High Temperature Annealing Effects Research Articles

High-temperature annealing effects on epitaxial TiN films on 4H-SiC

To gain deeper insights into the impact of very high-temperature annealing on TiN film quality and thermal diffusion phenomena, the deposited TiN films underwent annealing in an induction heating furnace across a temperature range from 1150 °C to 1700 °C. Our findings indicate that TiN films remain stable, and the full-width at half-maximum (FWHM) of TiN (111) noticeably reduced by about 30 % when annealed at 1250 °C. However, as the annealing temperature rises to 1400 °C, the film composition gradually enriches with carbon as TiCxN1-x with x up to 0.5. After annealing at 1700 °C, the film is further enriched with x larger than 0.5. For a long time annealing at 1700 °C, the decomposition of SiC substrate with void formation is verified from observations by cross-sectional transmission electron microscopy.

High temperature annealing effects on optical performance of TiAlN-based solar selective absorber with TiN IR reflector

Higher operating temperature of concentrating solar power plant could help to improving the solar-electricity conversion efficiency. However, solar selective absorber with stability higher than 700 °C is still lacking. Here, we explored the potential of a tandem structure absorber of TiN/Ti0.5Al0.5N/Ti0.33Al0.67N/CrAlSiO. The as-deposited tandem absorber had a solar selectivity of 0.887/0.134, which was maintained at 800 °C for 1 h. With the annealing temperature increasing from 800 °C to 1000 °C, the solar absorptance first slowly decreased from 0.887 to 0.866, then dramatically decreased to 0.7 after annealing at 1100 °C. Optical simulation indicated that thermal annealing would induced higher optical constants both for the Ti0.5Al0.5N and Ti0.33Al0.67N layers, which is caused by the spinodal decomposition of the cubic TiAlN phase. While the thermal emittance slightly increased from 0.134 to 0.154, as the TiN IR reflector maintained its layer structure even up to 1100 °C.

High temperature annealing effects on spectral, microstructural and laser damage resistance properties of sputtered HfO2 and HfO2-SiO2 mixture-based UV mirrors

Hafnium oxide is widely used as high refractive index material for making high power laser coatings for UV spectral range. Thermal annealing is one of the most efficient post-processing techniques for improving optical coating stress, its absorption, and resistance to laser radiation. In this article we investigate high temperature annealing effects on optical, microstructural, surface and laser radiation resistance properties of pure hafnia and two different hafnia-silica mixture-based sputtered dielectric mirrors for 266 nm wavelength. Three distinct annealing temperatures were selected for different coatings, leading to amorphous and polycrystalline phases of high refractive index layers. Annealing increased reflectance of all mirrors. Annealing at high temperatures that triggered crystallization considerably increased LIDT of all coatings. In addition, substantial increase in transmittance at shorter wavelength range was registered. Our results suggest that high temperature annealing above crystallization onset of HfO2 and HfO2-SiO2 mixture based dielectric mirrors has a great potential of increasing their damage resistance for UV laser pulses.

High-temperature annealing induced evolution of strain in AlN epitaxial films grown on sapphire substrates

High-temperature (HT) annealing effects on the evolution of strain in AlN films grown on sapphire have been investigated. It is found that there is a significant transition behavior from tensile to compressive strain in AlN before and after HT annealing at an optimal temperature of 1700 °C. Based on a microstructural analysis, it is clarified that the HT annealing will result in the (1) disappearance of grains that account for the tensile stress before HT annealing, (2) generation of a new interface that has little influence on the lattice constant upper/below this interface, and (3) regular 8/9 arrangement of misfit dislocation at the AlN/sapphire interface that relieves almost all stress associated with lattice mismatch. It is thus deduced that the remnant compressive strain in AlN after HT annealing mainly comes from the cooling down process due to thermal mismatch between sapphire and AlN. This understanding of the annealing effect is certainly of great significance in AlN materials science and technology.

High temperature annealing effects on the chemical and mechanical properties of inductively-coupled plasma-enhanced chemical vapor deposited a-SiC:H thin films

This paper reports the impact of thermal annealing up to temperatures of 1200°C on the chemical and mechanical properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films. These layers were deposited using an inductively-coupled plasma-enhanced chemical vapor deposition process with methane, silane and argon as precursor gases. The results of mass effusion measurements up to 1000°C are presented and the temperature-dependent effusion characteristics are compared to changes in the Fourier-transform infrared spectra. Furthermore, a simple method is presented that enables us to detect the onset of nanocrystallization in the a-SiC:H films caused by the high temperature annealing. The changes in chemical and crystallographic properties are discussed and related to the mechanical thin film properties, such as a substantial increase in Young's modulus from 176 up to 267GPa, in hardness from 24 up to 34.5GPa, as well as in residual film stress from −683 up to +3800MPa. Additionally, the decrease in layer thickness to about 70% of the initial value and the increase in refractive index from 2.33 to 2.78 are explained.

