A study on the properties of composite structure of ZnO nanowires and nanocrystalline diamond thin films

[[abstract]]In this study, the nanocrystalline diamond film was deposited on silicon substrate using methane/hydrogen/oxygen (30/169/0.2 sccm) mixed gas by microwave plasma chemical vapor deposition (MPCVD) system. Different synthetic techniques, hydrothermal technique and vapor liquid solid (VLS) technique, are used to grow Zinc oxide (ZnO) nanowires on nanocrystalline diamond films (nano-diamond films). For the hydrothermal technique, a 180 nm thick of ZnO film is coated as a seeded layer on nano-diamond film. ZnO nanowires are grown by immersing in a mixture of solution (Zinc nitrate (Zn(NO3)2 . 6H2O) and Hexamethylenetetramine (HMTA) in deionized water) at 90 oC for 3 hours. For the VLS technique, a 10 nm thick of Au layer is coated on nano-diamond films as catalyst. ZnO nanowires are synthesized using a mixture of ZnO and graphite powder as the source in a furnace at 850 oC with 100 sccm of Ar gas at 20 torr for 30 min. However, it is indicated that the field enhancement factor are both improved for the ZnO/nano-diamond structure compared to ZnO/Si structure by hydrothermal (307 to 1286) and by VLS (386 to 1565). ZnO nanowires are treated by Ar and H2 plasma for 1, 3 and 5 min. It is observed that the field enhancement factor of Ar plasma treatment for 1 min are 526. It is noted that the turn on field and critical current density of H2 plasma treatment for 3 min are 903. The best condition of turn on field and field enhancement factor are 6.6 V/μm and 1951, which is obtained from the VLS ZnO NW/ND and then treated by H2 plasma for 3 min.