Aluminum Nitride Research Articles

Improvement of AlGaN/ GaN based HEMT with high performance rate for integrated circuit design for wide range of applications

In the current research work, we focused on the design and analysis of a semiconductor device called High-Elec-tron-Mobility Transistor (HEMT) based on the AlGaN/GaN material system. An Aluminum Nitride spacer,Layer of Nucle-ation along with cap as a AlGaN and barrier of GaN with the channel of AlGaN are incorporated to enhance HEMT device performance.The electrical characteristics of the proposed HEMT are an-alyzed. The Drain Current is found to be 0.18A/mm, indicating the device's ability to handle high current levels. The Electron Concentration is observed to have a maximum value of -96.12electrons/cm3 and varying based on the position in the channel for GaN Barrier thickness is 0.15mm. In the analysis of AC such as Gain of the Maximum Unilateral Power is deter-mined to be 83.41dB, indicating the ability of the device to am-plify signals. The Y-parameters, which characterize the de-vice's behavior at various frequencies of operation, are also de-termined. The capacitance between the electrode region Gate-Source (CGSMIN) is found to be 1.70×10^-11 F/mm, and alike The Capacitance between the electrode region the Gate-Drain Ca-pacitance (CGDMIN) is determined to be 4.7×10^-12 F/mm. Fur-thermore, an Electric Field of 96.51×10^3 V/mm is observed, in-dicating the strength of the electric field across the device. For HEMT device the simulation,The TCAD Silvaco software is be-ing practiced.

In-situ preparation of porous metal-ceramic composite from secondary aluminum dross and red mud for adsorption of organic pollutant

Secondary aluminum dross (SAD) and red mud (RM) are solid waste discharged from aluminum industry. SAD contains 10–25 wt% aluminum nitride (AlN) and RM contains 20–50 wt% iron oxide. In this work, porous metal-ceramic composite was in-situ made from SAD and RM. Iron oxide was reduced into Fe2Si by AlN, and the generated nitrogen created pores. It was studied that effect of raw material and thermal treatment on pore structure and properties of the composite. Porosity, bulk density and compressive strength of composite were 65.78%, 1.03 g/cm3 and 17.77 MPa, when SAD content was 40 wt% and sintering temperature was 1450 °C. About 95.9% of malachite green in waste water was adsorbed by composite after 24 h. The composite could be recycled by magnetic separation after adsorption, attributed to the magnetic Fe2Si. This work proposed a novel idea of making recyclable porous material for adsorption of organics in waste water.

Impact of Nb and Al content in arc evaporation targets on Ti1−x−yAlxNbyN coating properties

Titanium-based physical vapor deposition (PVD) coatings, such as titanium nitride (TiN) and titanium niobium nitride (TiNbN), are common solutions for surface modifications in medical applications. Ex vivo studies of retrieved knee implants indicate the demand for increased scratch and abrasion resistance of PVD coatings in clinical applications. Based on the promising mechanical performance of titanium aluminum nitride (TiAlN) as a coating for tools, the aim of this study was to evaluate the impact of the chemical composition of titanium-based nitride coatings with aluminum (Al) and niobium (Nb). Nine titanium aluminum niobium nitride (Ti1−x−yAlxNbyN) coatings with 0.4 ≤ x < 0.7 and 0 ≤ y ≤ 0.18, as well as commercial TiN and TiNbN, were coated in an industrial scale arc PVD process, following a randomized, multifactorial response surface design. The deposition rate, the scratch resistance, and the hardness were measured following standardized protocols. The microstructure of the coating was analyzed by SEM and XRD. In addition, the surface roughness was determined by laser scanning microscopy. A quadratic regression was performed to determine the impact of the chemical composition on coating properties. Experimental results and regression analyses revealed the significant impact of the chemical composition of Ti1−x−yAlxNbyN on the coating microstructure, mechanics, and morphology. Scratch resistance for initial crack formation and cohesive failure could be increased decisively, compared to TiN.

