Fast Thermal Annealing Research Articles

Boosting phonon transport across AlN/SiC interface by fast annealing amorphous layers

The high increase in interface density has become the main bottleneck for heat dissipation in gallium nitride/aluminum nitride (AlN)/silicon carbide (SiC) based nanodevices. In this paper, the interfacial thermal conductance (ITC) of AlN/SiC interface is investigated by non-equilibrium molecular dynamics simulation. It is found that introducing amorphous layers at AlN/SiC interface will result in an enhancement of its ITC by 2.32 times. Three different amorphous layers are investigated and can be achieved by fast thermal annealing. Among them, the amorphous SiC layers work best, and the amorphous AlN layers work worst. Further spectral analysis reveals that the enhancement of ITC comes from the strengthening of interfacial inelastic phonon processes, which boosts the transport of modes at a wide frequency range. What is more, as the thickness of amorphous layers increases, the enhancement of ITC weakens. This research provides a highly operational strategy to enhance ITC and enriches our understanding of inelastic phonon process at interface.

Enhanced visible-light photocatalytic hydrogen evolution using two-dimensional carbon nitride sheets with the removal of amine groups

Two-dimensional (2D) carbon nitride sheets (CNs) with atomically thin structures are regarded as one of the most promising materials for solar energy conversion. However, due to their substantially enlarged bandgap caused by the strong quantum size effect and their incomplete polymerisation with a large number of non-condensed surface amino groups, the practical applicability of CNs in photocatalysis is limited. In this study, CNs with broad visible-light absorption were synthesised using a 5-min fast thermal annealing. The removal of uncondensed amine groups reduces the bandgap of CNs from 3.06 eV to 2.60 eV, increasing their absorption of visible light. Interestingly, the CNs were distorted after annealing, which can differentiate the spatial positions of electrons and holes, enhancing the visible-light absorption efficiency. As a result, when exposed to visible light, the photocatalytic hydrogen production activity of atomically thin 2D CNs rose by 8.38 times. This research presents a dependable and speedy method for creating highly effective visible-light photocatalysts with narrowed bandgaps and improved visible-light absorption.

Effect of Rapid Thermal Annealing Conditions on the Specific Resistance of the Ohmic Contacts of Ti/Al/Ni/Au Metallization to the GaN/AlGaN Heterostructure

Effect of rapid thermal annealing conditions on the specific resistance of the ohmic contacts of Ti/Al/Ni/Au metallization with layer thicknesses of 20/120/40/40 nm to the GaN/AlGaN heterostructure with a two-dimensional electron gas on a sapphire substrate has been discovered by transmission line measurement. Rapid thermal annealing of the samples was carried out by the contact heating from the sapphire substrate side in a nitrogen atmosphere at the temperature range from 750 to 1000 °C for 30, 60, and 90 s. It has been discovered that the dependence of the specific contact resistance on the temperature contains two temperature optimums, at which the specific contact resistance of the ohmic contact is less than 1 ⋅ 10–4 Ohm⋅ cm2. The appearance of the first temperature optimum is due to the decrease of the distance from the diffusion front of the low-resistance layer of intermetallic compounds formed during the rapid thermal annealing of the Ti/Al/Ni/Au metallization to the region of the two-dimensional electron gas. Outside the first temperature optimum, an increase in the specific contact resistance of up to 9 ⋅ 10–3 Ohm⋅ cm2 is observed, due to the absorption of the AlGaN layer by a low-resistance layer of intermetallic compounds, which leads to the degradation of the two-dimensional electron gas under the contacts and deterioration of its conductive properties. The second temperature optimum is due to the passage of the diffusion front of the two-dimensional electron gas region and the establishment of a side contact between the low-resistance intermetallic layer and the two-dimensional electron gas, which leads to the decrease in the specific contact resistance. With an increase in the fast thermal annealing time from 30 to 90 s the shift of the interval of the first temperature optimum from 800 to 775 °C for the lower boundary and from 825 to 800 °C for the upper boundary, and for the second temperature optimum from 875 to 850 °C for the lower boundary, and from 950 to 875 °C for the upper boundary is observed, which is due to an equivalent increase in the diffusion depth of the Ti/Al/Ni/Au metallization components. The results obtained can be used in the technology for creating GaN-based products with a two-dimensional electron gas.

Enhanced Photoluminescence of Hydrogenated Amorphous Silicon Carbide Thin Films by Means of a Fast Thermal Annealing Process.

