Decrease Of Annealing Temperature Research Articles

Enhancing the Performance of Quantum Dot Light-Emitting Diodes Using Solution-Processable Highly Conductive Spinel Structure CuCo2O4 Hole Injection Layer.

Charge imbalance in quantum-dot light-emitting diodes (QLEDs) causes emission degradation. Therefore, many studies focused on improving hole injection into the QLEDs-emitting layer owing to lower hole conductivity compared to electron conductivity. Herein, CuCo2O4 has a relatively higher hole conductivity than other binary oxides and can induce an improved charge balance. As the annealing temperature decreases, the valence band maximum (VBM) of CuCo2O4 shifts away from the Fermi energy level (EF), resulting in an enhanced hole injection through better energy level alignment with hole transport layer. The maximum luminance and current efficiency of the CuCo2O4 hole injection layer (HIL) of the QLED were measured as 93,607 cd/m2 and 11.14 cd/A, respectively, resulting in a 656% improvement in luminous performance of QLEDs compared to conventional metal oxide HIL-based QLEDs. These results demonstrate that the electrical properties of CuCo2O4 can be improved by adjusting the annealing temperature, suggesting that solution-processed spinel can be applied in various optoelectronic devices.

Ideal simple shear strengths of two HfNbTaTi-based quinary refractory multi-principal element alloys

Atomistic simulations are employed to investigate chemical short-range ordering in two body-centered cubic refractory multi-principal element alloys, HfMoNbTaTi and HfNbTaTiZr, and its influence on their ideal simple shear strengths. Both the alias and affine shear strengths are analyzed on the {110} and {112} planes in the two opposing 111 directions. In both quinary alloys, local ordering of NbNb, TaTa, HfNb, HfTa, and NbTa is preferred as the annealing temperature decreases from 900 to 300 K. The pair that achieves the highest degree of local ordering is TiTi in HfMoNbTaTi and HfTi in HfNbTaTiZr. Subject to the affine shear, these alloys yield by first phase transformation at the most likely pairs followed by deformation twinning at those sites.

An innovative annealing treatment method and its mechanism to refine deformed mixed grains of initial aged GH4169 superalloy

The deformed mixed grains of the initial aged GH4169 superalloy need to be refined by annealing treatment. However, for the isothermal annealing treatment, the deformed mixed grains can only be refined to about 10 µm because the increase of nucleation rate needs to increase the temperature while the decrease of grain growth rate requires to decrease temperature. In the paper, an innovative method including an aging treatment and a subsequent continuous-cooling recrystallization annealing treatment (CC-RAT) is proposed. This method can not only increase the nucleation rate but decrease the grain growth rate. The effects of heat treatment parameters on microstructure are investigated. Besides, the grain refinement mechanism is studied using a developed cellular automaton (CA) model. The results show that the recrystallization takes place slowly during aging, while large number of δ precipitates appear. In subsequent CC-RAT, increasing starting temperature (Ts), decreasing cooling rate (V) or ending temperature (Te) can remarkably promote recrystallization, thereby refining grain microstructure. This attributes to the increase of recrystallization nucleation rate and the effective control of grain growth rate. In the early stage of CC-RAT, δ precipitates hinder the quick growth of recrystallized grains nucleated firstly. Moreover, the increase of Ts accelerates the nucleation rate, and the decrease of V prolongs the time for nucleation. Both of them promote the rapid formation of new recrystallized nuclei, especially at δ phase boundaries. As the annealing temperature decreases, newborn grains grow slowly, and these new grains restrict the growth of grains nucleated first. Therefore, a fine and uniform microstructure with an average grain size of 5.82 µm is obtained. However, when Ts is too high or V is too low, some coarse recrystallized grains appear. Hence, the feasible process is concluded as follows: aging treatment (900 °C×12 h), followed by CC-RAT (Ts = 990–1010 °C, V=1–2 °C/min, Te=950–970 °C).