Drop-on-demand metal jetting of pure copper: On the interaction of molten metal with ceramic and metallic substrates

Copper, renowned for its exceptional electrical and thermal conductivity at a low cost, holds great promise in electronic applications. While additive manufacturing of copper has attracted interest, the exploration of applying Drop-on-demand Metal Jetting (DoD-MJ) to 3D print pure copper remains uncharted. To fill this research gap, we employed an in-house DoD-MJ platform, MetalJet, to generate Cu microdroplets and deposit them onto ceramic and metallic substrates, a first-time achievement in this research context. Our study demonstrates the successful generation of uniform Cu microdroplets, emphasising the pivotal role of oxygen content control in preventing nozzle-level reactions, a factor that can disrupt droplet formation. Both alumina and aluminium nitride substrates exhibited poor wettability with molten Cu droplets, and no interface formed between these surfaces due to thermodynamically unfavourable reactions. Nevertheless, the irregular surface of alumina displayed an interesting capability to enable the adhesion of Cu droplets to the substrate through an interlocking mechanism. Lastly, the electrical resistivity of MetalJet printed pillars was measured as low as 6.75×10-8Ωm without any post-treatment, offering exciting possibilities for applications in 3D electronics.

Induced porous structure with a slight change in mechanical properties of hydroxyapatite-based nanocomposites synthesized from waste bovine bone and their bioactivity

Porous hydroxyapatite (HAp) ceramics have been widely used in several biomedical applications. However, efforts to enhance the porous structure in HAp ceramics often lead to a decline in their mechanical properties. In the present study, by adding a small amount of aluminum nitride (AlN) nanoparticles to HAp ceramics, we achieved the formation of porous HAp with a slight change in grain size and mechanical properties. The starting powder of the HAp was obtained from a natural source of bovine bone. The HAp/xAlN nanocomposites were fabricated by a simple conventional technique. The 0.06 mol% AlN-added sample (HAp/0.06AlN) presented the maximum mechanical properties (Vickers hardness = 3.68 GPa, elastic modulus = 94.04 GPa, and fracture toughness = 0.97 MPa∙m1/2) with favorable porosity. Simulated body fluid and cell viability assays showed that all the studied nanocomposites possessed desirable bioactivity with high cell viability. The HAp/0.06AlN samples were coated with antimicrobial agents. The samples coated with silver nitrate (AgNO3) had high antibacterial efficiency against S. aureus (66.2%) and P.aeruginosa (67.3%). Based on the obtained results, the nanocomposites exhibited promising potential for development and utilization in biomedical applications.

The effect of hybrid thermal fillers on thermal conductivity of carbon fiber reinforced polybutylene terephthalate composites

AbstractThe use of functional polymeric composites with superior thermal properties, capable of replacing conventional polymers, has increased in recent years, particularly in the electrical‐electronics sector where thermal management is crucial. Carbon fiber (CF) polymer–matrix structural composites have relatively high in‐plane thermal conductivity but low through‐plane conductivity. In order to further enhance the through‐plane and in‐plane conductivity of CF‐reinforced polybutylene terephthalate (PBT) composite, a hybrid loading approach was employed, incorporating synthetic graphite (SG), boron nitride (hBN), aluminium nitride (AlN) and graphene (G) in composite formulations. It was found that the in‐plane conductivity of PBT‐20CF‐20SG‐3G and the through‐plane conductivity of PBT‐20CF‐20SG‐3AlN are 69% and 25% higher, respectively, than those of PBT‐40CF. However, the mechanical properties of hybrid composites exhibit lower values compared to those of CF‐reinforced PBT composites. The tensile strength value of PBT‐40CF is about 33% and 57% higher than those of PBT‐20CF‐20SG‐3G and PBT‐20CF‐20SG‐3AlN. Moreover, the flexural strength of PBT‐40CF is about 48% and 38% higher than those of PBT‐20CF‐20SG‐3G and PBT‐20CF‐20SG‐3AlN, respectively. The density value of PBT‐40CF is lower than that of the composites of PBT‐20CF‐20SG. From TGA it was observed that the thermal stability of PBT‐40CF is comparable to that of the composites PBT‐20CF‐20SG. From the conducted study, it can be proposed that the hybrid combination of SG, hBN, AlN and G can be utilized to achieve higher thermal conductivity values, instead of relying solely on CF in the composites. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Enhancing heat dissipation in polyurethane sheets through the incorporation of freeze‐dried aluminum nitride nanofiber

