contribution of longitudinal acoustic and lowest-energy optical modes is not ignorable. From the specific analysis of the vibration modes, we found that the negative thermal expansion in ZnO is dominated by the tension effect. [ABSTRACT FROM AUTHOR]

The effect of vacancies introduced by rapid thermal annealing (RTA) on the oxygen precipitation in germanium-doped Czochralski (GCZ) silicon has been investigated. GCZ silicon is annealed at 650–1050 °C to facilitate the precipitation of oxygen. It is observed that the oxygen precipitation in silicon is enhanced by both the vacancies introduced during RTA pretreatment and the doping of germanium. Especially, we find that the enhancement effect of vacancies on the precipitation of oxygen is larger than that of germanium atoms. In contrast to non-RTA pretreatments, RTA pretreatments lead to less significant oxygen precipitation in GCZ silicon than in conventional Czochralski (CZ) silicon at temperatures ranging from 850 to 950 °C. The mechanism for the interaction between vacancies and germanium atoms in CZ silicon is elucidated. [ABSTRACT FROM AUTHOR]

The electrical properties of highly phosphorus-doped crystalline silicon films deposited by pulse-magnetron sputtering were studied. The films were grown, 450 nm thick, on Si(100) and Si(111) wafers at low substrate temperatures Ts of 450–550 °C and post-treated by rapid thermal annealing (RTA) and plasma hydrogenation (PH). In the case of films grown on Si(100), at all values of Ts postgrowth treatment by RTA resulted in an increase in the dopant activation up to 100% and of the Hall mobility to about bulklike values of 50 cm2 V-1 s-1. This result suggests high structural quality of the films on Si(100). The Si(111) films, which are typically more defective, exhibit a completely different behavior with a strong dependence of the electrical dopant activation and the Hall mobility on Ts. By post-treatment a maximum P donor activation level of 22% could be obtained. The variation in the post-treatment procedure (RTA+PH and PH+RTA) for the films deposited at high Ts showed that PH results only in minor changes in the film properties. The different influence of RTA and PH is discussed in terms of the different defect structure of the films. These investigations reveal that high Ts and after-treatment by RTA are the main preconditions for optimal electrical film properties. [ABSTRACT FROM AUTHOR]

Thin epitaxial GaN films grown on 6H-SiC(0001) substrates were implanted with 180 keV Co ions at three different fluences. As-implanted samples were characterized with secondary ion mass spectrometry and Rutherford backscattering spectrometry to obtain the Co depth profiles and the maximum Co concentrations. As-implanted samples were annealed applying two different techniques: rapid thermal annealing and annealing by swift heavy ion irradiation. Rapid thermal annealing was done at two temperatures: 1150 °C for 20 s and 700 °C for 5 min. 200 MeV Ag ions at two fluences were used for annealing by irradiation. Crystalline structure of the pristine, as-implanted, and annealed samples was investigated using x-ray diffraction, and the results were compared. Improvement of the crystalline quality was observed for rapid thermal annealed samples at the higher annealing temperature as confirmed with rocking curve measurements. The results indicate the presence of Co clusters in these annealed samples. Swift heavy ion irradiation with the parameters chosen for this study did not lead to a significant annealing. [ABSTRACT FROM AUTHOR]

The effect of annealing atmosphere of Ar, N2, or O2 on the recombination activity of copper (Cu) precipitates, formed by the rapid thermal process (RTP), in conventional Czochralski (CZ) silicon and nitrogen-doped CZ (NCZ) silicon wafers have been investigated. It was revealed that the recombination activity of Cu precipitates formed under N2, Ar, and O2 atmospheres decreased in turn. Moreover, the RTP under O2 atmosphere led to a higher critical temperature for Cu precipitation in comparison with the RTP under Ar or N2 atmosphere. Furthermore, it was found that the Cu precipitates formed under the same conditions possessed stronger recombination activity in CZ silicon than in NCZ silicon. The above results have been tentatively explained. [ABSTRACT FROM AUTHOR]

Doubly stacked layers of silicon nanocrystals (nc-Si) in amorphous silicon nitride (α-SiNx) dielectric have been fabricated by plasma enhanced chemical vapor deposition and subsequent high-temperature thermal annealing. Capacitance-voltage (C-V) and current-voltage (I-V) measurements were used to investigate its charge trapping phenomena and confirmed the memory effects of the nc-Si, which exhibited capacitance hysteresis and asymmetric current peaks, respectively. This structure has realized a two-level charge storage by Fowler-Nordheim tunneling in high-field regime. While under low field, the resonant tunneling of holes into stacked nc-Si was responsible for current peaks. The transport property of stacked nc-Si was discussed and a model was put forward to explain the retention mechanism. [ABSTRACT FROM AUTHOR]