0.4 millimeters vertically aligned carbon nanotubes from a cold wall CVD system at low pressure – Temperature analysis

This paper reports a temperature study on the new method recently proposed by the author to grow tall vertically-aligned carbon nanotubes (VA-CNT) in a cold-wall system, using a two-phase deposition step at low pressure. The first test consists of run several growths varying the annealing and deposition temperature. Secondly, a third phase, with H 2 and higher temperature (850 °C), is added to the deposition step, including a purge between the three phases to recondition the chamber reactor. The goal here is to verify if the chamber reconditioning and an extra phase at higher temperature contributes to increase the height and the uniformity of the VA-CNT forests. After this test, a new test for the annealing temperature is performed to find the sweet spot (temperature for each the highest and uniform forest are obtained). The first test demonstrated that the VA-CNT forests are higher as the annealing temperature decreases. Moreover, the best results were obtained when the annealing temperature is inferior to the growth temperature. Adding a third phase with H 2 to the deposition step resulted in an increase in average height of the forests from 186 µm to 272 µm, an increase of almost 100 µm. Finally, adjusting the annealing temperature confirmed that the best results are found for lower values of temperature. The best average height, 404 µm, with a standard deviation of 16.3 µm, was achieved with a three-phase deposition step and an annealing temperature of 600 °C.

Effect of thermally induced B2 phase on the corrosion behavior of an Al0.3CoCrFeNi high entropy alloy

The corrosion resistance of Al-Co-Cr-Fe-Ni high entropy alloys (HEAs) is probably affected by B2 phases. In this paper, the effect of B2 phases on the corrosion behavior of Al0.3CoCrFeNi HEAs in 3.5 wt% NaCl solution is clarified in this paper by purposely controlling the formation of B2 phases using annealing treatment. The microstructure characterization reveals that the content of (Al, Ni)-rich and Cr-poor B2 phases increases and the electrochemical measurements show that the pitting corrosion resistance is deteriorated as the annealing temperature decreases. Accordingly, the B2 phase is confirmed to be detrimental to the corrosion resistance of Al0.3CoCrFeNi HEAs. It can be attributed to the preferential dissolution of B2 phases causing easier pit initiation, which is evidenced by the corrosion morphology observation and scanning Kelvin probe force microscopy measurements, and to the slower repassivation rate leading to easier pit propagation, as demonstrated by the quantitative analysis of potentiostatic polarization curves.

Identification of ferric oxide polymorphs in nanoparticles prepared by sol-gel method and maximization of ε-Fe2O3 content

Abstract The effects of annealing temperature (1000–1125 °C) and Fe2O3 mass fraction (0.3–0.5) in the initial mixture on the composition of ferric oxide polymorphs within the Fe2O3/SiO2 nanocomposite prepared by sol-gel method were investigated. The structural and magnetic properties of prepared samples were characterized in detail by combination of X-ray powder diffraction (XRPD), high-resolution transmission electron microscopy, magnetic measurements and a local probe technique - transmission Mossbauer spectroscopy (TMS). The optimal conditions for preparation of e-Fe2O3 rich sample were established and ∼91% of the e-phase was reached with the characteristic particle diameter of 25 nm. It was observed that with increasing mass fraction of Fe2O3 in the starting material, the optimal annealing temperature decreases, while the width of the particle size distribution tends to increase. The relative concentrations of the four present polymorphs derived from XRD and TMS are in very good mutual agreement.

Non-isothermal crystallization transformation kinetics analysis and isothermal crystallization kinetics in super-cooled liquid region (SLR) of (Ce0.72Cu0.28)90 − xAl10Fex (x = 0, 5 or 10) bulk metallic glasses