High temperature annealing effects on deep-level defects in a high purity semi-insulating 4H-SiC substrate

Effects of high-temperature annealing on deep-level defects in a high-purity semi-insulating 4H silicon carbide substrate have been studied by employing current-voltage, capacitance-voltage, junction spectroscopy, and chemical impurity analysis measurements. Secondary ion mass spectrometry data reveal that the substrate contains boron with concentration in the mid 1015 cm−3 range, while other impurities including nitrogen, aluminum, titanium, vanadium and chromium are below their detection limits (typically ∼1014 cm−3). Schottky barrier diodes fabricated on substrates annealed at 1400–1700 °C exhibit metal/p-type semiconductor behavior with a current rectification of up to 8 orders of magnitude at bias voltages of ±3 V. With increasing annealing temperature, the series resistance of the Schottky barrier diodes decreases, and the net acceptor concentration in the substrates increases approaching the chemical boron content. Admittance spectroscopy results unveil the presence of shallow boron acceptors and deep-level defects with levels in lower half of the bandgap. After the 1400 °C annealing, the boron acceptor still remains strongly compensated at room temperature by deep donor-like levels located close to mid-gap. However, the latter decrease in concentration with increasing annealing temperature and after 1700 °C, the boron acceptor is essentially uncompensated. Hence, the deep donors are decisive for the semi-insulating properties of the substrates, and their thermal evolution limits the thermal budget for device processing. The origin of the deep donors is not well-established, but substantial evidence supporting an assignment to carbon vacancies is presented.

Synthesis and Characterization of LPCVD Polysilicon and Silicon Nitride Thin Films for MEMS Applications

Inherent residual stresses during material deposition can have profound effects on the functionality and reliability of fabricated MEMS devices. Residual stress often causes device failure due to curling, buckling, or fracture. Typically, the material properties of thin films used in surface micromachining are not very well controlled during deposition. The residual stress, for example, tends to vary significantly for different deposition conditions; experiments were carried out to study the polysilicon and silicon nitride deposited by Low Pressure Chemical Vapor Deposition (LPCVD) method at wide range of process conditions. High temperature annealing effects on stress in case polysilicon are also reported. The reduced residual stress levels can significantly improve device performance, reliability, and yield as MEMS devices become smaller.

Effects of pre-irradiation annealing at high temperature on optical absorption and electron paramagnetic resonance of natural pumpellyite mineral

Natural silicate mineral of pumpellyite, Ca2MgAl2(SiO4)(Si2O7)(OH)2·(H2O), point group A2/m, has been studied concerning high temperature annealing and γ-radiation effects on Optical Absorption (OA) and Electron Paramagnetic Resonance (EPR) properties. Chemical analysis revealed that besides Si, Al, Ca and Mg, other oxides i.e., Fe, Mn, Na, K, Ti and P are present in the structure as impurities. OA measurements of natural and annealed pumpellyite revealed several bands in the visible region due to spin forbidden transitions of Fe2+ and Fe3+. The behaviour of bands around 900 and 1060nm, with pre-annealing and γ radiation dose, indicating a transition Fe2+→e−+Fe3+. On the other hand, EPR measurements reveal six lines of Mn2+, and satellites due to hyperfine interaction, superimposed on the signal of Fe3+ around of g=2. For heat treatment from 800°C the signal grows significantly and for 900°C a strong signal of Fe3+ hides all Mn2+ lines. The strong growth of this signal indicates that the transitions are due to Fe3+ dipole–dipole interactions.

Structural and Electrical Properties of Terbium Scandate Films Deposited by Atomic Layer Deposition and High Temperature Annealing Effects

In this work terbium scandate thin films have been deposited by atomic layer deposition (ALD) on SiO2/Si and Si3N4/SiO2/Si stacks and their structural and electrical behavior as a function of annealing temperature has been investigated. Films were grown using β-diketonate-based precursors and ozone at 300°C. The film crystallization in the cubic phase is induced as film thickness increases and enhanced by thermal annealing. The thermal stability of ALD TbScOx films and of their interfaces with SiO2 and Si3N4 is preserved after thermal treatment at 600°C, and their electrical characterization shows well-shaped capacitance-voltage curves, from which a k value of 16-18 is extracted. Annealing at 900°C largely affects the TbScOx/SiO2 interface, causing the formation of an intermixed layer and silicon diffusion in the film resulting in a reduction of its k value down to 12. On the contrary TbScOx/Si3N4 stack results stable upon 900°C thermal treatment, indicating the feasibility for terbium scandate integration as high k dielectric in charge trap memory devices.