In this study we report on field effect mobilities of charge carriers in materials used in polymer photovoltaics. The field effect mobilities of charge carriers in polymer and fullerene films and in various blend compositions were investigated for the effects of tempering. Contact resistances were considered for more accurate mobility estimations. The field effect mobilities of holes in films of the conjugated polymer poly(3-hexylthiophene) (P3HT) were found to be in the 10-3 cm2/V s range and the field effect mobilities of electrons in films of the methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were found to be in the order of 10-2 cm2/V s. The concentration of PCBM was then varied in P3HT:PCBM blends, and blend compositions with PCBM contents of 0%, 33%, 40%, 50%, 60%, 67%, and 100% weight percents were measured before and after tempering. Electron mobilities were not detected in untempered blend compositions with PCBM content lower than 67% PCBM. Tempering led to a large increase in the electron mobility in the blends, and electron mobilities were detected in all tempered blends with PCBM content above 40%. Electron and hole field effect mobilities were found to be roughly balanced in the 10-3 cm2/V s range for the tempered blend with 67% PCBM content. [ABSTRACT FROM AUTHOR]

The effects of postgrowth rapid thermal annealing on the electronic states in a relatively long wavelength (∼1.3 μm), self-assembled InAs/GaAs quantum-dot structure are investigated. We combine optical and electrical experiments, i.e., photoluminescence (PL) and deep-level transient spectroscopy (DLTS) measurements, to identify the underlying physical processes responsible for the changes in the PL spectra at different annealing temperatures. Physical parameters of the intrinsic and deep-level states are quantitatively determined in the DLTS experiments. These include the thermal excitation energies, densities, and their changes with the annealing temperature. We observe that the densities of the deep levels that coexist in the quantum-dot layer decrease and a new deep level, about 0.62 eV below the GaAs conduction band edge, is formed at elevated temperatures. Both effects explain the variations in the PL spectra. Moreover, beyond what can be revealed in the PL experiments, the DLTS spectra show a more complex electronic structure of both optically active and inactive states. [ABSTRACT FROM AUTHOR]

We have studied the effects of rapid thermal annealing at 1300 °C on GaN epilayers grown on AlN buffered Si(111) and on sapphire substrates. After annealing, the epilayers grown on Si display visible alterations with craterlike morphology scattered over the surface. The annealed GaN/Si layers were characterized by a range of experimental techniques: scanning electron microscopy, optical confocal imaging, energy dispersive x-ray microanalysis, Raman scattering, and cathodoluminescence. A substantial Si migration to the GaN epilayer was observed in the crater regions, where decomposition of GaN and formation of Si3N4 crystallites as well as metallic Ga droplets and Si nanocrystals have occurred. The average diameter of the Si nanocrystals was estimated from Raman scattering to be around 3 nm. Such annealing effects, which are not observed in GaN grown on sapphire, are a significant issue for applications of GaN grown on Si(111) substrates when subsequent high-temperature processing is required. [ABSTRACT FROM AUTHOR]

We have studied the effects of various conditions of rapid thermal annealing (RTA) on 10 nm GaInNAs/GaAs single quantum wells (SQWs) with fixed indium concentration and increasing nitrogen content to obtain photoluminescence (PL) in the telecom wavelength regime of 1.3 and 1.5 μm. Specifically, we analyzed the results of annealing for a fixed short time but at different temperatures and for longer times at a fixed temperature. In all experiments, InGaAs SQWs with the same In concentration were used as references. For both RTA conditions, the well-known blueshift of the band gap energy and the PL intensity improvement show trends that reveal that these are unrelated effects. At high RTA temperatures the PL efficiency reaches a maximum and then drops independently of N content. On the contrary, the blueshift experiences a rapid increase up to 700 °C (strong blueshift regime) and it saturates above this temperature (weak blueshift regime). Both these blueshift regimes are related to the nitrogen content in the SQWs but in different ways. In the strong blueshift regime, we could obtain activation energy for the blueshift process in the range of 1.25 eV, which increases with N content. Analysis with high-resolution x-ray diffraction (HRXRD) shows that the blueshift experienced in this regime is not due to a stoichiometric change in the QW. In the weak blueshift regime, the blueshift, which is only partly due to In outdiffusion, saturates more slowly the higher the N content. Annealing at the same temperature (600 °C) for a longer time shows that the blueshift saturates earlier than the PL intensity and that samples with higher nitrogen experience a larger blueshift. Only a small In outdiffusion for annealing at high temperatures (>650 °C) and long duration was observed. However, this modest stoichiometric change does not explain the large blueshift experienced by the GaInNAs SQWs. We conclude that the mechanism responsible for the drastic blueshift after annealing is related to the N content in the QW, while the improvement in PL integrated intensity is uniquely related to the annealing conditions. [ABSTRACT FROM AUTHOR]