Crystallization transformation kinetics in the non-isothermal and isothermal modes of (Ce0.72Cu0.28)90−xAl10Fex (x=0, 5 or 10) bulk metallic glasses was studied by differential scanning calorimetry (DSC). In the non-isothermal crystallization mode, the various heating rate (VHR) method and Kissinger–Akahira–Sunose (KAS) method were used to analyze the crystallization kinetics. The results revealed that the features of thermal–physical properties and crystallization kinetics are sensitive to iron content. (Ce0.72Cu0.28)90−xAl10Fex (x=0, 5 or 10) bulk metallic glasses show higher stability against crystallization with Fe content increased. The Johnson–Mehl–Avrami (JMA) model was used to analyze the crystallization kinetics in the non-isothermal and isothermal modes. In isothermal mode, the Avrami exponents n for x=0, 5 or 10 are 1.50, 1.86 and 1.56, respectively, which imply that the minor Fe addition might form a new atomic microstructure. The nucleation rate reaches zero when x=0 during the crystallization process; when x=5 or 10, the nucleation size increases by decreasing nucleation rate during crystallization process. In addition, the incubation time is sensitive to annealing temperatures, and the incubation period of crystallization becomes longer as annealing temperature decreases. Finally, the n values of (Ce0.72Cu0.28)90−xAl10Fex (x=0, 5 or 10) bulk metallic glasses were different in the non-isothermal and isothermal modes, indicating different nucleation and growth behaviors in the crystallization process.

Information in the Traveling Salesman Problem

In the Simulated Annealing algorithm applied to the Traveling Salesman Problem, the total tour length decreases with temperature. Empirical observation shows that the tours become more structured as the temperature decreases. We quantify this fact by proposing the use of the Shannon information content of the probability distribution function of inter–city step lengths. We find that information increases as the Simulated Annealing temperature decreases. We also propose a practical use of this insight to improve the standard algorithm by switching, at the end of the algorithm, the cost function from the total length to information content. In this way, the final tour should not only be shorter, but also smoother.

Residual stress-dependent electric conductivity of sputtered co-doped CeO2 thin-film electrolyte

Sm3+ and Nd3+ co-doped ceria thin-film electrolytes have been deposited on polycrystalline alumina substrates via RF magnetron sputtering. Electric conductivity is evaluated with respect to the residual stress in the film by sin2 ψ-methodology, indicating that an in-plane tensile stress is applied to the as-deposited film. The stress in the film increases as annealing temperature decreases, and there is an enlarged crystal lattice. The results also reveal that the annealed film with a greater stress shows a higher electric conductivity, which might be due to the lower activation energy. The conductivity of the film annealed at 600 °C is as high as 0.009 S cm−1 at 500 °C, and the residual stress is determined to be 542.70 MPa at room temperature.

Effects of strain on the optimal annealing temperature of GaInNAsSb quantum wells

Dilute nitride alloys have required postgrowth annealing to improve their luminescent efficiency. There exists an optimal annealing temperature that results in the highest photoluminescence intensity. Several series of GaInNAsSb samples with varying indium and antimony contents were grown to examine the effects of compositional and strain changes on this optimal annealing temperature. We show that a relationship exists between this temperature and the lattice strain of GaInNAsSb quantum wells. As strain increases in these alloys, the optimal annealing temperature decreases. Higher optimal anneal temperatures are found with lower lattice strain. This has important ramifications for the design of long-wavelength GaInNAsSb devices.

Photoluminescence origin of nanocrystalline SiC films

The nanocrystalline SiC films were prepared on Si (111) substrates by rf magnetron sputtering and then annealed at 800°C and 1000°C for 30 minutes in a vacuum annealing system. The crystal structure and crystallization of as-annealed SiC films were determined by the Fourier transform infrared (FTIR) absorption spectra and the X-ray diffraction (XRD) analysis. Measurement of photoluminescence (PL) of the nanocrystalline SiC (nc-SiC) films shows that the blue light with 473 nm and 477 nm wavelengths emitted at room temperature and that the PL peak shifts to shorter wavelength side and the PL intensity becomes stronger as the annealing temperature decreases. The time-resolved spectrum of the PL at 477 nm exhibits a bi-exponential decay process with lifetimes of 600 ps and 5 ns and a characteristic of the direct band gap. The strong blue light emission with short PL lifetimes suggests that the quantum confinement effect of the SiC nanocrystals resulted in the radiative recombination of the direct optical transitions.

