Post-annealing Times Research Articles

Effects of Post-annealing Condition on Interfacial Reaction and Bonding Strength of Cu/Sn-3.0Ag-0.5Cu/Al Joint for Heat Dissipation Module Application

The effects of post-annealing times at 150°C on the bonding strength and interfacial characteristics of Cu/Sn-3.0Ag-0.5Cu (SAC305)/Al were systematically evaluated. In the as-bonded sample, Cu<sub>6</sub>Sn<sub>5</sub> intermetallic compound (IMC) was formed at the upper Cu/SAC305 interface, while Ag<sub>3</sub>Al IMC was formed at the lower SAC305/Al interface, and a black layer of Al<sub>2</sub>Cu IMC was formed at a distance of about 20 µm from the Al interface. The Al atoms from the Al pad diffused towards the SAC305 solder during the bonding process and reacted with Cu to form the Al<sub>2</sub>Cu IMC. After post-annealing for 500 h at 150°C, the growth of Cu-Sn and Al<sub>2</sub>Cu IMCs followed a linear relationship with the square root of the annealing time, which could be understood by a diffusion-dominant mechanism. To measure the bonding strength, the lap shear test was evaluated on the Cu/SAC305/Al structure with time during post-annealing at 150°C. Initial bonding strength of around 118.80 MPa decreased to 92.4MPa after post-annealing for 200h, and then remained constant until 500 h. And the fracture locus was the mixed mode of SAC305/Al<sub>2</sub>Cu interface and cohesive inside SAC305 solder. Also, when the post-annealing time was increased from 150 h to 200 h, the fracture toughness decreased sharply from 438 J/m<sup>3</sup> to 100 J/m<sup>3</sup>. This decrease seems to be closely related to an increase in the SAC305/Al<sub>2</sub>Cu interface fracture mode. This is believed to be due to the increase in the SAC305/Al<sub>2</sub>Cu interface fracture mode due to the growth of the Al<sub>2</sub>Cu layer thickness.

Macroscopic Thermal Rectification Device Using Vanadium Dioxide Thin Film

A thermal rectifier is a device in which heat flows in the forward direction but very little can flow in the opposite direction. Because the heat current can be controlled, the device is promising for future practical applications. In this study, the experiments were performed to investigate temperature-gated thermal rectification using macroscopic vanadium dioxide $$(\hbox {VO}_{2})$$ thin films deposited on an asymmetric substrate. The $$\hbox {VO}_{2}$$ phase transition, occurred near 340 K, changed both the electrical and thermal properties. Therefore, we used these properties to investigate the thermal rectification. The $$\hbox {VO}_{2}$$ thin films were prepared on cover glass substrates by RF sputtering with a $$\hbox {VO}_{2}$$ disk target at $$500~{^{\circ }}\hbox {C}$$ . The morphology of the thin films was investigated. Silver paste and a copper band were used to connect the films with a heater and temperature controller. We observed thermal rectification in the temperature range of T = 310 K–370 K in several film samples obtained with different degrees of asymmetry, deposition times, and post-annealing times. It is found that $$60{^{\circ }}$$ triangular-shaped samples have a rectification coefficient of 1.14, and the rectification coefficient is increased with the increasing of the angle. In addition, the two rectangular-shaped samples have the coefficient of 1.06, which could also be enhanced by increasing the ratio of width.

Effect of post-annealing time on the properties of sputtered Al-doped ZnO thin films

Al doped ZnO (AZO) thin films prepared by RF magnetron sputtering were annealed in rapid thermal annealing system under various post-annealing times. The effect of post-annealing time on the structural, optical, and electrical properties of AZO film was investigated, systematically. As the post-annealing time elongated, the electrical resistivity was improved due to an increase in the carrier concentration and the mobility. X-ray photoelectron spectroscopy showed that the long post-annealing time increased the oxygen vacancy and decreased the surface bonding caused by the O2 absorption on surface, resulting in increase of the carrier concentration and the mobility. Therefore, the post-annealing time plays an important role in determining the nature of bonding in AZO thin films and is a powerful method to obtain better electrical properties.