AbstractInspired by a three‐dimensional (3D) structure, we demonstrate 3D aluminum nitride (AlN) nanofibers fabricated by a freeze‐drying technique using polyvinyl alcohol (PVA)/boehmite precursor nanofibers. After applying hot pressing, a series of PVA/boehmite precursor nanofibers were prepared with varying PVA‐to‐boehmite ratios (30/70 wt%, 50/50 wt%, and 70/30 wt%). Our findings reveal that the thermal conductivity of the AlN composite nanofibers is significantly affected by the relative proportions of PVA and boehmite, where the ratio of PVA should be more significant than that of boehmite. We produced AlN nanofibers at a lower temperature (1500°C) than the theoretical formation temperature of AlN (1664°C). The minimum specific surface area and pore volumes were 8.39 m2/g and 0.0166 cm3/g, respectively, at 1500°C. X‐ray photoelectron spectroscopy spectra measured 38.27% aluminum and 23.55% nitrogen in AlN nanofibers. The aligned AlN nanofibers mat was impregnated with polyurethane (PU), which showed good thermal conductivity in the planar (4.1–13.6 W/(m·K)) and thickness (1.5–4.9 W/(m·K)) directions at 18–56 vol% AlN nanofibers content. The heat‐dissipating sheet also showed superior electrical insulating (1.2 × 1012 Ω/cm2) properties. In this study, the author sought to develop a heat‐spreading material made of thermally conductive, but electrically insulating PU/AlN nanofibers that could efficiently dissipate heat from electric devices.

Effect of yttrium nitrate coating on the vat photopolymerization forming process and sintering properties of aluminum nitride ceramics

In this study, a ball-milling method was successfully used to coat yttrium nitrate on the surface of aluminum nitride (AlN) powder and the effects of yttrium nitrate content on the AlN powder particle size, viscosity and curing behavior of the AlN suspension, and performance and microstructure of the sintered AlN bodies were investigated. The results indicated that the AlN powder surface coating significantly reduced the viscosity of the suspension and enhanced the cure depth while increasing the powder particle size, which in turn reduced the stability of the suspension. By studying the performance of sintered bodies, it was found that as the yttrium nitrate content increased, the AlN thermal conductivity and flexural strength initially increased and then decreased. Microstructural analysis results revealed that the second phase in samples with 9.23 and 14.49 wt% yttrium nitrate exhibited an island-like distribution, whereas in samples with 19.18 wt% yttrium nitrate, the second phase exhibited a continuous distribution. Finally, the heat-dissipation performance of AlN components with different structures was also studied, and testing was conducted on the driving chip of a 3D printing device. The results indicated that complex-structured AlN ceramic components exhibited an excellent heat-dissipation performance.

In-situ preparation of alumina-based cermet after reduction of iron oxide in red mud with aluminum dross

Aluminum dross (AD) and red mud (RM) are waste discharged from aluminum industry. AD and RM contain 5-15 wt% of hazardous aluminum nitride (AlN) and 20–50 wt% of iron oxide, respectively. In this work, alumina-based cermet was in-situ prepared from AD and RM, after reduction of iron oxide with AlN by pyrometallurgy. Cermet was consisted of metal reinforcement phase about 1 μm, alumina matrix phase and low-melting aluminosilicate binder. Mechanism of in-situ preparation was studied after exploring phase composition of the cermet powder. Iron, silicon and titanium oxide from RM was reduced into Fe3Si and TiN, which acted metal reinforcement phase in cermet. Reaction was consisted of two steps, Fe2O3, TiO2 and AlN dissolving into low-melting aluminosilicate and electron transferring from AlN to Fe2O3, SiO2 and TiO2. Content of Fe in ceramic phase was decreased from 6 at.% to 1 at.% after reduction reaction. Low-melting aluminosilicate acted both reaction solvent for reduction reaction, and binder for metal reinforcement phase and alumina matrix phase. More low-melting aluminosilicate was formed when temperature was increased from 1200 °C to 1400 °C, which made more metal balls be formed. The metal ball and alumina were bonded by low-melting aluminosilicate, which increased the bond strength between reinforcement phase and ceramic phase in cermet. This work achieved a total recycle of AD and RM into cermet. It was proposed a novel idea of in-situ preparing cermet, which was generating metal reinforcement phase in ceramic matrix phase.

