Self-polarized energy harvesting materials have seen increasing research interest in recent years owing to their simple fabrication method and versatile application potential. In this study, we systematically investigated self-polarized P(VDF-TrFE)/carbon black (CB) composite thin films synthesized on flexible substrates, with the CB content varying from 0 to 0.6 wt.% in P(VDF-TrFE). The presence of –OH functional groups on carbon black significantly enhances its crystallinity, dipolar orientation, and piezoelectric performance. Multiple characterization techniques were used to investigate the crystalline quality, chemical structure, and morphology of the composite P(VDF-TrFE)/CB films, which indicated no significant changes in these parameters. However, some increase in surface roughness was observed when the CB content increased. With the application of an external force, the piezoelectrically generated voltage was found to systematically increase with higher CB content, reaching a maximum value at 0.6 wt.%, after which the sample exhibited low resistance. The piezoelectric voltage produced by the unpoled 0.6 wt.% CB composite film significantly exceeded the unpoled pure P(VDF-TrFE) film when subjected to the same applied strain. Furthermore, it exhibited exceptional stability in the piezoelectric voltage over time, exceeding the output voltage of the poled pure P(VDF-TrFE) film. Notably, P(VDF_TrFE)/CB composite-based devices can be used in energy harvesting and piezoelectric strain sensing to monitor human motions, which has the potential to positively impact the field of smart wearable devices.

A transparent indium tin oxide (ITO) contact to bulk n-GaN and n-GaN thin film on c-face sapphire with a specific contact resistivity of 8.06 × 10⁻⁴ Ω.cm² and 3.71 × 10⁻⁴ Ω.cm² was measured, respectively. Our studies relied on an RF sputtering system for ITO deposition. We have investigated the formation of the ITO-based contacts on untreated and plasma treated samples. A nonlinear I–V curve was observed for ITO deposited on untreated samples. On the other hand, an I–V curve with linear behavior was observed for plasma-treated samples, indicating the formation of ohmic contacts. From the C-V measurements, it was observed that there was also an increase in the carrier concentration in plasma treated samples compared to untreated samples. This can be attributed to the removal of surface oxide layer present on the GaN surface, and increase in nitrogen vacancies after SiCl₄ plasma treatment. In addition, the increase in nitrogen vacancies at the GaN surface can also enhance localized surface/sub-surface carriers, thereby reducing the contact resistance further.

This paper investigates an AlGaN/GaN triangular microcantilever with a heated apex for airflow detection utilizing a very simple two-terminal sensor configuration. Thermal microscope images were used to verify that the apex region of the microcantilever reached significantly higher temperatures than other parts under applied voltage bias. The sensor response was found to vary linearly with airflow rate when tested over a range of airflow varying from 16 to 2000 sccm. The noise-limited flow volume measurement yielded ~4 sccm resolution, while the velocity resolution was found to be 0.241 cm/s, which is one of the best reported so far for thermal sensors. The sensor was able to operate at a very low power consumption level of ~5 mW, which is one of the lowest reported for these types of sensors. The intrinsic response time of the sensor was estimated to be on the order of a few ms, limited by its thermal properties. Overall, the microcantilever sensor, with its simple geometry and measurement configurations, was found to exhibit attractive performance metrics useful for various sensing applications.