BISCCO Thin Films: Superconducting Phases, Irreversibility Line and Critical Current

The transport properties such as irreversibility line (IL), critical current density (Jc), and activation energy (Ea) were studied in highly oriented BISCCO thin films with different superconducting phase relations H-2223:L-2212 by ZFC-FC method in the low magnetic field region (less than 0.1 T). The c-axis oriented BISCCO thin films with different superconducting phases H-2223:L-2212, high Tc phase (110 K), and low Tc phase (80 K), respectively, as determined by x-ray diffraction (XRD), were produced by r.f. magnetron sputtering on MgO (100) substrates and different post-annealing duration times. Tirr(H) data appear to be dominated by the intergrain Josephson flux. They exhibit the behavior of the grain coupling systems (similar to that displayed by spin glasses) and can be well described by a power law behavior like Almeida-Thoules. The irreversibility line (IL), however, was shifted to lower temperatures by decreasing the phase relation. The IL shifting to lower temperatures increases the liquid vortex region and would decrease the critical current density. The critical current density (Jc) and the activation energy (Ea) were determined using the 10 μVolt criterion and from Arrhenius plots of resistance data, respectively. Both decreased by decreasing the phase relation, i.e., by increasing the low Tc phase, which can be related to an increase in the granularity of films. The film granularity has been assumed as any crystal lattice defect, which creates a local depression of the superconducting order parameter.

The Influence of Postannealing on Structural and Superconducting Properties of Bi-2212 Ceramics

The effect of postannealing on the structural and superconducting properties of Bi-2212 sintered ceramic samples prepared by the solid state reaction method has been investigated. Postannealing times were varied from 0 h to 192 h at 700 ∘C. Electrical resistivity studies showed that postannealed samples at 96 h have the lowest room temperature values while critical transition temperature does not change significantly. XRD data have shown that the Bi-2212 phase content does not change noticeably, independently of the postannealing length. In addition, J c values, calculated from the hysteresis loops using the Bean’s model, increased with increasing the postannealing time until 48 h and decrease for longer ones.

Solid-phase epitaxy of undoped amorphous silicon by in-situ postannealing

The solid phase epitaxy (SPE) of undoped amorphous Si (a-Si) deposited on SiO2 patterned Si(001) wafers by reduced pressure chemical vapor deposition (RPCVD) using a H2–Si2H6 gas system was investigated. The SPE was performed by applying in-situ postannealing directly after deposition process. By transmission electron microscopy (TEM) and scanning electron microscopy, we studied the lateral SPE (L-SPE) length on sidewall and mask for various postannealing times, temperatures and a-Si thicknesses. We observed an increase in L-SPE growth for longer postannealing times, temperatures and larger Si thicknesses on mask. TEM defect studies revealed that by SPE crystallized epi-Si exhibits a higher defect density on the mask than at the inside of the mask window. By introducing SiO2-cap on the sample with 180nm Si thickness following postannealing at 570°C for 5 h, the crystallization of up to 450nm epi-Si from a-Si is achieved. We demonstrated the possibility to use this technique for SiGe:C heterojunction bipolar transistor (HBT) base layer stack to crystallize Si-buffer layer to widen the monocrystalline region around the bipolar window and to improve base link resistivity of the HBT.

Solid-phase epitaxy of amorphous silicon films by in situ postannealing using RPCVD

Solid-phase epitaxy (SPE) of in situ As-doped amorphous Si (a-Si) deposited on SiO 2/Si 3N 4 patterned Si (1 0 0) wafers by reduced pressure chemical vapour deposition (RPCVD) using a H 2–Si 2H 6 gas system was investigated. The SPE was performed by applying in situ postannealing directly after deposition process. On the one hand, we studied the lateral SPE (L-SPE) length of As-doped Si on mask and their crystal quality by TEM/SEM characterisation for various postannealing temperatures (700–1000 °C for 60 s). We observed increase in L-SPE growth and decrease of dislocation density for higher postannealing temperatures. On the other hand, L-SPE length was also investigated for different postannealing times (0–120 min at 575 °C) and As concentrations. At these conditions the L-SPE length has increased with increasing postannealing time. For both, higher and lower annealing temperature region, crystallization has been inhibited for higher As concentrations. After modifying As-doping level, we were able to crystallize up to 500 nm of a-Si on mask to epi-Si by combination of 575 °C and 1000 °C postannealing.