Room-temperature, RF-activated, quantum effects via engineered defect sites in thin-film AlN, Al2O3, and SnOx

The behavior of a sine wave propagated through thin films of aluminum nitride (AlN), aluminum oxide (Al2O3), and tin oxide (SnOx) with engineered buried defect sites may suggest quantum excitation and defect-mediated waveform modulations. Two distinct methods to induce these buried defects, etch pattern defects (EPD) and indentation pattern defects (IPD), were employed to detect these interactions. All the experiments were conducted at room temperature (21 °C) over a frequency range between 5 and 1000 kHz. In addition, EPD and IPD devices were composed of AlN, Al2O3, and SnOx. An inverse relationship between excitation frequency and voltage is observed for all devices. All these devices exhibited a relaxation time ranging between 0.2 and 0.75 µs. Devices without these engineered defect sites preserve the waveform integrity, emphasizing the impact of the buried defect sites. This research focuses on the relationship between defect type, excitation frequency, and voltage to understand the deeper mechanisms at play in these quantum defect-driven wave alterations in AlN, Al2O3, and SnOx thin films.

High-temperature synthesis of cast vanadium nitrides and aluminum oxynitrides

This paper presents experimental results concerning the one-step preparation of cast divanadium nitride and aluminum oxynitride (AlON) by high-temperature synthesis under 5 MPa of N2 from green mixtures containing vanadium oxide, aluminum, and aluminum nitride. It was shown that the mixtures with a wide range of component ratios are capable to burn with the temperature exceeding the melting point of the final products, divanadium nitride and aluminum oxynitride, that makes it possible to obtain them in the form of a melt with subsequent separation of vanadium nitride (lower ingot) and aluminum oxynitride (upper ingot). The resulting products had no cohesion and were easily separated from each other. Variation in the content of aluminum nitride in the charge markedly affected the synthesis process, phase composition, and microstructure of the target products. The content of excess aluminum nitride in the starting mixture α = 10% was found to be optimum on a yield/composition of the target products.

Synthesis of Nano-aluminum Nitride powder at low temperature by Sol-gel method

In this paper, molecular-level mixed aluminum nitride has been prepared from aluminum sec-butyl alcohol, glucose, and urea by sol-gel processing. Then, the nano-aluminum nitride powder with uniform particle size distribution was obtained by carbothermal reduction nitridation reaction. The effects of different feed ratios, reaction temperatures, and holding times on the phase of AlN powder were systematically studied. The prepared nano-aluminum nitride powder has a uniform particle size and a near-spherical shape, and its grain size is approximately 20~30 nm. The preparation temperature in this method was significantly reduced from the same preparation method of aluminum nitride powder.

High damping, soft and reprocessable thermal interface materials inspired by the microstructure of skin tissue

Thermal interface materials (TIMs) play a critical role in heat dissipation of modern electronics with their development towards integration and miniaturization. Shock-induced vibration damage is another extremely harmful to electronics, which requires TIMs remarkable damping properties, reprocessability, softness, and high thermal conductivity. However, current TIMs still lack the ability to dampen vibrations and reprocessability, because integrating these properties into one TIM still remains a dilemma. Inspired by the synergistic effects of fiber networks and adipocytes in skin tissue, here, we report on a high damping, soft and reprocessable TIM, by infusing viscous polymer into polybutadiene bottlebrush polymer network meanwhile combing with aluminum nitride filler. The obtained TIMs show damping factor as high as 0.95–1.0 in the frequency range of daily life (1–300 Hz), excellent reprocessability efficiency (92 %), low Young's modulus (55.8 kPa) and thermal conductivity of 2.25 W m−1 K−1. Analyzing the polymer structure and chain dynamics by rheology, broadband dielectric spectroscopy, solid state nuclear magnetic resonance, and FTIR spectroscopy, we confirm that these excellent properties is attributed to the enhanced migration ability of polymer chains, thermally conductive aluminum nitride fillers, and hierarchical hydrogen bonds in the bottlebrush polymer network. We further demonstrate the potential application of the TIMs in heat dissipation of an electronic device under vibrations. The current work provides a unique structure design approach towards high-performance TIMs in shock-resistant electronics.