Postimplantation thermal processing of Be in molecular-beam-epitaxy-grown GaN by rapid thermal annealing (RTA) and pulsed laser annealing (PLA) was investigated. It has been found that the activation of Be dopants and the repair of implantation-induced defects in GaN films cannot be achieved efficiently by conventional RTA alone. On the other hand, good dopant activation and surface morphology and quality were obtained when the Be-implanted GaN film was annealed by PLA with a 248 nm KrF excimer laser. However, observations of off-resonant micro-Raman and high-resolution x-ray-diffraction spectra indicated that crystal defects and strain resulting from Be implantation were still existent after PLA, which probably degraded the carrier mobility and limited the activation efficiency to some extent. This can be attributed to the shallow penetration depth of the 248 nm laser in GaN, which only repaired the crystal defects in a thin near-surface layer, while the deeper defects were not annealed out well. This situation was significantly improved when the Be-implanted GaN was subjected to a combined process of PLA followed by RTA, which produced good activation of the dopants, good surface morphology, and repaired bulk and surface defects well. [ABSTRACT FROM AUTHOR]

In order to optimize the intrinsic gettering (IG) process based on the rapid thermal processing (RTP) for nitrogen-doped Czochralski (NCZ) silicon wafer, the effects of RTP and the following nucleation anneal on oxygen precipitation in NCZ silicon and conventional CZ silicon wafers have been comparatively investigated. It was found that, for NCZ silicon, the RTP at enough high temperature (e.g., 1250 °C) was necessary for generation of high density of bulk microdefects (BMDs) in the subsequent anneals despite the nitrogen enhancement effect on oxygen precipitation. With enough high concentration of vacancies introduced by the RTP at 1250 °C, for the conventional CZ silicon wafer, the vacancy enhancement effect on the nucleation of oxygen precipitates was most significant at 800 °C; while for NCZ silicon wafer, the vacancies and nitrogen atoms coacted most remarkably to nucleate the oxygen precipitates during the ramping anneal from 800 to 1000 °C. It was further found that the doped nitrogen is superior to the vacancy to enhance the nucleation of oxygen precipitates at temperatures of 900–1000 °C. Moreover, in order to maximize the density of BMDs, the RTP-based IG process for NCZ silicon wafer should be different from that for the conventional CZ silicon wafer. [ABSTRACT FROM AUTHOR]

The origins of ac losses in the high Tc superconductors are not addressed adequately in the literature. We found out that frequent Josephson junction (JJ) decoupling (both intergranular and interlayer) due to the flow of ac is one of the main origins of the ac losses in high Tc superconductors. We have determined the ac losses in superconductors in the rf range by measuring the absolute value of nonresonant rf power absorbed by the samples. Our data show that under certain conditions when both the number density of JJs present in the sample and the JJ critical current cross a threshold value, ac losses in the superconducting state keep on increasing with decreasing temperature below Tc. The underlying mechanism is an interesting interplay of JJ coupling energy and the amplitude of rf voltage applied to the sample. The effects of an applied magnetic field, variation of rf, and temperature were studied in detail. To find out the exact relation among the JJ coupling energy, JJ number density, applied ac frequency, the amplitude of ac, and the ac losses in superconductors, we have studied samples with different crystalline properties, different grain sizes, pressurized at different pressures, and sintered under different physical and chemical conditions. These results have important implications for the understanding of the origin of ac losses and the characterization of superconducting samples. In this paper we also extend the capability of the ac loss studies in superconductors for the characterization of materials for device applications. [ABSTRACT FROM AUTHOR]

We demonstrate the growth of high-quality and virtually strain-free bulklike GaN by hydride vapor-phase epitaxy in a vertical atmospheric-pressure reactor with a bottom-fed design. The 300-μm-thick GaN layer was grown on a 2″ (0 0 0 1) sapphire substrate buffered with a ∼2-μm-thick GaN layer grown by metal-organic chemical-vapor deposition. During the cool down process to room temperature, cracking was induced in the sapphire substrate, thereby allowing the bulklike GaN layer to relax without provoking cracking of itself. The crystalline quality and the residual strain in the 2″ GaN wafer were investigated by various characterization techniques. The lateral homogeneity of the wafer was monitored by low-temperature photoluminescence mapping. High-resolution x-ray diffraction and photoluminescence measurements proved the high crystalline quality of the material grown. The position of the main near-band-gap photoluminescence line and the phonon spectra obtained from infrared spectroscopic ellipsometry show consistently that the 2″ crack-free GaN is virtually strain-free over a diameter of approximately 4 cm. [ABSTRACT FROM AUTHOR]

