Si(001)衬底上闪锌矿ZnO的制备与分析

采用分子束外延方法在室温下于Si(001)表面上生长ZnO材料。实验发现:样品为闪锌矿和六角结构的ZnO混合多晶薄膜,其表面分布着一系列具一定取向的近似长方形的纳米台柱结构。在不同参数的高温退火后,这些梯形台柱将变小,形成梯形纳米环,或分解为较小的纳米柱及其团簇结构等。分析表明:ZnO混合多晶薄膜的形成,以及表面纳米台柱的演变,与Si(001)衬底、较低温的生长温度及热效应等因素相关联。

Growth and Investigation of Zincblende ZnO on Si(001)

In recent years, zinc oxide (ZnO) has received much attention due to its potential applications in blue and ultraviolet devices. High quality and high efficiency p-type doping is still a big challenge for their studies and device applications. Zincblende ZnO is suggested to be one possible key to overcome this obstacle. Metastable thin zincblende ZnO film has been realized on GaAs(001), sapphire, and Pt(111)/Ti/SiO2/Si(100) multilayered substrates using a ZnS buffer/interlayers for the growth. However, due to the very large lattice mismatching, silicon is not the idealist substrate for the epitaxial growth of single crystal ZnO, while a great variety of wurtzite ZnO nano-structures have been constructed on Si(001). In this work, a plasma assistant molecular beam epitaxy was employed to grow the zincblende ZnO directly on Si(001) substrate at room temperature, and the growth kinetics was simply explored. The samples were grown and post-annealed under modulated growth conditions. They were zincblende polycrystalline embedded with wurtzite subdomains revealed by in-situ scanning tunneling microscopy and X-ray diffraction measurements. Nano trapezoid columns were observed on the as-grown samples. Nanostructural rings and clusters were depicted during the surface evolution after annealing. Though the zincblende ZnO is quite stable in ambient conditions, the metastable phase can be realized only under some critical conditions, such as the initial stage of ZnO nucleation during the epitaxial growth. The wurtzite ZnO generally has a growth privilege over the zincblende ZnO. Since the silicon substrate has a cubic symmetry lattice, it could result in formation of the zincblende ZnO in square structure at the initial growth, especially under the very low epitaxial temperature, i.e. room temperature. With the increasing of the thin film thickness, the influence from the substrates decreases, then the growth turns to favor for more stable wurtzite structure. Thus, the samples became zincblende polycrystalline embedded with wurtzite subdomains. Though the surface experiences a series of evolutions under annealing, the investigations showed the phase transition from zincblende to wurtzite is not as remarkable as expected.