Controlled Growth Of One-dimentional ZnO Nano-composites And The Fabrication Of Ultra-violet Photodetector

The properties of a certain material changed a lot once the name had been prefixed with ?nano?.Since the carbon nanotube had been discovered by Iijima in 1991,one and quasi-one dimensional nanomaterials such as nanowire,nanotube,nanorod and nanobelt have been applied in the emerging applications,including nanoelectronics,catalysis,LED and chemical and biological sensors due to their unique optical and electrical properties.Basically,these advantages of nanomaterials over the bulk ones are originated from the vastly reduced sizes.As the semiconductors shrinking to the nanosize,their surface to volume ratio,chemical sensitivity and quantum size effect are increasing and dominate the exceptional properties.ZnO nanomaterial is one of the most promising candidates involved in the next generation nanosized optoelectronic device owing the direct band gap,high exciton binding energy and easily controlled microstructure.Nowadays,UV lithography and EBL are commonly used to fabricate the nanodevice following the top-down techniques,but it is too expensive and not so efficient to fabricate the device in 10 nm scale with integrated multifunctional components.The priority here is focusing on the controlled synthesis of various ZnO nanostructures to take advantage of the exceptional properties;Then,new assembly methods are investigated and used to fabricate low-cost but high performance nanodevices based on the bottom-up strategies.The four main achievements are as below:1.Double Schottky Barriers(SB)UV photodetector made of single ZnO nanowire/Ag nanoparticles composite was fabricated by eletric-field guided assembly process and the improved performance is associated with the enhanced surface trap states and LSPR effect from the uniform Ag nanoparticles.The device shows that the responsivity and photoconduction gain could reach 4.91×106 A/W and 1.67×107 under 5 V bias,respectively.2.Using chemical vapor transport techniques,ZnO nanotube,nanowire/nanotube and nanorod/nanotube hybrid nano-composites were synthesized via one-pot process on different substrates including Si and aluminum foil in a controlled and efficient way.3.The continuously tunable PL emission was observed on the one step synthesized 3D hybrid ZnO nanowire/nanotube composites on single chip,which ranges from the band edge UV emission region to the defects related broad green emission region.Interestingly,the hydrophobicity was also regulated by the morphology evolution of the hybrid nanostructure.4.It was confirmed that a ultrafast photogenerated carrier separation process existed in the 3D hybrid ZnO nanowire/nanotube nanostructure due to the built-in electrical field,which induced by the unique homojunction interface,using time resolved absorption and PL spectroscopy.The results indicate that certain hybrid nanostructure could effectively modulate the carrier transport and light emission process.Therefore,the 3D hybrid composite is suitable for being adopted in the applications such as photovoltaic device and photocatalysis.