Carrier-concentration and mobility profiles formed in Si by BF2 implantation and by subsequent rapid thermal annealing (RTA) have been examined by differential Hall-effect measurements. B-concentration profiles are measured before and after RTA by a secondary-ion-mass spectroscopic technique. It is shown that a significant amount of B atoms, over 40% of an effective implant dose, is lost during RTA if the substrate is dipped in a dilute HF solution prior to annealing. The loss of B atoms gives rise to the increase in sheet resistivity of the formed p-type layers. It is revealed that an approximately 1.3–1.5-nm-thick, native oxide layer acts as an encapsulant and depresses the loss of implanted B atoms from the substrate during RTA at/above 950 °C, resulting in the formation of an electrical profile with a long tail. The redistribution of B atoms during RTA is suppressed in the sample from which the native oxide has been stripped. Also, an approximately 25-nm-thick, p+ layer with a maximum carrier concentration of 1×1020/cm3 is formed by 3-keV BF2 implantation and subsequent RTA at 1000 °C. Experimental data indicate that the HF dipping effect is negligibly small if BF2 implantation is carried out above 40 keV. [ABSTRACT FROM AUTHOR]

The morphological stability of NiSi1-uGeu ternary alloy films formed by reacting Ni with single-crystal (sc) and polycrystalline (poly) Si1-xGeu is studied (u can be different from x). The agglomeration of NiSi1-uGeu films on Si0.7Ge0.3 occurs at 550°C after rapid thermal processing for 30 s, independently of the crystallinity of the Si1-xGeu. This behavior distinctly different from NiSi: NiSi films on poly-Si display a poorer morphological stability and degrade at lower temperatures than NiSi on sc-Si. On strained Si1-xGex, the presence of Ge simultaneously gives rise to two effects of different origin: mechanical and thermodynamic. The main driving forces behind the agglomeration of NiSi1-uGeu on sc-Si1-xGex are found to be the stored strain energy in the Si1-xGex and the larger (absolute) free energy of formation of NiSi compared to NiGe. The latter constitutes the principal driving force behind the agglomeration of NiSi1-uGeu on poly-Si1-xGex and is not affected by the degree of crystallinity of Si1-xGex. The total free-energy change also includes terms corresponding to the entropy of mixing of Si and Ge in both Si1-xGex and NiSi1-uGeu. Calculations show that the strain energy and the total free-energy change can be 5–7 times (with 30 at.% Ge) the surface/interface and grain-boundary energies in a NiSi film or the grain-boundary energy in an underlying poly-Si. These latter energies are responsible for the agglomeration of NiSi on sc- and poly-Si. The agglomeration takes place primarily via the interdiffusion of Si and Ge between Si1-xGex and NiSi1-uGeu. A structure likely to improve the stability of NiSi1-uGeu/Si1-xGex is discussed. [ABSTRACT FROM AUTHOR]

The morphological stability of NiSi1-uGeu ternary alloy films formed by reacting Ni with single-crystal (sc) and polycrystalline (poly) Si1-xGeu is studied (u can be different from x). The agglomeration of NiSi1-uGeu films on Si0.7Ge0.3 occurs at 550°C after rapid thermal processing for 30 s, independently of the crystallinity of the Si1-xGeu. This behavior distinctly different from NiSi: NiSi films on poly-Si display a poorer morphological stability and degrade at lower temperatures than NiSi on sc-Si. On strained Si1-xGex, the presence of Ge simultaneously gives rise to two effects of different origin: mechanical and thermodynamic. The main driving forces behind the agglomeration of NiSi1-uGeu on sc-Si1-xGex are found to be the stored strain energy in the Si1-xGex and the larger (absolute) free energy of formation of NiSi compared to NiGe. The latter constitutes the principal driving force behind the agglomeration of NiSi1-uGeu on poly-Si1-xGex and is not affected by the degree of crystallinity of Si1-xGex. The total free-energy change also includes terms corresponding to the entropy of mixing of Si and Ge in both Si1-xGex and NiSi1-uGeu. Calculations show that the strain energy and the total free-energy change can be 5–7 times (with 30 at.% Ge) the surface/interface and grain-boundary energies in a NiSi film or the grain-boundary energy in an underlying poly-Si. These latter energies are responsible for the agglomeration of NiSi on sc- and poly-Si. The agglomeration takes place primarily via the interdiffusion of Si and Ge between Si1-xGex and NiSi1-uGeu. A structure likely to improve the stability of NiSi1-uGeu/Si1-xGex is discussed. [ABSTRACT FROM AUTHOR]

