Novel AlN/Pt/ZnO Electrode for High Temperature SAW Sensors

Thermoluminescent characteristics of UV-irradiated Aluminum nitride (AlN)

This paper presents results of studying the thermoluminescence (TL) properties of aluminum nitride (AlN) synthesized by chemical vapor deposition (CVD) method. Previously to study the TL properties, the phosphor was characterized by means of X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), photoluminescence (PL), and electron microscopy (EDS-SEM). TL studies were performed after ultraviolet (UV) irradiation using the whole spectrum of the xenon (Xe) lamp. XRD results show that AlN has a hexagonal crystalline structure. EDS-SEM analysis revealed the presence of oxygen (O) and Carbon (C) impurities in the powders. FT-IR spectroscopy lets us discuss the distribution of these impurities in the crystalline structure. The sample with 9.54% of C and 7.36% of O exhibits a TL glow curve with a predominant peak around 450 K, and according to the deconvolution method was found that the glow curve is composed by six peaks each one centered at 383, 446, 478, 540, 587 and 637 K. The TL response as a function of dose fits a logarithmic increasing function along the dose range studied: These results suggest that AlN is a promising material for application as a TL dosimeter for UV radiation.

Improvement of High-Temperature Stability of Al₂O₃/Pt/ZnO/Al₂O₃ Film Electrode for SAW Devices by Using Al₂O₃ Barrier Layer

In order to develop film electrodes for the surface acoustic wave (SAW) devices operating in harsh high-temperature environments, novel Al₂O₃/Pt/ZnO/Al₂O₃ multilayered film electrodes were prepared by laser molecular beam epitaxy (LMBE) at 150 °C. The first Al₂O₃ layer was used as a barrier layer to prevent the diffusion of Ga, La, and Si atoms from the La₃Ga₅SiO₁₄ (LGS) substrate to the film electrode and thus improved the crystalline quality of ZnO and Pt films. It was found that the resistance of the Al₂O₃/Pt/ZnO/Al₂O₃ electrode did not vary up to a temperature of 1150 °C, suggesting a high reliability of electrode under harsh high-temperature environments. The mechanism of the stable resistance of the Al₂O₃/Pt/ZnO/Al₂O₃ film electrodes at high temperature was investigated by analyzing its microstructure. The proposed Al₂O₃/Pt/ZnO/Al₂O₃ film electrode has great potential for application in high-temperature SAW devices.

Mechanical, Corrosion and Biological Properties of Room-Temperature Sputtered Aluminum Nitride Films with Dissimilar Nanostructure

Aluminum Nitride (AlN) has been long time being regarded as highly interesting material for developing sensing applications (including biosensors and implantable sensors). AlN, due to its appealing electronic properties, is envisaged lately to serve as a multi-functional biosensing platform. Although generally exploited for its intrinsic piezoelectricity, its surface morphology and mechanical performance (elastic modulus, hardness, wear, scratch and tensile resistance to delamination, adherence to the substrate), corrosion resistance and cytocompatibility are also essential features for high performance sustainable biosensor devices. However, information about AlN suitability for such applications is rather scarce or at best scattered and incomplete. Here, we aim to deliver a comprehensive evaluation of the morpho-structural, compositional, mechanical, electrochemical and biological properties of reactive radio-frequency magnetron sputtered AlN nanostructured thin films with various degrees of c-axis texturing, deposited at a low temperature (~50 °C) on Si (100) substrates. The inter-conditionality elicited between the base pressure level attained in the reactor chamber and crystalline quality of AlN films is highlighted. The potential suitability of nanostructured AlN (in form of thin films) for the realization of various type of sensors (with emphasis on bio-sensors) is thoroughly probed, thus unveiling its advantages and limitations, as well as suggesting paths to safely exploit the remarkable prospects of this type of materials.