Four-inch high quality crack-free AlN layer grown on a hightemperature annealed AlN template by MOCVD

In this work,based on physical vapor deposition and high-temperature annealing(HTA),the 4-inch crack-free high-quality AlN template is initialized.Benefiting from the crystal recrystallization during the HTA process,the FWHMs of X-ray rocking curves for(002)and(102)planes are encouragingly decreased to 62 and 282 arcsec,respectively.On such an AlN template,an ultra-thin AlN with a thickness of~700 nm grown by MOCVD shows good quality,thus avoiding the epitaxial lateral over-growth(ELOG)process in which 3-4μm AlN is essential to obtain the flat surface and high crystalline quality.The 4-inch scaled wafer provides an avenue to match UVC-LED with the fabrication process of traditional GaN-based blue LED,therefore significantly improving yields and decreasing cost.

Effect of annealing temperature on microstructure and mechanical properties of Mg-Zn-Zr-Nd alloy with large final rolling deformation

In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.

Photoluminescence and defect evolution of nano-ZnO thin films at low temperature annealing

Nano-ZnO thin films composed of nanoparticles with sizes of 10-16 nm on silicon substrates at low temperature were prepared by sol-gel method.By placing the nano-ZnO thin films at room temperature or annealing at 100°C in air for 10 h intermittently,within a total 70 h annealing time,the evolution of PL spectra of the nano-ZnO thin films were studied in detail.As the annealing time increases,the PL peaks shift from violet to blue and green bands.The PL peaks at violet and blue bands decrease with the annealing time,but the PL peaks at green band are opposite.The PL spectra are related to the defects in the nano-ZnO thin films.The PL peaks positioned at 430 nm are mainly related to defects of zinc interstatials(Zni),oxygen vacancies and(Vo);the ones at 420 nm to oxygen interstitials(Oi),Zinc vacancies(Vzn),Zni ;and the ones at 468 nm to Vzn,Zni,and charged oxygen interstatials(Vo+).The green luminescence is related to Oi,Vo and Zni.The evolutions of PL spectra and the defects are also related to the concentrations of Zn in the thin films,the thicknesses of the films and the annealing time.For the films with 0.5 M and 1.0 M Zn concentrations,after 20 h and 30 h annealing in air at 100°C,respectively,either placing them in air at room temperature or continuing anneal in air at 100°C,the PL spectra are stable.Under the low temperature annealing,Zni decreases with the annealing time,and Oi increases.Sufficient Oi favors to keep the nano-ZnO thin films stable.This result is important to nano-ZnO thin films as electron transport layers in inverted or tandem organic solar cells.

Effect of low temperature annealing on the electrical properties of an MOS capacitor with a HfO_2 dielectric and a TiN metal gate

Abstract： The effects of low temperature annealing, such as post high-k dielectric deposition annealing （PDA）, post metal annealing （PMA） and forming gas annealing （FGA） on the electrical characteristics of a metal-oxidesemiconductor （MOS） capacitor with a TiN metal gate and a Hf02 dielectric are systematically investigated. It can be found that the low temperature annealing can improve the capacitance-voltage hysteresis performance signifi- cantly at the cost of increasing gate leakage current. Moreover, FGA could effectively decrease the interfacial state density and oxygen vacancy density, and PDA could make the flat band positively shift which is suitable for P-type MOSs. Key words： ALD Hf02; TiN; low temperature annealing; hysteresis

Insight into the influence of high temperature annealing on the onset potential of Ti-doped hematite photoanodes for solar water splitting

For Ti-doped hematite photoanodes, high temperature annealing drastically increases the water oxidation plateau photocurrent, but also induces an anodic shift of onset potential by about 100 m V, thus hindering the performance under low applied bias. To the best of our knowledge, the effects of high temperature annealing on the onset potential have been rarely studied. Herein, both X-ray photoelectron spectroscopy（XPS） measurements and theoretical calculations indicated that the increase of surface Ti/Fe atomic ratio after high temperature annealing decreased the adsorption capacity of hydroxide ions on the hematite surface. Subsequently, the flatband potential（i.e., the theoretical onset potential） of Ti doped hematite photoanodes positively shifted, which was supported by the Mott-Schottky measurements.