This work demonstrates the possibility of decreasing the C54-TiSi[sub 2] formation temperature during rapid thermal annealing (RTA) by more than 50 °C using a two-step binary Ti-Si codeposition process on Si (100) substrates. This process is based on codepositing a particular double-layer microstructure. The first layer is an amorphous Ti-Si alloy codeposited on Si (100) with a composition close to Ti[sub 5]Si[sub 3]. After crystallizing this first layer at temperatures near 600 °C, a second layer is formed by room-temperature codeposition of an amorphous capping layer with a composition close to TiSi[sub 2]. Analyses by Rutherford backscattering spectrometry and film-thickness measurements by transmission electron microscopy on samples constructed according to this method show a structure of 20 nm TiSi[sub 1.3]/45 nm Ti[sub 3.7]Si[sub 3]/Si. On rapid thermal annealing (3 °C/s to 710 °C), C49-TiSi[sub 2] formation occurs at the silicide/silicon interface keeping Ti[sub 5]Si[sub 3] as an intermediate layer, and the capping layer is transformed to C54-TiSi[sub 2]. This microstructure is fundamentally different from that developed after RTA of Ti/Si bilayers in which C49-TiSi[sub 2] forms and subsequently transforms to C54 at temperatures ∼800 °C. The two-step process studied here places hexagonal Ti[sub 5]Si[sub 3] in close contact with the amorphous capping layer. This layer acts as a catalyst for the formation of C54-TiSi[sub 2] by decreasing the energy barrier for C54 nucleation. The present experiments also suggest that the transformation from C49 to C54 can be mediated by a layer of Ti[sub 5]Si[sub 3] in much the same fashion as metal-mediated crystallization processes. The enhanced formation of C54-TiSi[sub 2] using the two-step silicidation of binary Ti-Si alloys is an attractive alternative to other methods which lower the C54 formation temperature by introducing a third element. Such a third element can produce thermodynamica... [ABSTRACT FROM AUTHOR]

Spherical and uniform CdS nanoclusters were synthesized by hydrothermal microemulsion. The reaction of Cd[sup 2+] ions with S[sup 2-] ions generated from the decomposition of thioacetamide proceeded in water microdroplets. The mean diameter of the CdS nanoclusters can be varied from 20 to 80 nm by increasing the reaction temperature from 30 to 120 °C. XRD results indicate that the resulting CdS nanoclusters have a reduced and distorted hexagonal lattice compared to bulk materials. Two intense luminescence bands, i.e., green and red, were observed to coexist in the CdS nanoclusters. Their peak positions and relative intensities were found to be sensitive to the size and structure of nanoclusters. These emissions are attributed to surface defects (green emission) and the Cd-Cl composite vacancies (red emission). © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reliability of through silicon via (TSV) structures is a critical issue in the industrialization of TSV technology. One of the most important problems for TSV reliability is the thermal stress induced by a large coefficient of thermal expansion mismatch between different materials in the TSV structure. This mismatch could seriously deteriorate the performance of the TSVs, and even lead to failure. Here, the influence of heating temperature on the microstructure evolution in the TSV structure was investigated. The microstructures of Cu-filled TSV samples under different annealing conditions were characterized, and the phenomenon of global Cu protrusion and local grain-like Cu protrusion were observed in Cu-filled TSVs. Mechanisms of Cu protrusion in TSVs during heat treatment were analyzed, and possible factors involving thermal stress, grain growth, and void formation are discussed. The results showed that the origin of local grain-like TSV-Cu protrusion might be related to grain growth of Cu and the elastic modulus mismatch between coarse Cu grains. [ABSTRACT FROM AUTHOR]

Focuses on the defect-state generation in unimplanted silicon after rapid thermal annealing (RTA) as a function of the annealing parameters. Description and features of RTA; Importance of accurate temperature measurements and control in understanding and fundamental studies of material processing; Electrical characterization of silicon after RTA.

Deals with the use of cathodoluminescence (CL) to investigate the nature of a type of indium phosphorus (InP) directly underneath gold germanium nickel ohmic contacts subjected to various heat treatments. Information on a method for producing ohmic contacts to III-V semiconductors; Explanations for the observed reduction in CL efficiency obtained from the InP close to the contact interface.

Deals with the suppression of the dominant recombination center in n-type gallium arsenide (GaAs) by proximity annealing of wafers. Technique in achieving large increases in hole diffusion lengths in bulk n-type GaAs; Examination of the effect of annealing on shallow levels in GaAs; Explanation for the increase in diffusion lengths which result from proximity annealing of GaAs.

Presents a study which investigated the effects of rapid thermal annealing on the composition and structure of Al(0.8% Si)/Ti:W/a-Si contacts. Details of experimental procedures; Technique for eliminating interdiffusion between aluminum thin films and a-Si; Discussion on the electrical behavior of the contacts.

Investigates the electronic properties of thin CdSe films prepared through physical vapor transport. Background on the technical applications of CdSe thin films; Overview of previous studies on the photoluminescence of CdSe; Effects of annealing on the thin CdSe films.

Examines the effect of heat treatment on an indium-gallium arsenide ohmic contact. Dependence of ohmic contact resistance on heat treatment temperature; Analysis of the indium ohmic contact to gallium arsenide using secondary ion mass spectroscopy.