Structural and Optical Properties of Aluminium Nitride Thin Films Fabricated Using Pulsed Laser Deposition and DC Magnetron Sputtering on Various Substrates

Abstract Aluminium nitride thin films were fabricated using pulsed laser deposition and DC magnetron sputtering. Different technological parameters and the effects of different substrates on the optical and structural parameters of AlN samples were studied. An X-ray diffraction study was performed for the layer deposited on the Si3N4 substrate. A high-energy electron diffraction study was also carried out for the layer deposited on a KCl substrate. Transmission spectra of layers on quartz, sapphire, and glass substrates were obtained. An evaluation of the optical band gap of the obtained layers was carried out (Eg form 3.81 to 5.81 eV) and the refractive index was calculated (2.58). The relative density of the film (N1TN-AlN sample) is 1.26 and was calculated using the Lorentz-Lorentz relationship. Layers of aluminium nitride show an amorphous character with a polycrystalline region. It was shown that the properties of AlN films strongly depend on the method, growth conditions, and substrate used.

A Novel Nondestructive Testing Probe Using AlN-Based Piezoelectric Micromachined Ultrasonic Transducers (PMUTs).

Ultrasonic nondestructive testing (NDT) usually utilizes conventional bulk piezoelectric transducers as transceivers. However, the complicated preparation and assembly process of bulk piezoelectric ceramics limits the development of NDT probes toward miniaturization and high frequency. In this paper, a 4.4 mm × 4.4 mm aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT) array is designed, fabricated, characterized, and packaged for ultrasonic pulse-echo NDT of solids for the first time. The PMUT array is prepared based on the cavity silicon-on-insulator (CSOI) process and packaged using polyurethane (PU) material with acoustic properties similar to water. The fabricated PMUT array resonates at 2.183 MHz in air and at around 1.25 MHz after PU encapsulation. The bandwidth of the packaged PMUT receiver (244 kHz) is wider than that of a bulk piezoelectric transducer (179 kHz), which is good for axis resolution improvement. In this work, a hybrid ultrasonic NDT probe is designed using two packaged PMUT receivers and one 1.25 MHz bulk transmitter. The bulk transmitter radiates an ultrasonic wave into the sample, and the defect echo is received by two PMUT receivers. The 2D position of the defect could be figured out by time-of-flight (TOF) difference, and a 30 mm × 65 mm detection area is acquired. This work demonstrates the feasibility of applying AlN PMUTs to ultrasonic NDT of solids and paves the way toward a miniaturized NDT probe using AlN PMUT technology.

Corrosion resistance and conductivity behavior of Cr-Al-N MAX phase coatings prepared by magnetron sputtering technology

Chromium aluminum nitride (CrAlN) coatings containing Cr2AlN phase were prepared by unbalanced magnetron sputtering followed by annealing at 1000 °C. The crystal structures, X-ray diffraction patterns, and selected area electron diffraction patterns of the Cr2AlN phase were modeled using computer software and compared with experimental observations. A good agreement was found between the two sets of results, thereby confirming the presence of Cr2AlN phase in the coatings. While previous studies have demonstrated the formation of Cr2AlN phase theoretically, this study presents experimental evidence of its physical existence. The potentiodynamic polarization results and interfacial contact resistance measurements show that the CrAlN coating with Cr2AlN phase has excellent corrosion resistance (a corrosion current density of 5.35 × 10−7 A/cm2 and electrical conductivity of 5.5 mΩ·cm2) and is thus a promising candidate for the protection of fuel cell bipolar plates.

