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This work presents for the first time underwater 2D localization of a reflector through only two pulse echo measurements using a trilateration methodology with a pair of lead zirconate titanate PZT piezoelectric micromachined ultrasonic transducer pMUT arrays A matched filter method is used to compute the range values for the received signals Trilateration is employed to determine the absolute location of the reflector via the estimated range values through the use of the geometry of circles Experimental data are collected using two PZT pMUTs which exhibit impressive transmit and receive sensitivities immersed in a FC 70 fluid for the validation of the method with the results highlighting the suitability of the proposed method for underwater 2D acoustic object localization thus paving the way for the use of pMUTs towards new immersion applications

We report preliminary wafer level measurement results of air coupled phase vapor deposition PVD PZT pMUTs for ranging applications recently fabricated in our Lab in Fab 8 inch line Dual port PVD PZT pMUTs designed to resonate in the 100kHz range were fabricated based on a boldsymbol 2 mu mathbf m thick PZT film on a boldsymbol 4 mu mathbf m thick silicon diaphragm The standard deviation of the PZT stack capacitance was 2 across the wafer Despite the sensitivity of compliant diaphragms to film residual stress the standard deviation of frequency was 5 Out of 16 sites across wafer probed all devices were verified to be in good working condition Given the strong piezoelectric constant of the PZT film mathbf e boldsymbol 31 mathbf f boldsymbol sim 16 mathbf C mathbf m boldsymbol 2 and compliance of the diaphragm designed for ranging applications we demonstrate large tunability in frequency 120 210kHz mathbf K mathbf t boldsymbol 2 1 7 3 and quality factor 50 100 for a bias voltage range of0 40V Results have been obtained without poling of the PVD PZT film No unresponsive devices were found

The growth dynamics of Ga(In)N semiconductors by Plasma-Assisted Molecular Beam Epitaxy (PAMBE) at low temperatures (T = 450 °C) is here investigated. The presence of droplets at the growth surface strongly affects the adatom incorporation dynamics, making the growth rate a decreasing function of the metal flux impinging on the surface. We explain this phenomenon via a model that considers droplet effects on the incorporation of metal adatoms into the crystal. A relevant role is played by the vapor-liquid-solid growth mode that takes place under the droplets due to nitrogen molecules directly impinging on the droplets. The role of droplets in the growth dynamics here observed and modeled in the case of Nitride semiconductors is general and it can be extended to describe the growth of the material class of binary compounds when droplets are present on the surface.

We investigate the effect of surface Ga accumulation on the growth of In0.5Ga0.5N by PAMBE at low temperatures (T= 440 °C). We find that the control of the surface metal condition is very important because the crystallization process strongly depends on the metal flux impinging on the surface. The growth rate rapidly decreases when the supply of metal flux exceeds certain amount. Such phenomenon can be explained by the model taking into account droplet effects on the incorporation of metals adatom into the crystal.