Vargas Ortiz, Cristina M.

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    Environmental nanotechnology: Building of sensor devices for the detection of hazardous gases at low concentrations
    (2023-05-04) Vargas Ortiz, Cristina M.; Otaño Rivera, Wilfredo; College of Engineering; Padovani Blanco, Agnes; Torres Candelaria, Jessica; Department of Materials Science and Engineering; Acevedo Vélez, Claribel
    This research focuses on the growth of zinc oxide (ZnO) thin films and their incorporation into chemiresistor sensors used for the detection of hazardous gases at low concentrations. Research areas such as environmental nanotechnology study these types of devices due to their low cost of production and use. Furthermore, thin films with nanometric scales have been shown to enhance important properties becoming significant components in sensing devices. Zinc oxide is intensely used due to its high sensitivity as transductor material for the detection of several gases of environmental concern. The zinc oxide thin films were created using a physical vapor deposition technique known as radiofrequency magnetron sputtering. Oxygen and argon gases were used for the creation of the plasma in a technique known as reactive sputtering. Oxygen: argon ratios of 30, 50, and 70% and sputtering powers of 50, 100, 150, and 200 Watts were used for the deposition. The films were deposited directly on glass and silicon oxide substrates, on electrospun fibers, and on a commercial platform that was used to test their electrical response when subjected to partial pressures of potentially hazardous gases such as hydrogen (H2) and nitrogen dioxide (NO2). The samples were characterized using profilometry to determine the thickness of the film as a function of deposition time, oxygen-argon ratio, and sputtering power. X–ray diffraction was used to characterize the crystallinity that corresponds to the zinc oxide wurtzite structure with a preferred growth of the (002) plane perpendicular to the substrate. Samples prepared under different deposition parameters were used to test their electrical responses in the presence of the above gases. Samples made out of thin films and nanoshells showed a response between 5 and 81%.