Evolution of Oxygen Associated Defects in Cz Silicon during Thermal Annealing Treatments: Comparison between Experiment and Simulation

High temperature annealing effects on Oxygen-induced defects formation has been studied by IR-LST, FTIR and TEM techniques. The results show that most defects are amorphous oxygen precipitates and/or dislocations. Ham’s theory has been modified in order to take into account the variations of interstitial oxygen concentration during the formation of precipitates. Comparison between experimental data and simulation shows that the specificity of annealing cycle is to combine both nucleation and growth stages. The morphology and stoechiometry of SiOx precipitates are also studied.

High temperature annealing effects on low energy iron implanted SiO 2

15 keV Fe ions were implanted into a thermally grown silica film with a fluence of 1 × 10 16 at./cm 2 resulting in a near Gaussian concentration profile peaking at 8 at.% about 15 nm under the surface. High vacuum (∼10 −7 mbar) furnace annealing and electron beam annealing at high temperature resulted in diffusion of Fe inside the oxide film. Segregation of Fe atoms at the SiO 2 surface and SiO 2/Si interface was observed in both cases. EBA resulted in faster precipitation and lower out-diffusion of Fe. In-situ Rutherford Backscattering Spectrometry was performed during high vacuum annealing and is shown to be an appropriate method to investigate the diffusion rate. The differences observed between the methods are explained by the effect of excess electrons and ionization induced by the electron beam on the oxygen-vacancy mediated displacement mechanism and on the reduction of Fe oxides.

Flatband Voltage Tuning of HfSiON-Based Gate Stacks: Impact of High Temperature Activation Annealing and LaOx Capping Layers

We have investigated high temperature annealing effects on the flatband voltage (Vfb) modulation of TiN/LaOx/HfSiON/SiON/Si gate stacks with different LaOx thicknesses. Using hard X-ray photoelectron spectroscopy with synchrotron radiation and capacitance versus voltage measurements, we show band alignments shifts of the gate stacks attributed to La diffusion into the bottom HfSiON/SiON interface and the subsequent creation of an interfacial dipole. From electrical measurements on beveled oxide capacitors, we demonstrate that the effective work function of the metal can be increased to the desired value for transistor operation, which is a key point for optimizing these advanced devices.

Thermoluminescence properties of natural zoisite mineral under γ-irradiations and high temperature annealing

Natural silicate mineral of zoisite, Ca 2Al 3(SiO 4)(Si 2O 7)O(OH), has been investigated concerning γ-radiation, UV-radiation and high temperature annealing effects on thermoluminescence (TL). X-ray diffraction (XRD) measurement confirmed zoisite structure and X-ray fluorescence (XRF) analysis revealed besides Si, Al and Ca that are the main crystal components, other oxides of Fe, Mg, Cr, Na, K, Sr, Ti, Ba and Mn which are present in more than 0.05 wt%. The TL glow curve of natural sample contains (130–150), (340–370) and (435–475) °C peaks. Their shapes indicated a possibility that they are result of composition of two or more peaks strongly superposed, a fact confirmed by deconvolution method. Once pre-annealed at 600 °C for 1 h, the shape of the glow curves change and the zoisite acquires high sensitivity. Several peaks between 100 and 400 °C appear superposed, and the high temperature peak around 435 °C cannot be seen. The ultraviolet radiation, on the other hand, produces one TL peak around 130 °C and the second one around 200 °C and no more.

Vacuum-annealing induced band bending in phosphorus-doped (111) diamond

High-temperature annealing effects on hydrogen (H)-terminated phosphorus (P)-doped diamond (111) surfaces were investigated by X-ray photoelectron spectroscopy (XPS) and reflection high energy electron diffraction (RHEED) experiments. Thermally activated, surface band bending was observed, which is clearly attributed to surface structural changes and adsorbates dynamics. The XPS results are compared between boron (B)- and P-doped diamond surfaces and an energy band model has been introduced to the P-doped diamond surface. The annealing process induces downward band bending (to a maximum of 1.3 eV) in B-doped diamond whereas it reduces the internal barrier height (by about 1 eV) in P-doped diamond and finally, the surface bands are pinned in the middle of the band gap. The depletion layer widths are calculated for both diamond surfaces. The band bending imposed by the annealing process can be effective in tuning the surface barrier height.