Effect of annealing temperature on joints of diffusion bonded Mg/Al alloys

To study the effect of annealing temperature on the joints between magnesium and aluminum alloys, and improve the properties of bonding layers, composite plates of magnesium alloy（AZ31 B） and aluminum alloy（6061） were welded using the vacuum diffusion bonding method. The composite specimens were continuously annealed in an electrical furnace under the protection of argon gas. The microstructures were then observed using scanning electron microscopy. X-ray diffractometry was used to investigate the residual stresses in the specimens. The elemental distribution was analyzed with an electron probe micro analyzer. The tensile strength and hardness were also measured. Results show that the diffusion layers become wide as the heat treatment temperature increases, and the residual stress of the specimen is at a minimum and tensile strength is the largest when being annealed at 250 ℃. Therefore, 250 ℃ is the most appropriate annealing temperature.

Effect of annealing temperature on martensitic transformation of Ti_(49.2)Ni_(50.8) alloy processed by equal channel angular pressing

The effect of annealing temperature on the martensitic transformation of a Ti49.2Ni50.8 alloy processed by equal channel angular pressing （ECAP） was investigated by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and differential scanning calorimetry （DSC）. The as-ECAP processed and subsequently annealed Ti49.2Ni50.8 alloys consist of B2 parent phase, Ti4Ni2O phase and B19′ martensite at room temperature. Upon cooling, all samples show B2→R→B19′ two-stage transformation. Upon heating, when the annealing temperature is less than 400℃, the samples show B19′→R→B2 two-stage transformation; when the annealing temperature is higher than 500 ℃, the samples show B19′→B2 single-stage transformation. The B2-R transformation is characterized by wide interval due to the dislocations introduced during ECAP.

Effects of annealing temperature on the microstructure and properties of the 25Mn-3Si-3Al TWIP steel

Microstructures and mechanical properties of the 25Mn twinning induced plasticity （TWIP） steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000℃, the 25Mn steel showed excellent comprehensive mechanical properties, the tensile strength was about 640 MPa, the yield strength was higher than 255 MPa, and the elongation was above 82%. The microstructure was analyzed by optical microscopy （OM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Before deformation the microstructure was composed of austenitic matrix and annealing twins at room temperature; at the same time, a significant amount of annealing twins and stacking faults were observed by TEM. Mechanical twins played a dominant role in deformation and as a result the mechanical properties were found to be excellent.

Effect of annealing temperature on microstructure and electrochemical performance of La_(0.75)Mg_(0.25)Ni_(3.5)Co_(0.2) hydrogen storage electrode alloy

To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM）, X-Ray Photoelectron Spectroscopy （XPS）, and electrochemical experiments. The results obtained by XRD and SEM showed that the as-cast and annealed （1123 K） alloys had multiphase structure containing LaNis, （La, Mg）2（Ni, Co）7 and few LaNi2 phases. When annealing temperatures approached 1223 and 1323 K, LaNi2 phase disappeared. The annealed alloys at 1223 and 1323 K were composed of LaNi5, （La, Mg）2（Ni, Co）7 and （La, Mg）（Ni, Co）3 phases. With increasing annealing temperature, the maximum discharge capacity of the alloy decreased monotonously, but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing, as well as the enhancement of anti-oxidation/corrosion ability and the suppression of pulverization during cycling in KOH electrolyte.

Effect of Zr additions and annealing temperature on electrical conductivity and hardness of hot rolled Al sheets

The influence of annealing cycles up to 650 °C on the specific conductivity and hardness（HV） of hot-rolled sheets of Al alloys containing up to 0.5% Zr（mass fraction） was studied.Using analytical calculations of phase composition and experimental methods（scanning electron microscopy,transmission electron microscopy,electron microprobe analysis,etc）,it is demonstrated that the conductivity depends on the content of Zr in the Al solid solution which is the minimum after holding at 450 °C for 3 h.On the other hand,the hardness of the alloy is mainly caused by the amount of nanoparticles of the L12（Al3Zr） phase that defines the retention of strain hardening.It is shown that the best combination of electrical conductivity and hardness values can be reached within an acceptable holding time at the temperature about 450 °C.

Effects of substrate temperature and annealing treatment on the microstructure and magnetic characteristics of TbDyFe films

A series of TbDyFe films were prepared by DC magnetron sputtering. The effects of substrate temperature and annealing temperature on the phase structure and the magnetic properties of the sample films were investigated. The an-nealing treatment has a significant influence on the microstructure and the magnetic properties of the sample. The results obtained by XRD indicate that the films deposited at a temperature lower than 525℃ are amorphous and have an easy magnetization direction perpendicular to the film plane. An RFe2 phase is formed in the sample annealed at 550℃ and the residual phases observed are Fe and rare earth oxide. The magnetic properties Hc and Mr/Ms of the film annealed at 550℃ obtain the maximum values,for which the formation of the RFe2 phase is mainly responsible. An annealing treatment leads to a rotation of the sample’s easy axis from being parallel to the film surface to becoming vertical.

