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Zheng Wei Pan

Publications and source records attributed to Zheng Wei Pan.

4 recordsLinked to original sources
PubMed2005

Nanowire array gratings with ZnO combs.

Diffraction gratings are mainly manufactured by mechanical ruling, interference lithography, or resin replication, which generally require expensive equipment, complicated procedures, and a stable environment. We describe the controlled growth of self-organized microscale ZnO comb gratings by a simple one-step thermal evaporation and condensation method. The ZnO combs consist of an array of very uniform, perfectly aligned, evenly spaced and long single-crystalline ZnO nanowires or nanobelts with periods in the range of 0.2 to 2 microm. Diffraction experiments show that the ZnO combs can function as a tiny three-beam divider that may find applications in miniaturized integrated optics such as three-beam optical pickup systems.

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PubMed2002

Growth and structure evolution of novel tin oxide diskettes.

The novel SnO diskettes have been synthesized by evaporating either SnO or SnO(2) powders at elevated temperature. Disregard the source material being SnO or SnO(2), the SnO diskettes are formed at a low-temperature region of 200-400 degrees C. Two types of diskette shapes have been identified: the solid-wheel shape with a drop center rim (type I) and the diskette with cone peak(s) and spiral steps (type II). The diskettes are determined to be tetragonal SnO structure (P4/nmm), with their flat surfaces being (001). The formation of the SnO diskettes is suggested to result from a solidification process. The structural evolution from SnO diskettes to SnO(2) diskettes has been investigated by oxidizing at different temperatures. The result shows that the phase transformation from SnO to SnO(2) occurs in two processes of decomposition and oxidization, and the decomposition process consists of two steps: first from SnO to Sn(3)O(4) and then from Sn(3)O(4) to SnO(2).

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PubMed2002

Molten gallium as a catalyst for the large-scale growth of highly aligned silica nanowires.

The vapor-liquid-solid (VLS) process is a fundamental mechanism for the growth of nanowires, in which a small size (5-100 nm in diameter), high melting point metal (such as gold and iron) catalyst particle directs the nanowire's growth direction and defines the diameter of the crystalline nanowire. In this article, we show that the large size (5-50 microm in diameter), low melting point gallium droplets can be used as an effective catalyst for the large-scale growth of highly aligned, closely packed silica nanowire bunches. Unlike any previously observed results using gold or iron as catalyst, the gallium-catalyzed VLS growth exhibits many amazing growth phenomena. The silica nanowires tend to grow batch by batch. For each batch, numerous nanowires simultaneously nucleate, grow at nearly the same rate and direction, and simultaneously stop growing. The force between the batches periodically lifts the gallium catalyst upward, forming two different kinds of products on a silicon wafer and alumina substrate. On the silicon wafer, carrot-shaped tubes whose walls are composed of highly aligned silica nanowires with diameters of 15-30 nm and length of 10-40 microm were obtained. On the alumina substrate, cometlike structures composed of highly oriented silica nanowires with diameters of 50-100 nm and length of 10-50 microm were formed. A growth model was proposed. The experimental results expand the VLS mechanism to a broader range.

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