Enhancement of exchange field (Hex) and thermal stability of the textured CoFe/IrMn with Os/Cu buffer layer and Os diffusion barrier layer were studied. As revealed by x-ray Diffraction (XRD), an Os (0002) surface mesh was observed to form on Cu (100)/Si (100). The growth of CoFe (111)/IrMn (111) on such a template is parallel to the Os (0002). With the Os/Cu buffer layer, the CoFe/IrMn presents an enhancement of 70 Oe on Hex larger than that without Os/Cu. The Hex of the textured sample was 230 Oe at room temperature and it was increased to 330 Oe after 250 °C annealing. When the temperature reached 350 °C, Hex vanished. The increment of the temperature at which the textured and the nontextured sample obtaining their maximum Hex and the vanishing temperature of Hex were 50 and 75 °C, respectively. Furthermore, the CoFe/Os (d)/IrMn slowed down the Hex degradation. The sample with d=0.3 nm obtained its maximum Hex at 250 °C and vanished when it reached 400 °C. The combination of CoFe/IrMn with Os/Cu buffer layer and Os barrier layer made the Hex higher and also better thermal stability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thin films of antimony selenide (Sb 2 Se 3) were deposited via thermal evaporation. • The duration of pre-annealing at 100 °C influenced the morphology of Sb 2 Se 3 films. • Pre-annealing for 40 min resulted in optimized crystallinity of Sb 2 Se 3. • The highest efficiency of 1.47% is achieved for the Sb 2 Se 3 /CdS heterojunction. Abstract Sb 2 Se 3 is one of the alternative absorber materials for thin-film solar cells (TFSCs) comprising non-toxic and low-cost elements. The duration of pre-annealing at 100 °C prior to rapid thermal annealing (RTA) influenced the final morphology, crystallinity, and preferred orientation of thermally evaporated Sb 2 Se 3. Pre-annealing for 40 min promoted the crystallization of pure Sb 2 Se 3 phase following RTA; however, a long pre-annealing time such as 100 min rendered morphology similar to that of the reference absorber that was not pre-annealed, as ascertained by detailed scanning electron microscopy, X-ray diffraction, and Raman spectroscopic analyses. Furthermore, Sb 2 Se 3 /CdS TFSCs were fabricated with Sb 2 Se 3 pre-annealed for various durations. The highest efficiency of 1.47% was achieved for the optimized 40-min pre-annealed absorber, enabling a smooth current flow. Our results emphasize the detailed optimization of pre-annealing time for achieving efficient TFSCs. [ABSTRACT FROM AUTHOR]

A thermodynamic model is proposed to study the collective effect of size and dimension dependent specific heat capacity along with phonon surface scattering on thermal conductivity as well as on diffusivity of nanostructured semiconductors. Thermal conductivity and diffusivity of pure and compound semiconducting nanomaterials for partially smooth and rough surfaces of different sizes and dimensions have been calculated. Thermal conductivity and diffusivity decrease with size and increases while moving towards the specular surfaces. Incorporation of size and dimension effect of specific heat capacity with phonon-interface scattering gives the better explanation of thermal conductivity, whereas classical approach alone is inadequate. To validate the obtained results, we have compared our results with the experimental data and other model reported in the literature. [ABSTRACT FROM AUTHOR]

In the current investigation a series of oxygen-rich bismuth oxychloride Bi12O17Cl2 samples through an ethylene glycol-solvothermal route were constructed at different calcination temperatures and fully characterized by X-ray diffraction patterns, scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectra, X-ray energy dispersion spectroscopy, and photoluminescence spectra. It was demonstrated that the calcination temperatures indeed had a crucial effect on the crystallinity, grain size, morphology, optical property, and charge carrier separation of Bi12O17Cl2 series. These Bi12O17Cl2 samples showed significantly improved photocatalytic degradation over dye Rhodamine B and colorless antibiotic tetracycline hydrochloride. Particularly, the best candidate, the sample 350 °C—Bi12O17Cl2 could show apparent reaction rate constants that were nearly 28.2, 1.2 times of N-TiO2 over Rhodamine B and tetracycline hydrochloride, respectively. The possible reason of enhancing photocatalytic performance by various Bi12O17Cl2 samples calcined at different temperatures was discussed and major oxidative radicals maybe generated during photocatalytic processes were detected. [ABSTRACT FROM AUTHOR]

Nb3Sn strands, whose properties are very sensitive to stress/strain, are utilized for ITER cable-in-conduit conductor (CICC) of the central solenoids. The Nb3Sn strands experience temperature range of ~1000 K from the temperature of the heat treatment with the initiation of the Nb3Sn reaction to the operation temperature of ~4 K. Due to this large temperature range, large thermal strain is induced in the Nb3Sn filaments due to the differences between the coefficients of thermal expansion and Young's moduli of the components of the strand. Therefore, it is considered that initial performance of the CICC is influenced by the thermal strain on the Nb3 Sn, and it is important to evaluate the strain state of the Nb3Sn strand at low temperature. In this study, the thermal strain of the components of free Nb3Sn strand was measured by neutron diffraction and stress/strain state was assessed from room temperature to low temperature. As the results of diffraction measurements, it was found that 0.111% and 0.209% compressive strain were generated in Nb3Sn filaments at 300 and 10 K, respectively. [ABSTRACT FROM AUTHOR]