Effects of annealing temperature on microstructure and ferroelectric properties of Bi_(0.5)(Na_(0.85)K_(0.15))_(0.5)TiO_3 thin films

Bi0.5(Na0.85K0.15)0.5TiO3(BNKT15) thin films were synthesized by metal-organic decomposition(MOD) at annealing temperatures of 650,680,710 and 740℃,and the effects of annealing temperature on the microstructure,dielectric properties,remnant polarization(2Pr) and leakage current density were studied with X-ray diffractometer,atomic force microscope,precision impedance analyzer,ferroelectric analysis station and semiconductor parameter tester.The results show that the thin film annealed at 710℃ exhibits a typical perovskite structure without predominant orientation and a smooth surface with evenly distributed grains.2Pr value(67.4 μC/cm2 under 830 kV/cm) and the leakage current density(1.6×10-6 A/cm2 at 170 kV/cm) for BNKT15 thin film annealed at 710℃ are better than those for thin films annealed at other temperatures.

Annealing Temperature Effects of TiO2 Nanofiber Anodes for the Rechargeable Lithium Ion Batteries

TiO2 nanofibers（TiO2/NFs） have been synthesized through an electrospinning method and annealed at 400, 500 and 600 ℃ to optimize their systems. The effects of annealing temperature on the electrochemical properties for lithium ion batteries（LIBs） are assessed. The obtained LIB properties for TiO2 nanofiber anodes annealed at 400 ℃（denoted as TiO2/NFs-400） are much better than those of TiO2/NFs-500 and TiO2/NFs-600. The TiO2/NFs-400 anodes show good LIB performance with capacities of 180 and 150 m Ah/g tested at 200 and 600 m A/g after 100 cycles with almost no capacity loss and superb rate performance. The XRD results show that the pure anatase phase TiO2 can form at 400 ℃ for TiO2/NFs-400, while mixed phases of anatase and rutile are emerged at TiO2/NFs-500 and TiO2/NFs-600. Furthermore, the TiO2 nanoparticles are combined in nanofibers, and their corresponding crystal particle size for TiO2/NFs-400 was smaller than that of the other two samples. It is concluded that the superior electrochemical performance of the TiO2/NFs-400 anodes could be due to their pure crystal of anatase, small nanoparticles and non-ideal crystal lattices.

Annealing Temperature dependence of Photoluminescence from Silicon-rich silica Films

The silicon-rich silica films were prepared by a dual-ion-beam co-sputtering method from a composite Target in an argon atmosphere. The structure of the films studied by the aid of TEM and XRD is amorphous. The photoluminescence (PL) spectra were found to have a 4- luminescent band peak at 320 nm, 410 nm, 560 nm, and 630 nm, respectively, at room temperature. The intensity and the wavelength position of PL are dependent on annealing temperature (Ta), and the luminescent mechanism is analyzed.

Effect of Annealing Temperature on the Formation of Silicides and the Surface Morphologies of PtSi Films

The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-st with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.

Effect of the annealing temperature on the long-term thermal stability of Pt/Si/Ta/Ti/4H–SiC contacts

The Pt/Si/Ta/Ti multilayer metal contacts on 4H-Si C are annealed in Ar atmosphere at 600°C-1100°C by a rapid thermal processor（RTP）. The long-term thermal stability is evaluated by aging the annealed contact at 600°C in air. The contact＇s properties are determined by current-voltage measurement, and the specific contact resistance is calculated based on the transmission line model（TLM）. Transmission electron microscope（TEM） and energy-dispersive x-ray spectrometry（EDX） are used to characterize the interface morphology, thickness, and composition. The results reveal that a higher annealing temperature is favorable for the formation of an Ohmic contact with a lower specific contact resistance, and causes the rapid degradation of the Ohmic contact in the aging process.