Growth behavior of compound layers in Sn/Cu/Sn diffusion couples during annealing at 433–473 K

The kinetics of the reactive diffusion between Cu and Sn at solid-state temperatures was experimentally examined using Sn/Cu/Sn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed at temperatures between T = 433 and 473 K for various times in an oil bath with silicone oil. Due to annealing, compound layers consisting of Cu 3Sn and Cu 6Sn 5 are formed at the Cu/Sn interface. In most of the annealed diffusion couples, grains of CuSnO exist in the Cu 6Sn 5 layer. However, the CuSnO grain scarcely influences the growth behavior of the compound layers. The thickness of the Cu 6Sn 5 layer is around twice greater than that of the Cu 3Sn layer. The difference between their thicknesses slightly increases with increasing annealing temperature. At a constant temperature, the ratio of the thicknesses remains constant independent of the annealing time. The total thickness l of the compound layers monotonically increases with increasing annealing time t according to equation l = k( t/ t 0) n , where t 0 is unit time, 1 s. The observations provide n = 0.37, 0.43 and 0.50 at T = 433, 453 and 473 K, respectively. The value n = 0.5 indicates that the volume diffusion is the rate-controlling process for the reactive diffusion at T = 473 K. As the annealing temperature decreases, the grain boundary diffusion will contribute to the rate-controlling process. Thus, the values of n smaller than 0.5 yield that there is the contribution of the grain boundary diffusion and the grain growth occurs at certain rates at T = 433 and 453 K. Since the ratio between the thicknesses of the compound layers is kept constant during isothermal annealing, the same rate-controlling process is expected to work in both compound layers.

Reactive Diffusion between Ag and Sn at Solid State Temperatures

The reactive diffusion at solid-state temperatures was experimentally studied for the binary Ag-Sn system. Sn/Ag/Sn diffusion couples were prepared by a diffusion bonding technique and then annealed at temperatures between T ¼ 433 and 473 K for various periods in an oil bath with silicone oil. After annealing, layers of the (Ag3Sn) andcompounds were observed to form at the Sn/Ag interface. Furthermore, a thin layer alloyed with Sn was produced into the Ag specimen from the � /Ag interface owing to diffusion induced recrystallization (DIR). The thickness is about one order of magnitude greater for the layer than for theand DIR layers. The total thickness l of the andlayers is described as a function of the annealing time t by the equation l ¼ kðt=t0Þ n . Here, t0 is unit time, 1 s. The exponent n is 0.40, 0.38 and 0.36 at T ¼ 433, 453 and 473 K, respectively. If the reactive diffusion is controlled by the volume diffusion, n is equal to 0.5. However, n is actually smaller than 0.5 at all the annealing temperatures. This indicates that the grain boundary diffusion contributes to the reactive diffusion and the grain growth occurs at certain rates. As the annealing temperature decreases, the contribution of the grain boundary diffusion should be more remarkable, but the grain growth will become sluggish. This is the reason why the value of n increases with decreasing annealing temperature.

Kinetics of reactive diffusion between Au and Sn during annealing at solid-state temperatures

Abstract The reactive diffusion between Au and Sn was experimentally studied at solid-state temperatures using Sn/Au/Sn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were annealed at temperatures of T = 393 and 473 K for various times in an oil bath with silicone oil. After annealing, compound layers composed of AuSn4, AuSn2 and AuSn were recognized to form at the Au/Sn interface. The thickness of the AuSn4 layer is about six and four times greater than those of the AuSn2 and AuSn layers at T = 393 and 473 K, respectively. The ratio of the thicknesses of the compound layers is kept constant independently of the annealing time. The total thickness l of the compound layers is described as a function of the annealing time t by the equation l = k(t/t0)n, where t0 is unit time, 1 s. The exponent n is nearly equal to 1/2 at T = 393 K but takes a value between 1/4 and 1/2 at T = 473 K. Such an intermediate value of n at T = 473 K indicates that the grain boundary diffusion contributes to the reactive diffusion and the grain growth occurs at certain rates. As the annealing temperature decreases, the contribution of the grain boundary diffusion should become more remarkable, but the grain growth will slow down. Consequently, n becomes close to 1/2 at T = 393 K. According to the constancy of the ratio of the thicknesses, it is concluded that the same rate-controlling process works in the AuSn4, AuSn2 and AuSn layers at a constant annealing temperature.