In this paper, the photoluminescence (PL) of hydrogenated amorphous silicon carbide (a-Si1−xCx:H) thin films obtained by Plasma Enhancement Chemical Vapor Deposition (PECVD) is reported. Strong PL is obtained after a fast annealing process for 60 s at temperatures of 200, 400, 600, and 800 °C. The thin films are characterized using Fourier Transform Infrared spectroscopy (FTIR), PL spectroscopy, and Energy-Dispersive X-ray Spectroscopy (EDS). According to the results of the structural characterization, it is deduced that a structural rearrangement of the amorphous matrix is carried out during the fast annealing process, which results in different degrees of oxidation on the a-Si1−xCx:H films. The PL peak position shifts towards higher energies as the temperature increases. The sample deposited with a silane/methane flux ratio of 37.5 at an Radio Frequency (RF) power of 6 W experiences an increase in PL intensity of more than nine times, with a displacement in the peak position from 2.5 eV to 2.87 eV, at 800 °C. From the PL analysis, we observe two emission bands: one centered in the near infrared and other in the visible range (with a blue peak). This study opens the possibility to use such thin films in the development of optoelectronics devices, with potential for application in solar cells.

Rapid thermal annealing on the atomic layer-deposited zirconia thin film to enhance resistive switching characteristics

The resistive switching random access memory (RRAM) device has received a great interest for the next-generation non-volatile memory application, and resistive switching (RS) characteristics are mainly affected by conductive oxygen vacancies ([V··]) within switching material. Various effective approaches with materials, doping, and thermal treatments have been attempted to achieve the stable RS behaviors. Particularly, thermal annealing is considered as an efficient knob to control [V··] compared to other approaches. However, research on thermal treatment still lacks results and further research efforts are still needed to improve the RS characteristics of the devices. In this work we investigated the RS characteristics of Ti/ZrOx/Pt-structured RRAM device in comparison without and with postrapid thermal annealing (RTA) temperature range under oxygen ambient. The as-fabricated device with atomic layer-deposited ZrOx switching layer exhibited conducting characteristics, which is related to a relatively high amount of [V··] within switching medium. It indicates that moderate amount of [V··] apparently determines the appropriate RS behaviors. With this regard, we modulated the [V··] in ZrOx thin films by employing RTA in the ranges of 500 °C to 800 °C at the oxygen ambient for 60 s. Unlike device without RTA, we observed the stable RS characteristics from device with RTA and device annealed at 700 °C exhibits the excellent bipolar RS characteristics such as higher Ron/Roff, smaller cycle-to-cycle switching variation, better endurance, and longer retention among RTA conditions, indicating moderate amount of [V··] formed within ZrOx thin film layer. Moreover, increasing ALD ZrOx thickness shows the further improvement in the RS characteristics and RTA on the thicker ZrOx device still improves the RS behaviors. This research indicates that modulating [V··] by fast thermal annealing on the ALD zirconia material can provide the proper RS characteristics of the non-volatile memory applications.

One-step deposition of hydrophobic coatings on paper for printed-electronics applications

The ability to pattern highly conductive features on paper substrates is critically important for applications in radio frequency identification (RFID) tags, displays, sensors, printed electronics, and diagnostics. Ink-jet printing particle-free reactive silver inks is an additive, material efficient and versatile strategy for fabrication of highly conductive patterns; however, the intrinsic wetting properties of cellulose based papers are not suitable to serve as substrates for this process. This study reports one-step and practical modification of the surface of paper substrates using industrially available materials. The paper substrates were dip-coated with films of hydrocarbon and fluorocarbon based polymeric resins. Ink-jet printing particle-free reactive silver inks on the modified paper substrates followed by fast thermal annealing resulted in highly conductive patterns. The coatings improved the conductivity of the patterns and reduced the number of printing layers required to obtain conductivity. We finally demonstrated fabrication of a printed RFID tag on the coated paper substrates operating at the frequency range of 865–870 MHz.

Photoluminescence profiles and fast/slow annealing effects of Eu(III)/Tb(III)‐codoped silica phosphor materials

A silica (SiO2) nanoparticle matrix was codoped with luminescent Eu(III) and Tb(III) ions using a modified Stöber method. The effects of fast and slow thermal annealing on photoluminescence profile imaging were examined. Slow annealing treatment suppressed more quenching sites than fast thermal annealing to further increase the photoluminescence signals. The photoluminescence signals observed between 450 and 720 nm were assigned to the (5)D(0) → (7)F(J) (J = 0,1,2,3,4) of Eu(III) and the (5)D(4) → (7)F(J) (J = 6,5,4,3) transitions of Tb(III). Photoluminescence was largely sensitized by indirect excitation and was much stronger than that generated by direct excitation. The Eu(III) and Tb(III) ions were doped at lower symmetry sites in the silica matrix.

Efficient removal of organic ligands from supported nanocrystals by fast thermal annealing enables catalytic studies on well-defined active phases.