Characterisation of high-temperature annealing effects on α—Al2O3(0001) substrates

High temperature annealing in air has been applied as an effective ex-situ surface treatment for the α —Al2O3(0001) substrates used in molecular beam epitaxy (MBE) growth of III-nitrides. The method is based on the criterion that atomically smooth surface of terrace-and-step like structure, which is considered to be crucial in obtaining a high quality epilayer, could be produced upon high temperature annealing. The annealed surface was mostly studied by atomic force microscopy (AFM) imaging. In this work, the effects of high temperature annealing on the surface morphology, crystalline quality, optical quality and surface reconstruction behaviour of α —Al2O3(0001) substrates were fully studied using AFM, triple-axis high resolution X-ray diffraction (THRXRD), spectroscopic ellipsometry (SE) and in-situ reflection high-energy electron diffraction (RHEED). A new strategy, H2 thermal cleaning at 1100°C followed by O2 annealing at 1300°C was proposed as an efficient surface treatment for α —Al2O3(0001) substrates for MBE growth

High temperature annealing effects on chromel (Ni90Cr10) thin films and interdiffusion study for sensing applications

Metal embedded thin film thermocouples are very attractive for various applications in harsh environments. One promising technique to embed thin films micro sensors is diffusion bonding, which requires high temperatures and pressures typically in a vacuum. In this study, high temperature annealing effects on chromel (Ni90Cr10) thin film, an important sensor material as one of the components in type K thermocouple, were investigated in a diffusion bonding environment. Annealing was carried out at 800 °C for one hour in a diffusion bonder under vacuum without applying pressure. Under such conditions; surface, interface and interdiffusion phenomena were investigated using different characterization techniques including X-ray Diffraction, X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive Spectroscopy. Results indicate that the present combination of dielectrics is quite reliable and Ni90Cr10 films of 500 nm thickness can be used for applications at least up to 800 °C due to a protective thin chromium oxide layer formation on top of the sensor film during annealing.

High-pressure and high-temperature annealing effects of boron-implanted diamond

We show that high-pressure and high-temperature (HPHT) annealing of ion-implanted diamond is efficient as a doping technique. The HPHT annealing condition is located in the thermodynamically stable region for diamond. The HPHT annealing is highly effective for the recovery of damage induced by ion implantation. In the entire annealing temperature range, the HPHT annealing is more efficient than conventional thermal annealing methods such as vacuum annealing. At 1400 °C, we obtained the highest boron doping efficiency of 7.1%, which is ten times higher than that by vacuum annealing.

High-pressure and high-temperature annealing effects on CVD homoepitaxial diamond films

High-pressure and high-temperature (HPHT) annealing effects on the chemical vapor-deposited (CVD) homoepitaxial diamond films were investigated. By the HPHT annealing, the intensity of free-exciton (FE)-related emission was increased by ∼ 2 times and the luminescence bands from 270 to 320 nm, which originate from 5RL and 2BD bands, were almost completely eliminated in the cathodoluminescence (CL) spectrum. The CL intensity of band-A emission, which is related to crystal defects in diamond, was also decreased. The hole mobility at room temperature was increased from 826 to 1030 cm 2/Vs by HPHT annealing. These results suggest that HPHT annealing decreases the crystalline defects and improves the optical and electronic properties of homoepitaxial diamond films.

High temperature annealing effects on carbon spheres and their applications as anode materials in Li-ion secondary battery

Carbon spheres (CSs) have been subjected to a high temperature annealing process at 2800 °C under an Ar atmosphere. These high temperature annealed carbon spheres (HTACSs) have been characterised by SEM, HRTEM, BET surface area, XRD, Raman, SQUID and TGA techniques. The study indicates that the original spheroidal morphology of CSs have been converted to polyhedral. The graphitic flakes possessing relatively short range order of which the original are composed of appear to have coalesced into more extended graphitic layers possessing long range order. Furthermore three dimensional interplanar graphitic ordering occurs. Charge–discharge capacity measurements have been performed on both carbon materials to access the potential of these materials in Li-ion secondary battery applications. The measurements indicate that HTACSs exhibit better performance than CSs in terms of greater reversible capacity and their longer plateau in voltage profiles.

X-ray diffraction characterization of MBE grown Pr 1− xSr xMnO 3 thin films on NGO(1 1 0)

Oxygen plasma-assisted molecular beam epitaxial (MBE) growth of Pr 1− x Sr x MnO 3 (PSMO) thin films has been carried out on NdGaO 3(1 1 0) (NGO) substrates. The growth parameters have been optimized to realize 2D layer-by-layer growth. XRD results of the epilayers show that the PSMO/NGO(1 1 0) thin films are of high crystal quality, as clear diffraction peaks can be observed belonging to the film and the substrate, respectively. Based on analysis of the peaks, it was concluded that epitaxial relation is PSMO(1 1 0)//NGO(1 1 0), i.e., the c-axis being parallel to the surface. Both single scans ( ω scan, 2 θ/ ω scan) and 2-axis reciprocal space mapping (RSM) were performed in an effort to assess the crystal structure, crystalline quality, surface and interface properties of the epitaxial layers. High temperature annealing effects on lattice structure and crystal quality have been studied and discussed. Transport property measurement of the PSMO thin film samples has been carried out and main features discussed.