Growth, Cathodoluminescence and Field Emission of ZnS Tetrapod Tree‐like Heterostructures

Abstract

We report the growth mechanism, cathodoluminescence and field emission of dual phase ZnS tetrapod tree‐like heterostructures. This novel heterostructures consist of two phases: zinc blende for the trunk and hexagonal wurtzite for the branch. Direct evidence is presented for the polarity induced growth of tetrapod ZnS trees through high‐resolution electron microscopy study, demonstrating that Zn‐terminated ZnS (111)/(0001) polar surface is chemically active and S‐terminated (${\bar 1}$${\bar 1}$${\bar 1}$)/(000$\bar 1$) polar surface is inert in the growth of tetrapod ZnS trees. Two strong UV emissions centered at 3.68 and 3.83 eV have been observed at room temperature, which are attributed to the bandgap emissions from the zinc blende trunk and hexagonal wurtzite branch, indicating that such structures can be used as unique electromechanical and optoelectronic components in potential light sources, laser and light emitting display devices. In addition, the low turn‐on field (2.66 Vµm−1), high field‐enhancement factor (over 2600), large current density (over 30 mAcm−2 at a macroscopic field of 4.33 Vµm−1) and small fluctuation (∼1%) further indicate the availability of ZnS tetrapod tree‐like heterostructures for field emission panel display. This excellent field‐emission property is attributed to the specific crystallographic feature with high crystallinity and cone‐shape patterned branch with nanometer‐sized tips. Such a structure may optimize the FE properties and make a promising field emitter.

ZnS Branched Architectures as Optoelectronic Devices and Field Emitters

“…5 nm, [14] such a small blue-shift may be attributed to the strain effect from the cone-shaped WZ nanowire of the branch, which is consistent with our observation in the ZnS dual-phase tetrapod treelike heterostructures. [28] A relatively low visible emission is centered on 570 nm, which may originate mainly from the twin planes, similar to results reported by Fang et al [35] The ZnS architectures were further painted on a highly doped silicon substrate covered with a Au layer of 300 nm thickness for FE measurements taking advantage of the tip shape of the branched nanowires (see the field-emitter cathode in Fig. S3 of the Supporting Information).…”

“…The inset of Figure 1d is a convergent beam electron diffraction (CBED) pattern that confirms the growth direction being [0001] (rather than [0001]), indicating that the branch growth is controlled by the (0001) Zn polarity-induced growth mechanism. [28] To elucidate the possible formation mechanism of these novel branched architectures, the intermediate product (with shorter growth time) was carefully characterized. SEM investigations showed that the intermediate product has a wirelike structure with a quasi-six-fold cross-section and contains a number of nuclei (embryos or initiated short nanowires).…”

Amorphous SiOx nanowires catalyzed by metallic Ge for optoelectronic applications

“…Various nanowires, such as Si [4], ZnO [5], ZnS [6,7], GaN [8], GaP [9] and SiO x [10] nanowires, have been synthesized by different methods. Among them, SiO x nanowires attract special attention in optoelectronic applications because of their high intense and stable blue light emission at the room temperature [11,12] and their potential applications in the field of light localizations [11,13], low dimensional waveguides [11,13,14], and scanning near-field optical microscopy [11,14,15].…”

Synthesis and field-emission properties of novel hierarchical ZnO hexagonal towers

“…[3]. Many reports were focused on the development of nanostructures with different morphology or shape, such as ZnS branched architectures [4], hierarchical single-crystalline ˇ-SiC nanoarchitectures [5], ZnS tetrapod tree-like heterostructures [6], carbon-in-Al 4 C 3 nanowires [7] and sixfold-symmetrical hierarchical ZnO [8].…”