Growth and characterization of a high-purity ZnO nanoneedles film prepared by microwave plasma deposition

A high-density crystalline ZnO nanoneedles film (⁠$∼5μm$ thick) has been fabricated using a microwave plasma enhanced chemical vapor deposition apparatus. The nanostructures and properties were examined by scanning electron microscopy, high resolution transmission electron microscopy, and x-ray diffraction. The results indicated that the ZnO nanoneedle possesses a wurtzite structure (hexagonal) with lattice constants of $a0=3.24Å$ and $C0=5.19Å$⁠, and an average length up to $5μm$⁠, while the diameters of the tip and the pillar of the nanoneedle are of $∼30$ and $∼300nm$⁠, respectively. The film density reaches $∼1011cm−2$⁠. The room-temperature photoluminescence spectrum reveals a strong and sharp near-UV emission band at $386nm$ and exhibits a very weak deep-level emission, which implies the high-purity nature of the ZnO nanoneedles film. The high specific surface of ZnO nanoneedles film has potential applications in chemical sensors while the excitation property has optoelectronic and photochemical applications.