Machine-learned atomic cluster expansion potentials for fast and quantum-accurate thermal simulations of wurtzite AlN

Thermal transport in wurtzite aluminum nitride (w-AlN) significantly affects the performance and reliability of corresponding electronic devices, particularly when lattice strains inevitably impact the thermal properties of w-AlN in practical applications. To accurately model the thermal properties of w-AlN with high efficiency, we develop a machine learning interatomic potential based on the atomic cluster expansion (ACE) framework. The predictive power of the ACE potential against density functional theory (DFT) is demonstrated across a broad range of properties of w-AlN, including ground-state lattice parameters, specific heat capacity, coefficients of thermal expansion, bulk modulus, and harmonic phonon dispersions. Validation of lattice thermal conductivity is further carried out by comparing the ACE-predicted values to the DFT calculations and experiments, exhibiting the overall capability of our ACE potential in sufficiently describing anharmonic phonon interactions. As a practical application, we perform a lattice dynamics analysis using the potential to unravel the effects of biaxial strains on thermal conductivity and phonon properties of w-AlN, which is identified as a significant tuning factor for near-junction thermal design of w-AlN-based electronics.

Stabilizing LiNi0.8Co0.1Mn0.1O2 cathode by combined moisture and HF digestion/adsorption for high-performance lithium metal batteries

Nickel-rich layered oxide cathodes such as LiNi0.8Co0.1Mn0.1O2 are promising to significantly increase the energy density of lithium metal batteries beyond 350 Wh kg−1. However, serious issues regarding cycle stability still remain when matching with conventional non-aqueous carbonate electrolytes that contain fluorine such as lithium hexafluorophosphate (LiPF6). Hydrolysis of LiPF6 generates corrosive hydrofluoric acid (HF), which destroys the cathode structure and accelerates the cathodic dissolution/anodic deposition of transition metal (TM) ions. Here, we demonstrate that ball milling NCM811 with carbon-coated aluminum nitride (AlN-C) remarkably enhances the capacity retention. AlN-C acts both as a scavenger and as an adsorption center to digest and adsorb H2O and HF, respectively. Thereby, it prevents the dissolution of TM ions, which would result in capacity decay and damage to the lithium metal anode. It is demonstrated that the addition of AlN-C via wet ball milling with NCM811 enables retaining a specific capacity of 149.9 mA h g−1 after 250 cycles (capacity retention: 85.2 %) at 1 C even in a high moisture electrolyte containing ∼0.2 % (v/v) H2O. Therefore, this work shows up a pathway to a rational enhancement of the capacity retention and cycle life of nickel-rich cathodes.

Strong green up-conversion luminescence and optical thermometry of Ho3+/Yb3+ Co-doped AlN submicron towers

Rare-earth (RE) doped aluminum nitride (AlN) holds great promise for integrated optoelectronic devices. Here, the Ho and Yb co-doped AlN (AlN:Ho3+/Yb3+) submicron towers were prepared by a direct nitridation route. XRD, Raman, XPS and EDS studies showed successful doping of Ho and Yb ions into AlN. SEM images show that the submicron towers have an interesting layered structure by layer-by-layer stacking of hexagonal AlN nanosheets. Under excitation at 980 nm, AlN:Ho3+/Yb3+ submicron towers exhibit up-conversion (UC) luminescence at 540, 550, 659, and 762 nm, which are due to Ho3+/Yb3+ system from 5F4, 5S2→5I8, 5F5→5I8, and 5F4, 5S2→5I7 respectively. Based on the intensity ratio and decay lifetime of UC luminescence, the optical temperature sensing characteristics are investigated from 298 K to 548 K. The maximum relative sensitivities associated with the intensity ratio of I540, 550 and I659 and decay lifetime of 659 nm are as high as 2.73% K−1 and 0.43% K−1, respectively. This work broadens the optoelectronic properties of RE doped AlN.

Fabrication of a wider bandgap θ-Al2O3 by oxidation of ultrathin AlN films for leakage current reduction

Aluminum oxide (Al2O3) films were fabricated through the oxidation of ultrathin aluminum nitride (AlN) films. The fabricated films exhibited a leakage current reduction compared to that of conventional Al2O3 films fabricated using atomic layer deposition. This reduction in the leakage current can be attributed to the formation of θ-Al2O3, which has a wider-bandgap than γ-Al2O3. The formation of θ-Al2O3 was attributed to the residual stress caused by the oxidation of the AlN thin films.