Study of the Crystallization Kinetics of Zr<SUB>60</SUB>Al<SUB>15</SUB>Ni<SUB>25</SUB> Bulk Glassy alloy by Differential Scanning Calorimetry

This paper investigates the crystallization kinetics of Zr 60 Al 15 Ni 25 bulk glassy alloy under isothermal annealing by differential scanning calorimetry (DSC). The results show that the incubation time is very small even at low annealing temperature (743 K) and increases slightly with the annealing temperature decreasing, which suggests a growth-controlled crystallization process. However, the exothermic peak width, reflecting the time for the actual crystallization process, increases greatly when annealing temperature decreases. The Avrami exponents indicate that the crystallization mechanism changes at different annealing temperatures. The change of the crystallization mechanism is attributed to the great difference of the mobility ability of atoms at different temperatures.

Study of the crystallization kinetics of Zr60Al15Ni2 5 bulk glassy alloy

This paper reports the investigation on the crystallization kinetics of Zr6 0 Al15Ni25 bulk glassy alloy under isothermal annealin g by differential scanning calorimetry. The results show that the incubation time is very smal l even at a low annealing temperature (743 K) and the exothermic peak width, ref lecting the time for the actual crystallization process, increases greatly when annealing temperature decreases. This suggests a growth-controlled crystallizati on process. The Avrami exponents indicate that the crystallization mechanism cha nges at different annealing temperatures. The change of the crystallization mech anism is attributed to the great change of the mobility of atoms at different te mperatures.

Effect of microsegregation and dislocations on the nucleation kinetics of precipitation in aluminium alloy AA3003

Nucleation kinetics of the precipitation for MnAl 6 and MnAl 12 in the aluminum alloy AA3003 alloy have been investigated experimentally and theoretically. The results show that cold rolling enhances the rate of precipitation and this effect increases as the annealing temperature decreases. Micro-segregation of the solute atom Mn at the dislocation network during cold deformation is found to have a significant effect on the nucleation kinetics of the precipitation of MnAl 6 and MnAl 12 in AA3003 in addition to the effect of dislocations, which increase the nucleation site density and reduce the nucleation barrier. A model to predict the start times of the precipitation during isothermal holding is constructed by considering the effects of dislocations and recovery as well as micro-segregation of Mn on the nucleation kinetics of precipitates. The predictions of the model are in good agreement with the experiment data.

Stability of ordered missing-dimer structures and the ordering dynamics on Si(001)

The stability of (2 × n)-ordered missing-dimer structures on Si(001) and the ordering dynamics of missing dimers are investigated. The surface free energy of (2 × n)-ordered missing-dimer structure was calculated under strains parallel or perpendicular to the dimer row using the Stillinger-Weber potential among Si atoms. The (2 × n)-ordered missing-dimer structure becomes more stable than the (2 × 1)-ordered surface without missing-dimers only if a compressive strain larger than 0.5% is applied parallel to the dimer row. The relaxation process towards the equilibrium configuration of excess missing dimers formed initially at random on the (001) surface was studied by a time-dependent Monte Carlo simulation based on the lattice gas model. The ordering of missing dimers towards the (2 × n) structure evolves via a three-stage relaxation process at 300 K, while it evolves via a one-stage, fast relaxation process at 600 and 900 K. The degree of ordering at equilibrium is significantly improved as the annealing temperature decreases and the missing-dimer concentration increases. The effect of the missing-dimer hopping across the dimer row is also studied.

Crystallization of Amorphous LPCVD Silicon Films and Application to Bipolar and Thin Film Transistors

ABSTRACTWe studied the crystallization of LPCVD amorphous silicon films by TEM and found that the grain size of crystallized films depends upon the deposition and annealing conditions. The grain size increases as the deposition and/or the annealing temperature decreases. We also investigated the application of crystallized films in the fabrication of polysilicon emitter bipolar transistors and thin film transistors. The performance of bipolar transistors was found to have a small dependence on the grain size. In contrast, the performance of thin film transistors was strongly dependent upon the grain size.