A mechanical lap joint of REBCO high-temperature superconducting (HTS) tapes with an indium foil inserted between joint surfaces has been proposed for segment-fabrication of HTS magnet of an advanced fusion reactor and various HTS applications. In a previous study, we successfully achieved a joint resistivity of about 3.5 pΩm2 by heat treatment during fabrication of the joint. In this study, improved heat treatment method was developed by controlling contact pressure and combining bake-out process. We evaluated joint resistance and critical current of the joint depending on the heating condition and bake-out condition. The joint resistivity after heat treatment was 2.5 pΩm2 without decreasing critical current with conditions of heating temperatures of 90–140 °C, a heating time of 30 min, a contact pressure of 100 MPa, a bake-out time of 30 min, and a bake-out temperature of 150 °C. Owing to applying the contact pressure when the indium becomes softer, the true area of contact increased and the thickness of the indium decreased greater than those in the previous method. In addition, it was shown that voids appearing by heating were removed by bake-out process from thermal desorption spectroscopy test. [ABSTRACT FROM PUBLISHER]

The magnetic stability of superconductor strands and cables is a key issue in the successful building and operation of high-field accelerator magnets. In this paper, we report the study of a state-of-the-art 0.7 mm Nb3Sn restacked-rod-process strand manufactured by Oxford Instrument Superconductor Technology. This conductor will be used in Rutherford cable for a 15-T Nb3Sn dipole demonstrator being built at Fermi National Accelerator Laboratory. Particularly, this study focuses on the impact of varying heat treatment conditions on the stability of the strand. Both the stability against internal flux jumps and external thermal perturbations are studied. [ABSTRACT FROM PUBLISHER]

Fermi National Accelerator Laboratory has been developing a 15-T Nb3Sn dipole demonstrator for a future very high energy pp collider based on an optimized 60-mm aperture four-layer “cos-theta” coil. To increase the magnet efficiency, the coil was graded by using two cables with same 15 mm width and different thicknesses made of two different restacked rod process (RRP) wires. Due to the nonuniform field distribution in dipole coils, the maximum field in the inner coil will reach 15–16 T, whereas the maximum field in the outer coil is 12–13 T. In preparation for the 15-T dipole coil reaction, heat treatment studies were performed on strands extracted from these cables with the goal of achieving the best coil performance in the corresponding magnetic fields. In particular, the effect of maximum temperature and time on the cable critical current was studied to take into account actual variations of these parameters during coil reaction. In parallel and in collaboration with Oxford Instruments-Superconducting Technology, development was performed on optimizing Nb3Sn RRP wire design and layout. [ABSTRACT FROM PUBLISHER]

We have measured the superconducting properties of the titanium alloy Ti-6Al-4V (Ti-64) as supplied and following two of the heat treatment schedules used for the Nb3Sn strands in the ITER tokamak. The Ti-64 alloy is the standard choice in the superconducting community for the barrels used to make critical current (I C) measurements in high magnetic fields at cryogenic temperatures. Ti-64, which has a two-phase alpha + beta microstructure and contains vanadium (n.b. TC(V) ∼ 5.4 K), is superconducting at 4.2 K in fields up to 3 T. We have also measured Ti-6Al-2Sn-4Zr-2Mo-0.2Si (Ti-6242), which is in the near alpha phase and contains tin (n.b. TC(Sn) ∼ 3.7 K). The critical temperature of Ti-6242 is 2.38 K, which is lower than the 5.12 K of Ti-64. Hence Ti-6242 is a better choice of barrel material for I C measurements required at 4.2 K in low fields up to 3 T, because it remains in the normal state. [ABSTRACT FROM PUBLISHER]

Atomic layer deposited (ALD) samples with layer stacks of HfO (3 nm)/SiO (0.7 nm)/ Si were subjected to 120 MeV Au ion irradiation at different fluences to study intermixing effects across the HfO/SiO interface. High-resolution Rutherford backscattering spectrometry (HRBS) and X-ray reflectivity (XRR) measurements confirm an increase in the interlayer thickness as a result of SHI induced intermixing effects. Current-voltage (I-V) measurements reveal an order of magnitude difference in the leakage current density between the pristine and irradiated samples. This can be explained by considering the increased physical thickness of interlayer (HfSiO). Furthermore, the samples were subjected to rapid thermal annealing (RTA) process to analyze annealing kinetics. [ABSTRACT FROM AUTHOR]

