Synthesis and properties of aligned ZnO microtube arrays

Two kinds of different aligned zinc oxide (ZnO) crystal microtube arrays were prepared on silicon (1 0 0) substrates by using of a simple thermal chemical reaction vapor transport deposition method. The synthesizing processes were done by using of heating the mixture of zinc oxide and graphite powders at 1150 8C in a quartz tube with one side opened to the air. The O2 gas (99.9%) and air had been introduced as the assistant gases, respectively. Both the flow rates were 100 ml/min. And the temperature of the Si (1 0 0) substrate region was about 400 8C. There is no other metal catalyst on the Si wafers in the process. After growing for 30 min, one kind of synthesized sample is trumpet-shaped hexagonal microtube arrays assisted with O2 gas and another produced sample is the uniform hexagonal microtubes only assisted with air. As the increasing of preparing time, their maximal lengths can range from several 10 mm to mm scale. The microstructure, room temperature photoluminescence properties and growth mechanism of both aligned microtube arrays were investigated and discussed