Influence of post-annealing time on blistering evolution in Si 〈1 0 0〉 implanted with high-fluence H ions

The influence of post-annealing time on blistering characteristics induced by 5×1016cm−2 ion-implanted H in Si <100> was studied in terms of the formation and growth of blisters. Ion energies consisted of 40 and 100keV. Post-annealing treatments were carried out using furnace annealing (FA) at 400 and 500°C for a duration of 0.25–3h in a nitrogen ambient. Raman scattering spectroscopy (RSS), optical microscopy (OM), atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS) were utilized to analyze the defect complex phases, the appearance of optically-detectable blisters and craters, the average depth of craters, and the hydrogen and oxygen depth profiles in the implanted layer, respectively. Furthermore, a characteristic time for the growth of optically-detectable blisters which was determined from the blister-covered fractions for various post-annealing times is proposed and used as a criterion to identify the effectiveness in the formation and growth of optically-detectable blisters. The results revealed that the characteristic time for the 400°C-annealed specimens in the 40keV implant is much shorter than it is in the 100keV one. However, the characteristic time for the 500°C-annealed specimens in the 40keV implant is slightly longer than it is in the 100keV implant. In addition, both the characteristic times for the 500°C-annealed specimens are much shorter than those for the 400°C ones. The above-mentioned phenomena hold true for craters.

Effects of postbombardment annealing on Ti diffusion in ion prebombarded MgO(100)

The effect of postbombardment annealing, or postannealing, has been investigated for Ti diffusion in ion prebombarded MgO(100). MgO postannealing was performed in ultrahigh vacuum after ion prebombardment of MgO and prior to Ti evaporation and diffusion. For postannealing temperatures of T=800, 900, and 1000 °C, Ti diffusion in 7 keV Ar+ prebombarded MgO exhibits the expected exponential decays with postannealing time and more rapid decays with higher temperatures. Cationic diffusion in the ion prebombarded sample proceeds in a nonsteady state condition of extra defects known as nonsteady state radiation enhanced diffusion (NSRED). Thermal dissociation of small vacancy clusters is responsible for NSRED. From the data of T⩽1000 °C, the derived dissociation energy of the vacancy clusters is only ∼10% of the normal value. For some specific postannealing times at T=1100 °C, the subsequent Ti diffusion was more enhanced than that without postannealing, a phenomenon which is contrary to the usual understanding of annealing effects. This same effect was also observed for Ti diffusion in 7 keV Cl+ prebombarded MgO postannealed at 1100 °C. Previous work indicates that the small vacancy clusters for NSRED are mainly Mg divacancies. We propose a divacancy creation mechanism that is due to the thermal dissociation of larger vacancy clusters during postannealing. The dissociation energy ratio of the effective large vacancy clusters (LVC) to that of the divacancies (DIV) is ELVC/EDIV∼1.4. The monovacancy coalescence was found to be unimportant for divacancy creation. A model based on this mechanism explains the unusual diffusion enhancement observed.

CO2 laser annealing of plasma-deposited high-T c superconducting thick films

Recent advances in the fabrication of high-T c superconducting thick films demand processing techniques which can eliminate film/substrate interdifiusion that occurs during subsequent post-annealing heat treatment after the film is deposited, thereby limiting the application of the thick films for devices. The present study evaluates laser annealing techniques for plasma-deposited Y-Ba-Cu-O thick films using a high-energy CO2 laser (10.6Μm) in a continuous wave mode. The results are compared with those obtained by conventional furnace annealing techniques necessary for post-heat treatment of as-deposited superconducting thick films. The high-T c superconducting phase is recovered by cationic diffusion during subsequent post-annealing heat treatment. Crystallographic phases and microstructural characterization have been performed using XRD, SEM, and EPMA analytical techniques. The significance of the technology lies in the elimination of film/substrate interdiffusion problems, thereby resulting in high-quality superconducting thick films. The technology will significantly reduce the post-annealing times usually required by conventional furnace annealing techniques.