Effect of annealing temperature on structure and electrochemical properties of LiCoO_2 cathode thin films

LiCoO2 thin films, which can be used as a cathode material in microbatteries, were deposited using radio frequency (r.f.) magnetron sputtering system from a LiCoO2 target and in an O2+Ar atmosphere. The films were characterized by various methods such as XRD, SEM and AFM. The LiCoO2 films were annealed in air at 300, 500, 700 and 800 ℃ respectively. The effect of the annealing temperature on the structure, the surface morphology and the electrochemical properties of the films were investigated. The LiCoO2 thin film deposited at room temperature is amorphous and has smaller grain size. With increasing of annealing temperature, the crystallinity of the films is promoted. When the annealing temperature increases to 700 ℃, the films have a perfect crystalline LiCoO2 phase. The LiCoO2 thin film without annealing has no discharge plateau and small discharge capacity (about 27 μAh·cm-2μm). The discharge capacity increases with the increasing of annealing temperature and reaches 47 μAh·cm-2μm for the film annealed with 700 ℃, which also shows the typical discharge plateau of 3.9 V. The cycle performance of LiCoO2 thin films of as grown and annealed at different temperatures were studied. In the case of the film without thermal treatment, the capacity fading is much faster than that of the film annealed at different temperature, showing about 40% capacity loss only after 25 cycles. However, in the case of the film annealed at 700 ℃, the capacity reaches to steady state gradually and maintained constantly with cycling. After 25 times cycling, the discharge capacity of the film annealed at 700 ℃ decreases to about 36.9 μAh·cm-2·μm, only 0.8% capacity loss per cycle.

Water-based processed and alkoxide-based processed indium oxide thin-film transistors at different annealing temperatures

In this study,indium oxide（In2O3） thin-film transistors（TFTs） are fabricated by two kinds of low temperature solution-processed technologies（Ta ≤ 300℃）,i.e.,water-based（DIW-based） process and alkoxide-based（2-ME-based）process.The thickness values,crystallization properties,chemical structures,surface roughness values,and optical properties of In2O3 thin-films and the electrical characteristics of In2O3 TFTs are studied at different annealing temperatures.Thermal annealing at higher temperature leads to an increase in the saturation mobility（μsat） and a negative shift in the threshold voltage（VTH）.The DIW-based processed In2O3-TFT annealed at 300℃ exhibits excellent device performance,and one annealed at 200℃ exhibits an acceptable μsat of 0.86 cm^2/V·s comparable to that of a-Si：H TFTs,whereas the 2-ME-based TFT annealed at 300℃ exhibits an abundant μsat of 1.65 cm^2/Vs and one annealed at 200℃ is inactive.The results are attributed to the fact that the DIW-based process induces a higher degree of oxidation and less defect states than the 2-ME-based process at the same temperature.The DIW-based process for fabricating the In2O3 TFT opens the way for the development of nontoxic,low-cost,and low-temperature oxide electronics.

Effects of Annealing Temperature on the Electrical Conductivity and Mechanical Property of Cu-Te Alloys

The effects of annealing temperatre on the electrical conducitivity and mechanical property of Cu-Te alloys were studied via an AG-10TA electronic universal machine, an SB2230 digital electric bridge, SEM, EDS and XPS. The results show the electrical conductivity increases while the tensile strength fluctuates when the annealing temperature becomes higher because the recrystallization occurs during the annealing process, leading to the density of dislocation decreasing, grain size growing up, but the second phase precipitating sufficiently and simultaneously.

Effect of annealing temperature on interfacial and electrical performance of Au-Pt-Ti/HfAlO/InAlAs metal-oxide-semiconductor capacitor

HfAlO/InAlAs metal-oxide-semiconductor capacitor (MOS capacitor) is considered as the most popular candidate of the isolated gate of InAs/AlSb high electron mobility transistor (HEMT). In order to improve the performance of the HfAlO/InAlAs MOS-capacitor, samples are annealed at different temperatures for investigating the HfAlO/InAlAs interfacial characyeristics and the device's electrical characteristics. We find that as annealing temperature increases from 280 ℃ to 480 ℃, the surface roughness on the oxide layer is improved. A maximum equivalent dielectric constant of 8.47, a minimum equivalent oxide thickness of 5.53 nm, and a small threshold voltage of -1.05 V are detected when being annealed at 380 ℃;furthermore, a low interfacial state density is yielded at 380 ℃, and this can effectively reduce the device leakage current density to a significantly low value of 1×10-7 A/cm2 at 3-V bias voltage. Therefore, we hold that 380 ℃ is the best compromised annealing temperature to ensure that the device performance is improved effectively. This study provides a reliable conceptual basis for preparing and applying HfAlO/InAlAs MOS-capacitor as the isolated gate on InAs/AlSb HEMT devices.