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Preparation of high-quality stress-free (001) aluminum nitride thin film using a dual Kaufman ion-beam source setup
摘要： We proposed and demonstrated a preparation method of (001) preferentially oriented stress-free AlN piezoelectric thin films. The AlN thin films were deposited by a reactive sputtering technique at substrate temperatures up to 330 °C using a dual Kaufman ion-beam source setup. We deposited the AlN on Si (100), Si (111), amorphous SiO2, and a (001) preferentially oriented Ti thin film and compared their crystallographic, optical, and piezoelectric properties. The AlN thin films deposited on the (001) preferentially oriented Ti thin films have the highest crystallographic quality. The stress-free AlN reached a high value of the piezoelectric coefficient d33 = (7.33 ± 0.08) pC·N?1. The properties of the AlN thin film prepared at such low temperatures are suitable for numerous microelectromechanical systems, piezoelectric sensors, and actuators monolithically integrated with complementary metal-oxide-semiconductor signal-processing circuits.
关键词： Ellipsometry,Aluminum nitride thin film,Optical properties,d33 piezoelectric coefficient,Kaufman ion-beam source,Ion-beam sputtering deposition,(001) preferential orientation,X-ray diffraction
更新于2025-09-23 15:23:52
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Optimal target sputtering mode for aluminum nitride thin film deposition by high power pulsed magnetron sputtering
摘要： Low surface roughness, low residual stress, and (002) textured aluminum nitride (AlN) thin films are favored for applications in microelectronic and optoelectronic devices. In this paper, AlN thin films were deposited by reactive high power pulsed magnetron sputtering (HPPMS). The effect of aluminum target sputtering mode and sputtering power on thin film residual stress, crystalline structure, surface roughness, and morphology of AlN thin films was studied. The results indicate that, with Al target sputtering mode transfer from metallic mode to transitional and compound modes, respectively, the number of Al species decrease, and ion-to-neutral ratio of Al species increase. Comparing the AlN thin film deposited in compound mode with that deposited in transitional mode, the latter exhibited lower surface roughness and residual stress. In addition, AlN thin film with (002) texture and lower residual stress is obtained by increasing sputtering power in transitional mode. For fabricating AlN film via reactive HPPMS with a particular (002) texture, low surface roughness, and residual stress, sputtering the target in the transitional mode with high sputtering power is optimal.
关键词： Aluminum nitride,Microstructure,Texture,High power pulsed magnetron sputtering,Sputtering modes,Sputtering power
更新于2025-09-23 15:23:52
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Performance analysis of slot waveguide using aluminum nitride in slot region
摘要： The major obstacle to accomplish an efficient photonic slot waveguide is its comparatively high propagation loss. In the current work, the silicon-on-insulator based slot waveguide with ultra-low propagation loss has been presented using aluminum nitride (AlN) in the slot region. The performance analysis of the slot waveguide has been done by varying the slot gaps from 20 to 240 nm and by varying the arm width from 160 to 340 nm. As compared with the recently reported works based on different slot waveguides, relatively smaller propagation loss of ~ 0.7 dB/cm has been predicted using the AlN based slot waveguide having a slot gap of 120 nm and arm width of 240 nm. Simulation results have demonstrated that the presence of AlN in the slot gap/low-index region, sandwiched between two high-index (silicon) regions, causes the discontinuity of the electric field of quasi-TE mode between the high-index regions. This results in high confinement of light with the smaller propagation loss in the slot region. Along with this, it has also been observed that the presented slot waveguide has the appreciably good propagation length, with low dispersion characteristics. Hence, this kind of analysis can be extended to realize the various optical devices/applications, such as for coupling, sensing, switching, etc.
