Aluminum-doped zinc oxide films were deposited by dc and rf magnetron sputtering from ZnO(98%)Al2O3(2%) target at room temperature on silicon and glass substrates under a variety of process conditions with the goal of attaining the highest transmittance and lowest resistivity for photovoltaic applications. The magnetron power and pressure were varied. For many dielectric deposition systems, added oxygen is necessary to achieve the appropriate stoichiometry. The effect of oxygen on film properties was then studied by varying the oxygen partial pressure from 1.5×10−5 to 4.0×10−5 T at a constant Ar pressure, with the result that any added oxygen was deleterious. Films deposited under power, pressure, and low-oxygen conditions were then characterized for electrical and optical properties. Following this, the dc and rf sputtered films were annealed at up to 400 °C seconds using rapid thermal annealing (RTA), and the influence of annealing on resistivity, transmittance, band gap, as well as grain growth and stress was studied. The effect of RTA was immediate and quite significant on dc films while the effect on rf films was not as profound. As-deposited rf films had a higher average transmittance (87%) and lower resistivity (5.5×10−4 Ω cm) compared to as-deposited dc films (84.2% and 8.9×10−4 Ω cm). On the other hand, after RTA at 400 °C for 60 s, dc films exhibited better average transmittance (92.3%) and resistivity (2.9×10−4 Ω cm) than rf films (90.7% and 4.0×10−4 Ω cm). The band gap of dc films increased from 3.55 to 3.80 eV while that of rf films increased from 3.76 to 3.85 eV. Finally, dc and rf films were textured in 0.1% HCl and compared to U-type Asahi glass for resistivity and transmittance.
Manipulation and control of matter at the nanoscale and atomic scale levels are crucial for the success of nanoscale sensors and actuators. The ability to control and synthesize multilayer structures using carbon nanotubes that will enable the building of electronic devices within a nanotube is still in its infancy. In this paper, we present results on selective electric field-assisted deposition of metals on carbon nanotubes realizing metallic nanowire structures. Silver and platinum nanowires have been fabricated using this approach for their applications in chemical sensing as catalytic materials to sniff toxic agents and in the area of biomedical nanotechnology for construction of artificial muscles. Electric field-assisted deposition allows the deposition of metals with a high degree of selectivity on carbon nanotubes by manipulating the charges on the surface of the nanotubes and forming electrostatic double-layer supercapacitors. Deposition of metals primarily occurred due to electrochemical reduction, electrophoresis, and electro-osmosis inside the walls of the nanotube. SEM and TEM investigations revealed silver and platinum nanowires between 10 nm and 100 nm in diameter. The present technique is versatile and enables the fabrication of a host of different types of metallic and semiconducting nanowires using carbon nanotube templates for nanoelectronics and a myriad of sensor applications.
We report the sonochemical synthesis of platinum nanowires on carbon nanotube templates and their application in electrochemical actuation. The fabrication of platinum nanowires was achieved by suspending well separated single wall carbon nanotubes in isopropyl alcohol and ultra-sonically agitating the solution in the presence of dihydrogen hexachloroplatinate. The platinum nanowires were further processed into micro and macro scale free standing sheets by vacuum filtration. An electrochemical cantilever actuator was constructed using the platinum nanowire sheet which actuated under electrical bias. Displacement of '3 mm was readily achieved when the electrical potential was swept at low voltages between -2 V and 2 V at a scan rate of 200 mV/s. The actuator showed the metallic actuation characteristics instead of that from carbon nanotubes. These results show the applicability of metallic nanomaterials for actuation technologies.
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