The structural, optical and electrical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized with the application of thermal treatment. The films of thickness 400 nm were deposited on glass and ITO substrates followed by thermal treatment at 150 °C, 300 °C and 450 °C. The XRD study reveals that the films have cubic structure and polycrystalline nature along with predominant reflection (111). The optical transmittance is found to increase with annealing treatment while optical energy band gap is observed to decrease. The current-voltage measurements show ohmic behavior and electrical conductivity is found to increase with thermal treatment. The EDAX patterns exhibit the presence of Cd, Zn and Te elements in the deposited film. The experimental results confirm that the annealed films display a demanding behavior for tandem solar devices. [ABSTRACT FROM AUTHOR]

Recently, theorists have predicted many materials with a low magnetic moment and large spin-polarization for spintronic applications. These compounds are predicted to form in the inverse Heusler structure; however, many of these compounds have been found to phase segregate. In this study, ordered Cr2CoGa thin films were synthesized without phase segregation using molecular beam epitaxy. The present as-grown films exhibit a low magnetic moment from antiferromagnetically coupled Cr and Co atoms as measured with superconducting quantum interface device magnetometry and soft X-ray magnetic circular dichroism. Electrical measurements demonstrated a thermally-activated semiconductor-like resistivity component with an activation energy of 87 meV. These results confirm spin gapless semiconducting behavior, which makes these thin films well positioned for future devices. [ABSTRACT FROM AUTHOR]

The effect of CdCl 2 heat treatment on the ZnTe layer used as the back electron reflector layer in polycrystalline CdTe solar cells was investigated. A thin film of ZnTe was grown on top of polycrystalline CdTe layer using metalorganic vapor phase epitaxy, which was then subjected to CdCl 2 heat treatment. The effect was examined using various characterization techniques such as X-ray diffraction, energy dispersive X-ray spectroscopy and scanning electron microscope images and it was found that the ZnTe layer transformed into CdTe and ZnO due to the treatment. This was verified by performing CdCl 2 heat treatment on pure ZnTe thin layer directly grown on glass which also showed the conversion of ZnTe to CdTe and ZnO. To study the effect of this transformation on final device performance, thin film CdTe solar cell structures were fabricated with ZnTe electron reflector layer with and without the CdCl 2 heat treatment. The device without the ZnTe layer seemed to perform better than the devices with ZnTe layer and the CdCl 2 heat treatment. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the benefits of applying ultrashort pulsed lasers over nanosecond pulsed lasers for selective (i.e., superficial) heat treatment of materials in general and for selective heat treatment of thin films in particular. To this end, a background of the physics that govern the absorption of light and subsequent diffusion of heat in semiconductor and metallic materials is provided, when exposed to picosecond or nanosecond laser pulses, with a fluence below the ablation threshold. A numerical model was implemented using a commercial finite-element modeling package, to simulate the temperature fields in thin films induced by laser pulses. The results of the simulations provide insight in the temperature cycles and corresponding timescales, as function of the processing parameters, such as fluence, pulse duration, pulse repetition frequency, and laser wavelength. Numerical simulations were run for thin films of molybdenum (Mo) and zinc oxide (ZnO) on a glass substrate, which are materials commonly adopted as (back and front) electrodes in thin film solar cells. [ABSTRACT FROM AUTHOR]

Recent efforts have demonstrated enhanced tailoring of material functionality with mixed anion materials, yet exploratory research with mixed anion chemistries is limited by the sensitivity of these materials to synthesis conditions. Synthesis of a particular metal oxynitride compound by traditional reactive annealing requires specific, limited ranges of both oxygen and nitrogen chemical potentials to establish equilibrium between the solid-state material and a reactive atmosphere. Using Ta–O–N as an example system, we describe a combination of reactive sputter deposition and rapid thermal processing (RTP) for synthesis of mixed anion inorganic materials. Heuristic optimization of reactive gas pressures to attain a desired anion stoichiometry is discussed, and the ability of RTP to enable amorphous to crystalline transitions without preferential anion loss is demonstrated through the controlled synthesis of nitride, oxide, and oxynitride phases. [ABSTRACT FROM PUBLISHER]

Sodium diffusion has been studied in p-type 4H-SiC. Heat treatments have been performed from 1200 °C to 1800 °C for 1 minto4h. Secondary ion mass spectrometry has been used to measure the sodium distribution. We show that sodium has a considerable mobility at 1200 °C in p-type 4H-SiC. On the other hand for sodium atoms trapped at suitable sites the mobility is limited up to 1800 °C. Trap limited diffusion kinetics is suggested and an effective diffusivity has been extracted with an activation energy of 4 eV for sodium diffusion in p-type 4H-SiC. [ABSTRACT FROM AUTHOR]