关键词： Propagation loss,Aluminum nitride,Slot waveguide,Effective refractive index (ERI),Dispersion
更新于2025-09-23 15:21:01
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Young’s modulus and fatigue investigation of aluminum nitride films deposited on 304 stainless steel foils using micro-fabricated cantilevers
摘要： Aluminum nitride based (AlN-based) piezoelectric vibration energy harvesters (PVEHs) have been received much attention in the power generation for the device in microelectromechanical systems (MEMS). During the long-time vibration, PVEHs are suffering cyclically dynamic stress. This may result in the defect of the materials, and finally cause the failure of the device. To achieve a reliable design of the device that can work for a long time without failure, the investigation on the mechanical properties of Young’s modulus and fatigue were conducted for AlN films deposited on 304 stainless steel (SUS 304) foils in this study. Two kinds of materials were tested, SUS 304 foils with a thickness of 50 μm (SUS 304 (50 μm)) and a composite material of AlN films deposited on both sides of SUS 304 foils (AlN (1 μm)/ SUS 304 (50 μm)/ AlN (1 μm) structure). The samples were micro-fabricated to cantilevers. Young’s modulus was measured by the micro-cantilever resonance method. The resonant bending fatigue testing method was used to investigate the fatigue properties of the materials. The displacement amplitude of the samples was recorded during the tests. A new criterion by using the change of amplitude versus number of cycles was proposed to define the fatigue life. As results, the Young’s modulus was 184.9 and 342.9 MPa, for SUS 304 foil and AlN film, respectively. Stress-cycle (S-N) curves were plotted by using the proposed criterion successfully. The fatigue strength of SUS 304 foils and the material with AlN/ SUS 304/ AlN structure was estimated to be 294 and 327 MPa, respectively. Fatigue failures of stable crack, intrusions and extrusions, and slip bands, appeared on the surface of SUS 304 foils after the long time vibration. No fatigue failure or surface defect was observed on AlN films.
关键词： 304 stainless steel foil,aluminum nitride film,Young’s modulus,fatigue,micro-fabricated cantilever
更新于2025-09-23 15:21:01
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Fabrication of AlN/GaN MSM photodetector with platinum as schottky contacts
摘要： The epitaxial aluminium nitride (AlN) layer was fabricated on a silicon (111) substrate by solid phase radio frequency (RF) MBE The samples morphological characteristic was successfully studied by ?eld emission SEM. Low photo-response of the hetero-structure layers is one of the main obstacles in order to fabricate a high performance of photodetector device. The platinum contacts on AlN/GaN metal-semiconductor-metal (MSM) photodetector were formed by RF sputtering machine. The conductivity behaviours, Schottky barrier height (SBH), photo-responses of the device were examined by source meter measurement. The SBH values of photo-device sensing were calculated as 0.488 eV and 0.479 eV for dark current and photo current, respectively. Good response times of the device were recorded as 21.48 ms and 12.69 ms for the bias voltage of 1 volt.
关键词： AlN,photodetector,aluminum nitride
更新于2025-09-23 15:19:57
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An investigation of aluminum nitride thin films patterned by femtosecond laser
摘要： In this study, a femtosecond laser etching method is proposed to pattern an aluminum nitride (AlN) ?lm, grown by metal-organic chemical vapor deposition on sapphire. Via control of typical pulse energies, the designed pattern was precisely written in the AlN ?lm. The morphology of the patterned structures was characterized using a three-dimensional laser scanning confocal microscope and a scanning electron microscope; crystalline quality and ?lm strain were analyzed using a Raman spectrometer and a transmission electron microscope. The results indicate that consistent morphologies were achieved with only slight changes to the crystalline quality. The tensile stress of the AlN ?lm was released, and the ?lm surface was slightly compressed after laser patterning. Thus, femtosecond etching has the potential to be an in situ patterning method during ?lm growth.
关键词： film strain,patterning,crystalline quality,femtosecond laser,aluminum nitride,thin films
更新于2025-09-23 15:19:57
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Two-Stage Plasma-Thermal Nitridation Processes for the Production of Aluminum Nitride Powders from Aluminum Powders
摘要： The synthesis of aluminum nitride (AlN) powders is traditionally done via the thermal nitridation process, in which the reaction temperature reaches as high as 960 ?C, with more than several hours of reaction time. Moreover, the occurrence of agglomeration in melting Al particles results in poor AlN quality and a low ef?ciency of nitridation. In this study, an atmosphere-pressure microwave-plasma preceded the pre-synthesis process. This process operates at 550 ?C for 2–10 min with the addition of NH4Cl (Al: NH4Cl = 1:1) for generating a hard AlN shell to avoid the ?ow and aggregation of the melting Al metals. Then, the mass production of AlN powders by the thermal nitridation process can be carried out by rapidly elevating the reaction temperature (heating rate of 15 ?C/min) until 1050 ?C is reached. X-Ray Diffractometer (XRD) crystal analysis shows that without the peak, Al metals can be observed by synthesizing AlN via plasma nitridation (at 550 ?C for 2 min, Al: NH4Cl = 1:1), followed by thermal nitridation (at 950 ?C for 1 h). Moreover, SEM images show that well-dispersed AlN powders without agglomeration were produced. Additionally, the particle size of the produced AlN powder (usually < 1 μm) tends to be reduced from 2–5 μm (Al powders), resulting in a more ef?cient synthesizing process (lower reaction temperature, shorter reaction time) for mass production.