A simple yet efficient method to remove organic ligands from supported nanocrystals is reported for activating uniform catalysts prepared by colloidal synthesis procedures. The method relies on a fast thermal treatment in which ligands are quickly removed in air, before sintering can cause changes in the size and shape of the supported nanocrystals. A short treatment at high temperatures is found to be sufficient for activating the systems for catalytic reactions. We show that this method is widely applicable to nanostructures of different sizes, shapes, and compositions. Being rapid and effective, this procedure allows the production of monodisperse heterogeneous catalysts for studying a variety of structure-activity relationships. We show here results on methane steam reforming, where the particle size controls the CO/CO2 ratio on alumina-supported Pd, demonstrating the potential applications of the method in catalysis.

Characterization of Ultra Low-k SiOC(H) Film Deposited by Plasma-Enhanced Chemical Vapor Deposition (PECVD)

In this study, deposition of low-dielectric constant SiOC(H) films by conventional plasma-enhanced chemical vapor deposition (PECVD) were investigated through various characterization techniques. The results show that, with an increase in the plasma power density, the relative dielectric constant (k) of the deposited films decreases whereas the refractive index increases. This is mainly due to the incorporation of organic molecules with CH 3 group into the Si-O- Si cage structure. It is as confirmed by FT-IR measurements in which the absorption peak at 1,129 cm -1 corresponding to Si-O-Si cage structure increases with power plasma density. Electrical characterization reveals that even after fast thermal annealing process, the leakage current density of the deposited films is in the order of 10 -11 A/cm at 1.5 MV/ cm. The reliability of the SiOC(H) film is also further characterized by using BTS test.

Growth of buried silicon nitride layers induced by fast thermal annealing of N 2+ -implanted silicon substrates

p-type Si(100) wafers have been implanted at room temperature with 170 keV N 2 + ions with doses ranging between 10 17 and 10 18 cm −2. Samples were subsequently annealed at 1200 °C using a rapid thermal processing system for about 40 s. Samples were characterized before and after implantation by Rutherford backscattering spectroscopy, by transmission electron microscopy, by X-ray diffraction at glancing incidence and by Auger electron spectroscopy. These experiments give evidence of β-Si 3N 4 formation. The influence of the irradiation dose is discussed and a comparison with classical annealing is made.

Recrystallization Kinetics During Fast Thermal Annealing of Pfn+ Implanted Silicon+

ABSTRACTThe damage recovery and electrical activation of PFn+ (1 ≤n ⩽,5) implanted silicon layers during fast thermal annealing has been investigated. The <100> oriented wafers were implanted by glow discharge with 30 keV PFn+ ions at a dose of 2.5–3.1015 ions/cm2 and subsequently annealed using incoherent light pulses in the temperature range 600–1100°C with irradiation times of 1–15 secs.Our results show that the maximum electrical activity is obtained by about 750°C, 15 sec and the same activity is reached for shorter annealing times and higher temperatures (typically 820°/ 5 sec; 950°C / 1 sec). These values and Rutherford Backscattering analysis reveal that the velocity of regrowth of the PFn+-implantation amorphized layer is lower than in the case of P+ implantation and that the former requires a higher activation energync≃3.4 eV.TEM analysis reveals precipitates in 820°C/4 s annealed samples with the appearance of dislocation loops at 980°C/4 s annealing. Finally two characterizable defect levels (ETT = EV + 180 meV, ET2 = EV + 542 meV) are seen to remain in the PFn+ implanted samples examined by DLTS, even after annealing at 1100°C.

Rapic Thermal Annealing of W-TI Bilayers on Silicon

ABSTRACTW-Ti bilayers on Si have been processed by fast thermal annealing in air, in N2/H2 (5%), and vacuum (1 E-3 and 1 E-6 Torr). The results indicate that the W layer on top of Ti acts as an effective protection barrier against oxidation of Ti in all atmospheres except air. Titanium-rich silicides are formed after 500 °C, while TiSi2 is completed at about 600 °C. At 700 °C a bilayer of WSi2/TiSi2 is found. Silicon is found to be the diffusing specie during the formation of WSi2. Finally, a ternary silicide, Ti0.6W0.4Si2, starts to form after 780 °C. The final ternary silicide phase has'an Mlectrical resistivity of about 60 μΩ-cm.

Associated processes to the szilard-chalmers effect in crystals—I Hexammino-cobaltic nitrate. Section 2. Thermal annealing of the crystalline defects after irradiation

The thermal annealing of neutron irradiated {Co(NH 3) 6}(NO 3) 3 was investigated to determine the order of the fast annealing processes, the activation energy, the fraction annealing as a function of the temperature and the effect of the history of the sample on the annealing process. It was observed that the fast thermal annealing process formally obeys first-order kinetics. Strictly the kinetics may be explained by processes distributed in activation energy. The maximum of the activation energy spectrum is about 0·78 eV. The fraction destined to anneal is proportional to the temperature, but the saturation value of the retention for different samples heated at the same temperature, is not the same. It was observed that the radiation history of the sample has a great influence on the annealing process and a quantitative treatment of the effects is determined.