Zengcai Song

Field electron emission of layered Bi2Se3 nanosheets with atom-thick sharp edges

Field electron emission properties of solution processed few-layer Bi₂Se₃ nanosheets are studied for the first time, which exhibit a low turn-on field of 2.3 V μm(-1), a high field enhancement factor of up to 6860 and good field emission stability. This performance is better than that of the as reported layered MoS₂f sheets and is comparable to that of single layer graphene films. The efficient field emission behaviours are found to be not only attributed to their lower work function but also related to their numerous sharp edges or protrusion decorated structure based on our simulation results. Besides, the contribution of possible two-dimensional electron gas surface states of atom-thick layered Bi₂Se₃ nanosheets is discussed in this paper. We anticipate that these solution processed layered Bi₂Se₃ nanosheets have great potential as robust high-performance vertical structure electron emitters for future light weight and highly flexible vacuum micro/nano-electronic device applications.

Enhanced Field Emission From Aligned ZnO Nanowires Grown on a Graphene Layer With Hydrothermal Method

Zinc oxide (ZnO) nanowire arrays on silicon substrates with amorphous carbon or graphene as buffer layer for field electron emission application are obtained using hydrothermal method. It is found that graphene could optimize the structure and morphology of ZnO nanowires grown on it. Smaller nanowire diameter and larger length/diameter ratio are obtained for those grown on graphene buffer layer. ZnO nanowires grown on graphene layer has c-axis preferential orientation, while those grown on bare silicon wafer without any buffer layer has no obvious preferred growth orientation. Low turn-on electrical field of 1.59 V/μm and high field enhancement factor of 1625 are obtained from ZnO nanowires grown on graphene layer, which indicates that graphene is not only beneficial to the growth of ZnO nanowires by improving their configuration but can also enhance their field electron emission.

NH4F-assisted one-pot solution synthesis of hexagonal ZnO microdiscs for efficient ultraviolet photodetection

One-pot solution method to grow large hexagonal ZnO microdiscs with the aid of ammonium fluoride (NH4F) mineralizer has been realized. The size, morphology, crystallinity and optical properties of the synthesized ZnO microdiscs can be efficiently modulated by the concentration of NH4F. X-ray diffraction and scanning electron microscopy analyses illustrate that hexagonal ZnO microdiscs achieved at 0.03 M NH4F concentration have larger disc size and narrower full-width value at half maximum of (002) peak. It implies better crystal quality compared with those from other additive concentrations. Photoluminescence results also demonstrate the same trend. These results indicate that with proper addition of NH4F, the crystal quality of ZnO microdiscs has been improved and defects have been suppressed. Furthermore, a UV photodetector has been fabricated by simply transferring the ZnO microdiscs grown with 0.03 M NH4F onto a p-type silicon substrate. The device exhibits photosensitive behaviour at 365 nm UV light illuminating when −0.6 V is applied. The response time as well as recovery time is less than 0.1 s. The relatively large photoresponsivity of 1.19 A W−1 with power consumption less than 10 nW makes it possible in application field of highly efficient low power consumption UV detection.