关键词： agglomeration,aluminum nitride,thermal nitridation,plasma nitridation,pre-synthesis
更新于2025-09-19 17:15:36
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Stray light autocorrelation for the measurement of ultrashort laser pulses
摘要： Ultrashort laser pulses in the femtosecond range are of growing interest in medicine and micro material processing for industrial applications. The most interesting parameter is the pulse duration, which can only be measured by optical autocorrelation methods incorporating an optically nonlinear medium. Established methods mostly use monocrystalline beta barium borate (BBO) in transmission, exhibiting a high nonlinear conversion efficiency. However, this material is brittle, expensive and sophisticated in adjustment due to the necessary non-collinear phase matching. Since fiber-based high energy femtosecond laser systems become more and more achievable, the conversion efficiency of the nonlinear medium should no longer be seen as the restricting factor. Therefore, this research work discusses the suitability of several nonlinear media with differing translucency. Quartz, ammonium dihydrogen phosphate (ADP) and aluminum nitride (AlN) were compared in a standard autocorrelation setup and a novel versatile setup measuring frequency-doubled stray light. Best results were achieved with AlN, which appears to be a suitable and promising alternative material to BBO, reducing the expenses by two to three orders of magnitude.
关键词： autocorrelation,Stray light autocorrelation,aluminum nitride,ultrashort laser pulses
更新于2025-09-19 17:13:59
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Frequency Comb Generation at 800 nm in Waveguide Array Quantum Well Diode Lasers
摘要： A capacitive-piezoelectric transducer combines capacitive and piezoelectric mechanisms to achieve a combination of electromechanical coupling and Q higher than otherwise attainable by either mechanism separately, has allowed demonstration of a 1.2-GHz contour-mode aluminum nitride (AlN) ring resonator with Q > 3000 on par with the highest measured d31-transduced AlN-only piezoelectric resonators past 1 GHz, and a 50-MHz disk array with an even higher Q > 12 000. Here, the key innovation is to separate the piezoelectric resonator from its metal electrodes by tiny gaps to eliminate metal material and metal-to-piezoelectric interface losses thought to limit thin-film piezoelectric resonator Q, while also maintaining high electric field strength to preserve a strong piezoelectric effect. While Q increases, electromechanical coupling decreases, but the k2 · Q product can still increase overall. More importantly, use of the capacitive-piezo transducer allows a designer to trade electromechanical coupling for Q, providing a very useful method to tailor Q and coupling for narrowband radio frequency (RF) channel-selecting filters for which Q trumps coupling. This capacitive-piezo transducer concept does not require dc-bias voltages and allows for much thicker electrodes that reduce series resistance without mass loading the resonant structure. The latter is especially important as resonators and their supports continue to scale toward even higher frequencies.
关键词： electromechanical coupling,oscillator,Micromechanical resonator,self-alignment,small gap,aluminum nitride,equivalent circuit,quality factor,filter
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dark Pulses in a Long Ring Laser
摘要： A capacitive-piezoelectric transducer combines capacitive and piezoelectric mechanisms to achieve a combination of electromechanical coupling and Q higher than otherwise attainable by either mechanism separately, has allowed demonstration of a 1.2-GHz contour-mode aluminum nitride (AlN) ring resonator with Q > 3000 on par with the highest measured d31-transduced AlN-only piezoelectric resonators past 1 GHz, and a 50-MHz disk array with an even higher Q > 12 000. Here, the key innovation is to separate the piezoelectric resonator from its metal electrodes by tiny gaps to eliminate metal material and metal-to-piezoelectric interface losses thought to limit thin-film piezoelectric resonator Q, while also maintaining high electric field strength to preserve a strong piezoelectric effect. While Q increases, electromechanical coupling decreases, but the k2 · Q product can still increase overall. More importantly, use of the capacitive-piezo transducer allows a designer to trade electromechanical coupling for Q, providing a very useful method to tailor Q and coupling for narrowband radio frequency (RF) channel-selecting filters for which Q trumps coupling. This capacitive-piezo transducer concept does not require dc-bias voltages and allows for much thicker electrodes that reduce series resistance without mass loading the resonant structure. The latter is especially important as resonators and their supports continue to scale toward even higher frequencies.
关键词： electromechanical coupling,oscillator,Micromechanical resonator,self-alignment,small gap,aluminum nitride,equivalent circuit,quality factor,filter
更新于2025-09-19 17:13:59